rotein tyrosine kinase signaling Serge ROCHE CRBM CNRS/Montpellier University serge.roche@crbm.cnrs.fr
rotein phosphorylation on Tyr A central mechanism to control cell communication in a multicellular organism writer reader erasor
History 1911 1960 2001 Transforming virus RSV v-src is an oncogene v-src is a protein TyrK Imatinib, the first TK inhibitor in the clinic
Tyrosine kinome 90 TKs RTK U SH3 SH2 ctk Therapeutic target
Receptors TK
RTK activation Growth factor Inactive Active ptyr Recruitment of SH2-containing proteins
SH2-containing proteins Enzymes X SH2 SH2 SH3 Y SH3 SH2 KINASE Adaptors SH3 SH2 SH3 Grb2 TB SH2 Shc LC Src
SH2 domains 100 AA with >20% homology Specificity for ptyr binding C-terminal sequence involved in binding specificity ptyrx n (n<6) SH2-containing molecules include signalling proteins and transcription factors
SH2-pTyr binding specificity SrcSH2 Binding specific to ptyr Affinity is increased by the pyxxxxx sequence ptyr
Exemple of an SH2-dependent signaling Grb2 Ras SOS Grb2 SOS No signal SOS: GEF for Ras Ras signal
RTK-Ras-MAK signaling SOS Ras Raf Grb2 MEK MAK Jun Fos transcription growth RTK GTase S/T Kinase T/Y Kinase S/T Kinase Transcription
Summary Ligand induces RTK dimerization Dimerized RTK transphosphorylates in the kinase domain RTK phosphorylates on additionaltyr that create binding site for SH2-containing signaling proteins Signalling is regulated by enzymes and adaptors
Receptor signaling by cytoplasmic TKs Receptors devoid of TK recruits ctks to promote ptyrdependent signaling RTK cytokine R T and BCR Integrins Hormone R Lck, Fyn Jak Syk Src Fak Src yk2 ctk
The cytoplasmic TK Src Src the first oncogene and TK identified 8 members Central signaling proteins Redundant functions among Src members Display oncogenic activity when deregulated c-src Y 416 linker U SH3 SH2 KINASE Y 527
Src regulation by TKs and Ts CSK RT TK T
Src regulation by protein interaction SH3/SH2 interactor Activation by protein interaction
Integrin-SRC signaling
TK signaling RTK GTase S/T Kinase T/Y Kinase S/T Kinase Transcription R/cTK GTase S/T Kinase T/Y Kinase S/T Kinase Transcription
Summary Receptor without intrinsic TK activity recruits ctk for signaling Receptor/cTK complexes behave as RTK for signaling ctk play crucial roles in cell signaling induced by a large number of extracellular stimuli
Neoplastic transformation
The hallmark of cancer Hanahan & Weinberg Cell (2000) 100;57-70
TK signaling in cancer TKs are frequently deregulated in human cancer and display oncogenic properties TK
TK deregulation TK gene amplification HER2 in breast cancer TK mutation gain-of-function EGFR in lung cancer TK fusion protein BCR-ABL in CML leukemia
Bcr-Abl in CML Chromosomic rearrangement generates Bcr-Abl fusion TyrK in 90% of Chronic Myeloid Leukemia CML Bcr-Abl SH3 SH2 Kinase Bcr-Abl SH3 SH2 Kinase active SH3 SH2 Kinase Coil-coil Coil-coil Bcr SH3 SH2 Kinase Abl
Bcr-Abl signalling Raf Ras SOS Grb2 MEK Y 177 SH3 SH2 Kinase SH3 SH2 Kinase MAK A1 Gene expression tumor growth
Strategies to target TK TK domain Small lobe interface Big lobe
Imatinib is a specific inhibitor of ABL DGFR KIT ABL Imatinib Human kinome
Imatinib is a specific inhibitor of ABL Abl Hck Imatinib binding pocket AT binding site
Anti-tumoral activity of Imatinib in CML Imatinib is highly active at early phases of leukemia
Resistance to Imatinib..But, relapse is observed in CML at late phases Increase in BCR-ABL copy number participates in Imatinib resistance FISH Red: Abl gene Green: Bcr gene yellow: Bcr-Abl gene
Resistance to Imatinib Induction of mutations that lowers the affinity to Imatinib
Development of new TKIs for CML > >
Summary Targeted therapies based on TK inhibition. Resistance occurs due to mutations and/or increase in kinase level that both reduce drug efficiency Alternatives include more potent inhibitors and/or combined therapy that erodes leukemic stem cells
The oncogenic role of TK in invasive tumors DDR1 DDR1