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Cultured mesenchymal stromal cells (MSCs) from different sources represent a heterogeneous population of proliferating non-differentiated cells that contains multipotent stem cells capable of originating a variety of mesenchymal cell lineages. Despite tremendous progress in MSC biology spurred by their therapeutic potential, current knowledge on receptor and signaling systems of MSCs is mediocre. Here we isolated MSCs from the human adipose tissue and assayed their responsivity to GPCR agonists with Ca(2+) imaging. As a whole, a MSC population exhibited functional heterogeneity. Although a variety of first messengers was capable of stimulating Ca(2+) signaling in MSCs, only a relatively small group of cells was specifically responsive to the particular GPCR agonist, including noradrenaline. RT-PCR and immunocytochemistry revealed expression of α1B-, α2A-, and β2-adrenoreceptors in MSCs. Their sensitivity to subtype-specific adrenergic agonists/antagonists and certain inhibitors of Ca(2+) signaling indicated that largely the α2A-isoform coupled to PLC endowed MSCs with sensitivity to noradrenaline. The all-or-nothing dose-dependence was characteristic of responsivity of robust adrenergic MSCs. Noradrenaline never elicited small or intermediate responses but initiated large and quite similar Ca(2+) transients at all concentrations above the threshold. The inhibitory analysis and Ca(2+) uncaging implicated Ca(2+)-induced Ca(2+) release (CICR) in shaping Ca(2+) signals elicited by noradrenaline. Evidence favored IP3 receptors as predominantly responsible for CICR. Based on the overall findings, we inferred that adrenergic transduction in MSCs includes two fundamentally different stages: noradrenaline initially triggers a local and relatively small Ca(2+) signal, which next stimulates CICR, thereby being converted into a global Ca(2+) signal., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Recently, the novel peptide named purotoxin-1 (PT1) has been identified in the venom of the spider Geolycosa sp. and shown to exert marked modulatory effects on P2X3 receptors in rat sensory neurons. Here we studied another polypeptide from the same spider venom, purotoxin-2 (PT2), and demonstrated that it also affected activity of mammalian P2X3 receptors. The murine and human P2X3 receptors were heterologously expressed in cells of the CHO line, and nucleotide-gated currents were stimulated by CTP and ATP, respectively. Both PT1 and PT2 negligibly affected P2X3-mediated currents elicited by brief pulses of the particular nucleotide. When subthreshold CTP or ATP was added to the bath to exert the high-affinity desensitization of P2X3 receptors, both spider toxins strongly enhanced the desensitizing action of the ambient nucleotides. At the concentration of 50nM, PT1 and PT2 elicited 3-4-fold decrease in the IC(50) dose of ambient CTP or ATP. In contrast, 100nM PT1 and PT2 negligibly affected nucleotide-gated currents mediated by mP2X2 receptors or mP2X2/mP2X3 heteromers. Altogether, our data point out that the PT1 and PT2 toxins specifically target the fast-desensitizing P2X3 receptor, thus representing a unique tool to manipulate its activity., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The specific membrane glycoproteins with high affinity for camphor and decanal were isolated from rat olfactory epithelium. Antibodies to these glycoproteins inhibited both the electroolfactogram and the binding of odorants. The enzyme immunoassay has shown these glycoproteins to be present in the olfactory epithelium of rat, mouse, guinea-pig and hamster but not in that of frog and carp. The molecular mass of the odour-binding glycoproteins from rat olfactory epithelium solubilized by Triton X-100 was approx. 140 kDa. They consisted of two subunits (88 and 55 kDa). The 88 kDa subunit was capable of binding odorants. The data obtained suggest that the glycoproteins isolated have some properties that make them plausible candidates for olfactory receptor molecules.