title: Lipid-tuned Zinc Transport Activity of Human ZnT8 Protein Correlates with Risk for Type-2 Diabetes.
abstract: Zinc is a critical element for insulin storage in the secretory granules of pancreatic beta cells. The islet-specific zinc transporter ZnT8 mediates granular sequestration of zinc ions. A genetic variant of human ZnT8 arising from a single nonsynonymous nucleotide change contributes to increased susceptibility to type-2 diabetes (T2D), but it remains unclear how the high risk variant (Arg-325), which is also a higher frequency (>50%) allele, is correlated with zinc transport activity. Here, we compared the activity of Arg-325 with that of a low risk ZnT8 variant (Trp-325). The Arg-325 variant was found to be more active than the Trp-325 form following induced expression in HEK293 cells. We further examined the functional consequences of changing lipid conditions to mimic the impact of lipid remodeling on ZnT8 activity during insulin granule biogenesis. Purified ZnT8 variants in proteoliposomes exhibited more than 4-fold functional tunability by the anionic phospholipids, lysophosphatidylcholine and cholesterol. Over a broad range of permissive lipid compositions, the Arg-325 variant consistently exhibited accelerated zinc transport kinetics versus the Trp-form. In agreement with the human genetic finding that rare loss-of-function mutations in ZnT8 are associated with reduced T2D risk, our results suggested that the common high risk Arg-325 variant is hyperactive, and thus may be targeted for inhibition to reduce T2D risk in the general populations.
authors.affiliation: From the Department of Physiology, The Johns Hopkins School of Medicine, Baltimore, Maryland 21205 and.
authors.forename: Chengfeng
authors.initials: C
authors.lastname: Merriman
authors.affiliation: From the Department of Physiology, The Johns Hopkins School of Medicine, Baltimore, Maryland 21205 and.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Huang
authors.affiliation: the Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London W12 ONN, United Kingdom.
authors.forename: Guy A
authors.initials: GA
authors.lastname: Rutter
authors.affiliation: From the Department of Physiology, The Johns Hopkins School of Medicine, Baltimore, Maryland 21205 and dfu3@jhmi.edu.
authors.forename: Dax
authors.initials: D
authors.lastname: Fu
mesh_terms: D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000209:etiology* / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007328:Insulin / Q000378:metabolism; D008244:Lysophosphatidylcholines / Q000378:metabolism*; D009154:Mutation / Q000235:genetics*; D010743:Phospholipids / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*; D000075703:Zinc Transporter 8
chemical_list: D027682:Cation Transport Proteins; D007328:Insulin; D008244:Lysophosphatidylcholines; D010743:Phospholipids; C492522:SLC30A8 protein, human; D000075703:Zinc Transporter 8; D002784:Cholesterol; D015032:Zinc
keywords: diabetes; drug discovery; genetic polymorphism; kinetics; membrane transporter reconstitution; transporter; zinc