Examination of Cholesterol Dependent Regulation of SUR2 in HL-1 Cardiomyocytes, and Assessment of KATP Function and COVID-19 Related Drugs in hiPSC-Cardiomyocytes
Abstract
The ATP sensitive potassium channel (KATP) is a unique ion channel that links cellular metabolism to channel function. KATP is comprised of four pore forming Kir6.x subunits and 4 SURx regulatory subunits. The subunit isoforms are tissue specific and are thought to be regulated at the transcriptional level. While there have been extensive studies examining the structure and function of KATP, the regulatory mechanisms underlying subunit expression have not been fully characterized. Previous studies demonstrated that histone deacetylase inhibitors (HDACi) increased SUR2 expression in a cholesterol sensitive manner. In Chapter II, we show a cholesterol-dependent mechanism regulating SUR2 expression. We find that Trichostatin A (TSA) reduces cellular cholesterol levels, while at the same time increasing SUR2 expression. Furthermore, TSA is observed to activate SREBP cleavage/activation and cause nuclear translocation, while exogenous cholesterol inhibits these effects. We show that activated sterol response element binding protein (SREBP) significantly increases luciferase reporter gene expression driven by the upstream SUR2 promoter. Finally, we demonstrate that an SREBP inhibitor can reduceSUR2 expression. Taken together, we provide evidence that the cholesterol dependent regulation of SUR2 is mediated by SREBP. These results suggest that cholesterol homeostasis might affect cardiovascular KATP subunit expression .We previously examined KATP subunit expression in HL-1 cardiomyocytes, however hiPSC-derived cardiomyocytes (hiPSC-CM) offer a more comparable model to humans. Several ion channels have been characterized in this model, however there is little evidence showing expression of functional KATP channels. In Chapter III, we assess hiPSC-CM for the presence of KATP. We show Kir6.2 protein expression throughout differentiation, while the SURx subunits are expressed later in the time course.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 22, 2021
- Accession Number
- AD1183018
Entities
People
- Robert M. Geiger
Organizations
- Uniformed Services University of the Health Sciences