Chen H, Slepnev V I, Di Fiore P P, De Camilli P
Howard Hughes Medical Institute and Department of Cell Biology, Yale University School of Medicine, New Haven Connecticut 06510, USA.
J Biol Chem. 1999 Feb 5;274(6):3257-60. doi: 10.1074/jbc.274.6.3257.
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.
网格蛋白介导的内吞作用在有丝分裂中被证明会因网格蛋白包被小窝内陷受阻而停滞。非洲爪蟾有丝分裂磷蛋白MP90与一种丰富的哺乳动物神经末梢蛋白epsin非常相似，epsin可结合Eps15的Eps15同源（EH）结构域和网格蛋白衔接蛋白AP-2的α-衔接蛋白亚基。我们在此表明，大鼠epsin和Eps15都是有丝分裂磷蛋白，并且它们的有丝分裂磷酸化会抑制与α-衔接蛋白附属结构域的结合。与突触小泡内吞机制的其他胞质成分一样，epsin和Eps15在神经末梢都会经历组成性磷酸化和去极化依赖性去磷酸化。此外，它们在脑提取物中与AP-2的结合会因去磷酸化而增强。有人提出epsin与Eps15共同协助网格蛋白包被在内陷/分裂反应期间进行动态重排。它们的有丝分裂磷酸化可能是有丝分裂中网格蛋白包被小窝内陷受阻的机制之一，而它们在突触处的刺激依赖性去磷酸化可能有助于分泌刺激后内吞作用的补偿性爆发。
