Growth factor signaling, receptors and non-receptor tyrosine kinases

Question 1

True or False

___ The general structure of receptor tyrosine kinases is monomers, and when a signal comes in it will remain as a monomer.

___ Growth factors receptors can dimerize constitutively in absence of a ligand.

___ Binding to ligands stabilizes dimer and leads to allosteric changes in receptor structure needed for receptor activation and signaling.

___ Tyrosine kinases receptors have a single-pass transmembrane domain, large extracellular domain, tyrosine-kinase domain is intracellular, and ligand-induced is the main source of activation.

Answer 1

False, receptor tyrosine kinase is a monomer but when the signal binds it will dimerize the structure.

False, It can but it occurs at a very low frequency.

True

True

Question 2

Mutations in enzyme coupled receptors that lead to overexpression or overactivity are associated with and appear to be the primary basis of _______________.

Types of mutations in enzymes-coupled receptors:

In TM domains that caused receptors to dimerizes in the absence of ligand, and convert receptors from being ligand-induced dimers to constitutive dimer

In/near the catalytic domain that converts receptors from having ligand-induced enzyme activity to constitutive enzyme activity

Ovexpression of the receptor

Answer 2

numerous cancer

Question 3

Receptor Tyrosine Kinase (RTK) __________________ enhances RTK catalytic acitivty via conformational chnages in active site, autophosphohation and active other proteins.

Answer 3

Transautophosphorylation

Question 4

Fill in the blanks for Transautophosphorylation

Inactive RTKs, which are monomers, get activated (and become a dimer) by a signal protein causing _________________________.

Phosphorylation on tyrosine residues outside of the active site generates ___________________________.

_____________________ relay siganl downstream

Answer 4

Activating phosphorylation site within the active site

binding sites for other proteins

Activated signaling proteins

Question 5

Fill in the blanks

RTK Transautiphosylation creates binding sites for a variety of ___________containing proteins

Related but distinct ___________ on different proteins confer specificity for binding to different P-Tyr residues on RTKs

Answer 5

SH2 domains

Question 6

Fill in the blanks

_____________ Interactions Mediating SH2: P-Tyr Binding

SH2 performs ____________ between having high enough binding affinity for neighboring amino acid sequences to ensure specificity and having binding dependent on the phosphorylation state of the tyrosine

Answer 6

Non-covalent

balancing acts

Question 7

Why does the SH2 domain have two separate sites?

Answer 7

One binding site for neighboring amino acid side chains

and the other is for phosphotyrosine

Question 8

Drosophila Eye Development Pathway

Fill in the blanks

________ binds to the Sev RTK

_____________(Drk) will bind to _____________(Sos) which will activate a _____________ a form of GPCR.

Cause downstream signals which lead to expression in the R7 cell

Answer 8

Boss

adaptor protein

Ras-GEF

Ras protein

Question 9

True or False

Parallele RTK-Based Signaling Pathways Regulating Fly Eye Development and Human Cell Proliferation

Answer 9

True

Question 10

The ______________ is similar to heterotrimeric G protein alpha subunits:

Activated by GDP to GTP exchange triggered by upstream GEF

Undergoes local conformational change in guanine nucleotide-binding site depending on whether GDP or GTP is bound

Local changes at the guanine nucleotide-binding sites are allosterically coupled to changes in the switch region

Self-contained GTPase activity

Localized on the cytoplasmic face of the plasma membrane by covalent lipid modification

Activated by receptor-based signaling pathways

Answer 10

Ras family of monomeric G proteins

Question 11

True or False

Most frequent Ras GOF mutations in cancer

Common Mutations to change Gly12 to any amino acid converts proto-oncogene Ras to oncogenic Ras due to 90% inhibition of GTPase

Due to lack of activation of GTPase activity by GAPs (broken brake)

Can also get Ras GOF mutation in which GTP for GDP exchange occurs in absence of GEF

Answer 11

True

Question 12

True or False

LOF mutations in Ras-GAPs

Neurofibromatosis gene NF1 encodes a tumor suppressor RAS-GAP, eliminating GAP will eliminate GTPase activity

Answer 12

True

Question 13

True or False

__ Heterotrimeric G proteins alpha subunits have a critical Arg in the GTPase domain supplied by the switch I region.

__The critical Arg is also in Ras and does not need a trans by Arg787 from GAP (a protein)

__ Ras signaling has a set of protein kinases that carry out the phosphorylation reaction that changes the cell phenotype

Answer 13

True

False, Ras is lacking this residue. Ras need GAP protein for the GTPase activity

True

Question 14

What domains do the 8 non-receptor tyrosine kinases have?

Answer 14

SH1 –> Tyrosine kinase catalytic domain

SH2 –> as seen in the RTK

SH3 –> Bind Proline-rich sequences

Question 15

Where is Src located and how are they there?

Can these Src associate with receptors that have no function?

Can they be activated through diverse signaling pathways? Which one is the major one?

Answer 15

They are anchor to the inner face of plasma membranes which are covalently attached

Yes

yes, a major one being through protein tyrosine phosphtase

Question 16

True or False

__ 90-95% of Src in cells is maintained in a state of phosphorylated at Y527. Maintained in inhibited/restrained state: SH2 and SH3 domains participate in an inhibitory intramolecular interaction

__The latch is formed between SH3 domain binding to P-tyr527

__The clamp is formed by the SH2 domain binding to the backside of the kinase domain

___The switch is when Tyr-416 interferes with the active site when unphosphorylated.

Answer 16

True

False, the latch is formed between SH2 binding to P-tyr527

False, the clamp is formed by the SH3 domain

True

Question 17

_________- Dephosphorylation of P-tyr527 by a protein tyrosine phosphatase leads to loss of intramolecular P-Tyr:SH2 interaction

Primary mechanism

Answer 17

Unlatching

Question 18

True or False

Unclamping Could also occur via competition for SH3 domain binding by another protein, changes intramolecular interaction to intermolecular

Switching: intramolecular autophosphorylation of Tyr416, change in a structure near active site leading to enhanced catalytic activity. Similar to what occurs with trans autophosphorylation in RTKs Tyr416 could also be phosphorylated in an intermolecular manner by another TK

Answer 18

True

Question 19

V-Src: Mutant present in Rous sarcoma virus is missing _______, cant form the latch, tyrosine will always be unwound which would lead to unregulatory activation of Src

Answer 19

Tyrosine residue