Abstract
Clathrin-mediated endocytosis was shown to be arrested in mitosis due to a block in the invagination of clathrin-coated pits. A Xenopus mitotic phosphoprotein, MP90, is very similar to an abundant mammalian nerve terminal protein, epsin, which binds the Eps15 homology (EH) domain of Eps15 and the alpha-adaptin subunit of the clathrin adaptor AP-2. We show here that both rat epsin and Eps15 are mitotic phosphoproteins and that their mitotic phosphorylation inhibits binding to the appendage domain of alpha-adaptin. Both epsin and Eps15, like other cytosolic components of the synaptic vesicle endocytic machinery, undergo constitutive phosphorylation and depolarization-dependent dephosphorylation in nerve terminals. Furthermore, their binding to AP-2 in brain extracts is enhanced by dephosphorylation. Epsin together with Eps15 was proposed to assist the clathrin coat in its dynamic rearrangements during the invagination/fission reactions. Their mitotic phosphorylation may be one of the mechanisms by which the invagination of clathrin-coated pits is blocked in mitosis and their stimulation-dependent dephosphorylation at synapses may contribute to the compensatory burst of endocytosis after a secretory stimulus.
Highlights
Clathrin-mediated endocytosis was shown to be arrested in mitosis due to a block in the invagination of clathrin-coated pits
Epsin is highly homologous to the Xenopus mitotic phosphoprotein MP90, which was identified in a screen for substrates of mitotic kinases [21], and contains a single putative consensus site for Cdc2 kinase, which is conserved in mammalian epsin
We report here that both epsin and Eps15 are phosphorylated in mitosis and that their phosphorylation inhibits binding to the clathrin adaptor AP-2
Summary
Clathrin-mediated endocytosis was shown to be arrested in mitosis due to a block in the invagination of clathrin-coated pits. We show here that both rat epsin and Eps are mitotic phosphoproteins and that their mitotic phosphorylation inhibits binding to the appendage domain of ␣-adaptin Both epsin and Eps, like other cytosolic components of the synaptic vesicle endocytic machinery, undergo constitutive phosphorylation and depolarization-dependent dephosphorylation in nerve terminals. We report that both epsin and Eps, like other accessory proteins of clathrin-mediated endocytosis, undergo stimulation-dependent dephosphorylation in nerve terminals [22,23,24,25], with a resulting increase in their binding to each other and to AP-2 Their dephosphorylation may facilitate endocytosis of synaptic vesicle membranes following an exocytotic burst. Recent studies have implicated several cytosolic proteins besides clathrin and the clathrin adaptor AP-2 in clathrin-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
