Intracellular calcium ion response to glucose in beta-cells of calbindin-D28k nullmutant mice and in betaHC13 cells overexpressing calbindin-D28k

• Published in: Endocrine Vol. 18; no. 3; pp. 221 - 229
• Main Authors: Parkash, Jai, Chaudhry, Muhammad A, Amer, Ayman S, Christakos, Sylvia, Rhoten, William B
• Format: Journal Article
• Language: English
• Published: United States 01.08.2002
• Subjects: Animals; Calbindin 1; Calbindins; Calcium - metabolism; Calcium Channels, L-Type - metabolism; Cell Line; Glucose - pharmacology; In Vitro Techniques; Insulin - metabolism; Intracellular Membranes - metabolism; Islets of Langerhans - drug effects; Islets of Langerhans - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout - genetics; S100 Calcium Binding Protein G - genetics; S100 Calcium Binding Protein G - metabolism; Space life sciences; Tissue Distribution; Non-programmatic
• ISSN: 1355-008X

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.