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J. Cell Biol.,
Volume 141, Number 1, April 6, 1998 287-296
* Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106-4960; 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.
Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47097; § Department of Cell Biology,
Neurobiology and Anatomy, University of Cincinnati, Cincinnati, Ohio 45267; Department of Pathology, Yale University, New
Haven, Connecticut 06510-8023; and ¶ Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724-2208
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