Cell Exam 3

You want to design a drug that can relax both skeletal and smooth muscles. Which of the following proteins could be a target?

Voltage gated Ca2+ channel, voltage gated Na+ channel, ca2+ pump

which of the following compounds can not be a potential anti-cancer drug? a compound that blocks association of Ras-GEF w/ RTK, a compound that inhibits Ras-GAP, a compound that inhibits Ras-GEF, a compund that inhibits MAPKKK

A compound that inhibits Ras-GAP

To design a drug that can inhibit insulin secretion, which protein should not be chosen as the target? tubulin, kinesin, dyenin, or clathrin

Dyenin

activated myosin-11 cause

MLCK phosphorylates myosin light-chains

MT, AF, IF subunit, size and shape

MT: 25 nm, alpha/beta tubulin-dimer AF: 8nm , actin monomer IF: 10 nm, IF proteins

MT, AF, IF assembly and polarity

MT: GTP-dependent assembly, polar AF: ATP- dependent assembly, polar IF: multilevel assembly

MT, AF, IF associating proteins

MT: kinesin, dynein AF: myosin 1 and 2, filamin, ARP complex, cadherin, integrin, Rho family, tropomyosin, troponin IF: cadherin and integrin

During a drug screen you find a compound that can block the binding of Ca2+ to troponin. Predict the effect of this drug. A. Muscle spasm B. Muscle paralysis C. Hypnosis D. No effect

Muscle Paralysis

classic pathway of cell signaling

extracellular signal molecule > receptor > intracellular signaling molecules > target proteins > cell response (fate or behavior)

T/F: To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol

false

t/f a receptor found by only one type of signal molecule can mediate only one kind of cell response

false

t/f about intermediate filaments, they are made of globular subunits

false

t/f activated g protein produces 3 separate subunits that function independently

false

t/f all cells will respond to the endocrine signals as endocrine molecules are broadcast throughout the body

false

t/f each type of receptor must induce an independent signaling pathway and avoid interference with other intracellular signaling pathways

false

gap junction

forms channels that allow small, intracellular, water-soluble molecules, including inorganic ions and metabolites, to pass from cell to cell

4 signal molecules

gas, steroid, derivative from aa, protein

endocrine signal

global- in bloodstream, hormone released in blood

GTP tubulin

growing MT

Growth factor signaling pathway

growth factor > RTK > PI3K > AKT > BAD/BCl2 ( cell survival) OR AKT > mTOR (cell growth)

Cell movement involves the coordination of many events in the cell. Which of the following phenomena is NOT required for cell motility?

influx of Ca2+ into the cytoplasm

the members of the steroid hormone receptor family

interact with signal molecules that diffuse through the plasma memrbane

motor proteins

intracellular transport

adherens junction

joins an actin bundle in one cell to a similar bundle in a neighboring cell

desmosome

joins the intermediate filaments in one cell to those in a neighbor

To design a drug that can inhibit LDL uptake, which protein should not be chosen as a target? tubulin, kinesin, dyenin, or clathrin

kinesin

paracrine signal

local- effect adjacent cells

general functions of cytoskeleton

mechanical support, maintain cells shape, interacts with specialized proteins called motor molecules

Which of the following would you expect to see in a cell that has been exposed to colchicine?

mis-organized endomembrane system

lamin related disease (intergrin)

misregulation of the genome causing progeria

Which of the following proteins can move cargos through an actin filament?

myosin

nuclear intermediate filaments

nuclear lamins in all animal cells

causes of depolarization

open ACh gated cation channel

cause of calcium flooding

open calcium release channel on SR

cause of calcium influx

open voltage gated calcium channel on t-tubule

causes of firing action potential

open voltage gated sodium channels

step 1 (prometaphase)

phosphorylation of lamin and nuclear pore proteins > disassembly

Ca2+ release, causes what to occur with t-tubules

plasma membrane extend inward, surrounding each myofibril, allowing action potential to spread inward of muscle fiber

what determines the directions of MT growth and cargo transport

polarity, + end: beta, - end: alpha

3 assembly models for intracellular signaling complex

preassembly on ascaffold, assembly on activated receptor, assembly on docking sites on membrane

RHO

promotes actin filament bundling and contraction

Rac

promotes actin polymerization

CDC42

promotes protrusion of filapodia

fast response to signal

protein regulation: fast, short term

molecular switch

rapid on and off, phosphorylation and gtp coupled

ACh receptor and action

receptor: GPCR action: excitatory neurotransmitter at many nerve muscle synapses and in cNS

adrenaline receptor and action

receptor: GPCR action: increases BP, Heart rate and metabolism

insulin receptor and action

receptor: IR (type of RTK) Action: stimulate glucose uptake, protein synthesis and lipid synthesis in various cell types

cortisol receptor and action

receptor: adrenal gland action: affects metabolism of proteins, carbon and lipids in most tissues

Wnt receptor and action

receptor: frizzled family action: cell proliferation

ethylene receptors and actions

receptor: on ER membrane action: gene TF on, fruit ripening

delta receptor and actions

receptor: prospective neurons, various other developing cell types action: inhibits neighboring cells from becoming specialized in same way as the signaling cells

growth factor receptors and actions

receptors: RTK action: control cell survival and growth

troponin

regulates the position of tropomyosin, ca2+ binding

synaptic signal

release neurotransmitter in neuron

tight junctions

seals neighboring cells together in an epithelial sheet to prevent leakage of molecules between them, helps polarize them

autocrine signal

self- target on same cell

GDP tubulin

shrinking MT

contact dependent signal

signal molecule not released, transmembrane protein

mechanical signals

signal transduction

3 mechanism models of intracellular signaling pathways

signaling complex, second messenger, molecular switch

second messenger

small size- large amount, rapid diffusion. cAMP, DAG, IP3, Ca2+

IF functions

strengthen (desmosome), lamin (chromatin organization/regulation)

AF functions

support, transport (myosin 1), cell migration (steps, key proteins, regulator: Rho-GTPase), muscle contraction, skeletal muscle fiber structure, Ca2+ signaling

nuclear lamina and nuclear skeleton/matrix

supports nuclear envelope and chromatin organization

which of the following happens when a G-protein coupled receptor activates a G protein?

the alpha subunit exchanges it bound GDP to GTP

5 types of cell junctions in epithelia

tight junctions, adherens junctions, desmosome, gap junction, hemidesmosome

function of intracellular signaling complex

to enhance the specify and efficiency of signaling, the best strategy is to localize signaling proteins in the same part of the cell

slow response to signal

transcriptional response: slow, long term

MT functions

transport (vesicles) and organization (er/golgi), mitosis, cilia/flagella (dyenin, ATP)

t/f about intermediate filaments, each filament is about 10 nm in diameter

true

t/f about intermediate filaments, they can be anchored to the plasma membrane at a cell-cell junction

true

t/f about intermediate filaments, they can be found in the cytoplasm and the nucleus

true

t/f each calmodulin can bind to 4 calcium ions

true

t/f extracellular signal molecules that are hydrophilic must bind to a cell surface receptor so as to signal a target cell

true

t/f most g-protein coupled receptors are multipass transmembrane proteins with 7-alpha helixes

true

t/f receptor tyrosine kinases (RTK) always form dimers after binding with signal molecules

true

To study the function of keratin, which of the following models can be chosen?

zebrafish and mouse

gene regulation by mechanicotransduction

~mechanical stress > cytoskeleton >lamin >chromatin >transcription OR ~mechanical stress> cytoskeleton > chemical signals > chromatin > transcription (>transcription)

step 3 ( interphase nucleus)

continued fusion of nuclear envelope vesicles

ca2+ activates

contraction

filamin

cross-links actin filaments into network

3 types of cytoplasmic intermediate filaments

1. Keratin 2. Vimentin 3. Neurofillaments

In an experiment, you treated cells with a drug that blocks ATP synthesis, which of the following processes will be arrested immediately? Microtubule assembly, exocytosis, actin filament assembly, or cell migration

exocytosis, actin filament assembly, cell migration

To design a drug that can inhibit cancer cell migration, which protein may not be chosen as the target?

Kinesin

Taxol

binds and stabilizes microtubules

Colchicine, colcemid

binds tubulin dimers, and prevents their polymerization

Tropomyosin

blocks binding of myosin head to actin filament

GTP-tubulin leads to assembly

1. gtp tubulin diners add to growing end of mt 2. addition proceeds faster than gtp hydrolysis by the dimers

GDP-tubulin leads to disassembly

1. protofilaments containing gdp tubulin peel away from the mt wall 2. gdp tubulin is released to the cytosol

how many steps to nuclear envelope break down and reassembly

3

ACh signaling pathway

ACh > GPCR > BV (beta gamma) subunit of g protein > PLC > IP3 > Ca2 Release > calmodulin

AP pathway for contraction in skeletal muscle

AP reach t-tub. > open vol. gated Ca2+ chan > open Ca2+ release channels on SR > Ca2+ flooding > influx of Ca2+ in cytosol ? muscle contraction

Researchers studying vesicular transport assembled several transport components in vitro (in a test tube). They set up the stabilized microtubules, then added vesicles and kinesin. When they put everything together, there was no movement of transport vesicles along microtubule. What were they missing?

ATP

signaling complex

bridging signaling proteins at a specific location, allowing them to be activated at higher speed, efficiency and specifity

acetylcholine controls the contraction of skeleton muscle and smooth muscle using different signaling pathways. Which mechanism is shared by these two pathways?

Ca2+ release from SR

smooth muscle contraction, ACh binds to

GPCR, ACh receptor

Insulin signaling pathway

IRS to PI3K activates PIP2 to PIP3 to PDK1 to AKT > glut 4 release

which of the following mutations would lead to an excess in the amount of glucose in skeletal muscle cells?

a PKA mutant form in which the inhibitory subunits lose the binding ability to the kinase subunits

which of the following compounds can be potential anti-cancer drug?

a compound that activates Ras-GAP

cause of release calcium into cytosol

activate PLC-IP3 signaling pathway

adrenaline signaling pathway

adrenaline > GPCR > G protein > cAMP > PKA > PhK > metabolism

Hemidesmosomes

anchors intermediate filaments in a cell to the basal lamina

defective keratin

causes high vulnerability of the skin against mechanical injury

high dynamic structure

cell division and movement

filamentous architecture

cell shaping and organization

phalloidin

binds and stabilizes filaments

which of the following is not one of the pathways activated by RTKs?

cAMP-PKA

cause of MLCK activation

calcium binds and activates calmodulin

colchicine treatment

causes dramatic collapsing of ER around nucleus and fragment of golgi

step 2 (telophase)

dephosphorylation of these proteins > re-assembly

in MT, atp hydrolysis provides energy to

drive conformational change

To study the function of lamin, which of the following models can be chosen?

drosophila, zebrafish and mouse (can be yeast too under certain circumstances)