An Unbiased Screen Identified the Hsp70-BAG3 Complex as a Regulator of Myosin-Binding Protein C3
Year: 2023
Type: article
Abstract: Structured Abstract Objective We aim to identify regulators of myosin binding protein C3 (MyBP-C) protein homeostasis. Background Variants in myosin binding protein C3 ( MYBPC3 ) account for approximately 50% of familial hypertrophic cardiomyopathy (HCM). Most pathogenic variants in MYBPC3 are truncating variants that lead to reduced total levels of MyBP-C protein. Elucidation of the pathways that regulate MyBP-C protein homeostasis could uncover new therapeutic strategies that restore normal protein levels. Method We developed a high-throughput screen to identify compounds that can increase or decrease steady-state levels of MyBP-C in an induced pluripotent stem cell cardiomyocyte (iPSC-CM) model derived from a patient with HCM. To normalize results, we also monitored effects on myosin heavy chain (MYH) and focused on those molecules that selectively modulated MyBP-C levels. Results Screening a library of 2,426 known biologically active compounds, we identified compounds which either decreased (241/2426, 9.9%) or increased (29/2426, 1.2%) MyBP-C/MYH levels. After a rigorous validation process, including a counter screen for cellular toxicity, two compounds (JG98 and parthenolide) were confirmed as decreasing MyBP-C levels and no compounds were confirmed to increase MyBP-C levels. For further studies, we focused on JG98, which is an allosteric modulator of heat shock protein 70 (Hsp70), inhibiting its interaction with BAG domain co-chaperones. We found that genetic reduction of BAG3 phenocopies treatment with JG98 by reducing MyBP-C protein levels. Conclusion An unbiased compound screen identified the Hsp70-BAG3 complex as a regulator of MyBP-C stability. Thus, approaches that stimulate this complex’s function may be beneficial in the treatment of HCM. Highlights - Hypertrophic cardiomyopathy (HCM) is commonly caused by pathogenic MYBPC3 variants that reduce total wild-type MyBP-C (the protein encoded by MYBPC3 ). - It is critical to understand the regulators of MyBP-C protein homeostasis to uncover novel therapeutic strategies. - We developed and executed a high-throughput chemical screen in iPSC-CMs to identify compounds which alter steady-state levels of MyBP-C protein, revealing two compounds, JG98 and parthenolide, that significantly reduced MyBP-C levels. - Validation studies suggest that the complex between heat shock protein 70 (Hsp70) and its co-chaperone BAG3 is a dynamic regulator of MyBP-C stability, suggesting that this axis could be a new therapeutic target for HCM.
Language: English
Topic: Heat shock proteins research
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $4,530
Funders: Howard Hughes Medical Institute, Bristol-Myers Squibb, Pfizer, Alnylam Pharmaceuticals, Vanderbilt University, University of Pennsylvania, University of Michigan, University of Arizona, Universiteit Leiden, National Institutes of Health, National Heart, Lung, and Blood Institute, National Institute of Neurological Disorders and Stroke, National Institute of Arthritis and Musculoskeletal and Skin Diseases
Awards: G3549828030, The Molecular Genetics of Hemostasis, G6971475997, G839474415, Pathogenic mechanisms of myosin binding protein C missense variants within hypertrophic cardiomyopathy, Training in Muscle Biology and Muscle Disease, Molecular Chaperones and Small Molecules, Multidisciplinary Cardiovascular Research Training
OpenAlex ID: W4385480774