Receptor Protein Tyrosine Phosphatase-Receptor Tyrosine Kinase Substrate Screen Identifies EphA2 as a Target for LAR in Cell Migration

Abstract

Receptor tyrosine kinases (RTKs) exist in equilibrium between tyrosyl-phosphorylated and dephosphorylated states. Despite a detailed understanding of how RTKs become tyrosyl phosphorylated, much less is known about RTK tyrosyl dephosphorylation. Receptor protein tyrosine phosphatases (RPTPs) can play essential roles in the dephosphorylation of RTKs. However, a complete understanding of the involvement of the RPTP subfamily in RTK tyrosyl dephosphorylation has not been established. In this study, we have employed a small interfering RNA (siRNA) screen to identify RPTPs in the human genome that serve as RTK phosphatases. We observed that each RPTP induced a unique fingerprint of tyrosyl phosphorylation among 42 RTKs. We identified EphA2 as a novel LAR substrate. LAR dephosphorylated EphA2 at phosphotyrosyl 930, uncoupling Nck1 from EphA2 and thereby attenuating EphA2-mediated cell migration. These results demonstrate that each RPTP exerts a unique regulatory fingerprint of RTK tyrosyl dephosphorylation and suggest a complex signaling interplay between RTKs and RPTPs. Furthermore, we observed that LAR modulates cell migration through EphA2 site-specific dephosphorylation.

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SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01708-12.

ACKNOWLEDGMENTS

We thank David Stern, Ruey-Hwa Chen, and Paola Chiarugi for reagents and cell lines and Kyunghee Kim for assistance with data analysis. We are grateful to Murim Choi and Lisa Mijung Chung for bioinformatics assistance and Baehoon Kim for assistance with microscopic analyses.

A.M.B. was supported by NIH grant R01 GM099801, and H.L. was supported by a Leslie H. Warner Postdoctoral Fellowship.