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Caveolin-1 and a 29-kDa caveolin-associated protein are phosphorylated on tyrosine in cells expressing a
C Corley Mastick1, A R Sanguinetti, J H Knesek
1Department of Biochemistry, University of Nevada, Reno, Nevada 89557, USA. cmastick@med.unr.edu
Abstract:
Caveolin-1 was originally identified as a tyrosine-phosphorylated protein in v-Src-transformed cells and it was suggested that phosphorylation of this protein could mediate transformation by the tyrosine kinase class of oncogenes (J. R. Glenney, 1989, J. Biol. Chem. 264, 20163--20166). We found that caveolin-1 is also phosphorylated on tyrosine in v-Abl-transformed cells. In fact, caveolin-1 and a caveolin-associated protein of 29 kDa are among the strongest phosphotyrosine signals detected in the Abl-expressing cells. In addition, v-Abl shows a preferential phosphorylation of caveolin-1 and the 29-kDa caveolin-associated protein over other proteins in the caveolin-enriched Triton-resistant cell fraction. These data indicate that caveolin-1 and the 29-kDa caveolin-associated protein may be preferred substrates of the Abl kinase. Caveolin-1 is phosphorylated at tyrosine 14 in v-Abl-expressing cells as has been observed previously in v-Src-expressing cells. However, using a temperature-sensitive allele of v-Abl (ts120 v-Abl) we provide evidence that caveolin-1 phosphorylation is not sufficient to mediate the loss of caveolin expression or loss of cell adhesion induced by v-Abl.
Insights
Caveolin-1 phosphorylation by v-Abl kinase is observed, but it does not solely cause cell changes. This finding impacts understanding of oncogene-driven cell transformation and tyrosine kinase substrates.
Area of Science:
- Cell Biology
- Molecular Oncology
- Biochemistry
Background:
- Caveolin-1, a protein involved in cell signaling, was initially linked to oncogenic transformation via tyrosine phosphorylation.
- Tyrosine kinases, such as v-Src, can phosphorylate caveolin-1, suggesting a role in cancer development.
Purpose of the Study:
- To investigate the interaction and phosphorylation of caveolin-1 by the v-Abl tyrosine kinase.
- To determine if caveolin-1 phosphorylation is sufficient to induce cellular changes associated with v-Abl transformation.
Main Methods:
- Analysis of phosphotyrosine signals in v-Abl-transformed cells.
- Biochemical assays to identify preferred kinase substrates.
- Use of a temperature-sensitive v-Abl allele (ts120 v-Abl) to study functional consequences.
Main Results:
- Caveolin-1 and a 29 kDa associated protein are highly phosphorylated on tyrosine in v-Abl-expressing cells.
- v-Abl kinase preferentially phosphorylates caveolin-1 and the 29 kDa protein.
- Phosphorylation of caveolin-1 at tyrosine 14 occurs but does not lead to loss of caveolin expression or cell adhesion.
Conclusions:
- Caveolin-1 and the 29 kDa protein are likely direct substrates of the Abl kinase.
- Caveolin-1 phosphorylation, while occurring in v-Abl-transformed cells, is not the sole mediator of v-Abl-induced cellular alterations like loss of adhesion.