Gleason Adenrele M, Nguyen Ken C Q, Hall David H, Grant Barth D
Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854.
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461.
Mol Biol Cell. 2016 Sep 14;27(23):3746-56. doi: 10.1091/mbc.E16-02-0116.
Syndapin/Pascin family F-BAR domain proteins bind directly to membrane lipids and are associated with actin dynamics at the plasma membrane. Previous reports have also implicated mammalian syndapin 2 in endosome function during receptor recycling, but precise analysis of a putative recycling function for syndapin in mammalian systems is difficult because of syndapin effects on the earlier step of endocytic uptake, and potential redundancy among the three separate genes that encode mammalian syndapin isoforms. Here we analyze the endocytic transport function of the only C. elegans syndapin, SDPN-1. We find that SDPN-1 is a resident protein of the early and basolateral recycling endosomes in the C. elegans intestinal epithelium, and sdpn-1 deletion mutants display phenotypes indicating a block in basolateral recycling transport. sdpn-1 mutants accumulate abnormal endosomes positive for early endosome and recycling endosome markers that are normally separate, and such endosomes accumulate high levels of basolateral recycling cargo. Furthermore, we observed strong colocalization of endosomal SDPN-1 with the F-actin biosensor Lifeact, and found that loss of SDPN-1 greatly reduced Lifeact accumulation on early endosomes. Taken together our results provide strong evidence for an in vivo function of syndapin in endocytic recycling, and suggest that syndapin promotes transport via endosomal fission.
Syndapin/Pascin家族的F-BAR结构域蛋白直接与膜脂结合，并与质膜上的肌动蛋白动力学相关。先前的报道也表明，哺乳动物的Syndapin 2在受体循环利用过程中的内体功能中发挥作用，但由于Syndapin对胞吞摄取早期步骤的影响，以及编码哺乳动物Syndapin异构体的三个独立基因之间可能存在的冗余性，因此很难在哺乳动物系统中对Syndapin假定的循环利用功能进行精确分析。在此，我们分析了秀丽隐杆线虫唯一的Syndapin即SDPN-1的胞吞运输功能。我们发现，SDPN-1是秀丽隐杆线虫肠道上皮细胞早期和基底外侧循环内体的驻留蛋白，而sdpn-1基因敲除突变体表现出的表型表明基底外侧循环运输受阻。sdpn-1突变体积累了异常的内体，这些内体对通常是分开的早期内体和循环内体标记呈阳性，并且此类内体积累了高水平的基底外侧循环货物。此外，我们观察到内体SDPN-1与F-肌动蛋白生物传感器Lifeact有强烈的共定位现象，并发现SDPN-1的缺失极大地减少了Lifeact在早期内体上的积累。综合我们的结果为Syndapin在胞吞循环中的体内功能提供了有力证据，并表明Syndapin通过内体裂变促进运输。
