Baldini G, Scherer P E, Lodish H F
Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
Proc Natl Acad Sci U S A. 1995 May 9;92(10):4284-8. doi: 10.1073/pnas.92.10.4284.
Rab3A is a small GTP-binding protein expressed predominantly in brain and neuroendocrine cells, in which it is associated with synaptic and synaptic-like vesicles, respectively. Here we report that adult mouse fat cells and 3T3-L1 adipocytes also express Rab3A mRNA and protein. They do not express synaptophysin, an abundant protein in synaptic vesicles or synaptic-like vesicles. The amount of Rab3A mRNA and protein, like that of the highly homologous isoform Rab3D, increases severalfold during differentiation of 3T3-L1 fibroblasts into mature adipocytes. In fat cells, most Rab3D and Rab3A protein is bound to membrane, irrespective of insulin addition. Rab3A and Rab3D are localized in different subcellular compartments, since about half of the Rab3A, but none of the Rab3D, is associated with a low-density organelle(s). Rab3D and Rab3A may be involved in different pathways of regulated exocytosis in adipocytes. Moreover, in adipocytes Rab3A may define an exocytic organelle that is different from synaptic vesicles or synaptic-like microvesicles found in neuronal and endocrine cells.
Rab3A是一种小的GTP结合蛋白，主要在大脑和神经内分泌细胞中表达，在这些细胞中，它分别与突触小泡和类突触小泡相关。在此我们报告，成年小鼠脂肪细胞和3T3-L1脂肪细胞也表达Rab3A mRNA和蛋白。它们不表达突触素，突触素是突触小泡或类突触小泡中的一种丰富蛋白质。Rab3A mRNA和蛋白的量，与高度同源的异构体Rab3D的量一样，在3T3-L1成纤维细胞分化为成熟脂肪细胞的过程中增加了几倍。在脂肪细胞中，无论是否添加胰岛素，大多数Rab3D和Rab3A蛋白都与膜结合。Rab3A和Rab3D定位于不同的亚细胞区室，因为大约一半的Rab3A，但没有Rab3D，与低密度细胞器相关。Rab3D和Rab3A可能参与脂肪细胞中受调控的胞吐作用的不同途径。此外，在脂肪细胞中，Rab3A可能定义了一种不同于神经元和内分泌细胞中发现的突触小泡或类突触微泡的胞吐细胞器。
