Zinc transporters regulate subcellular zinc distributions with sharp transmembrane zinc gradients among intracellular organelles. The spatiotemporal zinc dynamics provides crucial cellular signaling opportunities, but also challenges intracellular zinc homeostasis with broad disease implications. Our long-term goal is to understand structures and mechanisms of zinc transporters and their functional regulations. This proposal is a competitive renewal of a continuing research project focusing on zinc-efflux transporters from the Cation Diffusion Facilitator (CDF) family. In the past decade, we have elucidated the molecular architecture, coordination chemistry and structural dynamics of a bacterial CDF homolog. While we are making progress on the basic research front, a human CDF, hZnT8 has been identified as a major autoantigen in type-1 diabetes as well as a major risk factor associated with type-2 diabetes. A critical barrier to therapeutic translation of hZnT8 is the lack of knowledge about the molecular mechanism responsible for diabetes association and the functional consequences of susceptibility hZnT8 variations. To fill in this knowledge gap, our research focus in the next budget cycle will shift from a bacterial CDF model to hZnT8 with four specific aims: (1) to understand the mechanism of allosteric regulation of zinc transport. (2) to characterize transport kinetics of purified hZnT8 and its genetic variants, (3) to define the functional roles of hZnT8 and its genetic variants in pancreatic beta cells, (4) to develop hZnT8-specifc mAbs and determine their effects on insulin storage and secretion. The planned research will revolve around functional regulation of CDFs to understand how allosteric regulation of zinc transport occurs in real time (aim-1), how hZnT8 is affected by diabetes-associated genetic variations (aim-2), how hZnT8 modulates vesicular zinc dynamics and insulin secretion in response to glucose stimulations (aim-3), and whether hZnT8 can be blocked by conformation-specific monoclonal antibodies targeting extracellular epitopes (aim-4). The knowledge gained will be used to elucidate the molecular underpinning of hZnT8-based diabetes therapy.

Public Health Relevance

The proposed research is to understand the molecular underpinning of hZnT8-based diabetes therapy, and to develop hZnT8-specific monoclonal antibodies that can be used for early diagnosis of type-1 diabetes and for potential treatments of type-2 diabetes by a novel allosteric inhibitory mechanism.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM065137-15
Application #
9042378
Study Section
Biochemistry and Biophysics of Membranes Study Section (BBM)
Program Officer
Chin, Jean
Project Start
2002-04-01
Project End
2019-03-31
Budget Start
2016-04-01
Budget End
2017-03-31
Support Year
15
Fiscal Year
2016
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Physiology
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21205
Merriman, Chengfeng; Huang, Qiong; Gu, Wei et al. (2018) A subclass of serum anti-ZnT8 antibodies directed to the surface of live pancreatic ?-cells. J Biol Chem 293:579-587
Merriman, Chengfeng; Li, Hua; Li, Huilin et al. (2018) Highly specific monoclonal antibodies for allosteric inhibition and immunodetection of the human pancreatic zinc transporter ZnT8. J Biol Chem 293:16206-16216
Wan, Hao; Merriman, Chengfeng; Atkinson, Mark A et al. (2017) Proteoliposome-based full-length ZnT8 self-antigen for type 1 diabetes diagnosis on a plasmonic platform. Proc Natl Acad Sci U S A 114:10196-10201
Huang, Qiong; Merriman, Chengfeng; Zhang, Hao et al. (2017) Coupling of Insulin Secretion and Display of a Granule-resident Zinc Transporter ZnT8 on the Surface of Pancreatic Beta Cells. J Biol Chem 292:4034-4043
Merriman, Chengfeng; Huang, Qiong; Rutter, Guy A et al. (2016) Lipid-tuned Zinc Transport Activity of Human ZnT8 Protein Correlates with Risk for Type-2 Diabetes. J Biol Chem 291:26950-26957
Fu, Dax; Finney, Lydia (2014) Metalloproteomics: challenges and prospective for clinical research applications. Expert Rev Proteomics 11:13-9
Gupta, Sayan; Chai, Jin; Cheng, Jie et al. (2014) Visualizing the kinetic power stroke that drives proton-coupled zinc(II) transport. Nature 512:101-4
Hoch, Eitan; Lin, Wei; Chai, Jin et al. (2012) Histidine pairing at the metal transport site of mammalian ZnT transporters controls Zn2+ over Cd2+ selectivity. Proc Natl Acad Sci U S A 109:7202-7
Lin, Wei; Chai, Jin; Love, James et al. (2010) Selective electrodiffusion of zinc ions in a Zrt-, Irt-like protein, ZIPB. J Biol Chem 285:39013-20
Lu, Min; Chai, Jin; Fu, Dax (2009) Structural basis for autoregulation of the zinc transporter YiiP. Nat Struct Mol Biol 16:1063-7

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