Abstract
We have isolated a novel isoform of phospholipase A(2). This enzyme was designated srPLA(2) because it was discovered while analyzing the proteins interacting with different forms of the v-Src oncoproteins isolated from Rous sarcoma virus-transformed hamster cells. It contains all the functional regions of the PLA(2) group IIA proteins but differs at its C-terminal end where there is an additional stretch of 8 amino acids. The SrPLA(2) isoform was detected as a 17-kDa precursor in cells and as a mature 14-kDa form secreted in culture medium. A direct interaction of the 17-kDa precursor with the Src protein was observed in lysates of transformed cells. Both the 17- and 14-kDa forms were found to be phosphorylated on tyrosine. To our knowledge, this is the first report of a PLA(2) group II protein that is tyrosine phosphorylated. We surmise that srPLA(2) interacts with the Src protein at the cell membrane during the process of its maturation.
Highlights
Previous work in our laboratories has focused on several transformed hamster cell lines named HET-SR, HET-SR-1, and HET-SR-8
Cells transformed with retroviral vectors carrying srcHM and srcLM display differences in morphology and in vivo metastatic activities, and we showed that structural changes in the C-terminal region of the v-Src proteins account for these differences in the metastatic properties of the corresponding transformed cells [5]
The ability of this clone to interact with two different regions of Src proteins, v-SrcHMN (v-Src without the HMC region), v-SrcHMC and v-SrcLMC was assessed by a two-hybrid test
Summary
Previous work in our laboratories has focused on several transformed hamster cell lines named HET-SR, HET-SR-1, and HET-SR-8. Cells transformed with retroviral vectors carrying srcHM and srcLM display differences in morphology and in vivo metastatic activities, and we showed that structural changes in the C-terminal region of the v-Src proteins account for these differences in the metastatic properties of the corresponding transformed cells [5]. To assess the molecular mechanisms underlying the v-srcHMdependent high metastatic activity (or lack of such an activity) in v-srcLM-transformed cells, we tried to identify the products of cellular genes associated with the unique C-terminal regions of both v-Src variants, using a two-hybrid approach and a cDNA library made from low metastatic parental hamster fibroblasts. Several proteins interacting with v-Src via its Cterminal fragments were identified that were not characterized previously as v-Src protein partners
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