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PHA112 > Tyrosine Kinase Linked Receptors (Insulin) > Flashcards

Tyrosine Kinase Linked Receptors (Insulin) Flashcards

1
Q

state the transduction system and ligands for tyrosine kinase receptors?

A

ligand stimulated TK

insulin, EGF

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2
Q

state the transduction system and ligands for tyrosine kinase linked receptors?

A

associate with cytoplasmic TK

growth hormone

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3
Q

state the transduction system and ligands for guanylate cyclase receptors?

A

ligand stimulated guanylate cyclase

atrial natriuretic polypeptide

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4
Q

state the transduction system and ligands for serine/threonine kinase receptors?

A

ligand stimulated ser/threo kinase

transforming growth factor beta

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5
Q

state the transduction system and ligands for tyrosine phosphatase?

A

intrinsic tyrosine phosphatase

unknown

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6
Q

what is an essential feature of the activation of tyrosine kinase containing receptors?

A

binding of ligand results in dimerisation of receptors

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7
Q

what is PDGF and therefore what is EGF?

A

dimeric ligand

EGF = monomeric ligand

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8
Q

the dimerised, phosphorylated receptor initiates a series of signal transduction cascades through association with a number of proteins.

state these events?

A
  • altered gene expression via MAP kinase (MAPK)
  • activation of Ras
  • signalling via PI3 kinase (PI3K)
  • activation of PLC-gamma and PLA2
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9
Q

what is the best characterised signal transduction pathway?

A

MAP kinase

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10
Q

what are RTKs activated by?

A

growth factors, hormones

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11
Q

what does the activation of RTKs result in?

A

activation of adaptor protein Ras GTPase

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12
Q

what does Ras do?

A

induces signal cascade

starts with kinase - RAC
culminated in activation of MAP kinase (MAPK)

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13
Q

what does MAPK activation result in?

A

translocation into nucleus

phosphorylates diff proteins, inc TF that regulate gene expression

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14
Q

what is Ras?

A

GTP-binding protein similar to G-alpha subunit of G proteins

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15
Q

how does Ras become activated?

A
  • accelerated by guanine exchange factor (GEF)
  • binds to Ras.GDP complex (inactive) —> dissociation of bound GDP
  • GTP binds to Ras, releasing GEF (active form)
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16
Q

describe the signalling downstream of Ras?

A
  • Ras activated by exchange of GTP for GDP
  • active Ras binds and activates Raf
  • GTP hydrolysis —> dissociation of Ras from Raf
  • Raf activates MEK
  • MEK activates MAPK
  • dimeric form of active MAPK translocates to nucleus
  • activates TF
17
Q

EGF signalling

A
  • hormone binding —> dimerisation + phosphorylation of cytosolic receptor tyrosine residues
  • GRB2 and Sos couples receptor to inactive Ras
  • Sos promotes dissociation of GDP from Ras
  • GTP binds
  • active Ras dissociates from Sos
18
Q

why do we focus on EGF?

A

human carcinomas show high levels of receptors in EGF family

19
Q

what do Herceptin and iressa both do?

A

stop tyrosine kinase activity

20
Q

give examples of small molecule inhibitors that help in treatment in rebound cancer?

A
  • erlotinib
  • iressa
  • sorafenib
  • sunitinib
21
Q

what is insulin?

A

polypeptide hormone made from 2 chains, alpha and beta

22
Q

where is insulin produced?

A

pancreas in beta cells of islets of Langerhan

23
Q

after formation of 3 disulphide bonds, what do peptidases do?

A

cleave proinsulin to insulin

24
Q

insulin release mechanism-

A
  • mediated by GLUT2
  • glucose phosphorylated by glucokinase
  • then metabolised = ATP
  • ATP gated K+ channels in membrane close to prevent leak
  • depolarisation
  • voltage-gated ca2+ channels activated
  • inc in intracellular ca2+ —> exocytosis of insulin containing granules
25
Q

what are the substrates that insulin receptors phosphorylate?

A
  • IRS proteins 1-4
  • Shc
  • Gab 1
  • Cbl
  • APS
  • p60dok
26
Q

what do IRS-1 knockout mice exhibit?

A

growth retardation due to insulin resistance + IGF-1 + impaired glucose tolerance

27
Q

what do IRS-2 knockout mice exhibit?

A

severe insulin resistance in liver + peripheral tissues + develop type II diabetes

28
Q

what does PI3K play a vital role in?

A

metabolic + mitogenic actions of insulin

29
Q

what is PI3K?

A

heterodimeric enzyme consisting of p85 regulatory subunit + p110 catalytic subunit

30
Q

phospholipids recruit … and …. by binding to PH domain

A

PI3K dependent serine/threonine kinases

Akt

31
Q

what isoforms does Akt exist in?

A

alpha
beta1
beta2
gamma

32
Q

what does Akt regulate and phosphorylate?

A
  • glucose transporter (GLUT4) complex
  • protein kinase C (PKC) isoforms
  • GSK3 (glycogen synthase kinase 3)
33
Q

what does inhibition of PI3K block?

A

insulin-stimulated translocation of GLUT4 to cell surface + glucose uptake into cells

PHA112 (37 decks)

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