There is a growing body of evidence to implicate reversible tyrosine phosphorylation as an important mechanism in the control of the adhesive function of cadherins. We previously demonstrated that the receptor protein tyrosine phosphatase PTPμ associates with the cadherin–catenin complex in various tissues and cells and, therefore, may be a component of such a regulatory mechanism (Brady-Kalnay, S.M., D.L. Rimm, and N.K. Tonks. 1995. J. Cell Biol. 130:977– 986). In this study, we present further characterization of this interaction using a variety of systems. We observed that PTPμ interacted with N-cadherin, E-cadherin, and cadherin-4 (also called R-cadherin) in extracts of rat lung. We observed a direct interaction between PTPμ and E-cadherin after coexpression in Sf9 cells. In WC5 cells, which express a temperature-sensitive mutant form of v-Src, the complex between PTPμ and E-cadherin was dynamic, and conditions that resulted in tyrosine phosphorylation of E-cadherin were associated with dissociation of PTPμ from the complex. Furthermore, we have demonstrated that the COOH-terminal 38 residues of the cytoplasmic segment of E-cadherin was required for association with PTPμ in WC5 cells. Zondag et al. (Zondag, G., W. Moolenaar, and M. Gebbink. 1996. J. Cell Biol. 134: 1513–1517) have asserted that the association we observed between PTPμ and the cadherin–catenin complex in immunoprecipitates of the phosphatase arises from nonspecific cross-reactivity between BK2, our antibody to PTPμ, and cadherins. In this study we have confirmed our initial observation and demonstrated the presence of cadherin in immunoprecipitates of PTPμ obtained with three antibodies that recognize distinct epitopes in the phosphatase. In addition, we have demonstrated directly that the anti-PTPμ antibody BK2 that we used initially did not cross-react with cadherin. Our data reinforce the observation of an interaction between PTPμ and E-cadherin in vitro and in vivo, further emphasizing the potential importance of reversible tyrosine phosphorylation in regulating cadherin function.
Dynamic Interaction of PTPμ with Multiple Cadherins In Vivo
S. Brady-Kalnay is funded by a Junior Faculty Investigator Award from the Case Western Reserve University/University Hospitals Ireland Cancer Center from an ACS Institutional Research Grant (IRG 186), a Case Western Reserve University Research Initiation Grant, and a grant from the American Cancer Society, Ohio Division Inc., Cuyahoga Unit. N.K. Tonks is funded by a grant from the National Institutes of Health (GM55989).
Address all correspondence to N.K. Tonks, Cold Spring Harbor Laboratory, One Bungtown Road, Cold Spring Harbor, NY 11724-2208. Tel.: (516) 367-8846. Fax: (516) 367-6812. E-mail: [email protected]
Susann M. Brady-Kalnay, Tracy Mourton, Joseph P. Nixon, Gregory E. Pietz, Michael Kinch, Haiyan Chen, Robert Brackenbury, David L. Rimm, Robert L. Del Vecchio, Nicholas K. Tonks; Dynamic Interaction of PTPμ with Multiple Cadherins In Vivo . J Cell Biol 6 April 1998; 141 (1): 287–296. doi: https://doi.org/10.1083/jcb.141.1.287
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