Overexpression of the catalytic subunit of protein phosphatase 2A impairs cardiac function

Area of Science:

• Molecular Biology
• Cardiovascular Physiology
• Enzymology

Background:

• Protein phosphorylation is a key regulator of cellular processes.
• The function and regulation of protein phosphatases, like protein phosphatase 2A (PP2A), are not fully understood.
• Understanding PP2A's role is crucial for comprehending cardiac function and disease.

Purpose of the Study:

• To investigate the in vivo role of cardiac-specific overexpression of the catalytic subunit alpha of protein phosphatase 2A (PP2Acalpha).
• To determine the impact of increased PP2A activity on cardiac structure, function, and protein phosphorylation.

Main Methods:

• Generation of transgenic mice overexpressing PP2Acalpha in the heart using the alpha-myosin heavy chain promoter.
• Analysis of transgene RNA and protein levels, PP2A enzyme activity, and myocardial morphology.
• Assessment of protein phosphorylation states and cardiac function using biplane echocardiography.

Main Results:

• Successful cardiac-specific overexpression of PP2Acalpha led to increased PP2A enzyme activity.
• Transgenic hearts exhibited necrosis, fibrosis, cardiac hypertrophy, reduced contractility, and dilatation.
• Key cardiac phosphoproteins, including phospholamban and troponin inhibitor, showed reduced phosphorylation.

Conclusions:

• PP2A plays a fundamental role in maintaining normal cardiac function.
• Dysregulation of PP2A expression or activity can lead to cardiac disease.
• These findings provide insights into the pathophysiology of cardiac disorders involving phosphatases.