Vps4 and the MVB sorting pathway

Vps4 和 MVB 排序路径

• 批准号: 7103216
• 负责人: MARKUS BABST
• 金额: $ 28.41万
• 依托单位: UNIVERSITY OF UTAH
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-05 至 2011-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7103216
• 关键词: SDS polyacrylamide gel electrophoresis; adenosinetriphosphatase; cell component structure /function; enzyme activity; lipid metabolism; lipid transport; lysosomes; molecular assembly /self assembly; protein degradation; protein protein interaction; protein purification; protein structure; protein structure function; protein transport

DESCRIPTION (provided by applicant): In eukaryotes, the 'multivesicular body' (MVB) pathway delivers transmembrane proteins and lipids into the lumen of the lysosome for degradation. As a consequence, MVBs are essential for regulating cell surface protein composition and maintaining lysosomal function. Numerous cellular functions, such as nutrient uptake, cell communication and immune response are dependent on MVBs. The MVB sorting machinery performs a unique membrane budding event, which results in the formation of vesicles into the lumen of the endosome. Retroviruses such as HIV co-opt the MVB machinery during viral infection to complete formation of viral particles via a similar membrane budding event at the plasma membrane. Therefore, the MVB sorting machinery has been recognized as a target for the development of new drugs combating HIV infection, a disease that kills more than 2 million people per year worldwide. Several multiprotein complexes, called the ESCRTs, execute cargo sorting and vesicle formation at the MVB. To perform their function, the soluble ESCRT complexes are recruited from the cytoplasm and sequentially assemble on the endosomal membrane where they sort ubiquitinated cargo into forming vesicles. To complete vesicle formation, the ESCRT complexes are disassembled by the activity of the AAA-type ATPase Vps4. Without Vps4 function, the ESCRT machinery remains on the membrane and MVB vesicle formation is inhibited. Up until now, it had been thought that the disassembly function of Vps4 was a constitutive process. However, our preliminary studies have identified three proteins that regulate the activity of Vps4 on several levels. Vta1 appears to enhance the disassembly reaction that stimulates Vps4 ATPase activity. Fti1 works together with Vta1 in the activation of Vps4. Ist1 interferes with Vps4 function and Ist1 activity itself appears to be regulated by its stability. Based on these findings we propose a revised model in which the Vps4-dependent disassembly of the ESCRT complexes represents a key regulatory step within the MVB pathway. We propose that eukaryotic cells modulate the activity of the MVB pathway by regulating the degradation rate of Ist1, thereby regulating the activity of Vps4.

描述（由申请人提供）：在真核生物中，“多囊体”（MVB）途径将跨膜蛋白和脂质传递到溶酶体的腔内以降解。结果，MVB对于调节细胞表面蛋白组成和维持溶酶体功能至关重要。许多细胞功能，例如养分吸收，细胞通信和免疫反应取决于M​​VB。 MVB排序机械执行了独特的膜出现事件，从而导致囊泡形成到内体的腔内。病毒感染期间的逆转录病毒，例如HIV选择MVB机械，通过质膜上的类似膜出芽事件完成病毒颗粒的形成。因此，MVB分类机械被公认为是打击艾滋病毒感染的新药的目标，这种疾病每年在全球范围内造成超过200万人。几种称为ESCRT的多蛋白络合物在MVB处执行货物排序和囊泡形成。为了执行其功能，可溶性ESCRT复合物是从细胞质中募集的，并在内体膜上依次组装，在那里它们将泛素化货物分类为形成囊泡。为了完成囊泡的形成，ESCRT复合物被AAA型ATPase VPS4的活性拆卸。没有VPS4功能，ESCRT机械保留在膜上，并且MVB囊泡的形成受到抑制。到目前为止，人们一直认为VPS4的拆卸功能是一个构成过程。但是，我们的初步研究已经确定了三种蛋白质，这些蛋白质在多个级别上调节VPS4的活性。 VTA1似乎增强了刺激VPS4 ATPase活性的拆卸反应。 FTI1在VPS4的激活中与VTA1一起工作。 IST1干扰VPS4函数，IST1活动本身似乎受其稳定性的调节。基于这些发现，我们提出了一个修订的模型，其中ESCRT复合物的VPS4依赖性拆卸代表了MVB途径内的关键调节步骤。我们建议真核细胞通过调节IST1的降解速率来调节MVB途径的活性，从而调节VPS4的活性。