Pflügers Archiv - European Journal of Physiology

, Volume 467, Issue 12, pp 2461–2472 | Cite as

Ca2+ clearance by plasmalemmal NCLX, Li+-permeable Na+/Ca2+ exchanger, is required for the sustained exocytosis in rat insulinoma INS-1 cells

  • Young-Eun Han
  • Shin-Young Ryu
  • Sun-Hyun Park
  • Kyu-Hee Lee
  • Suk-Ho Lee
  • Won-Kyung HoEmail author
Ion channels, receptors and transporters


Na+/Ca2+ exchangers are key players for Ca2+ clearance in pancreatic β-cells, but their molecular determinants and roles in insulin secretion are not fully understood. In the present study, we newly discovered that the Li+-permeable Na+/Ca2+ exchangers (NCLX), which were known as mitochondrial Na+/Ca2+ exchangers, contributed to the Na+-dependent Ca2+ movement across the plasma membrane in rat INS-1 insulinoma cells. Na+/Ca2+ exchange activity by NCLX was comparable to that by the Na+/Ca2+ exchanger, NCX. We also confirmed the presence of NCLX proteins on the plasma membrane using immunocytochemistry and cell surface biotinylation experiments. We further investigated the role of NCLX on exocytosis function by measuring the capacitance increase in response to repetitive depolarization. Small interfering (si)RNA-mediated downregulation of NCLX did not affect the initial exocytosis, but significantly suppressed sustained exocytosis and recovery of exocytosis. XIP (NCX inhibitory peptide) or Na+ replacement for inhibiting Na+-dependent Ca2+ clearance also selectively suppressed sustained exocytosis. Consistent with the idea that sustained exocytosis requires ATP-dependent vesicle recruitment, mitochondrial function, assessed by mitochondrial membrane potential (ΔΨ), was impaired by siNCLX or XIP. However, depolarization-induced exocytosis was hardly affected by changes in intracellular Na+ concentration, suggesting a negligible contribution of mitochondrial Na+/Ca2+ exchanger. Taken together, our data indicate that Na+/Ca2+ exchanger-mediated Ca2+ clearance mediated by NCLX and NCX is crucial for optimizing mitochondrial function, which in turn contributes to vesicle recruitment for sustained exocytosis in pancreatic β-cells.


Ca2+ transport Na+/Ca2+ exchanger Exocytosis Capacitance Pancreatic β-cell 



This work was supported by the National Research Foundation of Korea (NRF) grant (No. 2014051826) funded by the Korea government Ministry of Science, ICT and Future Planning (MSIP)

Conflict of interest

The authors declare that they have no competing interest.

Supplementary material

424_2015_1715_MOESM1_ESM.pdf (260 kb)
ESM 1 (PDF 259 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Young-Eun Han
    • 1
  • Shin-Young Ryu
    • 1
  • Sun-Hyun Park
    • 1
  • Kyu-Hee Lee
    • 1
  • Suk-Ho Lee
    • 1
  • Won-Kyung Ho
    • 1
    Email author
  1. 1.Department of Physiology and Biomembrane Plasticity Research CenterSeoul National University College of MedicineSeoulRepublic of Korea

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