title: Intracellular calcium ion response to glucose in beta-cells of calbindin-D28k nullmutant mice and in betaHC13 cells overexpressing calbindin-D28k.
abstract: This article describes studies on the glucose-induced responses of intracellular Ca2+ concentration ([Ca2+]i), insulin release, and redistribution of calbindin-D28k, a calcium-binding regulatory protein, in beta-cells of pancreatic islets of calbindin-D28k knockout (KO) and wild-type mice (C57BL6) as well as in betaHC-13 control cells and betaHC-13 CaBP40 cells (beta-cell line overexpressing calbindin-D28k). Upon increasing the glucose concentration from 2.8 to 30 mM, islets of KO mice showed a significantly greater increase in [Ca2+]i (mean increase in [Ca2+]i, i.e., delta[Ca2+]i, was 296 nM) compared with wild-type mice (delta[Ca2+]i = 97 nM). betaHC-13 CaBP40 cells showed little change in [Ca2+]i upon elevation of glucose from 5.5 to 32.7 mM, whereas betaHC-13 control cells exhibited significant increases in [Ca2+]i, (delta[Ca2+]i = 510 nM). Similarly, upon addition of 30 mM glucose, the rate of insulin release increased from 25.2 (basal rate) to 145.2 pg/mL/min in betaHC-13 control cells, whereas in betaHC-13 CaBP40 cells the rate of insulin release was only 27.5 pg/mL/min in high glucose. Thus, levels of calbindin-D28k in beta-cells affect both [Ca2+]i and insulin secretion in response to glucose. The three-dimensional reconstruct of confocal immunofluorescent images showed that glucose caused redistribution of calbindin-D28k resulting in co-localization in the region of L-type voltage-dependent calcium channels (VDCC). This co-localization may be an important regulatory function concerning Ca2+ influx via L-type VDCC and exocytosis of insulin granules.
authors.affiliation: Department of Anatomy, Cell and Neurobiology, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25704-9388, USA. parkash@marshall.edu
authors.forename: Jai
authors.initials: J
authors.lastname: Parkash
authors.forename: Muhammad A
authors.initials: MA
authors.lastname: Chaudhry
authors.forename: Ayman S
authors.initials: AS
authors.lastname: Amer
authors.forename: Sylvia
authors.initials: S
authors.lastname: Christakos
authors.forename: William B
authors.initials: WB
authors.lastname: Rhoten
mesh_terms: D000818:Animals; D064092:Calbindin 1; D064026:Calbindins; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002460:Cell Line; D005947:Glucose / Q000494:pharmacology*; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism*; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout / Q000235:genetics; D064030:S100 Calcium Binding Protein G / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: C576499:Calb1 protein, mouse; D064092:Calbindin 1; D064026:Calbindins; D020746:Calcium Channels, L-Type; D007328:Insulin; D064030:S100 Calcium Binding Protein G; D005947:Glucose; D002118:Calcium