Defining the Sarcomeric Proteoform Landscape in Ischemic Cardiomyopathy by Top-Down Proteomics

Area of Science:

• Cardiovascular Biology
• Proteomics
• Molecular Mechanisms of Disease

Background:

• Ischemic cardiomyopathy (ICM) is a major cause of heart failure with complex, understudied molecular underpinnings.
• Sarcomeric protein alterations, including post-translational modifications (PTMs) and isoform switching, are critical in cardiac pathophysiology.

Purpose of the Study:

• To define the sarcomeric proteoform landscape in end-stage ICM.
• To identify molecular changes in sarcomeric proteins contributing to ICM pathogenesis.

Main Methods:

• Implemented a top-down liquid chromatography-mass spectrometry (LC-MS)-based proteomics approach.
• Analyzed myocardial samples from non-heart disease donors (n=16) and end-stage ICM patients (n=16).

Main Results:

• Identified significant alterations in PTMs and expression of multiple sarcomeric proteins in ICM hearts.
• Observed altered phosphorylation and expression of cardiac troponin I (cTnI) and enigma homologue 2 (ENH2).
• Detected increased phosphorylation of muscle LIM protein (MLP) and calsarcin-1 (Cal-1) in ICM.

Conclusions:

• The sarcomeric contractile apparatus is severely dysregulated in ICM.
• This study provides the first comprehensive LC-MS-based top-down proteomic analysis of sarcomeric protein changes in ICM.
• Findings offer insights into ICM molecular mechanisms and potential therapeutic targets.