IDENTIFICATION OF A NOVEL MEMBER OF THE RAB8 FAMILY FROM THE RAT BASOPHILIC LEUKEMIA-CELL LINE, RBL.2H3

We describe the cloning of a cDNA from the rat basophilic leukaemia ce ll line (RBL.2H3) encoding a novel member of the Rab family of small G TP binding proteins, The novel clone, which we call Rab8b, is most hig hly related to the Rab8 family with substantial divergence in the vari able C-terminal domain, Northern blot analysis reveals highest levels of expression of Rab8b in the spleen, testis and brain, which is in ma rked contrast to the tissue distribution of Rab8, The Rab8b cDNA was m odified to introduce a c-myc epitope tag at the extreme N terminus of the protein, and transient transfection studies were performed to anal yse the intracellular localization of Rab8b by confocal microscopy, Tr ansient expression of the c-myc/Rab8b fusion protein in both PC12 and RBL.2H3 cells shows staining of both the plasma membrane and ill-defin ed vesicular structures, and in the case of RBL.2H3 cells appears to i nduce striking outgrowths of the plasma membrane.