RGS-GAIP, a GTPase-activating protein for Gαi heterotrimeric G proteins, is located on clathrin-coated vesicles
RGS-GAIP, a GTPase-activating protein for Gαi heterotrimeric G proteins, is located on clathrin-coated vesicles
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DOI：
10.1091/mbc.9.5.1123
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发表时间：
1998-05-01
影响因子：
3.3
通讯作者：
Farquhar, MG
中科院分区：
文献类型：
--
作者：
De Vries, L;Elenko, E;Farquhar, MG
RGS- gaip （G α相互作用蛋白）是RGS （G蛋白信号传导调节因子）蛋白家族的成员，其功能是下调G α (i)/G α (q)相关信号传导。GAIP是一种GAP或鸟苷三磷酸酶激活蛋白，最初因其与质膜（PM）和高尔基膜上的异三聚体G蛋白G α (i3)结合的能力而被发现。先前，我们证明，与大多数其他gap相反，GAIP是膜锚定和棕榈酰化的。在这项工作中，我们使用细胞分离和免疫细胞化学来确定GAIP与哪些特定的膜相关。在垂体细胞中，我们发现GAIP与细胞膜分离，而不是PM；免疫金标记法在高尔基区网格蛋白包被的芽或囊泡（ccv）上发现GAIP。在大鼠肝脏中，GAIP主要集中在囊泡载体组分中；在高尔基或pm富集组分中均未发现。通过免疫金标记，在位于正窦PM附近的网格蛋白包被凹坑或ccv上检测到它。这些结果表明GAIP可能与tgn衍生的ccv和pm衍生的ccv有关。GAIP是在ccv或任何其他细胞膜上发现的第一个GAP。ccv上GAP的存在提示了一种模型，即GAP在空间中与其靶G蛋白分离，两者在囊泡融合时接触。
RGS-GAIP (G alpha-interacting protein) is a member of the RGS (regulator of G protein signaling) family of proteins that functions to down-regulate G alpha(i)/G alpha(q)-linked signaling. GAIP is a GAP or guanosine triphosphatase-activating protein that was initially discovered by virtue of its ability to bind to the heterotrimeric G protein G alpha(i3) which is found on both the plasma membrane (PM) and Golgi membranes. Previously, we demonstrated that, in contrast to most other GAPs, GAIP is membrane anchored and palmitoylated. In this work we used cell fractionation and immunocytochemistry to determine with what particular membranes GAIP is associated. In pituitary cells we found that GAIP fractionated with intracellular membranes, not the PM; by immunogold labeling GAIP was found on clathrin-coated buds or vesicles (CCVs) in the Golgi region. In rat liver GAIP was concentrated in vesicular carrier fractions; it was not found in either Golgi-or PM-enriched fractions. By immunogold labeling it was detected on clathrin-coated pits or CCVs located near the sinusoidal PM. These results suggest that GAIP may be associated with both TGN-derived and PM-derived CCVs. GAIP represents the first GAP found on CCVs or any other intracellular membranes. The presence of GAIP on CCVs suggests a model whereby a GAP is separated in space from its target G protein with the two coming into contact at the time of vesicle fusion.