Mutational analysis of the interaction between the bovine papillomavirus E5 transforming protein and the endogenous beta receptor for platelet-derived growth factor in mouse C127 cells.

AUTOR(ES)

Nilson, L A

RESUMO

The bovine papillomavirus E5 protein is a 44-amino-acid membrane-associated protein that forms a stable complex with the endogenous platelet-derived growth factor (PDGF) beta receptor in rodent and bovine fibroblasts, resulting in sustained receptor activation and cell transformation. We report here that high-level expression of the E5 protein caused a reduction in the level of the mature form of the PDGF beta receptor in acutely and stably transformed mouse C127 cells. To explore in more detail the interaction of the E5 protein and the PDGF beta receptor, we tested the abilities of various E5 point mutants to bind the PDGF receptor, to induce PDGF receptor down-regulation and tyrosine phosphorylation, and to transform cells. A transformation-competent mutant, like the wild-type E5 protein, bound the receptor and induced receptor tyrosine phosphorylation and down-regulation. Transformation-defective E5 proteins either failed to interact with the endogenous PDGF beta receptor in mouse fibroblasts or underwent an aberrant interaction with the receptor. Mutation of glutamine at position 17, aspartic acid at position 33, or both carboxyl-terminal cysteine residues required for E5 homodimerization interfered with stable complex formation with the PDGF receptor, tyrosine phosphorylation and down-regulation of the receptor, and cell transformation. Point mutations at several other carboxyl-terminal positions generated transformation-defective E5 proteins that formed a complex with the PDGF receptor and induced receptor tyrosine phosphorylation but did not induce PDGF receptor down-regulation. Either PDGF receptor activation is not sufficient for transformation of C127 cells or the receptors that are tyrosine phosphorylated in response to these mutant E5 proteins are not fully activated and therefore are not able to deliver a mitogenic signal.

Documentos Relacionados

• Stable association between the bovine papillomavirus E5 transforming protein and activated platelet-derived growth factor receptor in transformed mouse cells.
• Specific interaction between the bovine papillomavirus E5 transforming protein and the beta receptor for platelet-derived growth factor in stably transformed and acutely transfected cells.
• Mutational analysis of the beta-type platelet-derived growth factor receptor defines the site of interaction with the bovine papillomavirus type 1 E5 transforming protein.
• The Bovine Papillomavirus E5 Protein Requires a Juxtamembrane Negative Charge for Activation of the Platelet-Derived Growth Factor β Receptor and Transformation of C127 Cells
• Activation of the platelet-derived growth factor receptor by the bovine papillomavirus E5 transforming protein.