TMEM65 regulates NCLX-dependent mitochondrial calcium efflux

Area of Science:

• Mitochondrial biology
• Cellular physiology
• Cardiovascular research

Background:

• Mitochondrial calcium (_mCa²⁺) balance is vital for ATP production; dysregulation leads to cell death.
• The mitochondrial sodium-calcium exchanger (NCLX) regulates _mCa²⁺ efflux and is a therapeutic target for calcium overload.

Purpose of the Study:

• To identify novel regulators of NCLX function using proteomic screening.
• To elucidate the role of TMEM65 in mitochondrial calcium homeostasis and NCLX activity.

Main Methods:

• Proximity biotinylation proteomic screening to identify NCLX interactors.
• Pharmacologic and genetic manipulation of NCLX and TMEM65.
• Co-fractionation, in silico structural modeling, and in vivo studies in mouse models.

Main Results:

• TMEM65 was identified as a NCLX-proximal protein that enhances sodium-dependent _mCa²⁺ efflux.
• TMEM65 is required for NCLX function; TMEM65 knockdown impairs cardiac and neuromuscular function due to _mCa²⁺ overload.
• TMEM65 overexpression protects against cell death during calcium stress.

Conclusions:

• TMEM65 is essential for regulating NCLX-dependent _mCa²⁺ efflux in excitable tissues.
• Loss of TMEM65 function leads to pathogenic _mCa²⁺ overload and organ dysfunction.
• Modulating TMEM65 offers a novel therapeutic strategy for controlling _mCa²⁺ homeostasis.