The interaction of epsin and Eps15 with the clathrin adaptor AP-2 is inhibited by mitotic phosphorylation and enhanced by stimulation-dependent dephosphorylation in nerve terminals

Clathrin-mediated endocytosis was shown to be arrested in mitosis due to a block in the invagination of clathrin-coated pits. A Xenopus mitotic phosph oprotein, MP90, is very similar to an abundant mammalian nerve terminal pro tein, epsin, which binds the Eps15 homology (EH) domain of Eps15 and the al pha-adaptin subunit of the clathrin adaptor AP-2, We show here that both ra t epsin and Eps15 are mitotic phosphoproteins and that their mitotic phosph orylation inhibits binding to the appendage domain of alpha-adaptin. Both e psin and Eps15, like other cytosolic components of the synaptic vesicle end ocytic machinery, undergo constitutive phosphorylation and depolarization-d ependent dephosphorylation in nerve terminals. Furthermore, their binding t o AP-2 in brain extracts is enhanced by dephosphorylation, Epsin together w ith Eps15 was proposed to assist the clathrin coat in its dynamic rearrange ments during the invagination/fission reactions. Their mitotic phosphorylat ion may be one of the mechanisms by which the invagination of clathrin-coat ed pits is blocked in mitosis and their stimulation-dependent dephosphoryla tion at synapses may contribute to the compensatory burst of endocytosis af ter a secretory stimulus.