Tyrosine kinases. Cell surface receptors ligand binding. Producer cell RNA. Target cell

Transcription

1 Tyrosine kinases roducer cell Signaling molecules Receptor binding Signal transduction Target cell Activation of Gene expression RNA Biological responses proliferation, differentiation, migration, metabolism, etc. Michael Jeltsch Cell surface receptors ligand binding Receptor Tyrosine Kinases NH 2 ion-channel-linked enzyme-linked G-protein-linked extracellular guanylyl cyclases tyrosine kinases tyrosine kinase associated tyrosine phosphatases serin/threonine kinases transmembrane juxtamembrane tyrosine kinase carboxy-terminal tail AT substrate binding COOH

2 VEGF x VEGF-R1 RTK subclasses I II III IV ss ss ss ss Michael Jeltsch EGF-R IGF-1-R DGF-Rα VEGF-R3 FGF-R Modular structure of EC domains RTK ligands Cytokines (EGF, FGF, CSF-1, insulin) Membrane-bound proteins (ephrins) Extracellular matrix components (HSGs) Some RTKs need two ligands for activation

3 Signaling through an RTK Dimerization or oligomerization Bivalent ligand (e.g. VEGF, DGF) Ligand-induced conformational change (probably EGF) Intracomplex conformational change (e.g. insulin) Transmembrane signal transfer Exact mechanism unknown Same or similar mechanism for all RTKs (evidence from hybrid receptors) Autophosphorylation Specific Tyr residues, usually outside the tyrosine kinase domain (juxtamembrane domain, cytoplasmic tail, kinase insert) urposes: - Regulation of tyrosine kinase activity - Recruitment of signaling molecules

4 SH3 & WW H/FYVE/DZ Signaling proteins are modular molecules SH2 TB SH3 H/FYVE ZB WW SH2 (Src-homolgy 2) TB (phosphotyrosine binding) SH3 (Src-homolgy 3) H (pleckstrin homology)/fyve DZ WW SH2 (Src-homology 2)/ TB (phosphotyrosine binding) Bind to Y (and sometimes Y) Specificity is achieved through the context SH2: 1-6 amino acids C-terminal to Y TB: 3-5 amino aids N-terminal to Y (or Y) SH3 (Src-homology 3) Binds to proline motif XX WW Binds to proline motif XX H (pleckstrin homology)/fyve H domain binds to phosphoinositides (membranelocalization) FYVE domain binds specifically tdins-3- DZ (SD-95, DDL, Z1) Bind to hydrophobic C-terminal strtches of target proteins

5 Assembly of a specific signaling complex Docking proteins Indirect recruitment is the main recruitment method for some receptors (insulin receptor, FGF receptors) Membrane localization Receptor binding Tyrosines TB SH2 membrane H/FYVE SH3 WW DZ Cellular Targets Enzymatic activity Kinases hosphatases LC-γ Ras-GA Rho-GRF FRS2α,β Dos LAT Myristyl. TB H TM Topics in activation of effector proteins Activation of signaling molecules: DGF receptor 1. Membrane translocation 1. Activation by Membrane Translocation 2. Activation by a Conformational Change 3. Activation by Tyrosine hosphorylation 2. Conformational Change 3. Tyrosine hosphorylation

6 3 Steps to activation Intracellular Signaling athways Signal Termination Intracellular vs. Transmembrane Receptor Tyrosine Kinases: hylogenetic tree of tyrosine kinases Ligand-induced oligomerization or conformational change Autophosphorylation/crossphosphorylation Recruitment of signaling molecules to phosphorylated tyrosines ( signaling complexes ) Termination of Signaling (endocytosis)

7 Cytoplasmic Tyrosine Kinases Tyrosine kinase-derived oncogenes oncogene v-src v-erbb v-fms v-kit v-abl retrovirus Rous sarcoma avian erythroblastosis McDonough feline sarcoma feline sarcoma Abelson murine leukemia cellular counterpart c-src EGF receptor CSF-1 receptor SCF receptor c-abl v-sis simian sarcoma DGF Dominant Negative Receptors: VEGFR-3 mutations in hereditary lymphedema Further reading Schlessinger, J. (2000): Cell Signaling by Receptor Tyrosine Kinases. Cell, Vol. 103, S641 ss 1114L VEGF-R3