title: Calcium-sensing receptor activation increases cell-cell adhesion and β-cell function.
abstract: OBJECTIVE
  The extracellular calcium-sensing receptor (CaR) is expressed in pancreatic β-cells where it is thought to facilitate cell-to-cell communication and augment insulin secretion. However, it is unknown how CaR activation improves β-cell function.
  
  
  METHODS
  Immunocytochemistry and western blotting confirmed the expression of CaR in MIN6 β-cell line. The calcimimetic R568 (1µM) was used to increase the affinity of the CaR and specifically activate the receptor at a physiologically appropriate extracellular calcium concentration. Incorporation of 5-bromo-2'-deoxyuridine (BrdU) was used to measure cell proliferation, whilst changes in non-nutrient-evoked cytosolic calcium were assessed using fura-2-microfluorimetry. AFM-single-cell-force spectroscopy related CaR-evoked changes in epithelial (E)-cadherin expression to improved functional tethering between coupled cells.
  
  
  RESULTS
  Activation of the CaR over 48hr doubled the expression of E-cadherin (206±41%) and increased L-type voltage-dependent calcium channel expression by 70% compared to control. These changes produced a 30% increase in cell-cell tethering and elevated the basal-to-peak amplitude of ATP (50µM) and tolbutamide (100µM)-evoked changes in cytosolic calcium. Activation of the receptor also increased PD98059 (1-100µM) and SU1498 (1-100µM)-dependent β-cell proliferation.
  
  
  CONCLUSIONS
  Our data suggest that activation of the CaR increases E-cadherin mediated functional tethering between β-cells and increases expression of L-type VDCC and secretagogue-evoked changes in [Ca(2+)](i). These findings could explain how local changes in calcium, co-released with insulin, activate the CaR on neighbouring cells to help ensure efficient and appropriate secretory function.
authors: Schools of Life Sciences, University of Warwick, Coventry, UK.
authors: Claire E
authors: CE
authors: Hills
authors: Mustafa Y G
authors: MY
authors: Younis
authors: Jeanette
authors: J
authors: Bennett
authors: Eleftherios
authors: E
authors: Siamantouras
authors: Kuo-Kang
authors: KK
authors: Liu
authors: Paul E
authors: PE
authors: Squires
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D057966:Calcimimetic Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002934:Cinnamates / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007150:Immunohistochemistry; D050417:Insulin-Secreting Cells / Q000378:metabolism; D051379:Mice; D044169:Receptors, Calcium-Sensing / Q000378:metabolism*; D014044:Tolbutamide / Q000494:pharmacology
chemical_list: D015820:Cadherins; D057966:Calcimimetic Agents; D020746:Calcium Channels, L-Type; D002934:Cinnamates; D005419:Flavonoids; D007004:Hypoglycemic Agents; D044169:Receptors, Calcium-Sensing; C483044:SU 1498; D000255:Adenosine Triphosphate; D014044:Tolbutamide; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium