Reddy, E. | Search bioRxiv

bioRxiv2026

NLRX1 is an essential, druggable regulator of mitochondrial permeability transition

The molecular composition of the mitochondrial permeability transition pore (mPTP) remains contested, and several efficacious mPTP inhibitors act through undefined, cyclophilin D (CypD)-independent targets. Using two structurally distinct chemotypes of optimised, brain-penetrant mPTP inhibitors as chemical probes, we applied affinity-based chemoproteomics to identify the mitochondrial NOD-like receptor NLRX1 as their shared target. Both chemotypes bind NLRX1, and binding potency across a compound series tracks mPTP-inhibitory activity. Using CRISPR-Cas9-edited human cells and Nlrx1-/- mouse tissues, we show that NLRX1 is required for normal calcium-induced mPTP opening: its loss raises the calcium threshold for pore opening and its overexpression lowers it, independently of CypD. NLRX1 associates with postulated mPTP components, including ATP synthase and the adenine nucleotide translocase, in a compound-sensitive manner, and sustains mitochondrial protein homeostasis over longer timescales. The lead compound, GSK900, is orally bioavailable, brain-penetrant, and active in an mPTP-sensitive neurological injury model. These findings, converging with recent genetic studies, establish NLRX1 as an essential, CypD-independent regulator of mitochondrial permeability transition and provide brain-penetrant chemical tools to interrogate this biology.

cell biology↗

bioRxiv2024

The mitochondrial stress- induced protein carboxyl-terminal alanine and threonine tailing (msiCAT-tailing) promotes glioblastoma tumorigenesis by modulating mitochondrial functions

The rapid and sustained proliferation of cancer cells necessitates increased protein production, which, along with their disrupted metabolism, elevates the likelihood of translation errors. Ribosome-associated quality control (RQC), a recently identified mechanism, mitigates ribosome collisions resulting from frequent translation stalls. However, the precise pathophysiological role of the RQC pathway in oncogenesis remains ambiguous. Our research centered on the pathogenic implications of mitochondrial stress-induced protein carboxyl-terminal alanine and threonine tailing (msiCAT-tailing), a specific RQC response to translational arrest on the outer mitochondrial membrane, in glioblastoma (GBM). The presence of msiCAT-tailed mitochondrial proteins was observed commonly in glioblastoma stem cells (GSCs). The exogenous introduction of the mitochondrial ATP synthase F1 subunit alpha (ATP5) protein, accompanied by artificial CAT-tail mimicking sequences, enhanced mitochondrial membrane potential ({Delta}{Psi}m) and inhibited the formation of the mitochondrial permeability transition pore (MPTP). These alterations in mitochondrial characteristics provided resistance to staurosporine (STS)-induced apoptosis in GBM cells. Consequently, msiCAT-tailing can foster cell survival and migration, whereas blocking msiCAT-tailing via genetic or pharmacological intervention can impede GBM cell overgrowth. Impact StatementThe Carboxyl-Terminal Alanine-Threonine-tailed protein ATP5 helps glioblastoma mitochondria maintain a high membrane potential and keep the permeability transition pore closed, thereby promoting tumor growth and increasing resistance to apoptosis. HighlightsO_LIGlioblastoma (GBM) cells have a disturbed RQC pathway C_LIO_LImsiCAT-tailing on ATP5 in GBM cells increases mitochondrial membrane potential C_LIO_LIThis msiCAT-tailing prevents MPTP opening C_LIO_LIATP5 msiCAT-tailing also inhibits drug-induced apoptosis in GBM cells C_LIO_LIBlocking msiCAT-tailing impedes the overall growth of GBM cells C_LI

cancer biology↗