Constitutive secretion from the trans-Golgi-network (TGN) is facilitated by a concerted regulation of vesicle biogenesis and fission processes. The protein kinase D family (PKD) has been previously described to enhance vesicle fission by modifying the lipid environment. PKD also phosphorylates the actin regulatory protein cortactin at S298 to impair synergistic actin polymerization. We here report additional functions for PKD2 (also known as PRKD2) and cortactin in the regulation of actin polymerization during the fission of transport carriers from the TGN. Phosphorylation of cortactin at S298 impairs the interaction between WIP (also known as WIPF1) and cortactin. WIP stabilizes the autoinhibited conformation of N-WASP (also known as WASL). This leads to an inhibition of synergistic Arp2/3-complex-dependent actin polymerization at the TGN. PKD2 activity at the TGN is controlled by active CDC42-GTP which directly activates N-WASP, inhibits PKD2 and shifts the balance to non-S298-phosphorylated cortactin, which can in turn sequester WIP from N-WASP. Consequently, synergistic actin polymerization at the TGN and constitutive secretion are enhanced.

中文翻译：

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肌动蛋白和PKD2在组成型分泌过程中对肌动蛋白聚合的协调调节。

反式高尔基体网络（TGN）的组成性分泌受到囊泡生物发生和裂变过程的协同调节的促进。先前已经描述了蛋白激酶D家族（PKD）通过修饰脂质环境来增强囊泡裂变。PKD还在S298处使肌动蛋白调节蛋白cortactin磷酸化，以损害协同性肌动蛋白聚合。我们在这里报告了PKD2（也称为PRKD2）和cortactin在转运蛋白从TGN分裂过程中在肌动蛋白聚合反应调控中的其他功能。S298上的cortactin磷酸化会削弱WIP（也称为WIPF1）和cortactin之间的相互作用。WIP可稳定N-WASP（也称为WASL）的自抑制构象。这导致在TGN处抑制协同的Arp2 / 3-复合物依赖性肌动蛋白聚合。TGN处的PKD2活性受活性CDC42-GTP的控制，该CDC42-GTP可直接激活N-WASP，抑制PKD2并将平衡转移至非S298磷酸化的视乳动蛋白，进而可以将WIP与N-WASP隔离。因此，在TGN处的协同肌动蛋白聚合和组成性分泌得到增强。