Sensitization of InsP3-dependent calcium signalling through structural modification of voltage-dependent calcium channel: a physiological relevance of the calcium channel beta subunit.
The expression in Xenopus oocytes of the human voltage-dependent Ca2+ channel (VDCC) beta 2 subunit subtype (h beta 2) enhances the endogenous Ca2+ channel activity. By using the native Ca(2+)-dependent chloride conductance to monitor fast intracellular Ca2+ variations, we point out that the beta-enhanced Ca2+ entry (T1 component) is currently associated with a second delayed elevation of internal Ca2+ (T2 component). Further experiments show that this additional component absolutely requires Ca2+ entry through the beta-modulated channels although it directly derives from a Ca2+ release from intracellular inositol (1,4,5)-trisphosphate (InsP3)-sensitive stores. Finally, our study demonstrates that InsP3-evoked response in oocytes is dramatically modified since it gains a new shape of voltage dependency directly derived from the beta-modified Ca2+ influx. The main conclusion is that the spatiotemporal pattern of InsP3-dependent Ca2+ release may be closely influenced by the intrinsic characteristics of working VDCCs.
Matifat
F
F
Laboratoire de Neurobiologie Cellulaire, Université de Picardie Jules Verne Faculté des Sciences, Amhiens, France.
Collin
T
T
Humez
S
S
Brûle
G
G
Fournier
F
F
D000818:Animals; D001483:Base Sequence; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000096:biosynthesis / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D017931:DNA Primers; D005260:Female; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D046911:Macromolecular Substances; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014982:Xenopus laevis
D015220:Calcium Channels; D002712:Chlorides; D017931:DNA Primers; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D002104:Cadmium; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002118:Calcium