Subcellular localization of a novel G protein XLGalpha(olf).

XLGalpha(olf) was identified as a transcriptional variant of the heterotrimeric G protein, Galpha(olf). Previous work showed that XLGalpha(olf) couples with adenosine A2a receptor and dopamine D1 receptor in vitro. However, physiological functions of XLGalpha(olf) remain to be elucidated. In this study, we performed indirect immunofluorescence confocal analyses to examine the subcellular localization of XLGalpha(olf). With overexpression, surprisingly, many large endosomes resulted. We also observed that XLGalpha(olf) localizes at the Golgi apparatus. The N-terminal region of XLGalpha(olf) appears necessary for both endosome formation and the Golgi localization. The results indicate that XLGalpha(olf) and Galpha(olf) play distinctly separate roles. Moreover, XLGalpha(olf) colocalized with Rab3A and Rab8A, as well as partially with Rab11A, but not with other endocytotic endosomes. We could confirm the interaction between XLGalpha(olf) and Rab3A/Rab8A by co-immunoprecipitation experiments. Our study provides important clues toward understanding physiological functions of XLGalpha(olf).