Endolysosomal two-pore channels regulate autophagy in cardiomyocytes

Area of Science:

• Cardiovascular Biology
• Cellular Physiology

Background:

• Autophagy is vital for heart remodeling and stress response.
• Endolysosomal two-pore channels (TPCs), TPC1 and TPC2, regulate autophagy.
• TPCs control endolysosomal fusion, a key process in autophagic flux.

Purpose of the Study:

• To investigate the role of TPC1 and TPC2 in basal and induced cardiac autophagic activity.
• To determine the impact of TPCs on cardiomyocyte viability under stress.
• To examine the differential expression of TPCs in male and female cardiac tissues.

Main Methods:

• Studied TPC expression (transcripts and protein) in cultured cardiomyocytes and cardiac tissues.
• Utilized small interfering RNA (siRNA) to deplete TPC1 and TPC2.
• Analyzed autophagic flux markers (LC3-II, p62) and cardiomyocyte viability.
• Examined cardiac lysosomal system in TPC knockout mice using electron microscopy.

Main Results:

• Starvation increased TPC1 and TPC2 levels in cardiomyocytes, paralleling autophagy.
• TPC depletion reduced cardiomyocyte viability under starvation and simulated ischemia.
• Knockdown of TPCs impaired autophagic flux, especially under severe energy depletion.
• TPC knockout mice hearts showed smaller, immature lysosomes.
• TPC1 and TPC2 levels were higher in female than male human and rat hearts.
• TPC transcript levels negatively correlated with p62, a marker of autophagy.

Conclusions:

• TPC1 and TPC2 are essential for basal and induced autophagic flux in cardiomyocytes.
• TPCs are critical for maintaining cardiomyocyte viability during stress.
• Differential expression of TPCs in male and female hearts suggests sex-specific roles in cardiac autophagy.