Schulz Timothy A, Prinz William A
Laboratory of Cell Biochemistry and Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, US Department of Health and Human Services, Bethesda, MD 20892, USA.
Biochim Biophys Acta. 2007 Jun;1771(6):769-80. doi: 10.1016/j.bbalip.2007.03.003. Epub 2007 Mar 16.
Sterols such as cholesterol are a significant component of eukaryotic cellular membranes, and their unique physical properties influence a wide variety of membrane processes. It is known that the concentration of sterol within the membrane varies widely between organelles, and that the cell actively maintains this distribution through various transport processes. Vesicular pathways such as secretion or endocytosis may account for this traffic, but increasing evidence highlights the importance of nonvesicular routes as well. The structure of an oxysterol-binding protein homologue (OSH) in yeast (Osh4p/Kes1p) has recently been solved, identifying it as a sterol binding protein, and there is evidence consistent with the role of a cytoplasmic, nonvesicular sterol transporter. Yeast have seven such proteins, which appear to have distinct but overlapping functions with regard to maintaining intracellular sterol distribution and homeostasis. Control of sterol distribution can have far-reaching effects on membrane-related functions, and Osh proteins have been implicated in a variety of processes such as secretory vesicle budding from the Golgi and establishment of cell polarity. This review summarizes the current body of knowledge regarding this family and its potential functions, placing it in the context of known and hypothesized pathways of sterol transport in yeast.
诸如胆固醇之类的甾醇是真核细胞膜的重要组成部分，其独特的物理性质影响着各种各样的膜过程。已知膜内甾醇的浓度在不同细胞器之间差异很大，并且细胞通过各种转运过程积极维持这种分布。诸如分泌或内吞作用等囊泡途径可能解释了这种运输，但越来越多的证据也凸显了非囊泡途径的重要性。酵母中一种氧甾醇结合蛋白同源物（OSH）（Osh4p/Kes1p）的结构最近已被解析，确定它是一种甾醇结合蛋白，并且有证据表明它具有细胞质非囊泡甾醇转运蛋白的作用。酵母有七种这样的蛋白，在维持细胞内甾醇分布和稳态方面似乎具有不同但重叠的功能。甾醇分布的控制对膜相关功能可能产生深远影响，并且Osh蛋白已涉及多种过程，如从高尔基体出芽的分泌囊泡以及细胞极性的建立。本综述总结了关于这个家族及其潜在功能的当前知识体系，并将其置于酵母中已知和推测的甾醇运输途径的背景下。
