Characterizatin of mulitiple multivesicular body sorting determinants within Sna3: A role for the ubiquitin ligase Rsp5
Characterizatin of mulitiple multivesicular body sorting determinants within Sna3: A role for the ubiquitin ligase Rsp5
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DOI：
10.1091/mbc.e06-08-0680
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发表时间：
2007-02-01
影响因子：
3.3
通讯作者：
Katzmann, David J.
中科院分区：
文献类型：
--
作者：
Oestreich, Andrea J.;Aboian, Mariam;Katzmann, David J.
转运内体系统的蛋白质子集被引导到多泡体（MVBs）的腔内囊泡中。MVB的形成对多种细胞功能至关重要，包括受体下调、病毒出芽、抗原呈递和溶酶体相关细胞器的产生。跨膜蛋白进入MVB的腔内囊泡是一个高度调控的过程，由泛素共价修饰的货物正调节。为了识别额外的MVB分选信号，我们检查了先前描述的与泛素化无关的MVB货物Sna3。虽然Sna3泛素化不是必需的，但Sna3的泛素化对MVB分选有正向调节作用。对缺乏所有赖氨酸残基的Sna3形式中的MVB分选决定因子的检查确定了两个关键区域：氨基末端酪氨酸含有区域和羧基末端PPAY基序。这个PPAY基元与泛素连接酶Rsp5的WW结构域相互作用，WW或Rsp5的HECT结构域的突变对赖氨酸- Sna3的MVB靶向产生负面影响。这些数据表明，Rsp5功能是MVB靶向Sna3的必要条件，其能力超出了货物泛素化。这些结果揭示了一系列影响Sna3 MVB排序的决定因素，包括Rsp5意想不到的作用。
A subset of proteins that transit the endosomal system are directed into the intralumenal vesicles of multivesicular bodies (MVBs). MVB formation is critical for a variety of cellular functions including receptor down-regulation, viral budding, antigen presentation, and the generation of lysosome-related organelles. Entry of transmembrane proteins into the intralumenal vesicles of a MVB is a highly regulated process that is positively modulated by covalent modification of cargoes with ubiquitin. To identify additional MVB sorting signals, we examined the previously described ubiquitination-independent MVB cargo Sna3. Although Sna3 ubiquitination is not essential, Sna3 MVB sorting is positively modulated by its ubiquitination. Examination of MVB sorting determinants within a form of Sna3 lacking all lysine residues identified two critical regions: an amino-terminal tyrosine-containing region and a carboxyl-terminal PPAY motif. This PPAY motif interacts with the WW domains of the ubiquitin ligase Rsp5, and mutations in either the WW or, surprisingly, the HECT domains of Rsp5 negatively impacted MVB targeting of lysine-minus Sna3. These data indicate that Rsp5 function is required for MVB targeting of Sna3 in a capacity beyond cargo ubiquitination. These results uncover a series of determinants impacting Sna3 MVB sorting, including unexpected roles for Rsp5.