Biology subjects

Brady, N. R.

Publications and source records attributed to Brady, N. R..

3 recordsLinked to original sources

bioRxiv2025

The Cancer/Testis Antigen FATE1 Antagonizes Fission and Preserves Mitochondrial Network Integrity under Cytotoxic Stress

FATE1 (Fetal and Adult Testis Expressed 1), also known as BJ-HCC-2, is a cancer-testis antigen with highly restricted expression in normal tissues but aberrant activation in diverse tumor types, where it localizes to both the outer mitochondrial membrane and the endoplasmic reticulum (ER) and functions as a key survival factor. Although FATE1 shares sequence homology with the mitochondrial fission factor Mff, its role in regulating mitochondrial architecture has not been mechanistically defined. Here, we identify FATE1 as a novel modulator of mitochondrial morphology that acts through a mechanism distinct from Mff. Unlike Mff, FATE1 does not recruit Drp1 to mitochondria and therefore lacks canonical fission activity. Instead, FATE1 promotes mitochondrial hyperfusion and protects against mitochondrial fragmentation triggered by cytokines and mitochondrial uncoupler treatment. The pro-fusion activity of FATE1 requires its mitochondrial targeting and interaction with Mitofusin-2 (Mfn2). Our findings establish FATE1 as a cancer-selective regulator of mitochondrial dynamics that antagonizes fission and preserves network integrity under cytotoxic stress, revealing a potential mechanism by which tumor cells evade mitochondria-driven apoptotic signaling.

cell biology↗

bioRxiv2023

XIAP-mediated targeting of endolysosomes to stressed mitochondria occurs in a switch-like, global manner and results in autophagy-independent, sub-organelle level mitochondrial degradation

Damaged mitochondria can be subject to lysosomal degradation via mitophagy. However, whole-organelle degradation exhibits relatively slow kinetics and thus its impact may be limited in response to acute, fast-acting cellular stress. We previously reported that in Parkin-deficient cells endolysosomes directly target mitochondria when subjected to bioenergetic stress. Here, using high-resolution live cell imaging we reveal a striking level of dynamic targeting of Rab5+ early endosomes to stressed mitochondria, culminating in a switch-like accumulation in the entire mitochondrial population, independently of canonical autophagy. This process of rapid, largescale Rab5+ vesicle trafficking to mitochondria coincides with, and is mediated by, XIAP E3 ligase activated mitochondrial ubiquitylation and results in ultrastructural changes to, and degradation of, intra-mitochondrial components. Mitochondria-targeting vesicles include early endosomal subpopulations marked by Rab5 effector APPL1 and ubiquitin-binding endocytic adaptors OPTN, TAX1BP1 and Tollip, and Rab7-positive late endosomes/lysosomes. In Parkin expressing cells, XIAP- and Parkin-dependent mitochondrial targeting and resulting processing modes are competitively regulated. Together, our data suggest that XIAP-mediated targeting of endolysosomes to mitochondria functions as a stress-responsive, sub-organelle level mitochondrial processing mode that is distinct from, and competitive to, Parkin-mediated mitophagy.

cell biology↗

bioRxiv2017

Listeria monocytogenes virulence factors are secreted in biologically active Extracellular Vesicles

Outer membrane vesicles produced by Gram-negative bacteria have been studied for half a century but the possibility that Gram-positive bacteria secreted extracellular vesicles (EVs) was not pursued due to the assumption that the thick peptidoglycan cell wall would prevent their release to the environment. However, following discovery in fungi, which also have cell walls, EVs have now been described for a variety of Gram-positive bacteria. EVs purified from Gram-positive bacteriaare implicated in virulence, toxin release and transference to host cells, eliciting immune responses, and spread of antibiotic resistance. Listeria monocytogenes is a Gram-positive bacterium that is the etiological agent of listeriosis. Here we report that L. monocytogenes produces EVs with diameter ranging from 20-200 nm, containing the pore-forming toxin listeriolysin O(LLO) and phosphatidylinositol-specific phospholipase C (PI-PLC). Using simultaneous metabolite, protein, and lipid extraction (MPLEx) multi-omics we characterized protein, lipid and metabolite composition of bacterial cells and secreted EVs and found that EVs carry the majority of listerial virulence proteins. Cell-free EV preparations were toxic to the murine macrophage cell line J774.16, in a LLO-dependent manner, evidencing EV biological activity. The deletion of plcA increased EV toxicity, suggesting PI-PLC can restrain LLO activity. Using immunogold electron microscopy we detect LLO localization at several organelles within infected human epithelial cells and with high-resolution fluorescence imaging we show that dynamic lipid structures are released from L. monocytogenes that colocalize with LLO during infection. Our findings demonstrate that L. monocytogenes utilize EVs for toxin release and implicate these structures in mammalian cytotoxicity.

microbiology↗