Pancreatic ?-cells secrete insulin to maintain glucose homeostasis. The secretory activity of ?-cells is under the control of a constellation of ion channels. The long-term goal of this project is to understand how ion channels are regulated in ?-cells and how these regulations impact insulin secretion in health and disease. For the past 15 years of this project we have focused exclusively on the ATP-sensitive potassium (KATP) channel, which plays a key role in coupling glucose metabolism to ?-cell excitability. In this application, we have expanded our focus to include the voltage-gated delayed rectifier Kv2.1 channels, which are critical for repolarizing ?-cell membrane potential following action potential firing. This new focus is based on our recent finding that KATP and Kv2.1 channel densities in the ?-cell membrane are dynamically and concurrently regulated by the adipocyte-derived hormone leptin, which is known to suppress insulin secretion. We showed that leptin selectively recruits KATP and Kv2.1 channels to the ?-cell membrane via a common signaling mechanism dependent on the AMP-activated protein kinase (AMPK), cAMP-dependent protein kinase (PKA), and actin depolymerization. The goal of this renewal application is to build on the new, exciting research direction we have developed and further elucidate the signaling and cellular mechanisms by which leptin regulates trafficking of ?-cell KATP and Kv2.1 channels. Based on compelling preliminary data we hypothesize that leptin regulates trafficking of KATP and Kv2.1 channels in a concerted manner via a signaling mechanism involving the NMDA-subtype ionotropic glutamate receptor (NMDA receptor), the Ca2+/calmodulin dependent kinase CaMKK?, AMPK, PKA, and actin remodeling to achieve coordinated control of insulin secretion, and that this regulatory mechanism is lost in type 2 diabetic ?-cells. Three interrelated specific aims are proposed to test the hypothesis. (1) Elucidating the role of NMDA receptors in KATP and Kv2.1 channel trafficking regulation in ?-cells. (2) Mapping the leptin signaling network that regulates KATP and Kv2.1 channel trafficking, in particular focusing on dissecting the relationship between AMPK, PKA, and their downstream targets. (3) Identifying the subcellular vesicular localizations of KATP and Kv2.1 channels that underlie trafficking co-regulation by leptin. We will employ an integrated research design combining state-of-the-art electrophysiology, imaging, and proteomics techniques using both a ?-cell line model as well as primary human ?- cells from healthy and diabetic donors, to accomplish these aims. The research is innovative in testing the novel concept that trafficking regulation of KATP and Kv2.1 channels by leptin is a physiological mechanism to control insulin secretion and that defects in this mechanism may contribute to the pathogenesis of type 2 diabetes. As such, the research is highly significant to both basic science and human health. Successful outcome will significantly advance the scientific knowledge on this relatively new topic in the ?-cell biology/diabetes research field. The knowledge obtained will enable us to manipulate the system to better control insulin secretion and overcome metabolic diseases related to unbalanced insulin/leptin secretion or signaling.

Public Health Relevance

Regulated insulin secretion from pancreatic ?-cells in response to blood glucose levels and other hormonal signals maintains glucose in a physiological range. The goal of this project is to gain a thorough understanding of the molecular mechanisms by which the hormone leptin regulates insulin secretion and how the mechanisms are altered in diabetic ?-cells. The research may lead to novel prevention or therapeutic strategies for type 2 diabetes and related metabolic diseases.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Study Section
Cellular Aspects of Diabetes and Obesity Study Section (CADO)
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Sato, Sheryl M
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Oregon Health and Science University
Other Basic Sciences
Schools of Medicine
United States
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Kandasamy, Balamurugan; Shyng, Show-Ling (2018) Methods for Characterizing Disease-Associated ATP-Sensitive Potassium Channel Mutations. Methods Mol Biol 1684:85-104
Shyng, Show-Ling (2017) Targeting the Gut Microbiota-FXR Signaling Axis for Glycemic Control: Does a Dietary Supplement Work Magic? Diabetes 66:571-573
Wu, Yi; Fortin, Dale A; Cochrane, Veronica A et al. (2017) NMDA receptors mediate leptin signaling and regulate potassium channel trafficking in pancreatic ?-cells. J Biol Chem 292:15512-15524
Martin, Gregory M; Rex, Emily A; Devaraneni, Prasanna et al. (2016) Pharmacological Correction of Trafficking Defects in ATP-sensitive Potassium Channels Caused by Sulfonylurea Receptor 1 Mutations. J Biol Chem 291:21971-21983
Saint-Martin, C; Zhou, Q; Martin, G M et al. (2015) Monoallelic ABCC8 mutations are a common cause of diazoxide-unresponsive diffuse form of congenital hyperinsulinism. Clin Genet 87:448-54
Wu, Yi; Shyng, Show-Ling; Chen, Pei-Chun (2015) Concerted Trafficking Regulation of Kv2.1 and KATP Channels by Leptin in Pancreatic ?-Cells. J Biol Chem 290:29676-90
Devaraneni, Prasanna K; Martin, Gregory M; Olson, Erik M et al. (2015) Structurally distinct ligands rescue biogenesis defects of the KATP channel complex via a converging mechanism. J Biol Chem 290:7980-91
Zhou, Qing; Chen, Pei-Chun; Devaraneni, Prasanna K et al. (2014) Carbamazepine inhibits ATP-sensitive potassium channel activity by disrupting channel response to MgADP. Channels (Austin) 8:376-82
Zhou, Qing; Chen, Pei-Chun; Devaraneni, Prasanna K et al. (2014) Carbamazepine inhibits ATP-sensitive potassium channel activity by disrupting channel response to MgADP. Channels (Austin) 8:376-82
Faletra, Flavio; Snider, Kara; Shyng, Show-Ling et al. (2013) Co-inheritance of two ABCC8 mutations causing an unresponsive congenital hyperinsulinism: clinical and functional characterization of two novel ABCC8 mutations. Gene 516:122-5

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