Sphingosine 1-phosphate stimulates tyrosine phosphorylation of Crk.
The proto-oncogene molecule c-Crk plays a role in growth factor-induced activation of Ras. Sphingosine 1-phosphate (SPP), a metabolite of cellular sphingolipids, has previously been shown to play a role in growth factor receptor signaling (Olivera, A., and Spiegel, S. (1993) Nature 365, 557-560). SPP was found to strongly induce tyrosine phosphorylation of Crk, but not Shc, in NIH-3T3 parental, insulin-like growth factor-I receptor-overexpressing and Crk-overexpressing (3T3-Crk) fibroblasts. Sphingosine, a metabolic precursor of SPP, also produced a slight increase in tyrosine phosphorylation of Crk. In contrast, other sphingolipid metabolites including ceramide did not alter Crk tyrosine phosphorylation. Furthermore, Crk enhanced SPP-induced mitogenesis, as measured by SPP-stimulated [3H]thymidine incorporation in a manner proportional to the level of Crk expression in 3T3-Crk cells. This stimulation appears to be Ras-dependent, whereas SPP stimulation of MAP kinase activity is Ras-independent. These data indicate that SPP activates a tyrosine kinase that phosphorylates Crk and that Crk is a positive effector of SPP-induced mitogenesis.
Blakesley
V A
VA
Diabetes Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA.
Beitner-Johnson
D
D
Van Brocklyn
J R
JR
Rani
S
S
Shen-Orr
Z
Z
Stannard
B S
BS
Spiegel
S
S
LeRoith
D
D
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D051380:GRB2 Adaptor Protein; D008246:Lysophospholipids; D051379:Mice; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050737:Proto-Oncogene Proteins c-crk; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism*; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D008246:Lysophospholipids; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; C060506:sphingosine 1-phosphate; D014443:Tyrosine; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013110:Sphingosine