Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10769969 | Biochemical and Biophysical Research Communications | 2005 | 6 Pages |
Abstract
Sap-1/PTPRH, a receptor protein tyrosine phosphatase (RPTP), is a ubiquitously expressed enzyme that is upregulated in human gastrointestinal cancers. Using both chemical cross-linkers and co-immunoprecipitation we show that overexpressed full-length Sap-1 is present as a stable homodimer. Unlike a number of adhesion RPTPs which have tandem catalytic domains that are involved in dimerization, Sap-1 has a single catalytic domain, and we show that this domain is not required for Sap-1 dimerization, which is mediated instead by the large extracellular and transmembrane domains. Exposing cells that express the receptor to a reducing environment reversibly disrupts the Sap-1 dimer, suggesting that cysteine bonds play a role in dimer formation/stabilization. The switch between Sap-1 dimers and monomers is accompanied by an increase in catalytic activity as judged by its capacity to dephosphorylate and activate c-src, which we identify as a novel substrate for this phosphatase.
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Authors
Sébastien Wälchli, Xavier Espanel, Rob Hooft van Huijsduijnen,