Poon P P, Nothwehr S F, Singer R A, Johnston G C
Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7.
J Cell Biol. 2001 Dec 24;155(7):1239-50. doi: 10.1083/jcb.200108075. Epub 2001 Dec 17.
Many intracellular vesicle transport pathways involve GTP hydrolysis by the ADP-ribosylation factor (ARF) type of monomeric G proteins, under the control of ArfGAP proteins. Here we show that the structurally related yeast proteins Gcs1 and Age2 form an essential ArfGAP pair that provides overlapping function for TGN transport. Mutant cells lacking the Age2 and Gcs1 proteins cease proliferation, accumulate membranous structures resembling Berkeley bodies, and are unable to properly process and localize the vacuolar hydrolase carboxypeptidase (CPY) and the vacuolar membrane protein alkaline phosphatase (ALP), which are transported from the TGN to the vacuole by distinct transport routes. Immunofluorescence studies localizing the proteins ALP, Kex2 (a TGN resident protein), and Vps10 (the CPY receptor for transport from the TGN to the vacuole) suggest that inadequate function of this ArfGAP pair leads to a fragmentation of TGN, with effects on secretion and endosomal transport. Our results demonstrate that the Gcs1 + Age2 ArfGAP pair provides overlapping function for transport from the TGN, and also indicate that multiple activities at the TGN can be maintained with the aid of a single ArfGAP.
许多细胞内囊泡运输途径涉及在ArfGAP蛋白的控制下,由ADP核糖基化因子(ARF)类型的单体G蛋白进行GTP水解。在这里,我们表明,结构相关的酵母蛋白Gcs1和Age2形成了一个必需的ArfGAP对,为反式高尔基体网络(TGN)运输提供重叠功能。缺乏Age2和Gcs1蛋白的突变细胞停止增殖,积累类似伯克利小体的膜结构,并且无法正确加工和定位液泡水解酶羧肽酶(CPY)和液泡膜蛋白碱性磷酸酶(ALP),它们通过不同的运输途径从TGN运输到液泡。对蛋白ALP、Kex2(一种TGN驻留蛋白)和Vps10(从TGN运输到液泡的CPY受体)进行免疫荧光定位研究表明,这个ArfGAP对功能不足会导致TGN碎片化,影响分泌和内体运输。我们的结果表明,Gcs1 + Age2 ArfGAP对为从TGN的运输提供重叠功能,并且还表明借助单个ArfGAP可以维持TGN的多种活性。