CBNS101 Lecture 9: Enzyme-coupled receptors Flashcards

T/F Receptor tyrosine kinases (RTKs) are the most common class of enzyme-coupled receptors (60 RTKs in humans)

True. They are the most common class

T/F Enzyme coupled receptors usually have 20 transmembrane segments

False. Typically only 1 segment

Explain the process of RTK dimerization and autophosphorylation

When inactive they are far away from each other, but a signal to activate it, will bring the two "rods" closer together (dimerization). The close proximity makes them phosphorylate each other and then phosphorylate the rest of the spaces on the rods. That leads to docking "binding" points for them to start a signal cascade.

T/F RTKs are always symmetrical

False. One can solely be the activator and the other can solely be the receiver that phosphorylates both domains.

What domains do proteins use to dock to RTKs?

Src homology (SH2) domains or phosphotyrosine binding (PBT) domains

T/F Some docked proteins to RTK are only stimulatory

False. They can be inhibitory as well

*Ran is seen in ______, Rab is seen in ______, and Ras and Rho are seen in ________

Nuclear transport, vesicular traffic, and cell surface receptors.

T/F 30% of tumors have hyperactive mutant forms of Ras (Rat sarcoma)

True. Ras is a key oncogene. A gene that has the potential to cause cancer

Ras is a membrane bound ________ GTPase

a) heterotrimeric

b) monomeric

monomeric

How does Ras play a role in human cancers?

1/3 cancers are caused by Ras mutations. Meaning it loses the ability to hydrolyze GTP (always ON) so it leads to uncontrolled cell growth.

The mitogen-activated protein kinase pathway activates MAP _____ which phosphorylates MAP _____ which phosphorylates MAP _____ which phosphorylates _____. It is important for cell proliferation.

KKK, KK, K, target proteins

T/ F Humans have 12 MAPKs, 7 MAPKKs, and 7 MAPKKKs

True. All numbers are correct

How is unwanted cross activation of kinases avoided?

Scaffold proteins! So they can activate the assembled set before them and not get confused

*How does Rho GTPases transmit signals to the cytoskeleton?

Slide 14: During motor neuron axon growth/migration to the muscle target: Ephrin signals the incorrect cells to activate their Eph RTKs which activates RhoA. The RhoA regulates target proteins by reorganizing actin, collapsing the axon growth cone and repelling the axon growth in that direction