Gender‐dependent regulation of G‐protein‐gated inwardly rectifying potassium current in dorsal raphe neurons in knock‐out mice devoid of the 5‐hydroxytryptamine transporter

Agonists at G‐protein‐coupled receptors in neurons of the dorsal raphe nucleus (DRN) of knock‐out mice devoid of the serotonin transporter (5‐HTT^?/?) exhibit lower efficacy to inhibit cellular discharge than in wild‐type counterparts. Using patch‐clamp whole‐cell recordings, we found that a G‐protein‐gated inwardly rectifying potassium (GIRK) current is involved in the inhibition of spike discharge induced by 5‐HT_1A agonists (5‐carboxamidotryptamine (5‐CT) and (±)‐2‐dipropylamino‐8‐hydroxy‐1,2,3,4‐tetrahydronaphthalene hydrobromide (8‐OH‐DPAT); 50 nM–30 μM) in both wild‐type and 5‐HTT^?/? female and male mice. These effects were mimicked by 5′‐guanylyl‐imido‐diphosphate (Gpp(NH)p; 400 μM) dialysis into cells with differences between genders. The 5‐HTT^?/? knock‐out mutation reduced the current density induced by Gpp(NH)p in females but not in males. These data suggest that the decreased response of 5‐HT_1A receptors to agonists in 5‐HTT^?/? mutants reflects notably alteration in the coupling between G‐proteins and GIRK channels in females but not in males. Accordingly, gender differences in central 5‐HT neurotransmission appear to depend—at least in part—on sex‐related variations in corresponding receptor‐G protein signaling mechanisms. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006     

Extraribosomal functions of bacterial ribosomal proteins

Ribosomal proteins (r-proteins) constitute a considerable part of the cell proteome. Although their primary role in the cell is to serve as integral components of protein synthesis machinery, ribosomes, many of them have functions beyond the ribosome (the phenomenon known as moonlighting), acting either as individual regulatory proteins or in complexes with other cell components. Extraribosomal activities of some ribosomal proteins were observed as early as the 1970s–1980s. In recent years, both the list of moonlighting r-proteins and the repertoire of their additional functions beyond the ribosome was greatly expanded, mainly owing to new techniques developed for dissecting RNA/DNA-protein or protein-protein interactions within functional complexes involved in various cell processes. The review surveys information on the extraribosomal functions demonstrated experimentally or presumed for bacterial r-proteins.     

EZH2 Regulates Cofilin Activity and Colon Cancer Cell Migration by Targeting ITGA2 Gene

Reorganization of cytoskeleton via actin remodeling is a basic step of cell locomotion. Although cell migration of normal and cancer cells can be stimulated by a variety of intra- and extra-cellular factors, all paths ultimate on the regulation of cofilin activity. Cofilin is a small actin-binding protein able to bind both forms of actin, globular and filament, and is regulated by phosphorylation at Serine 3. Following phosphorylation at serine 3 cofilin is inactive, therefore cannot bind actin molecules and cytoskeleton remodeling is impaired. The histone methyltransferase EZH2 is frequently over expressed in many tumour types including colorectal cancer (CRC). EZH2 over activity, which results in epigenetic gene-silencing, has been associated with many tumour properties including invasion, angiogenesis and metastasis but little is known about the underneath molecular mechanisms. Herein, we report that EZH2 is able to control cofilin activity and consequently cell locomotion of CRC cell lines through a non-conventional novel axis that involves integrin signaling. Indeed, we show how genetic and pharmacological inhibition (DZNep and GSK343) of EZH2 function produces hyper phosphorylation of cofilin and reduces cell migration. We previously demonstrated by chromatin immuno-precipitation that Integrin alpha 2 (ITGα2) expression is regulated by EZH2. In the present study we provide evidence that in EZH2-silenced cells the signaling activity of the de-repressed ITGα2 is able to increase cofilin phosphorylation, which in turn reduces cell migration. This study also proposes novel mechanisms that might provide new anti-metastatic strategies for CRC treatment based on the inhibition of the epigenetic factor EZH2 and/or its target gene.     

Molecular differentiation of species of the genus Zungaro (Siluriformes, Pimelodidae) from the Amazon and Paraná-Paraguay River basins in Brazil

Fish species of the Zungaro genus (Siluriformes, Pimelodidae) are amongst the largest migratory fish in Latin America and have considerable economic importance for commercial fishing in Brazil. However, natural populations of this large catfish are experiencing a severe decline. There are significant taxonomical inconsistencies for this fish. Two geographically separated species of the fish were initially described, one endemic in the Amazon and another in the Paraná-Paraguay River basins. A taxonomic review had recently proposed that there is only one Zungaro species in Brazil, based on morphological data. We made a molecular study of Zungaro populations in an attempt to solve taxonomical inconsistencies and to analyze genetic diversity in natural populations of this genus. We analyzed two regions of the mitochondrial DNA (the control region and the ATPase 6 gene region) of individuals sampled from the Paraná-Paraguay River and Amazon River basins. Analyses based on p-distances and maximum likelihood phylogenetic models showed a genetic difference between populations corresponding to different species. Genetic differentiation between Zungaro populations was at the same level as that observed between other Siluriformes species, using the same DNA sequences. We conclude that Zungaro species of the Paraná-Paraguay River basin do not belong to the same species found in the Amazon basin. This finding has a significant implication for conservation of this fish, given that populations are disappearing at a high rate in the Paraná-Paraguay River basin, mainly due to impoundments.     

Ca2+ signaling during maturation of cumulus-oocyte complex in mammals

Under the influence of gonadotropins or growth factors, a close cooperation develops between cumulus cells and the oocyte that is implicated in transmitting signals involved in maintaining or releasing the meiotic arrest in the oocyte. While cyclic adenosine 5'-monophosphate (cAMP) is a key molecule in maintaining the meiotic arrest, calcium (Ca(2+)) may play a role in controlling either spontaneous or gonadotropin-induced oocyte maturation, possibly by modulating intracytoplasmic cAMP concentrations via Ca(2+)-sensitive adenylate cyclases. This review focuses on the mechanisms related to the origin of the Ca(2+) wave that travels from the cumulus cells to the oocyte, and discusses the source of variations affecting the dynamics of this wave.     

Phylogeny of Cercis based on DNA sequences of nuclear ITS and four plastid regions: implications for transatlantic historical biogeography

The disjunct genus Cercis has been used to test models of Northern Hemisphere historical biogeography. Previous phylogenetic estimates employing DNA sequences of the ITS region and (in one study) those of ndhF recovered a well supported clade of North American and western Eurasian species that was nested within a paraphyletic group of Chinese species. Resolution and clade support within the tree were otherwise low and the monophyly of Cercis canadensis was uncertain. Here we conduct a phylogenetic analysis of Cercis with a higher number of regions (ITS, ndhF, rpoB-trnC, trnT-trnD, and trnS-trnG) and samples than in previous studies. Results corroborate the initial divergence between the Chinese species Cercis chingii and the rest of the genus. Support is newly found both for a clade of the two North American species as sister to the western Eurasian species, and for the monophyly of C. canadensis. As in a previous study, divergence between North American and western Eurasian Cercis was estimated as mid-Miocene (ca. 13 million years ago), and the ancestor in which this divergence occurred was inferred to be xerophytic. Contrary to previous studies, however, our data infer strictly east-to-west vicariance. The timing of the transatlantic divergence in Cercis is too recent to be explained by a postulated continuous belt of semi-arid vegetation between North America and Europe in the Paleogene, suggesting instead the presence of a Miocene North Atlantic corridor for semi-arid plants. In the absence of strong evidence from other sources, the possibility that Cercis has been able to quickly adapt from mesophytic antecedents to semi-arid conditions whenever the latter have arisen in the Northern Hemisphere can be considered a plausible alternative, although parsimony optimization renders this scenario two steps longer.     

Interleukin-2-induced small unilamellar vesicle coalescence

Recombinant human interleukin-2 (rhIL-2) was incorporated in liposomes for potential therapeutic applications using a novel process. In this process, rhIL-2 caused the formation of large, unique multilamellar vesicles (MLVs) from small unilamellar vesicles (SUVs) of dimyristoylphosphatidylcholine (DMPC). Vesicle coalescence occurred most rapidly at 19 degrees C, between the pre- and main phase transition temperatures of DMPC, and showed a dependence upon pH (pH <5.5), ionic strength (>50 mM) and the initial size of the unilamellar vesicles (相似文献