title: Lack of association between receptor protein tyrosine phosphatase RPTP mu and cadherins.
abstract: RPTP mu is a receptor-like protein tyrosine phosphatase that mediates homophilic cell-cell interactions. Surface expression of RPTP mu is restricted to cell-cell contacts and is upregulated with increasing cell density, suggesting a role for RPTP mu in contact-mediated signaling. It was recently reported (Brady-Kalnay, S.M., D.L. Rimm, and N.K. Tonks. 1995. J. Cell Biol. 130:977-986) that RPTP mu binds directly to cadherin/catenin complexes, and thus may regulate the tyrosine phosphorylation of such complexes. Here we report that this concept needs revision. Through reciprocal precipitations using a variety of antibodies against RPTP mu, cadherins, and catenins, we show that RPTP mu does not interact with cadherin/catenin complexes, even when assayed under very mild lysis conditions. We find that the anti-RPTP mu antiserum used by others precipitates cadherins in a nonspecific manner independent of RPTP mu. We conclude that, contrary to previous claims, RPTP mu does not interact with cadherin complexes and thus is unlikely to directly regulate cadherin/catenin function.
authors.affiliation: Division of Cellular Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors.forename: G C
authors.initials: GC
authors.lastname: Zondag
authors.forename: W H
authors.initials: WH
authors.lastname: Moolenaar
authors.forename: M F
authors.initials: MF
authors.lastname: Gebbink
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D019556:COS Cells / Q000737:chemistry / Q000201:enzymology; D015820:Cadherins / Q000032:analysis / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000378:metabolism; D004848:Epithelium / Q000737:chemistry / Q000201:enzymology; D015870:Gene Expression / Q000502:physiology; D008168:Lung / Q000166:cytology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008907:Mink; D011233:Precipitin Tests; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators; D051176:beta Catenin
chemical_list: D000911:Antibodies, Monoclonal; D015820:Cadherins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D015534:Trans-Activators; D051176:beta Catenin; D017027:Protein Tyrosine Phosphatases; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8