TI  - Receptor protein tyrosine phosphatase   <prot>PTPmu</prot>   associates with  cadherins  and
       catenins  in vivo.
PG  - 977-86
AB  - The extracellular segment of the receptor-type type protein tyrosine
      phosphatase <prot>PTPmu</prot>, possesses an MAM domain, an immunoglobulin domain, and
      four fibronectin type-III repeats. It binds homophilically, i.e.,  <prot>PTPmu</prot>  on
      the surface of one cell binds to  <prot>PTPmu</prot>  on an apposing cell, and the
      binding site lies within the immunoglobulin domain. The intracellular
      segment of <prot>PTPmu</prot> has two PTP domains and a juxtamembrane segment that is
      homologous to the conserved intracellular domain of the cadherins. In
       cadherins , this segment interacts with proteins termed  catenins  to mediate
      association with the actin cytoskeleton. In this article, we demonstrate
      that  <prot>PTPmu</prot>  associates with a complex containing  <prot>cadherins ,  alpha</prot>- and
      <prot>beta-catenin</prot>  in mink lung (MvLu) cells, and in rat heart, lung, and brain
      tissues. Greater than 80% of the cadherin in the cell is cleared from
      Triton X-100 lysates of MvLu cells after immunoprecipitation with
      antibodies to <prot>PTPmu</prot>; however, the complex is dissociated when lysates are
      prepared in more stringent, SDS-containing RIPA buffer. In vitro binding
      studies demonstrated that the intracellular segment of  <prot>PTPmu</prot>  binds
      directly to the intracellular domain of  <prot>E-cadherin</prot> , but not to alpha- or
      <prot>beta-catenin</prot>. Consistent with their ability to interact in vivo,  <prot>PTPmu</prot> ,
       cadherins , andcatenins  all localized to points of cell-cell contact in
      MvLu cells, as assessed by immunocytochemical staining. After pervanadate
      treatment of MvLu cells, which inhibits cellular tyrosine phosphatase
      activity including <prot>PTPmu</prot>, the  cadherins  associated with  <prot>PTPmu</prot> are now
      found in a tyrosine-phosphorylated form, indicating that the  cadherins  may
      be an endogenous substrate for  <prot>PTPmu</prot> . These data suggest that <prot>PTPmu</prot> may be
      one of the enzymes that regulates the dynamic tyrosine phosphorylation,
      and thus function, of the  cadherin / catenin  complex in vivo.
AD  - Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724-2208,
