Modulation of N-type calcium channels translocation in RINm5F insulinoma cells.
An intracellular pool of N-type voltage-operated calcium channels has recently been described in both IMR32 human neuroblastoma and PC12 rat pheochromocytoma cells. These channels were found to be accumulated in subcellular fractions where the chromogranin B-containing secretory granules were also enriched. Upon exocytosis N-type calcium channels were reversibly inserted in the plasma membrane. We have now extended this study to RINm5F rat insulinoma cells, and characterized the parallelism between the 'regulated' secretion of serotonin and the recruitment of surface calcium channels. Exocytosis was stimulated by different means, such as depolarization with high KCl, high Ba(2+)alone or protein kinase C activation; on the other hand exocytosis was inhibited with the non-selective calcium channel antagonist Cd(2+)or with noradrenaline. Stimulated release was always accompanied, with parallel kinetics, by calcium channel recruitment, while inhibition of secretion blocked calcium channel recruitment too. During repetitive depolarizations we revealed a potentiation of [Ca(2+)]()i transients in single Fura-2 loaded RINm5F cells, that was accompanied by an increase in surface VOCCs, suggesting a physiological role for the newly recruited channels. 2000 Academic Press@p$hr
Passafaro
M
M
Department of Medical Pharmacology, CNR Molecular and Cellular Pharmacology Center, University of Milan, Milan, 20129, Italy.
Codignola
A
A
Rogers
M
M
Cooke
I
I
Sher
E
E
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000187:drug effects / Q000378:metabolism*; D004347:Drug Interactions; D006801:Humans; D007340:Insulinoma / Q000378:metabolism* / Q000473:pathology; D009281:Naphthalenes / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D016716:PC12 Cells; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured
D000903:Antibiotics, Antineoplastic; D020864:Calcium Channels, N-Type; D009281:Naphthalenes; D002104:Cadmium; D012701:Serotonin; D011189:Potassium Chloride; C058819:calphostin C; D002118:Calcium; D009638:Norepinephrine