Ca v 1.3 is preferentially coupled to glucose-stimulated insulin secretion in the pancreatic beta-cell line INS-1.
L-Type Ca(2+) channel blockers inhibit glucose and KCl-stimulated insulin secretion by pancreatic beta cells. However, the role of the two distinct L-type channels expressed by beta cells, Ca(v)1.2 and Ca(v)1.3, in this process is not clear. Therefore, we stably transfected INS-1 cells with two mutant channel constructs, Ca(v)1.2DHPi or Ca(v)1.3 DHPi. Whole-cell patch-clamp recordings demonstrated that both mutant channels are insensitive to dihydropyridines (DHPs), but are blocked by diltiazem. INS-1 cells expressing Ca(v)1.3/DHPi maintained glucose- and KCl-stimulated insulin secretion in the presence of DHPs, whereas cells expressing Ca(v)1.2/DHPi demonstrated DHP resistance to only KCl-induced secretion. INS-1 cells were also stably transfected with cDNAs encoding the intracellular loop between domains II and III of either Ca(v)1.2 or Ca(v)1.3 (Ca(v)1.2/II-III or Ca(v)1.3/II-III). Glucose- and KCl-stimulated insulin secretion in Ca(v)1.2/II-III cells were not different from untransfected INS-1 cells. However, glucose-stimulated insulin secretion was completely inhibited and KCl-stimulated secretion was substantially resistant to inhibition by DHPs, but sensitive to omega-agatoxin IVA in Ca(v)1.3/II-III cells. Moreover, the L-type channel agonist FPL 64176 markedly enhanced KCl-stimulated secretion by Ca(v)1.3/II-III cells. Together, our results suggest that Ca(2+) influx via Ca(v)1.3 is preferentially coupled to glucose-stimulated insulin secretion in INS-1 cells.
Liu
Guohong
G
Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana.
Dilmac
Nejmi
N
Hilliard
Nathan
N
Hockerman
Gregory H
GH
D020746:Calcium Channels, L-Type / Q000502:physiology*; D002460:Cell Line; D004095:Dihydropyridines / Q000494:pharmacology; D005947:Glucose / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism* / Q000502:physiology; D017434:Protein Structure, Tertiary
D020746:Calcium Channels, L-Type; D004095:Dihydropyridines; D007328:Insulin; C419385:L-type calcium channel alpha(1C); C038806:1,4-dihydropyridine; D005947:Glucose