Cellular 2

Cdks

. Checkpoint gatekeepers, control movement through cell cycle. Cyclin depended kinases. activites rise and fall throughout the cycle, but always present cyclical phosphorylation of proteins that initiate checkpoint passage. Controlled by cyclins. Need to be bound to to act. m-Cdk condenses chromosomes, induct mitotic spindle assembly, ensure chromatid par attached to opposite spindle. M Cdk phosphorylates proteins involved. Increased amount in G2 and M. Cdc25 removed inhibitory phosphates on M Cdk, can activate in positive feedback. Controlled by protein synthesis (cyclins), protein degradation, phosphorylation.de, CKIs When cyclin forms a complex with Cdk, the protein kinase is activated to trigger specific cell-cycle events. WIthout cyclin, Cdk is inacive. Cyclin dependent Kinases (Cdks) control movement through cell cycle. Movement through the cell cycle is through activation and deactivation of these kinases. Mitosis Dependent Factor was a Cyclin Dependent Kinase (Cdk) and an M phase cyclin. Activity of Cdks rise and fall as cell progresses through the cell cycle. Cdks control the cell cycle. What controls the cdks? 1. Control by protein synthesis (cyclins) If you don't express the proteins, you don't get it them. 2. Control by phosphorylation/dephosphorylation 3. Control by CKIs (CDK inhibitory proteins) Tumor repressor proteins. If CDK are engines driving the cell cycle, then they are acting hold back/pause the cell cycle. Tumor repressors. 4. Control by protein degradation (cyclins and others) Cyclins and activating phosphorylation by kinases are required for Cdk activity. CDK inactive. When it interacts with cyclin it is partially active, and ATP as binding site, gets phosphorylated to get fully active by Cdk activating kinase (CAK). Need cyclin and activating kinase for it to come on. T loop when inactive. Cyclin binding to Cdk pulls loop away from active loop, so that the CAK can phosphorylate the active site. CAK adds phosphate group to a threonine on the T loop.

ubiquitylation

Addition of ubiquitin to a molecule marking it for degradation. Activation of the enzyme APC leads to ubiquitylation of M cyclins and their destruction in the proteasome.

mitogens

Anything that stimulates cell proliferation. Stimulate cell division, trigger wave of G1,S Cdk activity that relieves intracellular negative controls. Ex: Platelet derived growth factor PDGF, Epidermal growth factor EGF

Bad

Bad = pro-apoptotic BH3-only protein

Bax

Bax = pro-apoptotic BH123 protein Main BH123 proteins in mammalian, one mimum rewired for intrinsic apoptosis pathway. Bak tightly bound to mitochondrial outer membrane even in apoptotic signal ansemse Bax manyl in cytosol and translocate to mitochondria only after apoptotic signal.

immortality

Cell lines that are not cancerous can be made immortal... telomerase? In cancer cells telomerase activity is increased and the telomeres are protected and stabilized, so the cell can go on dividing indefinitely without damage to the DNA.

senescence

Cells can only divide so many times, after a while enter a nondivind state from which they never recover. Seem to be caused by changes in telomeres. When too short, chromosomes ends exposed and sensed as DNA damage which activates p53 depended cell cycle arrest. A state that normal cells reach where the cell no longer divides

necrosis

Cells die accidentally in response to acute insult like trauma or lack of blood, swell and burst spill contents induce inflammatory response, programmed cell death type

anaplasia

Cells looking different. Sign of cancer, newly divided cells looking different than origin.

ubiquitin

Chain added onto molecules in ubiqitation that marks molecules for degradation. protein that becomes covalently attached to lysines. Attachment of a short chain of these can tag a protein for intracellular destruction by a proteasome (ubiquitylation/ubiquitination) Proteasome recognizes these chains of ubiquitin groups. Effective way to control proteins because we can target the polyubiquitin and kill that protein

Yeast G1 control

Checkpoint ca;;ed Stat near the end of G1 in yeast that cells must pass through to decide to grow and decide and enter s phase. Restrictive (high) temperature arrest cells in G1? To replicate eed correct nutrients, may sense the correct size needed to replicate, and mating pheromes can cause ( should I not because it would be better to mate?) In yeast cells, a single Cdk protein binds all classes of cyclins and triggers different cell-cycle events by changing cyclin partners at different stages of the cycle.

Cyclins

Cyclically synthesized and degraded. G1/S cyclins activate in late G1, activate through start levels fall in S phase, S cyclins bind after progression through start, help with chromosome duplication, remain elevated until mitosis, help with some mitotic events, M cyclins, activate Cdks that stimulate mitosis entry at G2/M checkpoint. G1 cylins last group help govern G1.S cyclin activity. Made of cyclin B and CDK1. Cyclins are proteins that are Cdk regulators. Without cyclin binding to Cdk, the Cdk remains inactive. Named cyclin because they undergo synthesis and degradation in each cell cycle. G1/S-cyclins activate Cdks in late G1 and thereby help trigger progression through G1, resulting in commitment to cell-cycle entry. Their levels fall in S phase. S-cyclins bind Cdks soon after progression through G1 and help stimulate chromosome duplication. S-cyclin levels remain elevated until mitosis. These cyclins also contribute to the control of some early mitotic events. M-cyclins activates Cdks that stimulate entry into mitosis at the G2/M checkpoint. G1-Cyclins helps govern the activities of the G1/S cyclins, which control progression through G1 checkpoint.

progression

Development of cancer. Requires a gradual accumulation of mutations in a number of different genes. Each cell generation becomes more deviant. Gains damaged with increased speed. -Cells become more deviant as time goes on; Earlier you can catch the cancerous tumor, more likely to be able to remove the tumor More divisions = more mutations

how DNA tumor viruses can cause cancer

Dna viruses that replication their DNA in cells, and either integrate their viral genome into one or more chromosome or for plasod that replicated with host chromosome. Integration into the chromosome can lead to malignant tumors, Encodes protein that inactivate tumor suppressor gene products Ex: viral Prtoein v7 binds up Rb so that transcription can continue , viral protein V6 binds p53 can't transcribe ex: papillomaviruses, cause warts, infect epithelium, latet in basal layers, outer layers of epithelial switch to replicative phase of viral particles, cells begin to differentiate whin normal would arrest to allow for vuris replication. Virus has to manipulate host cell's enzymes of DNA replication by its DNA getting integrated into the host chromosome. These enzymes are not expressed all the time. Virus comes in (circular chromosome in this picture). Gets transcribed and translated, makes proteins that bind to the tumor suppressor products. This little proliferation of cells that is self limiting is a wart.

telomerase

Enzyme, Replicate temoleric DNA sequences. Most cells low activity. Telomerase is an enzyme that helps to grow telomeres out. It's active originally during development to extend telomeres, but most regular cells in the adult body have little to no telomerase activity. Very active in germ cells because otherwise each generation would have shorter and shorter telomeres. In other cells less and less active as cells age, eventually reach senescence (where p53 is activated) and then crisis. In cancer cells, go past senescence and reach crisis, then telomerase activity is activated again and telomeres become stabilized, and cell becomes immortal. Telomerase are RNA enzymes. Use RNA as template for DNA synthesis. Extension. Release and binds again to extend and build the end. That doesn't keep you from losing them, but you can grow them back out, only loose a little bit each time. Most cells have no to very little telomerase activity. Telomerase maintains its activity in germ line cells because you wouldn't want to pass on short telomeres otherwise as generations pass then there would be shorter and shorter telomeres which is just bad. Stem cells have measurable telomerase activity, germ cells have tremendous amount of telomerase activity.

caspases (initiator and executioner)

Family of proteases cysteine at active site, cleave target proteins at specific aspartic acids. synthesized inactive precursors, procaspaces, activated by protelytic cleavage. procaspase slip into large and small subunit two dimers assemble for active tetramer. Caspase is cleaved and reassembled before eing activated. Target proteins cleaved include cytosolic proteins and nucear lamin. Caspases are at the heart of programmed cell death. Exist as inactive precursors with extra pieces on them, have to be proteolytically cleaved that cleaves off inhibitory domains and cleaves enzyme, then become active. - Exist in cascade, when caspases active (initiator caspases), activate other caspases (executioner caspases, go do the job). Should be inactive unless cell is doing apoptosis

CAK

Full activation of cyclin Cdk complex occurs when Cdk activatin kinase 9CAK0 phosphorylates amino acid near entrae of active site. Causes conformational change. Tyrosine kinase/ Cdk-activating Kinase phosphorylates an amino acid near the entrance of the Cdk active site, causing a small conformational change that further increases the activity of Cdk. This allows the kinase to phosphorylate its target proteins effectively and thereby induce specific cell-cycle events. Required to have fully activated Cdk.

Mitogens and G1 controls in mammalian cells

G1 control must pass through restriction point at the end og G1 in order to decide to more to S phase. Mitogen Growth factors - receptor tyrosine kinase - ras - MAPK - transcription factors- early gene expression- myc - delayed response cdks G1 G1/s cyclins - G1 G1/S phosphorylated Rb - Released E2f - S cyclin S Cdk made - S Cdk phosphorylated Rb - DNA synthesis enzymes made - S phase .

p53

Gene regulatory protein, tumor suppressor, stops cell cycle when DNA damage or excessive mitogenic stimulation, only activated with problems, promotes cell death if cells not fixed (FAK), p53 stimulates transcription of the gene encoding CKI protein p21, which inhibits G1/S and S Cdk complexes, blocking entry into cell cycle. DNA damage activates p53 indirectly. Undamaged cells, p53 highly unstable, low conc. Phosphorylation after DNA damage reduced Mdm2 binding to it. Mdm2 targets for destruction, ubiquilate. Upregulated BH3 only protein. Tumor suppressor protein; activates the transcription of genes that encode the BH3-only proteins (which promotes apoptosis). In cancer, p53 protein is mutated so it no longer promotes apoptosis in response to DNA damage. Lack of p53 function enables cancer cells to survive and proliferate even with damaged DNA. Need p53 to activate apoptosis and cell cycle arrest.

G0

Go is a phase cells can enter out of G1. It is a resting state cells can remain in theoretically forever without proliferating outside of cell cycle stably. If conditions are favorable or signals come like damage it can leave G0 and return to G1. Nondividing state, most body cells in.some more permanently, others transiently. Non dividing stage that cells can be in before G1 where they just go around doing whatever their cellular function is. If receive stimulatory signal can move out of G0 into G1 and start cell cycle.

p19/Arf

High Myc levels activate Arf: cell cycle inhibitor protein binds and inhibits Mdm2. p53 levels increase, induce cell cycle arrest or apoptosis. Arf inactivates Mdm2, Mdm2 inhibits activation of p53. So Arf relieves the inhibition of p53 by Mdm, allowing the cells to induce apoptosis when necessary.

intrinsic pathway of apoptosis

In intrinsic pathway One crucial protein cytochrome c, which is also important to electron transport and NAD generating which means it is essential to cell survival, when released from mitochondria into cytosol bind sto procapase activating adaptor protein Apaf1 causes it to oligomerize into wheel like shape apotosome. Recruit procaspase 9 proteins, activated by apotosome, cleave activate then activate downstream executioner caspases 3 , cytochrome c release mediated by Bcl2, Bcl2 proteins, Ba Bak part of intrinsic, Bcl2 is an anti-apoptotic protein. When it's active it blocks BH123 proteins from aggregating together in the mitochondrial outer membrane and forming pores that lets out cytochrome c. When an apoptotic stimulus is present it activates the BH3-only protein which inactivates Bcl2 which allows BH123 to aggregate and do it's things. Cytochrome C is loosely associated with inner membrane. If escapes, binds to Apaf1 in cytoplasm, unfolds and forms wheel thingy, attracts inactive form of procaspase 9, forms flower of death, causes caspase cascade that leads to apoptosis. Cytochrome C has another vitally important role in cells in energy metabolism, if cell is missing cytochrome c would not be able to live, so role in apoptosis was at first missed (because you couldn't study cells that lacked cytochrome C because they wouldn't survive). All cells can do this.

Wee1

Inhibits M Cdk activity by phosphorylation addition of amino acid above kinase active site on cyclin cdk complex. Wee1 mutant always active, smaller cell sizes due to short period in G2. Cdc25 Phosphorylation by the Wee 1 kinase near the active site inhibits activity. Unless this is removed by a phosphatase, the Cdk remains inactive. Build up inactive M-CDK, and then the inhibitory phosphates just holds it in its this form, and when ready just need to turn it all on. Hitting the Wee 1 to inactivate and then once you take of the inhibitory phosphate with a phosphatase, BOOM enzyme on This is triggering a massive process in the cell. You don't want to trigger it at the wrong time. You don't want them to make this decision at the wrong time.

MDM2

Interacts with p53, ubiquitin ligase that targets p53 fo destruction by proteasomes. Phosphorylation of p53 after DNA damage reduces Mdm2 binding to it. Protein that interacts with p53. Acts as a ubiquitin ligase that targets p53 for destruction by proteasomes. DNA damage reduces p53 binding to Mdm2 which enhances the ability of p53 to stimulate gene transcription.

nitric oxide signaling

Intracellular signaling, gas, ex: relaxing muscles, acetylcholine released, ethdothelial cells release NO, diffuse across membranes (hydrophobic ) locally into muscles cells binds to guanylyl cycles converts to GMP, releases. Nitric oxide made by deamination of arginine catalyzed by No synthases enzymes. only acts locally because has very short life in extracellular space betcause gets converted. Nitric Oxide (NO): Synthesized in some cells in response to neurotransmitter signals, made by the enzyme nitric oxide synthase. NOS activated by AcH in vascular endothelial cells No cell diffuses out of the cell and can act very locally, diffusing into other cells, binding in the active site of guanylyl cyclase, and stimulating cGMP production. Ex. In vascular smooth muscle cells, mGMP mediates relaxation so production by endothelial cells leads to dilation of blood vessels.In mammals NO's function is to relax smooth muscle, above figure shows this role in the walls of blood vessels. AcH is released by nerve terminals in blood vessel walls and activates NO synthase in endothelial cells lining the blood vessel, causing the endothelial cells to produces NO from arginine. The NO diffuses out of the endothelial cells and into the neighboring smooth muscle cells, where it binds and activates guanylyl cyclase to produce cyclic GMP. The cyclic GMP triggers a response that causes the smooth muscle cells to relax, enhancing the blood flow through the blood vessel. NO passes readily across membranes, and acts locally because it has a very short half life.

Hayflick limit

Limit cells can naturally divide. Related to senescence. Cells can only naturally divide so much, after which point they stop dividing and begin to reach a point closer to death. Related to telomerase?. Limit is reached depending on telomere length. Normal cells only divide a certain number of times in their lifetime before they reach senescence. Non immortal cells reach the "Hayflick limit" after a set number of divisions in culture. When the hayflick limit is reached depends upon the length of the cell's telomeres.

Myc

Map pathway leads to increase of gene regulatory proteins like Myc. Promote cell cycle entry by several mhanisms, including increased gene expression of G1 cyclins, increasing G1/S Cdk activity, increased phosphorylation of Rb through that. Increased E2F production. Entry into S phase due to. Overproduction can lead to Arf activation, form complex with Mdm2 inhibitor, stable p53. Myc activates p53 through Arf. So it activates Arf, which inactivates Mdm2 which relieves the inhibition on p53 allowing it to be active. Myc is a transcription factor

APC

Mediates metaphase to anaphase transition. Ubiquitin ligase family of enzymes. catalyzes ubiquitlyation an destruction of regulator proteins, involved primarily in exit from mitosis, including securin, whih proteins protein linkage holding gisster chromatid together, protease becomes active and separates sisters and inlees anaphase, it also ubiquitlates and destroys s and m cyclins Most Cdks are this inactivated and prtens phosphorylates by Cdks from S phase to early mitosis are dephosphorylated. That dephophorylation is required to complete M phase. Activated because of its association with an activating subunit, either Cdc20 metaphase to anaphase transition (m Cdk stimulated) or Cdh1 maintains APC activity after anaphase through G1, inhibited by Cdk activity. Activity is primarily m to G1. Active - targets M cyclin for degradation - proteasomes cut up. Anaphase promoting complex catalyzes the ubiquitylation and destruction of two major proteins. Targets M-cyclin for rapid degradation by adding ubiquitin groups --> ubiquitylation

survival factors

Need to keep cells from apoptosis, extracellular signal molecules that inhibit apoptosis. Continued signaling happened from other cells to avoid apoptosis, ensures cell survive, bind to cell surface receptors, activate signaling pathways suppress apoptosis, often through Bcl2, when deprived cells kill self y producing and activating proaptotic BH3 only proteins. Without survival signals can't properly import nutrients. promote cell survival by suppressing the form o programmed cell death known as apoptosis needed to keep cells from entering apoptosis.

E2F

Oncogene, Gene regulatory factors related to S phase entry transcribes G1/S clcins, S cyclins and proteins involved in DNA synthesis and chromosome duplication. absence of mitogen stimulation E2F dependent gene expression inhibited by interaction between E2F and Rb. Wen mitogens stimulate, Rb family phosphorylated, reduced E2F binding with, E2F then activate target genes. Positive feedback, increased G1/S and S Cdk activity increased Rb protein phospylation increased E2f. E2F is an important gene regulatory protein. When phosphorylated, Rb undergoes a shape change and lets go of E2F, which turns on transcription of many things including G1/S cyclins and cdks. - Positive feedback loops: E2F triggers its own transcription, Cdks phosphorylate Rb to keep it out of the way. Once you commit, you commit, hard to reverse

malignant

Only considered cancer if, the cells have ability to invade surrounding cells. Essential characteristic, allow to break loose, enter blood or lymph, form secondary tumors. Grows uicly, no capsule, invasive, may break off spread by circulation lymph, anplasitc

Role of P13 K in the cell survival

Pi3 K activate the AKT pathway which can involve Bad which will lead to inhibition of apoptosis. Receptor tyrosine kinase - Pi3K - PIP3 - AKT- Phosphorylates Bad, lets go of inhibitory apoptosis protein- survival. Integrins -> FAK -> P13kinase -> Akt which promotes activity of Mdm2 and inhibits p53 and inhibits Bad and Bax. P53 activates Puma , Puma Bad and Bax inhibit Bcl2 RTK also activates P13 kinase

apoptosis

Programmed cell death, most common, cells die, caused by gene expression, enzyme activation, undergo morphological changes, shrink, condense, cytoskeleton collapses, nuclear envelope disassembles, surface blebs, breaks up, neighboring cells engulf, dies in a clean way no inflammatory response. Cell death happens to unwanted cells, help sculpts in womb, sculpt hands and feet, cells die between digits, also quality control, example t cells overproduce kill non functioning receptors or self-reactive, can kill self due to damage, during apoptosis e donuclease cleave chromosomal DNA ino fragments,

how retroviruses can cause cancer

RNA tumor virus. When cell infected, RNA copied into cDNA by reverse transcription, DNA inserted into host genome where ican persist and be inherited by new generations. Can pic up oncogenes and mutate and be active. More cells - more viral success, wanted. Carries oncogene picked up by earlier cycle of mammalian infection. RNA viruses mutate really fast (1,000,000 times faster than even DNA viruses), so if they've picked up an oncogene from the host it's very likely that it will become activated by mutation, and if the virus infects a cell it will cause the cell to express this gene and rapidly proliferate.

Rb

Retinoblastoma protein. Tumor suppressor gene Binds to E2f and inhibits activity. Phosphorylated by G1/S and S cdk to cause release. Identified due to eye cancer in children retinoblastoma. Loss of both Rb gene copes leads to proliferation in retina, suggests Rb important for restraining division. If one mutation, more likely to get tumors. Inhibits in G0. Brake #1: The Rb protein binds up an important gene regulatory protein called E2F. When phosphorylated, Rb lets go of E2F, which turns on transcription of many things including G1/S cyclins. Rb is a tumor suppressor. Rb = retinoblastoma = cancer of the eye. Tumor suppressor gene found mutated in people who had tumors of the eye. Get tumors because they have inherited 1 mutant form that doesn't work and happened to wreck the other copy too. If only one good copy would still work.

CKIs (p21 and p27)

Tumor suppressor, Cdk inhibitor proteins regulate cyclin Cdk complexes. p27 in mammals suppresses G1/S cdk activies in G1, helps cells withdraw from cell cycles when terminally differentiate, phosphorylation by Cdk2 triggers it ubiquitlyation by SCF. P21 in mammals Suppresses G1.S Cad and S Cdk activates following DNA damage. p53can cause transcription APC Brake #2 = CKI's -Inhibitory proteins (CKIs) of the p21 and p27 families also regulate Cdk activity in G1 and S - Phosphorylation of CKIs can target them for ubiquitin-dependent proteolysis (degradation) - How to modulate activity: change transcription or regulate degradation p21: suppresses G1/S-Cdk and S-Cdk activities following DNA damage p27: suppresses G1/S-Cdk and S-Cdk activities in G1; helps cells withdraw from the cell cycle when they terminally differentiate; phosphorylation by Cdk2 triggers its ubiquitylation by SCF

initiator and executioner procaspases

When activated cleave and activate downstream execution procasesases, which cleave and activator other executioner procaspases as well as specific target proteins

tumor suppressor

a loss of function mutation can contribute to cancer, their action serves to suppress cancers. Genes involved in inhiiory contro of cell cycle. genes involved in inhibitory control of cell cycle (ex: p105Rb or p53)

cytokines

a signaling molecule that usually acts locally released from many types of cells (ex: immune cells) a signaling molecule that usually acts locally released from many types of cells. Ex. immune cell squirts it out at site of damage.

characteristics of cancer cells

abnormal growth, ability to invade, more self sufficient for growth and proliferation, relatively insensitive to anto proliferation extracellular signals, less prne to apoptosis, defective intracellular control mechanisms that stop cell division permanently in response to hypoxia or DNA damage, induce angiogenesis, genetically unstable, either produce telomerase or stabilize their telomeres other ways help from normal stromal cells induced reduced need for growth factors, morphological changes, transplantable, immortal, loss of anchorage dependent, loss of contact inhibition, progression, irreversibility of malignant phenotype . Characteristics of neoplastic cells 1.Reduced need or loss of requirement for growth factors (decreased density-dependent inhibition); less sensitive to growth inhibition by crowding (media depletion of growth factors and nutrients). 2. Morphologic changes can appear anywhere from well-differentiated to anaplastic high ratio of nucleus to cytoplasm (very "blue" when stained), characteristic of rapid growth (because dividing so fast doesn't have time to grow properly) 3. Transplantable may be grown in vitro or transplanted to genetically close host animal (difficult to do with most normal tissue) (combination of loss of need for social signals to grow and loss of ability for programmed cell death) 4. Immortal can be subcultured in vitro indefinitely; most normal cells have finite number of divisions before senescence (stop dividing) 5. Loss of anchorage-dependence for growth can grow/divide in semisolid (soft agar) or fluid medium (suspended); most normal cells need to be attached to a substrate to divide. 6. Loss of "contact inhibition" in culture, when cells form a monolayer, they don't stop growing (as do normal cells), but continue to grow and pile up on one another in disorganized fashion. 7 Exhibit "progression" each generation of cells becomes more "deviant". Acquiring a more malignant phenotype with cell division. Each division more mutations occur, more quality control lost. This is why we try to "catch cancers early". 8. Irreversibility of malignant phenotype when reached progression doesn't run backwards

activated oncogene

cancer promoting gene that is currently mutated so that it is cancerous, mutated, overexpressed or overactive forms of oncogenes. When oncogenes mutations are uncontrollable tor abnormally proliferating.

Apaf-1 and cytochrome C

cytochrome c released from between inner and outer membrane during apoptosis. Cytochrome C released into cytosol when in intrinsic pathway of apoptosis due to stress, damage, etc, binds to Apaf1 adaptor protein, oligomerizes into wheel shape apoptosome, recruits procaspase 9, activate by prodcimity to apoptosome cleaved and activated, activate downstream executioner to induce apoptosis.

Cdc25

dephosphorylates amino acid sites on kinase active site on cyclin Cdk complex that increases Cdk activity, activated M Cdk, can possible be activated by m Cdk resulting in positive feedback. Cdc25 mutation always active, larger cells size can't move out of G2. When it is active, it is a kinase. One of the thing it phosphorylates is Cdc25, you promote the activation of more M-Cdk. Positive feedback loop. Negative feedback loop, inhibits the Cdk inhibitory kinase Wee 1, stops putting on inhibitory phosphate. Dephosphorylation of phosphate at Cdc25 increases Cdk activity. Mutant Cdc25, can't remove inhibitory phosphate, so stuck in G2 Phosphatase that removes the inhibitory phosphate put on by Wee 1 kinase, so allows m cdk to become activated. Can't become activated during S phase because keeps M cdk from becoming activated and the cell entering m phase before ready. Entering M before DNA is fully replicated will cause DNA damage and harm to the cell, probably death. Positive feedback, inhibitory phosphate that have already been put on are going to be taken off, causing more activation. tyr-kinase CAK (cdk activating kinase) Positive feedback from activating M-cdk to cdc25 and negative feedback to Cdk inhibitory kinase.

extrinsic pathway of apoptosis

extrinsic pathway triggered by extracellular signal proteins binding to cell surface death receptors, transmembrane proteins containing extracellular ligand binding, transmembrane, and intracellular death domain. elond to tumor necrosis factor receptor family. Ex: Fas. Fas ligand on killer lyphosite activates Fas on surface, death domain recruit adaptor proteins, recruit initiator procaspases 8 or 10, formd death inducing signaling comples DISC. One in DISC activate cleave caspases and activate downstream executioner depends on release into cytosol of mitochondrial proteins usually in intermembrane space. The extrinsic pathway of apoptosis via Fas death receptors T cells have Fas ligands. Through juxtacrine signaling interact with Fas receptor on target cell and activates it. Assembly of adaptor proteins and procaspase 8 or 10 is formed, activates executioner caspases which causes apoptosis. Most cells have FAS receptor, Killer T cells check for any deformities in this receptor. Cells that are infected or have some sort of weird cell thing (cancerous cells) undergo extrinsic.

oncogene

genes in cell cycle control pthways, mutations alter expression lead to uncontrolled or abnormal proliferaction. cancer promoting genes, mutations in them contribute to cancer developing. Oncogene = genes involved in cell cycle control pathways, whose mutation or altered expression leads to uncontrolled or abnormal proliferation (when this happens they are now called activated oncogenes)

steroid hormone receptor signaling

hydrophobic signal molecules bind to intracellular receptors and are gene regulatory. Include cortisol, sex hormones, vitamin d. Most synthesized from cholesterol. Relatively insoluble in water, but bind to carrier proteins in order to be soluble for transport, dissociate before entering target cell. There is primary or rapid expression response om which primary proteins are produced by gene transcription and activate other genes and turn on the delayed secondary response. Receptor itself changes transcription. There is a ligand binding domain and transcription activating domain (DNA) when ligand binds shape changes, can be inhibited so no longer active due to shape change Glutacocor receptor activated by cortisol receptor in cytoplasm - ligand - shape change - dissociates from hsp90 can enter nucleus These steroid bind to their respective intracellular receptor proteins and alter the ability of these proteins to control the transcription of specific genes. So the proteins are both intracellular receptors and intracellular effectors for the signal. Steroids (Ligands): All have different chemical structure and function, they have similar mechanisms. Small hydrophobic signal molecules that diffuse directly across the plasma membrane of target cells and bind to intracellular receptors that are gene regulatory proteins. Sex Steroids: testosterone and estradiol, gender characteristics Vitamin D3: anticancer Cortisol: steroids, anti-inflammatory Thyroxine: very important for development (causes mutant frogs in water) Retinoic Acid: Basically Vitamin A, red fruits, carrots, retinoids, important for vision Metabolic Steroids Complex programs of development. These must be acting at the level of gene expression. Most of the steroid hormones derive the planar ring structure from cholesterol. Cholesterol is the building block from where steroids are derived. Cortisol: produced in the cortex of the adrenal glands and influences metabolism of many cell types. Sex steroid hormones: made in in testes and ovaries, responsible for secondary sex characteristics that distinguish males from females. Vitamin D: Synthesized in skin in response to sunlight. After conversion to active form in liver/kidneys, it regulates Ca2+ metabolism Retinoids: retinoic acid made from Vitamin A have important roles as local mediators in vertebrate development. Although all of these signal molecules are relatively insoluble in water, they are made soluble for transport in the bloodstream and other extracellular fluids by binding to specific carrier proteins, from which they dissociate before entering a target cell. Group of steroid hormone receptors (primary structure). All have in common a DNA binding domain, because they themselves are transcriptionally regulatory machines. The steroid receptors are the cells regulatory proteins. The receptors are all structurally related, part of the nuclear receptor family. Response element binds to receptor, receptor forms complexes. They can turn on and off transcription. Multi domain structure. Must have a place where ligands bind, binding site. Mostly transcriptional activators, so they have a domain available to act like that. Also inhibitory proteins bound to receptor when they are empty. When ligand binds it undergoes shape change that releases inhibitory protein and undergoes activation. End results: require binding of ligand to ligand binding domain in order to be in active conformation. Usually unable to bind to DNA unless the ligand binds. First genes are turned on to produce primary response proteins First response turn on genes that are themselves transcription factors, that then go back into nucleus and turn on gene. Primary Response: ligand binding activates transcription, direct stimulation of a small number of specific genes occurs occurs within about 30 min Secondary Response: the protein products of these genes activate other genes to produce delayed secondary response. Negative Feedback turn themselves off. Some of the proteins produced in the primary response may act back to inhibit the transcription of primary response genes, thereby limiting the response. Activate other proteins that do more stuff, second wave Slower response than ion channels, don't need to change back again really quick for another response, more profound response. Profound, some cannot go back, or they have made something happen work has been done. Cannot undo or rapidly clean up and respond. Heat shock protein 90, complexed with receptor in such a way that is blocking the nuclear localization signal, so this is a receptor that is forced to sit in the cytosol until its ligand, a steroid hormone cortisol binds to it and undergoes a change, inhibitory protein released.

contact inhibition

inhibition of cell growth due to cell to cell contact. In culture when cancerous cells form a monolayer on the bottom of the dish, they don't stop growing (as do normal cells) but continue to grow and pile up on one another in a disorganized fashion

density dependent inhibition

inhibition of proliferation due to certain cell interactions, when cell population in a dish divide until there is a monolayer and cells are in contact with other cells on all sides. Cancerous cells become less sensitive to growth inhibition by crowding (media depletion of growth factors and nutrients)

FAK

integrin- FAK- PI3K- Akt - dm2 blocks -53/blocks BH123/ inhibits Bad. must be in contact to get these signals. Most cells need to be adherent. Integrins, making connections between extracellular molecules. Focal adhesion kinase. Activator of PI3-Kinase, which activates Akt which inhibits Bad which promotes cell survival Integrins activate FAK, FAK activates PI3K, activates AKt, activates Mdm2. Inhibits Bad and Bax, inhibits p53. , BCL2 What can we inactivate to promote cell survival? P53 RTK RAS/RAF....MapK......Myc...>G1/S transition. RTK can also interact with PI3K Myc can activate p19arf, which blocks Mdm2 So, to cross G1/S boundry (without apoptosis) Active csk/G1cyclin —> 1. Rb phosphorylated (inactive) Integrins and no DNA damage —> 2. p53 not active G.F.s/integrin signals —> 3. stimulate/maintain Bcl-2 signal

neoplasia

literally new growth, a word for cancer

MPF

m phase promoting factor. Only present in mitosis, comaes and goes quickly, identified proteins called cyclings cyclically appear an go away correlates with MPF acitivty, cyclin level bilds up in cells synthesized slowly compared to MPF both drop quickly at end of mitosis. stimulates entrance into mitosis.

benign

neoplastic cells that do not become invasive. Abnormal cell growth, new growth, but not invasive. Remove mass, cure. Grws slowly, encapsulated, lovalized, can be remoced, differentiated.

proteasome

olecules that have been marked with ubiquitn through ubiuiltation will be moved here to be degraded. Protein complexes within Eukaryotes whose main function is to degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds.

phosphatidyl serine and annexin

proteins that are usually on the inside of the membrane, when the cell is going to undergo apoptosis they move to the outside where they can bind to a site on macrophages which will engulf them. Early when apoptosis is triggered membrane proteins start to reconfigure and phosphatidyl serine appears on outside of the cell where it never was before. Macrophages have receptor annexin on their surface which binds to phosphatidyl serine, so phagocytic cells can recognize cells in trouble in this way and kill them. We can also use annexin as a tag in lab to understand if cells are going in cell death.

Bcl2

regulate intrinsic pathway of apoptosis y controlling cyctrome c released and other intermembrane mitochondrial proteins into ctosis, some pro some anto apoptotic enhanve or block relase. Anti aptotit Bcl2, pro aptotic BH123, BH3 only. when aptosis stimulus triggers popaptosis BH123 become activated and aggregate to form oligomers in outer membrane induce cytochrome C and other release. Bcl2 mainly located on cytosolic surface of outer mitochondrial membrane, ER and nuclear envelope. , bind to BH123 peorwins ex:Bak, prevent from oligomerizing, inhibit cytochrome C release. BH3 only proteins overriding anti apotisi Bcl2 proteins. BH123 on mitochondria, Bcl2 block their action, BH3 bind up Bcl2 and override their blocking of BH123. Bcl-2 = anti-apoptotic Bcl-2 protein

Checkpoints

regulatory transitions in cell cycle, three, one in G2 before entering Mitosis, one in M before anaphase, and one in G1 before entering S phase. Progression locked if these checkpoints detect programs in or out of the cell. The cell-cycle control system triggers cell-cycle progression at three major regulatory checkpoints. 1. G1: late G1, cell commits to cell-cycle entry and chromosome duplication 2. G2/M Checkpoint: Control system triggers early mitotic events that lead to chromosome alignment on the spindle in metaphase. 3. Metaphase-to-anaphase transition: where control system stimulates sister chromatid separation, leading to the completion of mitosis and cytokinesis. Control system blocks progression through each of these checkpoints if it detects problems inside our outside of the cell (until conditions are favorable) G1 = sensing environment (signals from other cells). If checkpoint not passed will stay in G1 *Most important checkpoint in normal cells, if pass you will go on UNLESS something bad happens (other checkpoints = quality control checkpoints). This is the checkpoint where you make the key choice, replicate or not. Ask environment for answer, if signals not there will stay in G1.

telomeres

repetitive DNA sequences and associated proteins at the ends of chromosomes. Becomes shorter with every cell division, eventually add to senescence when too short and chromosome ends exposed. Can be replicated by enzymes telomerase. -sequences at the end of linear DNA sequences; shorten over time - long and repetitive sequences, provide a protective "cushion" for your DNA so your actual genes don't get chopped off during replication (during replication the very end of the lagging strand can't get replicated because there needs to be somewhere to put the primers out in front, so a small chunk of the end gets lost east replication and the DNA becomes shorter.

metastasis

spread of cancer to another site of body, metastases form secondary tumors? establishment of colonies in distant organs. Cells make and release digestive enzymes that break through outer layers so they can migrate into surrounding tissues

growth factors

stimulate cell growth increase in mass, promote synthesis of proteins and other macromolecular by inhibiting degradation. strictly anything that stimulates increases in cell size, protein content.

SCF

ubiquitin ligase. Ubiquitylates certain CKI proteins in late G1 including some CKIs, helps control S Cdk activation and Dna replication. Relies on F-box proteins units that it associates that help it recognize protein targets. SCF activity is constant through cell cycle, phosphorylation of target protein usually required. -Myc promotes transcription of SCF, brake (p27) removed, easier to keep G1 cdks Phosphorylation of CKIs can target them for ubiquitin-dependent proteolysis (degradation) SCF ubiquitylates CKI proteins in late G1, helps control activation of of S-Cdks and DNA replication. SCF activity is constant during the cell cycle. Ubiquitylation of SCF controlled by the phosphorylation of target proteins, such as CKI. After CKI is phosphorylated it is recognized by a specific F-box subunit. This leads to the degradation of CKI in the proteasome.

Western Blotting

way to visualize samples, how many, how much, and how large of fragments. After treating sample, lysing and whatever else, the samples can be run on a gel which can then be transferred to a membrane and will then be died. By died what I mean is that, first a primary antibody will be put on. This primary antibody will bind to whatever protein or whatever you're trying to look at. Net a secondary antibody can be added which will bind to your primary antibody. After adding some other enzyme substrate solvent it should bind o the secondary and form an substrate with color that can then be measured for intensity. This method allows for the coloration products to precipitate out and onto the membrane, rather than remaining soluble.