Human Vam6p promotes lysosome clustering and fusion in vivo.
Human Vam6p promotes lysosome clustering and fusion in vivo.
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DOI：
10.1083/jcb.200102142
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发表时间：
2001-07-09
影响因子：
7.8
通讯作者：
Bonifacino, J S
中科院分区：
文献类型：
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作者：
Caplan, S;Hartnell, L M;Aguilar, R C;Naslavsky, N;Bonifacino, J S
哺乳动物溶酶体的调节融合对于它们获得内化和生物合成材料的能力至关重要。在这里，我们报告了一种新的人类蛋白hVam6p的鉴定，它在体内促进溶酶体聚集和融合。虽然hVam6p与酿酒酵母空泡蛋白分选基因产物Vam6p/Vps39p具有同源性，但在NH2末端存在一个柠檬同源(CNH)结构域是人类蛋白质所特有的。HVam6p的过表达导致溶酶体和晚期内切体大量聚集并融合成大的(2-3μm)近核结构。这一效应使人联想到结构性激活的Rab7的表达所引起的效应。然而，hVam6p即使在存在显性负性Rab7的情况下也发挥作用，这表明它要么在Rab7下游发挥作用，要么与Rab7平行发挥作用。梯度分离、双杂交和免疫共沉淀分析的数据表明，hVam6p是一种纯低聚物，其自组装是由蛋白质中间的一个网状蛋白重链重复结构域介导的。CNH和cathrin重链重复结构域都是诱导溶酶体聚集和融合所必需的。这项研究表明，hVam6p是一种哺乳动物拴系/对接因子，具有促进体内溶酶体融合的内在能力。
Regulated fusion of mammalian lysosomes is critical to their ability to acquire both internalized and biosynthetic materials. Here, we report the identification of a novel human protein, hVam6p, that promotes lysosome clustering and fusion in vivo. Although hVam6p exhibits homology to the Saccharomyces cerevisiae vacuolar protein sorting gene product Vam6p/Vps39p, the presence of a citron homology (CNH) domain at the NH2 terminus is unique to the human protein. Overexpression of hVam6p results in massive clustering and fusion of lysosomes and late endosomes into large (2–3 μm) juxtanuclear structures. This effect is reminiscent of that caused by expression of a constitutively activated Rab7. However, hVam6p exerts its effect even in the presence of a dominant-negative Rab7, suggesting that it functions either downstream of, or in parallel to, Rab7. Data from gradient fractionation, two-hybrid, and coimmunoprecipitation analyses suggest that hVam6p is a homooligomer, and that its self-assembly is mediated by a clathrin heavy chain repeat domain in the middle of the protein. Both the CNH and clathrin heavy chain repeat domains are required for induction of lysosome clustering and fusion. This study implicates hVam6p as a mammalian tethering/docking factor characterized with intrinsic ability to promote lysosome fusion in vivo.