ISG15 Attenuates Post-Translational Modifications of Mitofusins and Congression of Damaged Mitochondria in Ataxia Telangiectasia Cells
Biochimica et Biophysica Acta - Molecular Basis of Disease
Mitophagy is defective in several neurodegenerative diseases, including Ataxia Telangiectasia (A-T). However, the molecular mechanism underlying defective mitophagy in A-T is unknown. Literature indicates that damaged mitochondria are transported to the perinuclear region prior to their removal via mitophagy. Our previous work has indicated that conjugation of SUMO2 (Small Ubiquitin-like Modifier 2) to mitofusins (Mfns) may be necessary for congression of mitochondria into SUMO2-/ubiquitin-/LC3-positive compact structures resembling mito-aggresomes at the perinuclear region in CCCP-treated HEK293 cells. Here, we demonstrate that Mfns are SUMOylated, and mitochondria are transported to the perinuclear region; however, mitochondria fail to congress into mito-aggresome-like structures in CCCP-treated A-T cells. Defect in mitochondrial congression is causally related to constitutively elevated ISG15 (Interferon-Stimulated Gene 15), an antagonist of the ubiquitin pathway, in A-T cells. Suppression of the ISG15 pathway restores mitochondrial congression, reduce oxidative stress, and level of unhealthy mitochondria, which is suggestive of restoration of mitophagy in A-T cells. ISG15 is also constitutively elevated and mitophagy is defective in Amytrophic Lateral Sclerosis (ALS). The constitutively elevated ISG15 pathway therefore appears to be a common unifying biochemical mechanism underlying defective mitophagy in neurodegenerative disorders thus, implying the broader significance of our findings, and suggest the potential role of ISG15 inhibitors in their treatment.
Juncker, Meredith; Kim, Catherine; Reed, Ryan; Haas, Arthur; Schwartzenburg, Joshua; and Desai, Shyamal, "ISG15 Attenuates Post-Translational Modifications of Mitofusins and Congression of Damaged Mitochondria in Ataxia Telangiectasia Cells" (2021). School of Graduate Studies Faculty Publications. 11.