Hicks Lawrence, Liu Guojun, Ukken Fiona P, Lu Sumin, Bollinger Kathryn E, O'Connor-Giles Kate, Gonsalvez Graydon B
Cellular Biology and Anatomy, Georgia Regents University, Augusta, GA 30912, USA.
Laboratory of Genetics, and Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Biol Open. 2015 Oct 12;4(11):1448-61. doi: 10.1242/bio.013755.
The mammalian Sorting Nexin 9 (Snx9) family consists of three paralogs: Snx9, Snx18 and Snx33. Most of the published literature to date has centered on the role of Snx9 in clathrin-mediated endocytosis (CME). Snx9 contains an Sh3 domain at its N-terminus and has been shown to interact with Dynamin and actin nucleation factors via this domain. In addition to the Sh3 domain, Snx9 also contains a C-terminal BAR domain. BAR domains are known to sense and/or induce membrane curvature. In addition to endocytosis, recent studies have implicated the Snx9 family in diverse processes such as autophagy, macropinocytosis, phagocytosis and mitosis. The Snx9 family is encoded by a single gene in Drosophila called sh3px1. In this report, we present our initial characterization of sh3px1. We found that depletion of Sh3px1 from Drosophila Schneider 2 (S2) cells resulted in defective lamellipodia formation. A similar phenotype has been reported upon depletion of Scar, the actin nucleation factor implicated in forming lamellipodia. In addition, we demonstrate that over-expression of Sh3px1 in S2 cells results in the formation of tubules as well as long protrusions. Formation of these structures required the C-terminal BAR domain as well as the adjacent Phox homology (PX) domain of Sh3px1. Furthermore, efficient protrusion formation by Sh3px1 required the actin nucleation factor Wasp. Tubules and protrusions were also generated upon over-expressing the mammalian orthologs Snx18 and Snx33 in S2 cells. By contrast, over-expressing Snx9 mostly induced long tubules.
哺乳动物分选连接蛋白9（Snx9）家族由三个旁系同源物组成：Snx9、Snx18和Snx33。迄今为止，大多数已发表的文献都集中在Snx9在网格蛋白介导的内吞作用（CME）中的作用。Snx9在其N端含有一个Sh3结构域，并且已证明通过该结构域与发动蛋白和肌动蛋白成核因子相互作用。除了Sh3结构域，Snx9还含有一个C端BAR结构域。已知BAR结构域可感知和/或诱导膜曲率。除了内吞作用外，最近的研究表明Snx9家族参与多种过程，如自噬、巨胞饮作用、吞噬作用和有丝分裂。Snx9家族由果蝇中一个名为sh3px1的单一基因编码。在本报告中，我们展示了对sh3px1的初步表征。我们发现，从果蝇施奈德2（S2）细胞中耗尽Sh3px1会导致片状伪足形成缺陷。在耗尽参与形成片状伪足的肌动蛋白成核因子Scar后，也报道了类似的表型。此外，我们证明在S2细胞中过表达Sh3px1会导致形成小管以及长突起。这些结构的形成需要Sh3px1的C端BAR结构域以及相邻的Phox同源（PX）结构域。此外，Sh3px1有效形成突起需要肌动蛋白成核因子Wasp。在S2细胞中过表达哺乳动物直系同源物Snx18和Snx33时也会产生小管和突起。相比之下，过表达Snx9主要诱导形成长小管。
