High-content screening identifies a role for Na+ channels in insulin production. Issue 12 (December 2015)

• Record Type: Journal Article
• Authors: Szabat, Marta; Modi, Honey; Ramracheya, Reshma; Girbinger, Vroni; Chan, Forson; Lee, Jason T. C.; Piske, Micah; Kamal, Sepehr; Carol Yang, Yu Hsuan; Welling, Andrea; Rorsman, Patrik; Johnson, James D.
• Is Part Of: Royal Society open science. Volume 2:Issue 12(2015)
• Publication Date: 2015-12
• Subjects: islet beta-cells -- insulin synthesis -- live-cell imaging -- sodium channels -- high-content screening; Science -- Periodicals; 500
• DOI: 10.1098/rsos.150306
• Languages: English
• ISSNs: 2054-5703

Abstract

Abstract : Insulin production is the central feature of functionally mature and differentiated pancreatic β -cells. Reduced insulin transcription and dedifferentiation have been implicated in type 2 diabetes, making drugs that could reverse these processes potentially useful. We have previously established ratiometric live-cell imaging tools to identify factors that increase insulin promoter activity and promote β -cell differentiation. Here, we present a single vector imaging tool with eGFP and mRFP, driven by the Pdx1 and Ins1 promoters, respectively, targeted to the nucleus to enhance identification of individual cells in a high-throughput manner. Using this new approach, we screened 1120 off-patent drugs for factors that regulate Ins1 and Pdx1 promoter activity in MIN6 β -cells. We identified a number of compounds that positively modulate Ins1 promoter activity, including several drugs known to modulate ion channels. Carbamazepine was selected for extended follow-up, as our previous screen also identified this use-dependent sodium channel inhibitor as a positive modulator of β -cell survival. Indeed, carbamazepine increased Ins1 and Ins2 mRNA in primary mouse islets at lower doses than were required to protect β -cells. We validated the role of sodium channels in insulin production by examining Nav1.7 ( Scn9a ) knockout mice and remarkably islets from these animals had dramatically elevated insulin content relative to wild-type controls. Collectively, our experiments provide a starting point for additional studies aimed to identify drugs and molecular pathways that control insulin production and β -cell differentiation status. In particular, our unbiased screen identified a novel role for a β -cell sodium channel gene in insulin production.