The ubiquitous eps15 protein was initially described as a substrate of the EGF receptor kinase. Its functions are not yet delineated and this work provides evidence for its possible role in endocytosis. A novel anti-eps15 antibody, 6G4, coimmunoprecipitated proteins of molecular mass 102 kD. In human cells, these proteins were identified as the alpha- and beta-adaptins of the AP-2 complex on the basis of their NH2-terminal sequence and their immunoreactivity with anti-alpha- and anti-beta-adaptin antibodies but not with anti-gamma-adaptin antibody. In addition, the anti-eps15 antibody coimmunoprecipitated metabolically labeled polypeptides with molecular mass of 50 and 17 kD, comparable to those of the two other components of the AP-2 complex, mu2 and sigma 2. Constitutive association of eps15 with AP-2 was confirmed by two sets of experiments. First, eps15 was detected in immunoprecipitates of anti-alpha- and anti-beta-adaptin antibodies. Second, alpha- and beta- but not gamma-adaptins were precipitated by a glutathione-S-transferase eps15 fusion protein. The association of eps15 with AP-2 was ubiquitous and conserved between species, since it was observed in human lymphocytes and epithelial cells and in murine NIH3T3 fibroblasts. Our results are in keeping with a recent study showing homology between the NH2-terminal domains of eps15 and the product of the gene END3, involved in clathrin-mediated endocytosis of the pheromone alpha factor in Saccharomyces cerevisiae, and suggest a possible role for eps15 in clathrin-mediated endocytosis in mammals.
The tyrosine kinase substrate eps15 is constitutively associated with the plasma membrane adaptor AP-2.
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A Benmerah, J Gagnon, B Bègue, B Mégarbané, A Dautry-Varsat, N Cerf-Bensussan; The tyrosine kinase substrate eps15 is constitutively associated with the plasma membrane adaptor AP-2.. J Cell Biol 15 December 1995; 131 (6): 1831–1838. doi: https://doi.org/10.1083/jcb.131.6.1831
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