Chapter 15 Assignments

Flashcards about cell signaling pathways.

All GPCRs act by increasing cAMP?

False

What domain of son of sevenless (Sos) recruits it to the plasma membrane so that it gets in close proximity to Grb2?

PH

Mutations altering the GPCR binding interface in arrestin are likely to…

prevent desensitization of GPCRs.

For Notch to be recognized by Delta, it has to be transported to the…

plasma membrane

PI3 Kinase primarily phosphorylates…

phospholipids

Which of these enzymes is bound to the cytosolic side of the plasma membrane and converts PI(4,5)P2 to IP3 and diacylglycerol?

Phospholipase C-Beta

Why doesn’t the beta subunit of the trimeric G-protein need a lipid anchor like the alpha and gamma subunits?

it effectively uses the gamma’s anchor.

Select the mechanism of activation of AKT by PI-3K?

It phosphorylates lipids that create a docking site for AKT.

G-proteins are bound to GPCRs…

at the intracellular side of the plasma membrane.

Mutations in Ras are found in a majority of cancers. Which of these mutations will lead to permanent activation of Ras-signaling?

Mutations that inhibit Ras-GTPase activity

Which of these kinases is activated by binding to diacylglycerol that is released by breakdown of PI(4,5)P2?

Protein Kinase C

Which of these factors belong to a family of local mediators that were originally identified as the gene important for wing development in Drosophila?

Wnt

Which mechanism is NOT likely to sharpen the cellular response to a signal?

Activating enzymes for the forward and back reactions sharpens the response

Which of these statements about nuclear receptors are true?

They can activate or repress transcription based on the type of receptor.

PI 3-kinase…

is counteracted by PTEN phosphatase.

Which of these do not describe Notch?

Notch tail is released to activate translation.

Mutations that disrupt the protease activity of gamma-secretase will…

inhibit transcription of Notch target genes.

Mutations in the SH2 domains of the Grb2 adaptor that inhibit recognition of RTKs will lead to…

inhibition of GTP binding to Ras.

Activation of the EGF receptor includes which of these mechanisms?

Conformational change in the receiver.

In reference to AKT-dependent regulation of Bad, select the statement that is false?

In the absence of a survival signal, Bad is phosphorylated

AKT and ERK activate mTORC1 activity by directly phosphorylating and inhibiting which of these GAPs?

TSC

Upon activation of Ras, the final kinase activated in the MAP Kinase module is…

Erk

What of these statements about mTORC1 or mTORC2 are true?

mTORC1 is sensitive to rapamycin.

The GEF that activates Rag GTPase is…

Ragulator

Mutations that inhibit TSC activity leads to the disease- Tuberous Sclerosis that has benign tumors and giant cells and this is due…

high mTORC1 activity.

Enhancement of Gator1 GAP activity will lead to…

inhibition of mTORC1 activity.

In the absence of a Wnt signal…

Beta-catenin is degraded.

Degradation of Beta-Catenin by the proteasome is stimulated by…

phosphorylation of Beta-Catenin by GSK3 and CK1.

Which of these events are likely to occur if Beta-Catenin is unable to bind to LEF1/TCF in the presence of Wnt signal?

Groucho will remain bound to LEF1/TCF.

A receptor tyrosine kinase-A (RTK-A) is activated by binding to a growth factor (GF). Which type of mutation is likely to inhibit the dimerization of RTK.

a mutation that prevents RTK-A from binding to GF

α subunit of G-protein is bound to _, that is replaced with __ upon activation of GPCR.

GDP, GTP

Inactivation of the α subunit of a trimeric G protein in enhanced by ….…

GAP activity of RGS.

cAMP is synthesized from ATP by…

Adenylyl cyclase

Response to a signal reaches a maximum level before it shuts itself off followed by another pulse of maximal response even in the presence of the signaling molecule leading to an oscillatory response due to…

negative feedback with a long delay persisting positive feedback.

PKA is activated by binding of cAMP to the…

regulatory subunits

Which type of mutation in the regulatory subunits of PKA would lead to a permanently inactive state?

Mutation in the regulatory subunits that prevents the release of the catalytic subunits.

NO produced in endothelial cells diffuses across the membranes into smooth muscle cells to stimulate synthesis of cGMP by binding to…

Guanylyl cyclase

NOS catalyzed deamination of which of these amino acids produces NO?

Arginine

Cholera toxin activates the alpha subunit of Gs by ADP ribosylation, which…

inhibits the GTP hydrolysis activity of alpha subunit.

Increase in cAMP levels by extracellular signals can be balanced by breakdown of cAMP by enzyme…

cAMP phosphodiesterase

Activation of phospholipase C by G protein leads to…

cleavage of inositol phospholipids.

Exposure of target cells to prolonged signals can lead to desensitization of GPCR by…

binding of arrestin to phosphorylated GPCR.

IP3 produced by phospholipase C activation binds to IP3 receptors and leads to…

release of calcium from ER into cytosol.

A GAP…

enhances the GTP hydrolysis rate of monomeric GTPase

An extracellular signal that is in the vicinity of the cell that secretes it and thereby activates signaling in the surrounding cells is classified as:

paracrine signaling

Endocytosis of receptors followed by degradation in lysosomes in response to a signal is a mode of

receptor desensitization

Which of these domains bind to proline-rich sequences?

SH3 domain

Which of these is not a type of Receptor?

monomeric G proteins

Which of these responses to a signal are likely to occur in seconds?

Protein phosphorylation

Which of these statements is false?

Phosphatases catalytically remove the phosphate from GTP in GTP-binding proteins.

____ cells in select tissues release hormones that are distributed to the rest of the body.

Endocrine

Among which of these signaling mechanisms (other than endocrine signaling) do signaling molecules move farthest away from the cells that release them?

Paracrine

Which of these are secreted extracellular signaling molecules that work only in the neighborhood they are released in?

Local mediators

Electrical impulses sent along a neuronal axon reaches the synapse and triggers secretion of a chemical called…

Neurotransmitter

Charged phosphoinositides are recognized and bound by

Pleckstrin Homology domain

Scaffold proteins affect amplification and speed of signal by…

limiting amplification but improving speed.

Src Homology Domains (SH2) bind to which of these residues on activated receptors?

Phosphorylated Tyrosine

Activation of which of these proteins leads to the activation of a monomeric GTPase by releasing GDP and binding GTP.

Guanine nucleotide exchange factor (GEF)

Which of these enzymes phosphorylate a protein by transferring the terminal phosphate from ATP onto a serine, threonine or tyrosine residue?

Kinase

A signaling molecule can generate a strong signaling response that persists even after the signaling molecule is removed and this can be due to:

Positive feedback

Amplification of response to a signal can be generated when receptor activation leads to generation of a large number of intracellular signaling molecules/chemicals called…

second messengers.