title: High-content screening identifies a role for Na(+) channels in insulin production.
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.
authors.affiliation: Department of Cellular and Physiological Sciences University of British Columbia Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Marta
authors.initials: M
authors.lastname: Szabat
authors.affiliation: Department of Cellular and Physiological Sciences University of British Columbia Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Honey
authors.initials: H
authors.lastname: Modi
authors.affiliation: Oxford Centre for Diabetes Endocrinology and Metabolism University of Oxford Churchill Hospital, Headington OX3 7LE, UK.
authors.forename: Reshma
authors.initials: R
authors.lastname: Ramracheya
authors.affiliation: Institut für Pharmakologie und Toxikologie der Technischen Universität 80802 München, Germany.
authors.forename: Vroni
authors.initials: V
authors.lastname: Girbinger
authors.affiliation: Department of Cellular and Physiological Sciences University of British Columbia Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Forson
authors.initials: F
authors.lastname: Chan
authors.affiliation: Department of Cellular and Physiological Sciences University of British Columbia Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Jason T C
authors.initials: JT
authors.lastname: Lee
authors.affiliation: Department of Cellular and Physiological Sciences University of British Columbia Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Micah
authors.initials: M
authors.lastname: Piske
authors.affiliation: Department of Cellular and Physiological Sciences University of British Columbia Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Sepehr
authors.initials: S
authors.lastname: Kamal
authors.affiliation: Department of Cellular and Physiological Sciences University of British Columbia Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Yu Hsuan
authors.initials: YH
authors.lastname: Carol Yang
authors.affiliation: Institut für Pharmakologie und Toxikologie der Technischen Universität 80802 München, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Welling
authors.affiliation: Oxford Centre for Diabetes Endocrinology and Metabolism University of Oxford Churchill Hospital, Headington OX3 7LE, UK.
authors.forename: Patrik
authors.initials: P
authors.lastname: Rorsman
authors.affiliation: Department of Cellular and Physiological Sciences University of British Columbia Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: James D
authors.initials: JD
authors.lastname: Johnson
keywords: high-content screening; insulin synthesis; islet beta-cells; live-cell imaging; sodium channels