Differential cytolocation and functional assays of the two major SLC30A8 (ZnT8) isoforms

TY - JOUR

T1 - Differential cytolocation and functional assays of the two major SLC30A8 (ZnT8) isoforms

AU - Carvalho, Sandra

AU - Molina-López, Jorge

AU - Parsons, Douglas

AU - Corpe, Christopher

AU - Maret, Wolfgang

AU - Hogstrand, Christer

PY - 2017/12

Y1 - 2017/12

N2 - The non-synonymous single nucleotide polymorphism (SNP) rs13266634 in human zinc transporter 8, ZnT8 (SLC30A8), leads to a R325 variant, which is associated with an increased risk of developing Type 2 Diabetes (T2D). Although the molecular details remain unknown, the mutation is thought to alter the kinetics of zinc transport into insulin granules in pancreatic β-cells. Nevertheless, analysis of ZnT8 sequences from several animals shows that the amino acid at position 325 is poorly conserved. Apart from this particular SNP, human ZnT8 also has two isoforms (splice variants) that differ in length regarding a 49 amino acid N-terminal extension. When expressed in human embryonic kidney (HEK293) cells, the long isoform was present in the plasma membrane in addition to internal membranes, whereas the short isoform was localized mostly to internal membranes. Our observation that human ZnT8 variants and isoforms expressed in Xenopus laevis oocytes are all localized at the cell surface allowed us to develop a zinc transport assay using the radioactive isotope 65Zn. We found no detectable differences in zinc transport between W and R variants and no statistically significant differences between long and short isoforms of the W325 variant. Our findings of different cytolocation of ZnT8 isoforms could be relevant for β-cell zinc metabolism in health and disease.

AB - The non-synonymous single nucleotide polymorphism (SNP) rs13266634 in human zinc transporter 8, ZnT8 (SLC30A8), leads to a R325 variant, which is associated with an increased risk of developing Type 2 Diabetes (T2D). Although the molecular details remain unknown, the mutation is thought to alter the kinetics of zinc transport into insulin granules in pancreatic β-cells. Nevertheless, analysis of ZnT8 sequences from several animals shows that the amino acid at position 325 is poorly conserved. Apart from this particular SNP, human ZnT8 also has two isoforms (splice variants) that differ in length regarding a 49 amino acid N-terminal extension. When expressed in human embryonic kidney (HEK293) cells, the long isoform was present in the plasma membrane in addition to internal membranes, whereas the short isoform was localized mostly to internal membranes. Our observation that human ZnT8 variants and isoforms expressed in Xenopus laevis oocytes are all localized at the cell surface allowed us to develop a zinc transport assay using the radioactive isotope 65Zn. We found no detectable differences in zinc transport between W and R variants and no statistically significant differences between long and short isoforms of the W325 variant. Our findings of different cytolocation of ZnT8 isoforms could be relevant for β-cell zinc metabolism in health and disease.

KW - Zinc

KW - vesicular CDF transporters

KW - ZnT8

KW - β-cell insulin granules

KW - diabetes

U2 - 10.1016/j.jtemb.2017.06.001

DO - 10.1016/j.jtemb.2017.06.001

M3 - Article

SN - 0946-672X

VL - 44

SP - 116

EP - 124

JO - Journal of Trace Elements in Medicine and Biology

JF - Journal of Trace Elements in Medicine and Biology

ER -