New members of the neurexin superfamily: multiple rodent homologues of the human CASPR5 gene

Proteins of the Caspr family are involved in cell contacts and communication in the nervous system. We identified and, by in silico reconstruction, compiled three orthologues of the human CASPR5 gene from the mouse genome, four from the rat genome, and one each from the chimpanzee, dog, opossum, and chicken genomes. Obviously, Caspr5 gene duplications have taken place during evolution of the rodent lineage. In the rat, the four paralogues are located in one chromosome arm, Chr 13p. In the mouse, however, the three Caspr5 genes are located in two chromosomes, Chr 1 and Chr 17. RT-PCR shows that all three mouse paralogues are being expressed. Common expression is found in brain tissue but different expression patterns are seen in other organs during fetal development and in the adult stage. Tissue specificity of expression has diverged during evolution of this young rodent gene family

Identification and characterization of Ca2+-activated K+ channels in granulosa cells of the human ovary

<p>Abstract</p> <p>Background</p> <p>Granulosa cells (GCs) represent a major endocrine compartment of the ovary producing sex steroid hormones. Recently, we identified in human GCs a Ca²⁺-activated K⁺channel (K_Ca) of big conductance (BK_Ca), which is involved in steroidogenesis. This channel is activated by intraovarian signalling molecules (e.g. acetylcholine) via raised intracellular Ca²⁺levels. In this study, we aimed at characterizing 1. expression and functions of K_Cachannels (including BK_Cabeta-subunits), and 2. biophysical properties of BK_Cachannels.</p> <p>Methods</p> <p>GCs were obtained from in vitro-fertilization patients and cultured. Expression of mRNA was determined by standard RT-PCR and protein expression in human ovarian slices was detected by immunohistochemistry. Progesterone production was measured in cell culture supernatants using ELISAs. Single channels were recorded in the inside-out configuration of the patch-clamp technique.</p> <p>Results</p> <p>We identified two K_Catypes in human GCs, the intermediate- (IK) and the small-conductance K_Ca(SK). Their functionality was concluded from attenuation of human chorionic gonadotropin-stimulated progesterone production by K_Cablockers (TRAM-34, apamin). Functional IK channels were also demonstrated by electrophysiological recording of single K_Cachannels with distinctive features. Both, IK and BK_Cachannels were found to be simultaneously active in individual GCs. In agreement with functional data, we identified mRNAs encoding IK, SK1, SK2 and SK3 in human GCs and proteins of IK and SK2 in corresponding human ovarian cells. Molecular characterization of the BK_Cachannel revealed the presence of mRNAs encoding several BK_Cabeta-subunits (beta2, beta3, beta4) in human GCs. The multitude of beta-subunits detected might contribute to variations in Ca²⁺dependence of individual BK_Cachannels which we observed in electrophysiological recordings.</p> <p>Conclusion</p> <p>Functional and molecular studies indicate the presence of active IK and SK channels in human GCs. Considering the already described BK_Ca, they express all three K_Catypes known. We suggest that the plurality and co-expression of different K_Cachannels and BK_Cabeta-subunits might allow differentiated responses to Ca²⁺signals over a wide range caused by various intraovarian signalling molecules (e.g. acetylcholine, ATP, dopamine). The knowledge of ovarian K_Cachannel properties and functions should help to understand the link between endocrine and paracrine/autocrine control in the human ovary.</p

Chlorido{N-[2-(diphenylphosphanyl)- benzyl]-1-(pyridin-2-yl)methanamine-kP} gold(I)

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