sGi2 is a spliced variant of the GTP-binding protein G αi2 . By difference with G αi2 , which is mainly present at the plasma membrane, sGi2 is localized in intracellular compartments. The splicing event generates a novel C-terminal region in sGi2, which is necessary for its intracellular localization. The role of sGi2 is presently unknown, although its intracellular localization might underlie a possible role in the regulation of trafficking of 7TM receptors. Here, we show that sGi2 complexes with dopamine D2 receptors (D2R) in striatal neurons. The sGi2-D2R complex is readily observed in immunoprecipitation studies using specific antibodies for both proteins on mouse striatal extracts, which identify D2-specific bands of >80 KDa suggesting sGi2 interactions with D2R dimers. Importantly, the sGi2-D2R complex in the absence of receptor stimulation is mostly found in intracellular perinuclear areas in primary neuronal cultures. Treatment of neurons with quinpirole, a D2-specific agonist, results into diffusion of D2R and sGi2 staining throughout the cell and into neurites and membranes. This suggests that dopamine could regulate availability of D2 receptors at the cell surface. The formation of sGi2-D2R complex is mediated through the interaction of sGi2 with the third intracellular loop of D2Rs. As functional consequence of the D2R-sGi2 interaction, we observed a reduction of D2 binding sites at the plasma membrane, when the two proteins are co-expressed in transfected cells. Altogether these studies identify sGi2 as a D2R interacting protein involved in the regulation of D2R at the membrane through a dopamine mediated mechanism.

The 4-m walking speed, measured early after surgical repair of hip fracture, has profound long-term prognostic implications. This assessment approach might prove helpful in clinical decision-making on the postoperative management of older hip fracture persons.

Using an anti-Fos family member antibody, we have previously described in Rana esculenta testis the presence of a nuclear, 43 kDa protein that we hypothesized to be Fra1. With the assistance of an antibody against Fra1 that does not cross-react with other Fos family members, here we report data on Fra1 expression, localization, and putative activity in Rana esculenta testis during its annual reproductive cycle. Western blot analysis confirms that the nuclear, 43 kDa protein is Fra1. Immunocytochemistry validates the Western blot results and shows cytoplasmic and nuclear immunostaining of Fra1 in peritubular myoid cells, efferent ducts, and blood vessels. We report for the first time in a vertebrate, experimental evidence showing that the expression of Fra1 is related to peritubular myoid cells during sperm transport from the tubular compartment to efferent ducts.

Using an anti-Fos family member antiserum, we previously described, in the testis of Rana esculenta, the presence of a nuclear 43-kDa protein that we hypothesized to be Fra-1. Using an antiserum against Fra-1, we here report on Fra-1 expression, localization, and putative activity in the R. esculenta testis during the annual reproductive cycle. Western blot analysis confirms that the nuclear 43-kDa protein is Fra-1. Immunocytochemistry demonstrates Fra-1 in peritubular myoid cells (PMC), efferent ducts, and blood vessels. We present, for the first time for a vertebrate, experimental evidence that the expression of Fra-1 in PMC is related to its activity during sperm transport from the tubular compartment to the efferent ducts.