Co-regulation of Caveolar and Cdc42-dependent Fluid Phase Endocytosis by Phosphocaveolin-1
Co-regulation of Caveolar and Cdc42-dependent Fluid Phase Endocytosis by Phosphocaveolin-1
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DOI：
10.1074/jbc.m109.069427
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发表时间：
2010-05-14
影响因子：
4.8
通讯作者：
Pagano, Richard E.
中科院分区：
文献类型：
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作者：
Cheng, Zhi-Jie;Singh, Raman Deep;Pagano, Richard E.
已经确定了几种不依赖网格蛋白的内吞机制，这些机制可以通过对某些蛋白质的特定需求来区分，例如小窝蛋白-1 （Cav1）和Rho GTPases， RhoA和Cdc42，以及特定的货物。一些内吞途径可能被共同调节，这样一种途径的破坏导致另一种途径的上调；然而，其潜在机制尚不清楚。据报道，Cav1可以作为鸟嘌呤核苷酸解离抑制剂（GDI），抑制Cdc42的激活。我们验证了Cav1可以调节依赖cdc42的流体期内吞作用的假设。我们发现，过表达的Cav1会减少液相内吞作用，而沉默的Cav1则会增强这一途径。使用磷酸酶抑制剂增强Cav1磷酸化可减少cdc42调节的胞饮作用，同时刺激小泡内吞作用。一种推测的拟磷突变体Cav1-Y14E的表达抑制了液相内吞作用，而缺磷突变体Cav1-Y14F则不受其抑制。过表达Cav2，或GDI区改变为Cav2中相应序列的Cav1突变体，不抑制流体期内吞作用。这些结果表明，Cav1的表达水平和磷酸化状态通过Cav1 GDI区和Cdc42的相互作用来调节流体期内吞作用。这些数据定义了一种新的分子机制，用于共同调节两种不同的网格蛋白独立的内吞途径。
Several clathrin-independent endocytosis mechanisms have been identified that can be distinguished by specific requirements for certain proteins, such as caveolin-1 (Cav1) and the Rho GTPases, RhoA and Cdc42, as well as by specific cargo. Some endocytic pathways may be co-regulated such that disruption of one pathway leads to the up-regulation of another; however, the underlying mechanisms for this are unclear. Cav1 has been reported to function as a guanine nucleotide dissociation inhibitor (GDI), which inhibits Cdc42 activation. We tested the hypothesis that Cav1 can regulate Cdc42-dependent, fluid phase endocytosis. We demonstrate that Cav1 overexpression decreases fluid phase endocytosis, whereas silencing of Cav1 enhances this pathway. Enhancement of Cav1 phosphorylation using a phosphatase inhibitor reduces Cdc42-regulated pinocytosis while stimulating caveolar endocytosis. Fluid phase endocytosis was inhibited by expression of a putative phosphomimetic mutant, Cav1-Y14E, but not by the phospho-deficient mutant, Cav1-Y14F. Overexpression of Cav2, or a Cav1 mutant in which the GDI region was altered to the corresponding sequence in Cav2, did not suppress fluid phase endocytosis. These results suggest that the Cav1 expression level and phosphorylation state regulates fluid phase endocytosis via the interaction between the Cav1 GDI region and Cdc42. These data define a novel molecular mechanism for co-regulation of two distinct clathrin-independent endocytic pathways.