Phosphorylation-dependent binding of 14-3-3 terminates signalling by the Gab2 docking protein.
Grb2-associated binder (Gab)2 functions downstream of a variety of receptor and cytoplasmic tyrosine kinases as a docking platform for specific signal transducers and performs important functions in both normal physiology and oncogenesis. Gab2 signalling is promoted by its association with specific receptors through the adaptor Grb2. However, the molecular mechanisms that attenuate Gab2 signals have remained unclear. We now demonstrate that growth factor-induced phosphorylation of Gab2 on two residues, S210 and T391, leads to recruitment of 14-3-3 proteins. Together, these events mediate negative-feedback regulation, as Gab2(S210A/T391A) exhibits sustained receptor association and signalling and promotes cell proliferation and transformation. Importantly, introduction of constitutive 14-3-3-binding sites into Gab2 renders it refractory to receptor activation, demonstrating that site-selective binding of 14-3-3 proteins is sufficient to terminate Gab2 signalling. Furthermore, this is associated with reduced binding of Grb2. This leads to a model where signal attenuation occurs because 14-3-3 promotes dissociation of Gab2 from Grb2, and thereby uncouples Gab2 from the receptor complex. This represents a novel regulatory mechanism with implications for diverse tyrosine kinase signalling systems.
Brummer
Tilman
T
Cancer Research Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.
Larance
Mark
M
Herrera Abreu
Maria Teresa
MT
Lyons
Ruth J
RJ
Timpson
Paul
P
Emmerich
Christoph H
CH
Fleuren
Emmy D G
ED
Lehrbach
Gillian M
GM
Schramek
Daniel
D
Guilhaus
Michael
M
James
David E
DE
Daly
Roger J
RJ
D048948:14-3-3 Proteins / Q000737:chemistry / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D025461:Feedback, Physiological; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
D048948:14-3-3 Proteins; D048868:Adaptor Proteins, Signal Transducing; C098587:GAB1 protein, human; C490895:GAB2 protein, human; D046912:Multiprotein Complexes; D011994:Recombinant Proteins