AKT1 and AKT2 induce distinct phosphorylation patterns in HL-1 cardiac myocytes

Area of Science:

• Molecular Cardiology
• Proteomics
• Cell Signaling

Background:

• The protein kinase AKT is crucial in cardiac function, regulating growth, survival, and metabolism.
• Understanding AKT isoform-specific signaling is vital for elucidating molecular mechanisms in the heart.

Purpose of the Study:

• To investigate AKT isoform-specific signaling pathways at the molecular level in HL-1 cardiomyocytes.
• To identify novel AKT targets and understand their role in cardiac processes, particularly excitation-contraction coupling.

Main Methods:

• Utilized isoform-specific knockdown of AKT1 or AKT2 in HL-1 cardiomyocytes.
• Employed stable isotope labeling combined with high-resolution mass spectrometry to analyze the phosphoproteome.
• Identified and quantified regulated phosphopeptides to assess isoform-specific signaling.

Main Results:

• Identified 377 regulated phosphopeptides, with the highest number in AKT2 knockdown cells.
• Insulin stimulation predominantly activated AKT2, potentially via interaction with mTORC2.
• Discovered novel AKT isoform-specific targets and phosphosites linked to cardiac excitation-contraction coupling, including key ion channels and regulatory proteins.

Conclusions:

• AKT isoform-specific knockdown coupled with quantitative phosphoproteomics is a powerful strategy to unravel complex signaling networks.
• AKT2 plays a significant role in insulin-mediated signaling and cardiac function.
• Specific AKT signaling pathways are directly involved in regulating cardiac excitation-contraction coupling.