Lec 2 Cell Communication
What is a G protein-coupled receptor
a type of cell-surface receptor that works with the help of a G protein
What happens when platelets in the blood encounter damaged tissue
The platelets release PDGF which bind to a receptor kinase which is located on the surface of cells at the site of the wound
What are signaling cells
The source of the signaling molecule
What is the ligand binding site
The specific part of the receptor protein where the signaling molecule binds to
What is binding affinity
The strength of a receptor to bind to a ligand, which as time passes, the ligand is loose than releases
Why does it take a series of protein kinase to activate one after the other until it reaches the nucleus
By phosphorylating each consecutive protein kinase, the signaling molecule causes a larger response
What is the transmembrane domain of a cell surface receptor
The part of the receptor protein that's inside the membrane
What is the signal transduction pathway in cell signaling
A chain reaction of events after the receptor protein is activated by the signaling molecule
What is the signaling molecule
A molecule in which carries information from one cell to another by binding to a receptor protein or a responding cell
What is a receptor kinases
A type of cell-surface receptor which is also an enzyme that adds a phosphate group to another molecule
What is a growth factor
A type of signaling molecule that causes the responding cell to grow or divide
What is a Ras G protein
An intracellular signaling protein which activates (replaces GDP to GTP) when it binds to a receptor kinase.
What is the ligand
Another name for a signaling molecule
How can one signaling molecule have different effects on different types of cells
Because a cell's response to a signaling molecule depends on the different proteins inside the cell
What receptor protein does adrenaline bind to
G protein-coupled receptor
What are the 3 types of cell-surface receptors
G protein-coupled receptors, receptor kinases, ion channels
What type of signaling molecule exists in paracrine signaling
Growth factor
What is the cytoplasmic domain of the cell surface receptor
The part of the receptor protein that's located in the intracellular space
What is the location of a receptor proteins largely dependent on
If the signaling molecule its receiving is polar or nonpolar
What happens when the alpha subunit of a G protein binds to a GTP and separates from the other subunits
In most cases it becomes active and binds to a target protein in the cell
Where are the receptor proteins for nonpolar signaling molecules located
In the cytosol of the responding cell
What are voltage-gated ion channels
Ion channels that open due to the change in voltage in the plasma membrane
What are ligand-gated ion channels
Ion channels that open when they bind to a signaling molecule
What happens when G protein-coupled receptors bind to a G protein
It activates G protein because it allows it to release GTP which it binds to.
What does Ras G protein do once it's activates
It activates a protein kinase in a series of protein kinases referred to as MAP. This series of activating the next protein kinase stops with the final one which enters the nucleus and targets transcription factors
What does the cAMP do (In the case of adrenaline)
It activates protein kinase A (PKA) which phosphorylates proteins in the heart muscle, increasing heart rate
What is the structure of receptor kinases
It contains an extracellular portion which binds to the signaling molecule and an intracellular portion which is the kinase enzyme that transfers a phosphate group to another molecule
What is the α (alpha) subunit of a G protein
The part of the G protein that's initially bound to GDP but replaces with GTP when a ligand binds to the receptor. When bounded to GTP, the subunit separates from the other subunits
At what state is the G protein when it binds to GDP
It's off (inactive)
At what state is the G protein when it binds to GTP
It's on (active)
Where are the receptor proteins for polar signaling molecules (like growth factors) located
On the outside surface of the responding cell
What are the steps of cell signaling
Receptor activation, signal transduction, response, and termination
What happens with receptor kinases activates
Phosphate groups bind to it at multiple sites, which allows further bonding of intracellular signaling proteins
What are the 3 characteristics all G protein-coupled receptors have in common
Share similar structure: single polypeptide chain, ligand-binding site is on the cell surface, and part that binds to G protein is inside the cell All bind with a G protein after being activated The response caused by the receptors are fast and short
What is the second messenger
Signaling molecules inside the cell that carry information to the next target in the signal transduction pathway
What is endocrine signaling
Signaling molecules that travel through the bloodstream
What is autocrine signaling
Signaling molecules that travel to the receptor proteins of the same cell
What happens when adrenaline binds to the G protein-coupled receptor
The G protein replaces the GDP nucleotide with the GTP nucleotide, activating the G protein
What is phosphorylation
The addition of a phosphate group to a protein by a receptor kinases. This results in an active protein which can change shape to bind with other proteins
What happens when the alpha subunit of G protein binds to adenylyl cyclase
The adenylyl cyclase becomes activated and converts the ATP into cAMP which acts as a second messenger
What happens (in the case of adrenaline) when the alpha subunit of the G protein separates from the other subunits
The alpha subunit binds to adenylyl cyclase, located at the cell membrane
What is the extracellular domain of a cell-surface receptor
The part of the receptor protein that binds to the polar signaling molecule and is located in the extracellular space
What do signaling molecules rely on when they have to travel a long way to bond to a responding cell
The bloodstream (circulatory system)
What happens when adrenaline releases from the G protein-coupled receptor
The g protein-coupled receptor inactivates, the g protein inactivates by turning GTP into GDP, cAMP is degraded by enzymes preventing PKA to occur
What is the receptor protein
The molecule on the responding cell that connects to the incoming signaling molecule
What common proteins can receptor proteins be
They can be enzyme or channels
How diverse are G protein-coupled receptors
They're found in almost every eukaryotic organism and consist of a large family
What is the response step of cell signaling
Whatever the cell does as a result of receiving a signal (ex. activate enzymes, change shape)
What is dephosphorylation?
When a phosphate is removed from an active protein by a phosphatase enzyme, turning it into an inactive protein
What is receptor activation in cell signaling
When a receptor protein physically changes when a signal molecule binds to it
What is contact-dependent signaling
When a signaling cell directly makes contact with a responding cell. The signaling molecule travels between the membrane of the two cells and is not released into the extracellular space
What is the termination step of cell signaling
When the cellular response is stopped to prevent the cell from overreacting
What does it mean when receptor kinases dimerizes
When the two pair of protein kinases pair up, holding the signaling molecule in place, activating the receptor
What are the four basic elements involved in cellular communication
signaling cell, signaling molecule, receptor protein, and responding cell
What is paracrine signaling
signaling molecules that travel a short distance using diffusion (20 cells apart)
What is the responding cell
the cell that receives information from the signaling molecule
What are the three subunits some G proteins are composed of
α (alpha), β (beta), and γ (gamma)
