Protein tyrosine phosphorylation and dephosphorylation is regulated by the action of protein tyrosine kinases (PTK) and phosphatases (PTP) respectively. The receptor type phosphatase, PTPmu, is located at the cell surface where it may function to regulate the phosphoryl status of members of the cadherin adhesion complex and thus cadherin function. We have investigated the association of PTPmu with E-cadherin and catenin molecules in human tumour cells and report that PTPmu; is associated with E-cadherin and alpha and beta-catenin in E-cadherin-positive cell lines. However, no association between PTPmu and catenin members could be detected in E-cadherin negative cells. These observations suggest that the association of PTPmu with catenin molecules may occur via E-cadherin rather than a direct interaction.

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