SLC30A8 encodes the Β-cell-specific zinc transporter-8 (ZnT-8) expressed in insulin secretory granules. The single-nucleotide polymorphism rs13266634 of SLC30A8 is associated with susceptibility to post-transplantation diabetes mellitus (PTDM). We tested the hypothesis that the polymorphic residue at position 325 of ZnT-8 determines the susceptibility to cyclosporin A (CsA) suppression of insulin secretion. INS (insulinoma)-1E cells expressing the W325 variant showed enhanced glucose-stimulated insulin secretion (GSIS) and were less sensitive to CsA suppression of GSIS. A reduced number of insulin granule fusion events accompanied the decrease in insulin secretion in CsA-treated cells expressing ZnT-8 R325; however, ZnT-8 W325-expressing cells exhibited resistance to the dampening of insulin granule fusion by CsA, and transported zinc ions into secretory vesicles more efficiently. Both tacrolimus and rapamycin caused similar suppression of GSIS in cells expressing ZnT-8 R325. However, cells expressing ZnT-8 W325 were resistant to tacrolimus, but not to rapamycin. The Down's syndrome candidate region-1 (DSCR1), an endogenous calcineurin inhibitor, overexpression and subsequent calcineurin inhibition significantly reduced GSIS in cells expressing the R325 but not the W325 variant, suggesting that differing susceptibility to CsA may be due to different interactions with calcineurin. These data suggest that the ZnT-8 W325 variant is protective against CsA-induced suppression of insulin secretion. Tolerance of ZnT-8 W325 to calcineurin activity may account for its protective effect in PTDM.
Bibliographical noteFunding Information:
We are grateful to Dr Fabrice Chimienti (Mellitech) for the ZnT-8-R325-EGFP construct, to Dr Claes Wollheim (University of Geneva) for the INS-1E cells and to Dr Young-Jin Cho (Catholic University, Korea) for the DSCR1-CT construct. We thank Dr Sang Sun Yoon for reading the manuscript. This study was supported by the Korea Science and Engineering Foundation (KOSEF) funded by the Korean Government (MEST) (2010-0001665) (to CH Kim), by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science, and Technology (No. 2009-0074746) (to CH Kim), by Korea Research Foundation Grant KRF-2008-331-E00118 (to ES Kang), funded by the Korean Government (MOEHRD Basic Research Promotion Fund) and by a grant from the Korean Diabetes Association (2007) (to ES Kang).
All Science Journal Classification (ASJC) codes
- Molecular Medicine