NO triggers RGS4 degradation to coordinate angiogenesis and cardiomyocyte growth

Area of Science:

• Cardiovascular Biology
• Molecular Cardiology
• Physiology

Background:

• Myocardial hypertrophy, an increase in heart tissue, requires coordinated growth of coronary vasculature to meet oxygen demands.
• The precise mechanisms coordinating angiogenesis and cardiomyocyte growth remain largely unknown.

Purpose of the Study:

• To elucidate the molecular mechanisms linking myocardial angiogenesis to cardiomyocyte growth and cardiac hypertrophy.
• To identify novel pathways involved in the coordination of vascular and cardiac muscle expansion.

Main Methods:

• Utilized transgenic mice with conditional overexpression of placental growth factor (PlGF) in cardiac tissue to induce angiogenesis.
• Investigated the role of nitric oxide (NO), Regulator of G protein Signaling 4 (RGS4), and downstream signaling pathways (Gβγ/PI3Kγ/AKT/mTORC1).
• Employed NOS inhibition (L-NAME) and eNOS knockout models to validate the NO-dependent mechanism.

Main Results:

• PlGF-induced myocardial angiogenesis promoted cardiomyocyte growth and cardiac hypertrophy via a novel NO-dependent mechanism.
• NO stimulated hypertrophy by promoting proteasomal degradation of RGS4, thereby activating the Gβγ/PI3Kγ/AKT/mTORC1 pathway.
• Concomitant RGS4 expression or NOS inhibition blocked hypertrophy; PlGF in eNOS knockout mice failed to induce hypertrophy.

Conclusions:

• A novel NO/RGS4/Gβγ/PI3Kγ/AKT pathway couples cardiac angiogenesis with cardiomyocyte growth and heart size.
• This mechanism provides critical insights into the physiological regulation of cardiac adaptation to hemodynamic stress.