TMEM65 regulates and is required for NCLX-dependent mitochondrial calcium efflux

Area of Science:

• Mitochondrial biology
• Cellular homeostasis
• Cardiovascular and neurological science

Background:

• Mitochondrial calcium (mCa2+) homeostasis is vital for cellular function and ATP production.
• The mitochondrial sodium-calcium exchanger (NCLX) is a key regulator of mCa2+ efflux, particularly in excitable tissues.
• Dysregulated mCa2+ overload is implicated in various pathologies, making NCLX a potential therapeutic target.

Purpose of the Study:

• To identify novel regulators of NCLX activity and mCa2+ efflux.
• To elucidate the molecular mechanisms governing NCLX-dependent mCa2+ transport.
• To investigate the physiological consequences of TMEM65 dysfunction in excitable tissues.

Main Methods:

• Proximity biotinylation proteomic screening to identify NCLX binding partners.
• Pharmacological inhibition and genetic deletion of NCLX.
• Loss-of-function studies utilizing TMEM65 knockdown.
• In vivo studies assessing cardiac and neuromuscular function in Tmem65 knockdown mice.

Main Results:

• TMEM65 was identified as a binding partner of NCLX, enhancing sodium (Na+)-dependent mCa2+ efflux.
• TMEM65 is essential for Na+-dependent mCa2+ efflux, as its loss-of-function ablates this process.
• Tmem65 knockdown in mice led to mCa2+ overload in cardiac and skeletal muscle, impairing organ function.

Conclusions:

• TMEM65 plays a critical role in regulating NCLX-dependent mCa2+ efflux in excitable tissues.
• Disruption of TMEM65 function leads to pathogenic mCa2+ overload, cell death, and organ dysfunction.
• Targeting TMEM65 presents a potential therapeutic strategy for diseases associated with mCa2+ dysregulation.