Michael Jeltsch

Tyrosine Tyrosine kinaseskinaseshttp://msbl.helsinki.fi/tkseminar

Producercell Target

cell

Receptor binding

Signaling molecules

Signal trans-duction

Activation ofGene expression

proliferation, differentiation, migration, metabolism, etc.proliferation, differentiation, migration, metabolism, etc.

RNA

Biological Biological responsesresponses

Cell surface Cell surface receptorsreceptors

ion-channel-linked

guanylylcyclases

tyrosinekinases

tyrosine kinaseassociated

tyrosinephosphatases

serin/threoninekinases

enzyme-linked G-protein-linked

extracellular

juxtamembranetransmembrane

tyrosine kinase

carboxy-terminal tail

a

ligand bindingNH2

COOH

ATP

substratebinding

Receptor Tyrosine Receptor Tyrosine KinasesKinases

Michael Jeltsch

VEGF xVEGF xVEGF-R1VEGF-R1

ssss

ss

ss

EGF-R IGF-1-R FGF-RPDGF-R VEGF-R3

RTK RTK subclassessubclasses

I II III IV

Modular structure of EC Modular structure of EC domainsdomains

RTK RTK ligandsligands

• Some RTKs need two ligands for activation

• Extracellular matrix components (HSPGs)

• Membrane-bound proteins (ephrins)

• Cytokines (EGF, FGF, CSF-1, insulin)

a

a

aa

PPPPPP

Signaling through an RTKSignaling through an RTK

aa

PPPPPP

a

a

a

a

a

a

a

a

a

Dimerization or oligomerizationDimerization or oligomerization

• Bivalent ligand(e.g. VEGF, PDGF)

• Ligand-induced conformational change(probably EGF)

• Intracomplex conformational change(e.g. insulin)

Transmembrane signal Transmembrane signal transfertransfer

• Exact mechanism unknown• Same or similar mechanism for all

RTKs (evidence from hybrid receptors)

AutophosphorylationAutophosphorylation

• Purposes:- Regulation of tyrosine kinase activity- Recruitment of signaling molecules

• Specific Tyr residues, usually outside thetyrosine kinase domain (juxtamembranedomain, cytoplasmic tail, kinase insert)

• SH2 (Src-homolgy 2)

• WW

• SH3 (Src-homolgy 3)• PH (pleckstrin homology)/FYVE

• PTB (phosphotyrosine binding)

Signaling proteins are modular moleculesSignaling proteins are modular molecules

SH2 PTB SH3 PH/FYVE PZB WW

• PDZ

SH2 (Src-homology 2)/SH2 (Src-homology 2)/PTB (phosphotyrosine binding)PTB (phosphotyrosine binding)

• Bind to PY (and sometimes Y)• Specificity is achieved through the context• SH2: 1-6 amino acids C-terminal to PY• PTB: 3-5 amino aids N-terminal to PY (or Y)

SH3 (Src-homology 3)SH3 (Src-homology 3)

• Binds to proline motif PXXP

WWWW

• Binds to proline motif PXPX

SH3 & SH3 & WWWW

PH (pleckstrin homology)/FYVEPH (pleckstrin homology)/FYVE• PH domain binds to phosphoinositides (membrane-

localization)• FYVE domain binds specifically PtdIns-3-P

PDZ (PSD-95, DDLP, ZP1)PDZ (PSD-95, DDLP, ZP1)• Bind to hydrophobic C-terminal strtches of target proteins

PH/FYVE/PDZPH/FYVE/PDZ

SH2PTB

P

P

PH/FYVE SH3 WW PDZ Enzymaticactivity

KinasesPhosphatasesPLC-Ras-GAPRho-GRF

Cellular Targets

membrane

Assembly of a specific signaling Assembly of a specific signaling complexcomplex

Myristyl. PTB

PH

TM P P P P P

P P P P P P

P P P

Membranelocalization

Receptorbinding Tyrosines

PP

P

FRS2

Dos

LAT

Indirect recruitment is the main recruitment methodfor some receptors (insulin receptor, FGF receptors)

Docking Docking proteinsproteins

Topics in activation of effector Topics in activation of effector proteinsproteins

1. Activation by Membrane Translocation

2. Activation by a Conformational Change

3. Activation by Tyrosine Phosphorylation

1. Membrane translocation

2.ConformationalChange 3. Tyrosine Phosphorylation

Activation of signaling molecules: PDGF Activation of signaling molecules: PDGF receptorreceptor

Intracellular Signaling Intracellular Signaling PathwaysPathways

Signal Signal TerminationTermination

• Ligand-induced oligomerization orconformational change

• Autophosphorylation/crossphosphorylation• Recruitment of signaling

molecules tophosphorylated tyrosines (“signalingcomplexes”)• Termination of Signaling (endocytosis)

3 Steps to 3 Steps to activationactivation

Intracellular vs. Transmembrane Receptor Tyrosine Intracellular vs. Transmembrane Receptor Tyrosine Kinases:Kinases:

Phylogenetic tree of tyrosine kinasesPhylogenetic tree of tyrosine kinases

Cytoplasmic Tyrosine Cytoplasmic Tyrosine KinasesKinases

Tyrosine kinase-derived Tyrosine kinase-derived oncogenesoncogenes

oncogene retrovirus cellular counterpart

v-src Rous sarcoma c-srcv-erbB avian erythroblastosis EGF receptorv-fms McDonough feline

sarcomaCSF-1 receptor

v-kit feline sarcoma SCF receptorv-abl Abelson murine

leukemiac-abl

v-sis simian sarcoma PDGF

ss

VEGF-R3

Dominant Negative Dominant Negative Receptors:Receptors:

VEGFR-3 mutations in hereditary lymphedema

S641P

P1114L

Further Further readingreading

Schlessinger, J. (2000): Cell Signaling by Receptor Tyrosine Kinases.Cell, Vol. 103, 211-225.