Department of Biomedicine, University of Bergen, Jonas Lies Vei 91, Bergen, Norway.
Traffic. 2010 May;11(5):637-50. doi: 10.1111/j.1600-0854.2010.01048.x.
Hormone- and neuropeptide-containing secretory granules (SGs) of neuroendocrine PC12 cells are formed at the trans- Golgi network as immature SGs. These intermediates are converted to mature SGs in a complex maturation process, including matrix condensation, processing of cargo proteins and removal of proteins and membrane in clathrin-coated vesicles. The resulting mature SGs undergo Ca2+-dependent exocytosis upon an appropriate stimulus. We here show that the motor protein myosin Va is implicated in a maturation step of SGs, their binding to F-actin and their stimulated exocytosis. Interference with myosin Va function blocked the removal of the transmembrane protein furin from maturing SGs without affecting condensation and processing of proteins of the SG lumen. Furthermore, the ATP-inhibited binding of SGs to F-actin decreased with progressive maturation and upon interference with myosin Va function. Moreover, the expression of a dominant-negative myosin Va-tail or shRNA-based downregulation of myosin Va interfered with stimulated exocytosis of SGs. In summary,our data suggest an essential function of myosin Va in the membrane remodeling of SGs during maturation and a role in their exocytosis.
神经内分泌 PC12 细胞的含激素和神经肽的分泌颗粒 (SGs) 在高尔基体内形成不成熟的 SGs。这些中间产物在一个复杂的成熟过程中转化为成熟的 SGs，包括基质凝聚、货物蛋白的加工以及网格蛋白包被小泡中蛋白质和膜的去除。成熟的 SGs 在适当的刺激下经历 Ca2+依赖性胞吐作用。我们在这里表明，肌球蛋白 Va 参与了 SGs 的成熟步骤，它们与 F-肌动蛋白的结合及其受刺激的胞吐作用。干扰肌球蛋白 Va 的功能会阻止跨膜蛋白 furin 从成熟的 SGs 中去除，而不会影响 SG 腔中蛋白质的凝聚和加工。此外，随着成熟的进行以及肌球蛋白 Va 功能的干扰，SGs 与 F-肌动蛋白的 ATP 抑制结合减少。此外，表达显性负性肌球蛋白 Va 尾巴或基于 shRNA 的肌球蛋白 Va 下调会干扰 SG 的受刺激的胞吐作用。总之，我们的数据表明肌球蛋白 Va 在 SG 成熟过程中的膜重塑中具有重要功能，并在其胞吐作用中发挥作用。
