Divalent cation chelators citrate and EDTA unmask an intrinsic uncoupling pathway in isolated mitochondria

Abstract

We demonstrate a suppression of ROS production and uncoupling of mitochondria by exogenous citrate in Mg2+ free medium. Exogenous citrate suppressed H2O2 emission and depolarized mitochondria. The depolarization was paralleled by the stimulation of respiration of mitochondria. The uncoupling action of citrate was independent of the presence of sodium, potassium, or chlorine ions, and it was not mediated by the changes in permeability of the inner mitochondrial membrane to solutes. The citrate transporter was not involved in the citrate effect. Inhibitory analysis data indicated that several well described mitochondria carriers and channels (ATPase, IMAC, ADP/ATP translocase, mPTP, mKATP) were not involved in citrate’s effect. Exogenous MgCl2 strongly inhibited citrate-induced depolarization. The uncoupling effect of citrate was demonstrated in rat brain, mouse brain, mouse liver, and human melanoma cells mitochondria. We interpreted the data as an evidence to the existence of a hitherto undescribed putative inner mitochondrial membrane channel that is regulated by extramitochondrial Mg2+ or other divalent cations.

The Regulatory Roles of Mitochondrial Calcium and the Mitochondrial Calcium Uniporter in Tumor Cells

“…Ca 2+ is the center that regulates the MPTP. It can directly regulate the MPTP itself and indirectly affect the MPTP by regulating the adenosine diphosphate (ADP)/ATP balance, mitochondrial membrane potential, and ROS/reactive nitrogen level [ 63 ]. The study found that the MPTP has an important property: the increase in ADP and the recovery of Mg 2+ /Ca 2+ caused by MPTP opening are reversible [ 64 ].…”

Role of Sodium dependent SLC13 transporter and its inhibitors in various metabolic disorders

“…The exogenous citrate in the Mg 2+ free medium has been shown to suppress the reactive oxygen species (ROS) and uncoupling of the mitochondria. It also suppresses the H 2 O 2 and the stimulation of respiration of mitochondria (suppress the depolarized mitochondria and amount of the citrate transporter) [9]. The sodium dependent SLC13 family transporters carry these intermediates from plasma membranes into the cells and is comprises of five genes.…”

Editorial note

“…Opening the issue, Starkov and collaborators present evidence of a putative new mitochondrial inner membrane channel regulated by magnesium (Starkov et al 2016). The evidence waits to be corroborated by direct path clamping, and such was the case for a number of channel activities initially hinted and later identified by Casey and her collaborators.…”