Intracellular Ca transients and enzyme linked receptors

Question 1

Regenerative Ca2+ induced Ca2+ release works how?

Answer 1

Ca2+ from ER/SR binds to Ca2+ channels causing an even greater increase in Ca2+.

Question 2

Ca2+ dependent inactivation works how?

Answer 2

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.

Question 3

What is the structure and function of Calmodulin.

Answer 3

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.

Question 4

CaMK:

Answer 4

Is a Serine/Threonine Kinase activated by Calmodulin’s inhibition of the Ca calmodulin kinases inhibitory domain..

Question 5

CaMK is a ____mer. How many subunits must be autophosphorylated for the enzyme to be temporally free of Cytosolic Ca2+ regulation?

Answer 5

12

2

The catalytic domain that is allowed to work by calmodulins inhibition of the regulatory domain is what autophosphorylates these two subunits.

Question 6

If Ca2+ transients are coming at a high enough frequency how does this effect CaMK?

Answer 6

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.

Question 7

What types of molecules can a kinase phosphorylate?

Answer 7

Proteins, lipids, carbohydrates, amino acids, or nucleotides. But kinases will generally be specific.

Question 8

What gives Kinases their specificity?

Answer 8

They only phosphorylate with a consensus sequence.

Question 9

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.

Answer 9

COOL! Inactivation of amino acids via replacement mutations can allow you to check if you are right.

Question 10

Humans have how many kinase genes?

Answer 10

~500

Question 11

Differentiate between:
Enzyme linked receptors
Receptor Tyrosine Kinases
Non-receptor Tyrosine kinases

Answer 11

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.

Question 12

Name the seven receptor tyrosine kinases:

Answer 12

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:

Question 13

What does epidermal growth factor involved in?

Answer 13

EGF activatse EGR which signals cell proliferation.

Question 14

Insulin receptor:

Answer 14

Stimulates uptake of glucose, carbohyrdate utilization and protein synthesis.

Question 15

What does insulin-like receptors do?

Answer 15

The stimulate cell growth. Dimerized RTK

Question 16

Nerve growth receptors:

Answer 16

Stimulate nerve growth. dimerized RTK

Question 17

Platelet-derive growth factors:

Answer 17

PDGF stimulates PDGR causing proliferation of various cell types, including probably, platelets.

Question 18

Macrophage-colony-stimulating factor

Answer 18

MCSF stimulates macrophage proliferation.

Question 19

Fibroblast growth factor:

Answer 19

Stimulates certain growth patterns inhibits others.

Question 20

Vascular endothelial growth factor: stimulates angiogenesis, aka blood vessel formation.

Answer 20

YEP.

Question 21

Ephrins stimulate angiogenesis and guide cell and axon migration during embryonic development.

Answer 21

ah huh.

Question 22

Dimerized ligands causes what?

Answer 22

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.

Question 23

What brings about trans-autophosphorylation?

What does it result in?

Answer 23

Ligand dimerization.

transautophosphorylation leads to modular protein domains created by phosphotyrosine residues.

Question 24

Epidermal growth factor and receiver activator activator system:

Answer 24

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.

Question 25

How does site-directed mutagenesis work?

Answer 25

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.

Question 26

RTKs do not have to be dimers to have multiple sites.

Answer 26

True.

Question 27

Modular protein domain.

Answer 27

Can be plugged into a protein without affecting altering their function.

Question 28

Name four modular protein domains.

Answer 28

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.

Question 29

Binding pocket:

Answer 29

Binds tyrosine, doesn’t mess up folding of protein!

Question 30

Vascular endothelial growth factor:

Answer 30

Is often overexpressed in tumor cells giving them unlimited access to blood.

Question 31

GRB-2 is a protein which binds to a phosphotyrosine residue on a RTK, what does it do?

Answer 31

It recruits RAS GEF, which activates RAS.

Question 32

RAS:
is activated by
is \_\_\_\_\_\_ monomeric G protein
stands for
associates with PM via
is structurally homologous to what subunit?

Answer 32

prototypical.
RAt Sarcoma.
Prenylated and palmitoyl groups
resembles Galpha subunit

Question 33

What do RAS Guanine-nucleotide dissociation inhibitors do?

Answer 33

Keep RAS inactive, stops RAS GEF.

Question 34

RAS GAP keeps RAS inactive how much of the time?

Answer 34

95% of the time!

Question 35

What does constitutively active RAS result in?

Answer 35

Tumor formation.