Cadherins mediate homotypic adhesion between various epidermal cells. E-, P- and N-cadherin facilitate high affinity adhesion only if they are coupled to the cytoskelelon via cytoplasmic proteins termed catenins. Differential association of catenins with cadherins or cytoskeletal elements, can regulate cadherin function. Adhesion of Langerhans cells (LC) to keratinocytes in vitro is mediated by E-cadherin (E-cad). To begin to study the regulation of this event, we characterized E-cad-associated proteins in FSDC. FSDC were expanded from d!6 C57BL/6 fetal skin in GM-CSF- CSF-1-supplemented media. After 2 wks, leukocytes that expressed E-cad and resembled LC in terms of morphology, phenotype and function were obtained. Western blots of FSDC nonionic detergent lysates revealed E-cad as well as a-, β-, y-catenin and src-substrate pHO0"5. Immunoprecipitation showed that E-cad in FSDC is associated with a-, β-, Y-catenin and p!2()Cas Several cadherin-associated proteins are substrates for tyrosine kinases. Tyrosine phosphorylation of catenins correlates with decreased cadherin affinity. Blotting of E-cad immunoprecipitates of lysates from pervanadate-treated FSDC with anti-pTyr mAb revealed phosphoproteins that comigrated with a-,β-, v-catenin and E-cad. These results indicate that E-cad in FSDC and cadherins in epithelial cells associate with similar proteins, including catenins and other proteins implicated in intracellular signaling. Furthermore, E-cad-associated proteins in FSDC are substrates for tyrosine kinases. Changes in tyrosine kinase activity may regulate E-cad function in FSDC and, by implication, in LC as well.
|State||Published - Dec 1 1996|