Nydegger Sascha, Khurana Sandhya, Krementsov Dimitry N, Foti Michelangelo, Thali Markus
Graduate Program in Microbiology and Molecular Genetics, University of Vermont, Burlington, VT 05405, USA.
J Cell Biol. 2006 Jun 5;173(5):795-807. doi: 10.1083/jcb.200508165. Epub 2006 May 30.
Specific spatial arrangements of proteins and lipids are central to the coordination of many biological processes. Tetraspanins have been proposed to laterally organize cellular membranes via specific associations with each other and with distinct integrins. Here, we reveal the presence of tetraspanin-enriched microdomains (TEMs) containing the tetraspanins CD9, CD63, CD81, and CD82 at the plasma membrane. Fluorescence and immunoelectron microscopic analyses document that the surface of HeLa cells is covered by several hundred TEMs, each extending over a few hundred nanometers and containing predominantly two or more tetraspanins. Further, we reveal that the human immunodeficiency virus type 1 (HIV-1) Gag protein, which directs viral assembly and release, accumulates at surface TEMs together with the HIV-1 envelope glycoprotein. TSG101 and VPS28, components of the mammalian ESCRT1 (endosomal sorting complex required for transport), which is part of the cellular extravesiculation machinery critical for HIV-1 budding, are also recruited to cell surface TEMs upon virus expression, suggesting that HIV-1 egress can be gated through these newly mapped microdomains.
蛋白质和脂质的特定空间排列对于许多生物过程的协调至关重要。四跨膜蛋白被认为通过彼此之间以及与不同整合素的特定关联在侧向组织细胞膜。在这里，我们揭示了在质膜上存在富含四跨膜蛋白的微结构域（TEMs），其中包含四跨膜蛋白CD9、CD63、CD81和CD82。荧光和免疫电子显微镜分析表明，HeLa细胞表面覆盖着数百个TEMs，每个TEMs延伸数百纳米，主要包含两种或更多种四跨膜蛋白。此外，我们发现指导病毒组装和释放的人类免疫缺陷病毒1型（HIV-1）Gag蛋白与HIV-1包膜糖蛋白一起聚集在表面TEMs处。TSG101和VPS28是哺乳动物ESCRT1（运输所需的内体分选复合物）的组成部分，ESCRT1是细胞外囊泡形成机制的一部分，对HIV-1出芽至关重要，在病毒表达时也被招募到细胞表面TEMs，这表明HIV-1的释放可以通过这些新发现的微结构域进行调控。
