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Unformatted text preview: Receptor Tyrosine Kinases Receptor binds peptide hormone/growth factor, and causes cell to grow, or differentiate.
See also table 15-4. Activation Activation of Receptor Tyrosine Kinases
Receptor Tyrosine Kinase Activation. Bind ligand. Dimerize Auto-phosphorylation on tyrosine Activate by trans- phosphorylation. Kinase activity required for function Shown by : Dead kinase mutant Dead kinase Dominant negative kinase What is target for Kinase? They do it to themselves! Recruitment into Complexes Activated RTK’s Assemble Large Multimolecular Complexes Protein Motifs Src Homology 2 (SH2) Protein Tyrosine Binding (PTB) Binds phosphorylated tyrosine Binds phosphorylated tyrosine SRC Homology 3 (SH3) Bind proline rich regions Pleckstrin Homology (PH) Domain Bind SH2 Src Homology 2 (SH-2) Domains Bind Phosphorylated Tyrosine (Y-P) SH2 Domains Recognize P-Y in Context of Target Peptide SH2 binds target only if tyrosine is phosphorylated Different SH2 domains bind to different target proteins.
MAP SH2 on Receptor P-Y Specific Effectors Bind Different Y-P PI-3K Ras GAP PLCγ
Methods to Map Proteins that Bind to Specific P-Y: Peptides with P-Y as inhibitors Tyrosine to phenylalanine mutations (Y to F) Purified SH2 Domain to select ligands from library of P-Y peptides
Pathway to Ras Pathway to Ras Adapter (Grb2) and GEF (SOS) Couple RTK to Ras
Grb2 has one SH2 (binds RTK) and two SH3 (bind SOS)
Ras Ras GTPase Cycle Ras GEF: Guanine Nucleotide Exchange Factor Ras GAP: GTPase Activating Protein Activated RTKs Control Control Ras GEF and Ras Ras GAP See also Fig. 3-71 Ras Structure Structure of Ras: Structure
Switch Regions Do Not Bind GDP, are displaced by SOS, and do contact GTP-gamma-phosphate.
Oncogenic Mutations Map to the GTP Binding Loop, Decrease GTPase, Maintain Ras in Active State. Active RAS-GTP in cells Ras-GTP Formation in Cells Ras-YFP GTP-red dye Form RAS-GTP FRET occurs Ras-GTP is transient GTP hydrolysis Ras-GAP MAP Kinases MAP Kinase Cascade: Three Protein Kinases
MAP KKK MAP KK MAP K RAF MEK ERK Inactive RAF is bound Inactive to 2 moles 14-3-3). Ras-GTP Displaces 14-3-3, and activates RAF. RAF. MEK is a S/T and Y MEK Kinase. Kinase.
MAP K Note: MAP K signals induce short term and long term (gene expression) responses. MAP Kinase Activation MEK phosphorylates substrates on ser/thr and tyr Activation lip in MAP K has T183 and Y185 Active form of MAP K leads to activation of transcription
Scaffolds caffolds Organize, Facilitate, and Specify Signaling Pathways; caffolds
ignaling Complexes Can Assemble Before or After Receptor Activation Fly Eye Pathway from Pathway Receptor Receptor Tyrosine Tyrosine Kinase to Ras in Fly Eye Overview of Pathways Overview of Signal Transduction Pathways Did we see this slide before?
Note examples of regulation by phosphorylation and by G proteins in signaling pathways. ...
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- Spring '08