Tyrosine phosphorylation of C-Cbl facilitates adhesion and spreading while suppressing anchorage-independent growth of V-Abl-transformed NIH3T3 fibroblasts.
The protooncogenic protein c-Cbl becomes tyrosine phosphorylated in normal cells in response to a variety of external stimuli, as well as in cells transformed by oncogenic protein tyrosine kinases. Tyrosine phosphorylation of c-Cbl upregulates its binding to multiple crucial signaling molecules. However, the biological consequences of c-Cbl-mediated signaling are insufficiently understood. To analyse the biological functions of c-Cbl, we overexpressed wild-type c-Cbl and its tyrosine phosphorylation-defective mutant form in v-Abl-transformed NIH3T3 fibroblasts. In this system, wild-type c-Cbl facilitated adhesion and spreading of v-Abl-transformed fibroblasts on the extracellular matrix, while reducing anchorage independence of these cells, as measured by their colony-forming efficiency in soft agar. Therefore, overexpression of wild-type c-Cbl exhibits an overall transformation-suppressing effect. By contrast, overexpression of a tyrosine phosphorylation-defective form of c-Cbl increases neither adhesion nor anchorage dependence of v-Abl-transformed fibroblasts. Analysis of the role of individual tyrosine phosphorylation sites of c-Cbl in these phenomena indicates that both phosphatidylinositol-3' kinase and the CrkL adaptor protein may be involved in the observed effects of c-Cbl. To summarize, the results presented in this report indicate that c-Cbl is involved in regulation of cell adhesion and cytoskeletal rearrangements, and that these effects of c-Cbl are dependent on its tyrosine phosphorylation.
Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
E A
EA
Feshchenko
S K
SK
Shore
A Y
AY
Tsygankov
D016475:3T3 Cells; D008841:Actin Cytoskeleton / Q000502:physiology / Q000648:ultrastructure; D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D018236:Carcinoma, Embryonal / Q000473:pathology; D002448:Cell Adhesion / Q000502:physiology*; D002455:Cell Division; D002461:Cell Line, Transformed; D048429:Cell Size; D002472:Cell Transformation, Viral; D003114:Colony-Forming Units Assay; D003599:Cytoskeleton / Q000502:physiology / Q000648:ultrastructure; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005109:Extracellular Matrix; D016313:Genes, abl; D007680:Kidney Neoplasms / Q000473:pathology; D051379:Mice; D009687:Nuclear Proteins / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000502:physiology*; D050721:Proto-Oncogene Proteins c-cbl; D015398:Signal Transduction / Q000502:physiology*; D014407:Tumor Cells, Cultured; D044767:Ubiquitin-Protein Ligases; D000077191:Wortmannin
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D000730:Androstadienes; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D000077191:Wortmannin; C082869:CRKL protein; C493849:Cbl protein, mouse