Identification of Protein Tyrosine Phosphatases Associating with the PDGF Receptor

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Abstract
Protein tyrosine phosphatase (PTP) in-gel assays were used to explore association of PTPs with the platelet-derived growth factor β-receptor (PDGFβR). Five PTP activity bands of ∼120, ∼70, ∼60, ∼53, and ∼45 kDa could be detected in PDGFβR immunoprecipitates and were identified by immunodepletion experiments as PTP-PEST, SHP-2, an active fragment of SHP-2, PTP-1B, and T-cell PTP, respectively. The PTP pattern that was obtained was similar in PDGFβR immunoprecipitates from HEK 293 cells overexpressing the human PDGFβR and from murine fibroblasts. Association of PTP-1B with the PDGFβR was stabilized by pretreatment of the cells with hydrogen peroxide. The epidermal growth factor receptor (EGFR) immunoprecipitated from fibroblasts, and c-Kit isolated from CHRF myeloid cells, were associated with partially overlapping but quantitatively different patterns of PTPs. PTP-PEST was the predominant PTP in EGFR immunoprecipitates, and SHP-1 appeared in c-Kit immunoprecipitates. We propose that the differential association of PTPs with different RTKs is related to their respective contributions to regulation of RTK signaling.