Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine and Institute of Biomembranes, Utrecht University, Utrecht, The Netherlands.
Immunol Cell Biol. 2010 Nov-Dec;88(8):851-6. doi: 10.1038/icb.2010.64. Epub 2010 May 11.
Professional antigen-presenting cells secrete major histocompatibility complex class II (MHC II) carrying exosomes with unclear physiological function(s). Exosomes are first generated as the intraluminal vesicles (ILVs) of a specific type of multivesicular body, and are then secreted by fusion of this compartment with the plasma membrane. We have previously shown that in contrast to the sorting of MHC II at lysosomally targeted multivesicular bodies, sorting of MHC II into exosomes does not rely on MHC II ubiquitination. In search for proteins that drive the incorporation of MHC II into exosomes or functionally discriminate exosomal from plasma membrane MHC II, we first analyzed the total proteome of highly purified B cell-derived exosomes using sensitive and accurate mass spectrometry (MS), and identified 539 proteins, including known and not previously identified constituents. Using quantitative MS, we then identified a small subset of proteins that were specifically co-immunoprecipitated with MHC II from detergent-solubilized exosomes. These include HSC71, HSP90, 14-3-3ɛ, CD20 and pyruvate kinase type M2 (PKM2), and we speculate on the functionality of their interaction with exosomal MHC II.
专业抗原呈递细胞分泌带有主要组织相容性复合体 II (MHC II) 的外泌体，其生理功能尚不清楚。外泌体最初作为特定类型多泡体的腔内小泡（ILVs）产生，然后通过该隔室与质膜融合而分泌。我们之前已经表明，与溶酶体靶向多泡体中 MHC II 的分选相反，MHC II 进入外泌体的分选不依赖于 MHC II 的泛素化。为了寻找驱动 MHC II 纳入外泌体的蛋白质或在功能上区分外泌体和质膜 MHC II 的蛋白质，我们首先使用灵敏和准确的质谱（MS）分析了高度纯化的 B 细胞衍生的外泌体的总蛋白质组，鉴定了 539 种蛋白质，包括已知和以前未鉴定的成分。然后，我们使用定量 MS 从去污剂溶解的外泌体中鉴定出与 MHC II 特异性共免疫沉淀的一小部分蛋白质。其中包括 HSC71、HSP90、14-3-3ɛ、CD20 和丙酮酸激酶 M2（PKM2），我们推测它们与外泌体 MHC II 的相互作用的功能。
