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Histamine-H1-receptor-mediated phosphoinositide hydrolysis, Ca2+ signalling and membrane-potential oscillations in human HeLa carcinoma cells.

ABSTRACT: In human HeLa carcinoma cells, histamine causes a dose-dependent formation of inositol phosphates, production of diacylglycerol and a transient rise in intracellular [Ca2+]. These responses are completely blocked by the H1-receptor antagonist pyrilamine. In streptolysin-O-permeabilized cells, formation of inositol phosphates by histamine is strongly potentiated by guanosine 5'-[gamma-thio]triphosphate and inhibited by guanosine 5'-[beta-thio]diphosphate, suggesting the involvement of a GTP-binding protein. Histamine stimulates the rapid but transient formation of Ins(1,4,5)P3, Ins(1,3,4)P3 and InsP4. InsP accumulates in a much more persistent manner, lasting for at least 30 min. Studies with streptolysin-O-permeabilized cells indicate that InsP accumulation results from dephosphorylation of Ins(1,4,5)P3, rather than direct hydrolysis of PtdIns. The rise in intracellular [Ca2+] is biphasic, with a very fast release of Ca2+ from intracellular stores, that parallels the Ins(1,4,5)P3 time course, followed by a more prolonged phase of Ca2+ influx. In individual cells, histamine causes a rapid initial hyperpolarization of the plasma membrane, which can be mimicked by microinjected Ins(1,4,5)P3. Histamine-induced hyperpolarization is followed by long-lasting oscillations in membrane potential, apparently owing to periodic activation of Ca2+-dependent K+ channels. These membrane-potential oscillations can be mimicked by microinjection of guanosine 5'-[gamma-thio]triphosphate, but are not observed after microinjection of Ins(1,4,5)P3. We conclude that H1-receptors in HeLa cells activate a PtdInsP2-specific phospholipase C through participation of a specific G-protein, resulting in long-lasting oscillations of cytoplasmic free Ca2+.

SUBMITTER: Tilly BC

PROVIDER: S-EPMC1131120 | biostudies-other | 1990 Feb

REPOSITORIES: biostudies-other

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Project description:Cell-to-cell diffusion of second messengers across intercellular channels allows tissues to co-ordinate responses to extracellular stimuli. Intercellular diffusion of inositol 1,4,5-trisphosphate, locally produced by focal stimulations, sustains the propagation of intercellular Ca(2+) waves, by stimulating the release of intracellular Ca(2+) in neighbouring cells. We previously demonstrated that in cultured articular chondrocytes and HIG-82 synovial cells, studied with digitial fluorescence video imaging, mechanical stimulation of a single cell induced intercellular Ca(2+) waves dependent on the presence of gap junctions. In the absence of extracellular Ca(2+) the propagating distance of the wave decreased significantly in HIG-82 cells, but appeared unaffected in chondrocytes. We now show that both cells types express connexin 43 and a similar functional coupling, thus suggesting that the different Ca(2+) sensitivity of intercellular waves is not due to major differences in gap junction constituent proteins. In HIG-82 synoviocytes, but not in chondrocytes, the Ca(2+) ionophore ionomycin stimulated phosphoinositide hydrolysis in a concentration-dependent manner, an effect strictly dependent on the presence of extracellular Ca(2+), suggesting the expression, in these cells, of a Ca(2+)-sensitive phospholipase C activity. Such an activity could be stimulated also by Ca(2+) influx induced by P(2Y) receptor activation and considerably amplifies ATP-induced inositol phosphate (InsP) production. In contrast, Ca(2+) influx did not affect considerably the response of chondrocytes to ATP stimulation. In HIG-82 cells, the combined application of ionomycin and ATP maximally stimulated InsP synthesis, suggesting the involvement of two independent mechanisms in inositol phosphate generation. These results suggest that in HIG-82 synovial cells the recruitment of a Ca(2+)-sensitive phospholipase C activity could amplify the cell response to a focally applied extracellular stimulus, thus providing a positive feedback mechanism for intercellular wave propagation.

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Histamine-H1-receptor-mediated phosphoinositide hydrolysis, Ca2+ signalling and membrane-potential oscillations in human HeLa carcinoma cells.

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