Intracellular Ca transients and enzyme linked receptors Flashcards
Regenerative Ca2+ induced Ca2+ release works how?
Ca2+ from ER/SR binds to Ca2+ channels causing an even greater increase in Ca2+.
Ca2+ dependent inactivation works how?
High enough levels of Ca2+ will no longer activate Ca2+ channels but will instead inhibit them. Reversing regenerative Ca2+ induced Ca2+ release. Similar to what Na channels do in AP.
What is the structure and function of Calmodulin.
Is a Ca2+ binding protein. Once it has bound Ca2+ it will interact with a specific protein, either inhibiting it, or enabling its activity. Example: troponin C, Recoverin, Frequenin.
CaMK:
Is a Serine/Threonine Kinase activated by Calmodulin’s inhibition of the Ca calmodulin kinases inhibitory domain..
CaMK is a ____mer. How many subunits must be autophosphorylated for the enzyme to be temporally free of Cytosolic Ca2+ regulation?
12
2
The catalytic domain that is allowed to work by calmodulins inhibition of the regulatory domain is what autophosphorylates these two subunits.
If Ca2+ transients are coming at a high enough frequency how does this effect CaMK?
CaMK will not have time to return to baseline, and the effect will stack upon itself, you’ll end up activating more and more CaMKs each transient.
What types of molecules can a kinase phosphorylate?
Proteins, lipids, carbohydrates, amino acids, or nucleotides. But kinases will generally be specific.
What gives Kinases their specificity?
They only phosphorylate with a consensus sequence.
Consensus sequences are found by looking at a large number of proteins which are all phosphorylated by the same kinase. And finding the common sequence.
COOL! Inactivation of amino acids via replacement mutations can allow you to check if you are right.
Humans have how many kinase genes?
~500
Differentiate between:
Enzyme linked receptors
Receptor Tyrosine Kinases
Non-receptor Tyrosine kinases
Enzyme linked receptors: may or may not have a transmembrane ligand binding receptor domain
Receptor Tyrosine Kinases: Have a transmembrane ligand binding receptor domain
Non-receptor
Tyrosine kinases: do not have a transmembrane ligand binding receptor domain.
Name the seven receptor tyrosine kinases:
Epidermal Growth Receptor (EGF): Insulin Receptor: Nerve growth receptor: Platelet-derived growth factor receptor. Macrophage-colony-stimulating factor: Fibroblast growth receptor: Vascular endothelial growth receptor: Ephrins (EPH) receptor:
What does epidermal growth factor involved in?
EGF activatse EGR which signals cell proliferation.
Insulin receptor:
Stimulates uptake of glucose, carbohyrdate utilization and protein synthesis.
What does insulin-like receptors do?
The stimulate cell growth. Dimerized RTK
Nerve growth receptors:
Stimulate nerve growth. dimerized RTK
Platelet-derive growth factors:
PDGF stimulates PDGR causing proliferation of various cell types, including probably, platelets.
Macrophage-colony-stimulating factor
MCSF stimulates macrophage proliferation.
Fibroblast growth factor:
Stimulates certain growth patterns inhibits others.
Vascular endothelial growth factor: stimulates angiogenesis, aka blood vessel formation.
YEP.
Ephrins stimulate angiogenesis and guide cell and axon migration during embryonic development.
ah huh.
Dimerized ligands causes what?
It brings receptors into close proximity. These receptors can then phosphorylate each other. Causing docking sites for other proteins which each cause their own signaling pathways deeper into the cell.
What brings about trans-autophosphorylation?
What does it result in?
Ligand dimerization.
transautophosphorylation leads to modular protein domains created by phosphotyrosine residues.
Epidermal growth factor and receiver activator activator system:
EGF will bing to two different Receptors an activator and a receiver. The receiver will push against the activator, freeing its catalytic site and allowing it to phosphorylate them both.
How does site-directed mutagenesis work?
You mutate tyrosine residues in a specific location in the receptor. You then see whether there is still activity in the cell. This is how they know that dimerized RTKs will often have different proteins binding to each catalytic site, each of which, has its own signalling pathway.
RTKs do not have to be dimers to have multiple sites.
True.
Modular protein domain.
Can be plugged into a protein without affecting altering their function.
Name four modular protein domains.
src homology 2: binds tyrosine phosphate
phoshpotyrosine binding domain: binds tyrosine phosphate
src homology 3 domain: binds proline rich regions ‘polyprolines’.
Pleckstrin homology domain: binds binds PIP2, PIP3 and Gby subunits of heterotrimeric G proteins.
Binding pocket:
Binds tyrosine, doesn’t mess up folding of protein!
Vascular endothelial growth factor:
Is often overexpressed in tumor cells giving them unlimited access to blood.
GRB-2 is a protein which binds to a phosphotyrosine residue on a RTK, what does it do?
It recruits RAS GEF, which activates RAS.
RAS: is activated by is \_\_\_\_\_\_ monomeric G protein stands for associates with PM via is structurally homologous to what subunit?
prototypical.
RAt Sarcoma.
Prenylated and palmitoyl groups
resembles Galpha subunit
What do RAS Guanine-nucleotide dissociation inhibitors do?
Keep RAS inactive, stops RAS GEF.
RAS GAP keeps RAS inactive how much of the time?
95% of the time!
What does constitutively active RAS result in?
Tumor formation.
