Robichaux, D. | Search bioRxiv

bioRxiv2025

Atad3 is Essential for Mitochondrial Permeability Transition Pore Opening and Cardiac Ischemia Reperfusion Injury.

The molecular identity of the mitochondrial permeability transition pore (mPTP) has remained elusive since the discovery of its existence over 75 years ago. Despite the numerous candidate proteins proposed, none have withstood genetic ablation, leaving them relegated to auxiliary regulatory roles. To date, no essential mPTP component has been identified. Here, we establish ATAD3 as the first essential component of the mPTP. Genetic deletion of Atad3 in cardiomyocytes and hepatocytes renders heart and liver mitochondria incapable of undergoing Ca2+-induced mPTP-dependent swelling. Moreover, these mitochondria exhibit the highest Ca2+ retention capacity ever reported following genetic perturbation of the mPTP. Furthermore, patch-clamp recordings of recombinant ATAD3a in liposomes reveal intrinsic channel activity. Given the established role of mPTP-dependent necrosis in driving ischemia/reperfusion (I/R) injury, we show that cardiac-specific Atad3 deletion markedly reduces infarct size following I/R, with no additive protection from cyclosporine A. Together, these findings establish ATAD3 as an core, putative pore-forming component essential for mPTP opening and mPTP-dependent necrosis, resolving a long-standing mystery in mitochondrial biology.

cell biology↗

bioRxiv2019

RELA is Sufficient to Mediate Interleukin-1 (IL-1) Repression of Androgen Receptor Expression and Activity in LNCaP Disease Progression Model

BackgroundThe Androgen Receptor (AR) nuclear transcription factor is a therapeutic target for prostate cancer (PCa). Unfortunately, patients can develop resistance to AR-targeted therapies and progress to lethal disease, underscoring the importance of understanding the molecular mechanisms that underlie treatment resistance. Inflammation is implicated in PCa initiation and progression and we have previously reported that the inflammatory cytokine, interleukin-1 (IL-1), represses AR mRNA levels and activity in AR-positive (AR+) PCa cell lines concomitant with the upregulation of pro-survival biomolecules. Thus, we contend that IL-1 can select for AR-independent, treatment-resistant PCa cells.\n\nMethodsTo begin to explore how IL-1 signaling leads to the repression of AR mRNA levels, we performed comprehensive pathway analysis on our RNA sequencing data from IL-1-treated LNCaP PCa cells. Our pathway analysis predicted Nuclear Factor Kappa B (NF-{kappa}B) p65 subunit (RELA), a canonical IL-1 signal transducer, to be significantly active and potentially regulate many genes, including AR. We used siRNA to silence the NF-{kappa}B family of transcription factor subunits, RELA, RELB, c-REL, NFKB1, or NFKB2, in IL-1-treated LNCaP, C4-2, and C4-2B PCa cell lines. C4-2 and C4-2B cell lines are castration-resistant LNCaP sublines and represent progression towards metastatic PCa disease; and we have previously shown that IL-1 represses AR mRNA levels in C4-2 and C4-2B cells.\n\nResultssiRNA revealed that RELA alone is sufficient to mediate IL-1 repression of AR mRNA and AR activity. Intriguingly, while LNCaP cells are more sensitive to IL-1-mediated repression of AR than C4-2 and C4-2B cells, RELA siRNA led to a more striking de-repression of AR mRNA levels and AR activity in C4-2 and C4-2B cells than in LNCaP cells.\n\nConclusionsThese data indicate that there are RELA-independent mechanisms that regulate IL-1-mediated AR repression in LNCaP cells and suggest that the switch to RELA-dependent IL-1 repression of AR in C4-2 and C4-2B cells reflects changes in epigenetic and transcriptional programs that evolve during PCa disease progression.

cancer biology↗