Biology subjects

Hamacher-Brady, A.

Publications and source records attributed to Hamacher-Brady, A..

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↗

bioRxiv2024

Stem cell models of TAFAZZIN deficiency reveal novel tissue-specific pathologies in Barth Syndrome

Barth syndrome (BTHS) is a rare mitochondrial disease caused by pathogenic variants in the gene TAFAZZIN, which leads to abnormal cardiolipin (CL) metabolism on the inner mitochondrial membrane. Although TAFAZZIN is ubiquitously expressed, BTHS involves a complex combination of tissue specific phenotypes including cardiomyopathy, neutropenia, skeletal myopathy, and growth delays, with a relatively minimal neurological burden. To understand both the developmental and functional effects of TAZ-deficiency in different tissues, we generated isogenic TAZ knockout (TAZ- KO) and WT cardiomyocytes (CMs) and neural progenitor cells (NPCs) from CRISPR-edited induced pluripotent stem cells (iPSCs). In TAZ-KO CMs we discovered evidence of dysregulated mitophagy including dysmorphic mitochondria and mitochondrial cristae, differential expression of key autophagy-associated genes, and an inability of TAZ-deficient CMs to properly initiate stress-induced mitophagy. In TAZ-deficient NPCs we identified novel phenotypes including a reduction in CIV abundance and CIV activity in the CIII2&CIV2 intermediate complex. Interestingly, while CL acyl chain manipulation was unable to alter mitophagy defects in TAZ-KO CMs, we found that linoleic acid or oleic acid supplementation was able to partially restore CIV abundance in TAZ-deficient NPCs. Taken together, our results have implications for understanding the tissue-specific pathology of BTHS and potential for tissue-specific therapeutic targeting. Moreover, our results highlight an emerging role for mitophagy in the cardiac pathophysiology of BTHS and reveal a potential neuron-specific bioenergetic phenotype.

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↗