title: Glucose-mediated spatial interactions of voltage dependent calcium channels and calcium sensing receptor in insulin producing β-cells.
abstract: OBJECTIVE
  The voltage dependent calcium channel (VDCC) e.g., L-type VDCC plays critical roles in the spatio-temporal regulation of intracellular calcium concentration ([Ca(2+)](i)) and insulin secretion by β-cell. This study describes the involvement of 2.5 to 15mM glucose-induced spatial interactions between a calcium sensing receptor (CaR) and L-type VDCC in controlling Ca(2+) channel activity and insulin secretion in β-cells in association with the nuclear translocation of a transcription factor nuclear factor kappa B (NF-κB).
  
  
  METHODS
  The insulin producing β-cells were exposed to 2.5, 5, 7.5, 10, and 15 mM glucose for 24 h at 37 °C. The confocal fluorescence imaging data was obtained by using antibodies against CaR and L-type VDCC. The nuclear translocation of NF-κB was measured by confocal fluorescence imaging using antibody against NF-κB. The insulin release was determined by enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  The confocal imaging data showed 6 to 12-fold enhancement in the colocalization correlation coefficient between CaR and VDCC in β-cells exposed to glucose thereby indicating increased membrane delimited spatial interactions between these two membrane proteins. The confocal fluorescence imaging data showed that addition of glucose to β-cells led to 1.8 to 2.7-fold increase in the nuclear translocation of NF-κB. The insulin ELISA data showed a significant increase in the 1st phase of glucose-induced insulin secretion in β-cells exposed to increasing concentrations of glucose.
  
  
  CONCLUSIONS
  The results described in the present study further strengthen that VDCC and CaR can interact spatially to allow control over calcium channel activity and therefore glucose-induced insulin secretion by β-cells.
authors.affiliation: Robert Stempel College of Public Health and Social Work, Department of Environmental and Occupational Health, Florida International University, Miami, FL 33199, USA. parkashj@fiu.edu
authors.forename: Jai
authors.initials: J
authors.lastname: Parkash
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000378:metabolism* / Q000502:physiology*; D018613:Microscopy, Confocal; D051381:Rats; D044169:Receptors, Calcium-Sensing / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D007328:Insulin; D044169:Receptors, Calcium-Sensing; D005947:Glucose