Calcium-sensing receptor activation increases cell-cell adhesion and ß-cell function

Article English OPEN
Hills, Claire E. ; Younis, Mustafa Y. G. ; Bennett, Jeanette ; Siamantouras, Eleftherios ; Liu, Kuo-Kang ; Squires, Paul E.

Background/Aims: 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. Conclusion: 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 [Ca2+]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.
  • References (10)

    10. Gray E, Squires PE, Muller D, Asare-Anane H, Cai Huang G, Amiel S, Persaud SJ, Jones PM: Activation of the extracellular calcium sensing receptor initiates insulin secretion from human islets of Langerhans: involvement of protein kinases. J Endocrinol 2006; 190: 711- 718.

    11. Squires PE: Non Ca2+-homeostatic functions of the extracellular Ca2+-sensing receptor (CaR) in endocrine tissues. J Endocrinology 2000; 165: 173-177.

    12. Hodgkin MN, Hills CE, Squires PE: The calcium-sensing receptor and insulin secretion: a role outside systemic control 15years on. J Endocrinol 2008; 199: 1-4.

    13. Bruce JI, Yang X, Ferguson CJ, Elliott AC, Steward MC, Case RM, Riccari D: Molecular and functional identification of a Ca2+ (polyvalent cation)-sensing receptor in rat pancreas. J Biol Chem 1999; 274: 20561-20568.

    14. Ray JM, Squires PE, Curtis SB, Meloche RM, Buchan AMJ: Expression of the calciumsensing receptor on human antral gastrin cells in culture. J Clin Invest 1997; 99: 2328-2333.

    15. Buchan AMJ, Squires PE, Ring M, Meloche RM: Mechanism of action of the calciumsensing receptor in human antral gastrin cells. Gastroenterology 2001; 120: 1128-1139.

    16. Squires PE, Meloche RM, Buchan AMJ: Bombesin-evoked gastrin release and calcium signaling in human antral G-cells in culture. Am J Physiol 1999; 276: G227-G237.

    17. Hofer AM, Curci S, Doble MA, Brown EM, Soybel DI: Intercellular communication mediated by the extracellular calcium-sensing receptor. Nature Cell Biol 2000; 2: 392-398.

    18. Hofer AM, Gerbino A, Caroppo R, Curci S: The extracellular calcium-sensing receptor and cell-cell signalling in epithelia. Cell Calcium 2004; 35: 297-306.

    19. Rogers GJ, Hodgkin MN, Squires PE: E-cadherin and cell adhesion: a role in architecture and function in the pancreatic islet. Cell Physiol Biochem 2007; 20: 987-994.

  • Metrics
    No metrics available
Share - Bookmark