title: The human L-type calcium channel Cav1.3 regulates insulin release and polymorphisms in CACNA1D associate with type 2 diabetes.
abstract: OBJECTIVE
  Voltage-gated calcium channels of the L-type have been shown to be essential for rodent pancreatic beta cell function, but data about their presence and regulation in humans are incomplete. We therefore sought to elucidate which L-type channel isoform is functionally important and its association with inherited diabetes-related phenotypes.
  
  
  METHODS
  Beta cells of human islets from cadaver donors were enriched using FACS to study the expression of the genes encoding voltage-gated calcium channel (Cav)1.2 and Cav1.3 by absolute quantitative PCR in whole human and rat islets, as well as in clonal cells. Single-cell exocytosis was monitored as increases in cell capacitance after treatment with small interfering (si)RNA against CACNA1D (which encodes Cav1.3). Three single nucleotide polymorphisms (SNPs) were genotyped in 8,987 non-diabetic and 2,830 type 2 diabetic individuals from Finland and Sweden and analysed for associations with type 2 diabetes and insulin phenotypes.
  
  
  RESULTS
  In FACS-enriched human beta cells, CACNA1D mRNA expression exceeded that of CACNA1C (which encodes Cav1.2) by approximately 60-fold and was decreased in islets from type 2 diabetes patients. The latter coincided with diminished secretion of insulin in vitro. CACNA1D siRNA reduced glucose-stimulated insulin release in INS-1 832/13 cells and exocytosis in human beta cells. Phenotype/genotype associations of three SNPs in the CACNA1D gene revealed an association between the C allele of the SNP rs312480 and reduced mRNA expression, as well as decreased insulin secretion in vivo, whereas both rs312486/G and rs9841978/G were associated with type 2 diabetes.
  
  
  CONCLUSIONS
  We conclude that the L-type calcium channel Cav1.3 is important in human glucose-induced insulin secretion, and common variants in CACNA1D might contribute to type 2 diabetes.
authors.affiliation: Department of Clinical Sciences, Islet Pathophysiology, Lund University Diabetes Centre, Jan Waldenströms gata 35, , Malmö, Sweden. thomas.reinbothe@med.lu.se
authors.forename: T M
authors.initials: TM
authors.lastname: Reinbothe
authors.forename: S
authors.initials: S
authors.lastname: Alkayyali
authors.forename: E
authors.initials: E
authors.lastname: Ahlqvist
authors.forename: T
authors.initials: T
authors.lastname: Tuomi
authors.forename: B
authors.initials: B
authors.lastname: Isomaa
authors.forename: V
authors.initials: V
authors.lastname: Lyssenko
authors.forename: E
authors.initials: E
authors.lastname: Renström
mesh_terms: D000328:Adult; D020746:Calcium Channels, L-Type / Q000235:genetics* / Q000378:metabolism*; D002478:Cells, Cultured; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*
chemical_list: C472073:CACNA1D protein, human; D020746:Calcium Channels, L-Type; D007328:Insulin