c-Crk, a substrate of the insulin-like growth factor-1 receptor tyrosine kinase, functions as an early signal mediator in the adipocyte differentiation process

Citation
Sh. Jin et al., c-Crk, a substrate of the insulin-like growth factor-1 receptor tyrosine kinase, functions as an early signal mediator in the adipocyte differentiation process, J BIOL CHEM, 275(44), 2000, pp. 34344-34352
Citations number
52
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
0021-9258 → ACNP
Volume
275
Issue
44
Year of publication
2000
Pages
34344 - 34352
Database
ISI
SICI code
0021-9258(20001103)275:44<34344:CASOTI>2.0.ZU;2-L
Abstract
Differentiation of 3T3-L1 preadipocytes into adipocytes is induced by a com bination of inducers, including a glucocorticoid, an agent that elevates ce llular cAMP, and a ligand of the insulin-like growth factor-1 receptor. Pre vious studies have implicated protein-tyrosine phosphatase (PTPase) HA2, a homologue of PTPase 1B, in the signaling cascade initiated by the different iation inducers. Vanadate, a potent PTPase inhibitor, blocks adipocyte diff erentiation at an early stage in the program, but has no effect on the mito tic clonal expansion required for differentiation. Exposure of preadipocyte s to vanadate along with the inducing agents led to the accumulation of pp3 5, a phosphotyrosyl protein that is a substrate for PTPase HA2. pp35 was pu rified to homogeneity and shown by amino acid sequence and mass analyses of tryptic peptides to be c-Crk, a known cytoplasmic target of the insulin-li ke growth factor-1 receptor tyrosine kinase. Transfection of 3T3-L1 preadip ocytes with a c-Crk antisense RNA expression vector markedly reduced c-Crk levels and prevented differentiation into adipocytes. Studies with C3G, a p rotein that binds to the SH3 domain in c-Crk, showed that phosphorylation o f c-Crk rendered the SH3 domain inaccessible to C3G. Taken together, these findings indicate that locking c-Crk in the phosphorylated state with vanad ate prevents its participation in the signaling system that initiates adipo cyte differentiation.