Researchers identified a receptor protein called NLRX1 as the primary regulator of the mitochondrial permeability transition pore. Scientists previously believed pore blockers acted primarily through cyclophilin D or unidentified pathways, but NLRX1 controls channel opening independently of that known factor. The protein sits in the mitochondria and physically links to channel components to dictate when calcium triggers the pore to open.
When cellular stress causes calcium levels to rise, NLRX1 binds to postulated pore machinery including ATP synthase and adenine nucleotide translocase. The protein acts like a pressure valve sensor that adjusts how much calcium is required before the channel opens. Removing NLRX1 raises this calcium threshold to keep pores closed, whereas adding excess NLRX1 lowers the threshold and promotes opening. Over longer periods, this physical interaction sustains protein balance across the entire mitochondrion.
The team used chemoproteomic probes alongside CRISPR-Cas9-edited human cells and tissue from genetically modified mice lacking NLRX1. They tested two distinct chemical classes and found that binding strength to NLRX1 directly tracked pore-blocking effectiveness. Their lead drug candidate, GSK900, was orally bioavailable, crossed the blood-brain barrier, and demonstrated activity in an injury model sensitive to pore opening.
These findings establish NLRX1 as a druggable control point for regulating mitochondrial permeability. The team developed brain-penetrant chemical tools that enable scientists to investigate this biology and target pore-driven neurological injuries.