A variety of animal species utilize the ultraviolet (UV) component of sunlight as their environmental cues, whereas physiological roles of UV photoreception in mammals, especially in human beings, remain open questions. Here we report that mouse neuropsin (OPN5) encoded by the Opn5 gene exhibited an absorption maximum (λmax) at 380 nm when reconstituted with 11-cis-retinal. Upon UV-light illumination, OPN5 was converted to a blue-absorbing photoproduct (λmax 470 nm), which was stable in the dark and reverted to the UV-absorbing state by the subsequent orange light illumination, indicating its bistable nature. Human OPN5 also had an absorption maximum at 380 nm with spectral properties similar to mouse OPN5, revealing that OPN5 is the first and hitherto unknown human opsin with peak sensitivity in the UV region. OPN5 was capable of activating heterotrimeric G protein Gi in a UV-dependent manner. Immuno-blotting analyses of mouse tissue extracts identified the retina, the brain and, unexpectedly, the outer ears as the major sites of OPN5 expression. In the tissue sections of mice, OPN5 immuno-reactivities were detected in a subset of non-rod/non-cone retinal neurons as well as in the epidermal and muscle cells of the outer ears. Most of these OPN5-immuno-reactivities in mice were co-localized with positive signals for the alpha-subunit of Gi. These results demonstrate the first example of UV photoreceptor in human beings and strongly suggest that OPN5 triggers a UV-sensitive Gi-mediated signaling pathway in the mammalian tissues.

We have determined the primary structure of a novel ␥ subunit (␥ 12 , previously designated ␥ S1 ) of G protein purified from bovine spleen. The mature ␥ 12 protein composed of 68 amino acids had acetylated serine at the N terminus and geranylgeranylated/carboxylmethylated cysteine at the C terminus. This was consistent with the C-terminal prenylation signal in the amino acid sequence, which was predicted from ␥ 12 cDNA isolated from a bovine spleen cDNA library. Western blots with the specific antibody against ␥ 12 showed that ␥ 12 is present in all tissues examined. Among various ␥ subunits (␥ 1 , ␥ 2 , ␥ 3 , ␥ 7 , and ␥ 12 ), ␥ 12 has a unique property to be phosphorylated by protein kinase C. The phosphorylated amino acid residue was Ser 1 (or Ser

Genetic variations in dysbindin-1 (dystrobrevin-binding protein-1) are one of the most commonly reported variations associated with schizophrenia. As schizophrenia could be regarded as a neurodevelopmental disorder resulting from abnormalities of synaptic connectivity, we attempted to clarify the function of dysbindin-1 in neuronal development. We examined the developmental change of dysbindin-1 in rat brain by western blotting and found that a 50 kDa isoform is highly expressed during the embryonic stage, whereas a 40 kDa one is detected at postnatal day 11 and increased thereafter. Immunofluorescent analyses revealed that dysbindin-1 is enriched at the spine-like structure of primary cultured rat hippocampal neurons. We identified WAVE2, but not N-WASP, as a binding partner for dysbindin-1. We also found that Abi-1, a binding molecule for WAVE2 involved in spine morphogenesis, interacts with dysbindin-1. Although dysbindin-1, WAVE2 and Abi-1 form a ternary complex, dysbindin-1 promoted the binding of WAVE2 to Abi-1. RNA interference-mediated knockdown of dysbindin-1 led to the generation of abnormally elongated immature dendritic protrusions. The present results indicate possible functions of dysbindin-1 at the postsynapse in the regulation of dendritic spine morphogenesis through the interaction with WAVE2 and Abi-1.

We previously reported that G␤␥ signaling regulates cell spreading or cell shape change through activation of a Rho family small GTPase, suggesting the existence of a G␤␥-regulated Rho guanine-nucleotide exchange factor (RhoGEF). In this study we examined various RhoGEF clones, found FLJ00018 to be a G␤␥-activated RhoGEF, and investigated the molecular mechanism of G␤␥-induced activation of Rho family GTPases. Co-expression of the genes for FLJ00018 and G␤␥ enhanced serum response element-mediated gene transcription in HEK-293 cells. Combined expression of G␤␥ and FLJ00018 significantly induced activation of Rac and Cdc42 but not RhoA. FLJ00018 also enhanced gene transcription induced by carbachol-stimulated m2 muscarinic acetylcholine receptor, and this enhancement was blocked by pertussis toxin. Furthermore, we demonstrated G␤␥ to interact directly with the N-terminal region of FLJ00018 and the N-terminal fragment of this molecule to inhibit serum response element-dependent transcription induced by G␤␥/FLJ00018 and carbachol. In NIH3T3 cells, FLJ00018 enhanced lysophosphatidic acid-induced cell spreading, which was also blocked by the N-terminal fragment of FLJ00018. These results provide evidence for a signaling pathway by which G i -coupled receptor specifically induces Rac and Cdc42 activation through direct interaction of G␤␥ with FLJ00018.Rho family small GTPases belong to the Ras superfamily, comprise more than 20 distinct proteins, and control a wide variety of cellular processes. First identified as regulators of the actin cytoskeleton rearrangements, RhoA, Rac1, and Cdc42 induce stress fibers, lamellipodia, and filopodia formation, respectively, and it is now clear that Rho family proteins play pivotal roles in cell migration, outgrowth, extension and pathfinding of neuritis, and gene transcription. Like other small GTPases, Rho GTPases cycle between an inactive GDP-bound state and an active GTP-bound state (1, 2). This cycling of Rho GTPases is controlled by three distinct classes of regulatory proteins, namely (i) guanine-nucleotide dissociation inhibitors, which stabilize the inactive form (3), (ii) guanine-nucleotide exchange factors (GEFs), 2 which catalyze GDP/GTP exchange (4, 5), and (iii) GTPases-activating proteins, which stimulate low, intrinsic GTPase activity of Rho GTPases (6). In particular, 60 different GEFs for Rho family members (RhoGEFs) have been described so far (4). A common feature of RhoGEFs is the Dbl homology (DH) domain responsible for exchange activity followed by a pleckstrin homology (PH) domain considered to be involved in subcellular localization. Besides this tandem motif, RhoGEFs often contain one or more additional signal transduction domains, such as PDZ, Src homology (SH) 2, SH3, and RGS (regulator of G protein signaling), which can function as molecular bridges between different signal transduction pathways.It is well established that a large variety of G protein-coupled receptors (GPCRs), particularly those coupling to the G 12/13 type of heterotrimeric G proteins...

The dentate gyrus of the hippocampus, generating new cells throughout life, is essential for normal recognition memory performance. Reduction of brain-derived neurotrophic factor (BDNF) in this structure impairs its functions. To elucidate the association between BDNF levels and hippocampal neurogenesis, we first conducted a search for compounds that stimulate endogenous BDNF production in hippocampal granule neurons. Among ion channel modulators tested, riluzole, a neuroprotective agent with anticonvulsant properties that is approved for treatment of amyotrophic lateral sclerosis, was highly effective as a single dose by an intraperitoneal injection, causing a rise in BDNF localized in dentate granule neurons, the hilus, and the stratum radiatum of the CA3 region. Repeated, but not single, injections resulted in prolonged elevation of hippocampal BDNF and were associated with increased numbers of newly generated cells in the granule cell layer. This appeared due to promoted proliferation rather than survival of precursor cells, many of which differentiated into neurons. Intraventricular administration of BDNF-specific antibodies blocked such riluzole effects, suggesting that BDNF increase is necessary for the promotion of precursor proliferation. Our results suggest the basis for a new strategy for treatment of memory dysfunction.