Intracellular Ca²⁺ Modulates PKA Compartmentalization and Dynamics in Human iPSC-Derived Cardiomyocytes

Area of Science:

• Cardiology
• Cellular Electrophysiology
• Mitochondrial Biology

Background:

• Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) exhibit automaticity governed by coupled Ca2+ and membrane clocks.
• Local Ca2+ releases (LCRs) and cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling coordinate these clocks.
• The role of PKA in hiPSC-CM energetics and its interaction with Ca2+ signaling remains incompletely understood.

Purpose of the Study:

• To investigate the role of PKA in hiPSC-CM energetics.
• To measure PKA dynamics in the cytosol and mitochondria and its crosstalk with Ca2+.
• To test hypotheses regarding Ca2+-activated PKA signaling, adenylyl cyclase activity, and Ca2+-dependent PKA compartmentalization, comparing hiPSC-CMs with rabbit sinoatrial node cells (SANCs).

Main Methods:

• Pharmacological inhibition of PKA (H-89).
• Ca2+ chelation (BAPTA) and mitochondrial Ca2+ blockade (Ru360).
• Measurement of PKA activity in different cellular compartments (cytosol, mitochondria).

Main Results:

• PKA inhibition, Ca2+ chelation, or mitochondrial Ca2+ blockade induced energy imbalance in hiPSC-CMs.
• H-89 treatment resulted in compartmentalized PKA activity within the cytosol and mitochondria.
• BAPTA treatment globally reduced PKA activity, indicating Ca2+ dependence.
• PKA dynamics and Ca2+-dependent regulation showed similarities between hiPSC-CMs and SANCs.

Conclusions:

• Intracellular Ca2+-mediated PKA compartmentalization is a key feature of hiPSC-CMs and SANCs.
• PKA signaling plays a critical role in maintaining hiPSC-CM energetics and automaticity.
• Findings highlight the importance of studying PKA localization and Ca2+ interactions in cardiac automaticity.