Abstract 454: Role of Foxf1 During Protein Quality Control in Cardiomyocytes

Abstract

Introduction: Impairment of protein quality control leads to the accumulation of intracellular misfolded protein aggregates, contributing to cardiac disease and heart failure. Essential protein quality control pathways, including proteasomal degradation and autophagy, are involved in maintaining cellular homeostasis and cardiac function during proteotoxic insult. In a prior study, we undertook an unbiased, total genomewide screen for RNA transcripts and their protein products that affect aggregate accumulations in the cardiomyocytes. Forkhead box F1 (Foxf1) gene was one of the hits from our high throughput screening. In this study, we have performed further validation of Foxf1, a transcription factor and previously unknown player in proteotoxic processes. Aims and Methods: The objective of this study was to validate Foxf1 as a contributor to protein quality control and understand its role in contributing to protein aggregate formation during proteotoxic-induced cardiac disease. We knocked down Foxf1 expression using siRNA mediated transfection in neonatal rat ventricular cardiomyocytes that expressed the protein aggregate inducing mutation of the chaperone α B crystallin (CryABR120G). Proteasomal function and relative activity in cells was analyzed using a degron-destablized green fluorescent protein (GFPu) based reporter protein. Similarly, autophagy activity was determined by autophagic flux assay using bafilomycin treatment. Results: CryABR120G expression leads to aggregate formation and decreased proteasomal function in cardiomyocytes. Knockdown of Foxf1 gene expression in CryABR120G-transfected cardiomyocytes reduced the proteotoxic sequelae, decreasing aggregate concentration. Knockdown of Foxf1 significantly increased proteasomal function in the model without altering autophagy activity. Conclusion: Decreased Foxf1 expression reduced CryABR120G induced aggregate protein accumulation and decreased proteotoxic stress in cardiomyocytes, likely through the maintenance of clearance of the misfolded protein via the proteasomal pathway.