Growth-Associated Protein-43 Loss Promotes Ca²⁺ and ROS Imbalance in Cardiomyocytes

Area of Science:

• Cardiovascular Physiology
• Cellular Biology
• Biochemistry

Background:

• Growth-Associated Protein-43 (GAP-43) is a calmodulin-binding protein involved in neuronal development.
• GAP-43 regulates intracellular calcium (Ca²⁺) dynamics in skeletal muscle.
• GAP-43 deficiency in mice leads to cardiac hypertrophy and altered Ca²⁺ handling.

Purpose of the Study:

• To investigate the role of GAP-43 in cardiomyocytes.
• To evaluate the impact of GAP-43 deficiency on intracellular Ca²⁺ variations and reactive oxygen species (ROS) levels.
• To explore the relationship between Ca²⁺, ROS, and cardiac hypertrophy in GAP-43 knockout mice.

Main Methods:

• Utilized cardiomyocytes derived from GAP-43 knockout (GAP-43^-/-) mice.
• Assessed intracellular Ca²⁺ levels and ROS production (specifically mitochondrial O₂^•-).
• Examined expression of cardiac hypertrophy markers and oxidized proteins.
• Administered calmodulin (CaM) inhibitor (W7) and mitochondrial Ca²⁺ uniporter inhibitor (Ru360) to assess their effects.

Main Results:

• GAP-43^-/- cardiomyocytes exhibited increased markers of cardiac hypertrophy, altered Ca²⁺ handling, and elevated mitochondrial ROS (O₂^•-) with increased oxidized proteins.
• Treatment with W7 restored Ca²⁺ and ROS homeostasis.
• Ru360 treatment abolished mitochondrial O₂^•- production, indicating a role for mitochondrial Ca²⁺ uptake.
• Results suggest GAP-43 regulates Ca²⁺ and ROS homeostasis via mitochondrial pathways.

Conclusions:

• GAP-43 plays a critical role in maintaining Ca²⁺ and ROS balance within cardiomyocytes.
• Dysregulation of this balance, due to GAP-43 deficiency, contributes to cardiac hypertrophy and potentially heart disease.
• Targeting Ca²⁺ and ROS pathways may offer therapeutic strategies for GAP-43-related cardiac conditions.