184 - Dysregulation of MnSOD-K68 acetylation status leads to neurological and tumor-permissive phenotypes

Abstract

Manganese superoxide dismutase (MnSOD) lysine acetylation is a critical post-translational modification that regulates its detoxification activity to direct cellular ROS levels and metabolic balance. In this regard, our lab has shown the change in structural configuration and gain of peroxidase function upon MnSOD-K68 acetylation. As such, this study aims to investigate the role of MnSOD-K68 acetylation (K68-Ac) status, as well as its potential biological significance both in vitro and in vivo. To experimentally evaluate the effects of MnSOD acetylation, recombinant mutants were constructed where lysine was substituted with glutamine (Q) or arginine (R), an acetylation or deacetylation mimic, respectively. The results showed that enforced expression of MnSODK68Q disrupts mitochondrial metabolism and ultrastructure, and functions as an in vitro oncogene. To examine the physiological significance of MnSOD acetylation, a genetically engineered whole-body MnSODK68Q knock-in mouse has been constructed. Biallelic knock-in (MnSODK68Q/K68Q) mice around 3 weeks of age display a significant phenotype that includes (1) small size, (2) lean body mass, (3) significant weight loss, and (4) a fatal neurological disorder involving loss of lower extremity movement, tremors, and dyskinesia. Daily injection of GC4419, a Mn-based chemical drug that replaces MnSOD activity by removing superoxide, extended the lifespan (from 25 days to 45 days), partially rescued motor coordination loss (as tested by rotarod) and delayed the onset of the profound neurological symptoms. In addition, electron microscopy identified disrupted mitochondrial structure in multiple tissues including liver, skeletal muscles, and the substantia nigra. Lastly, whole-body monoallelic female mice (MnSODWT/K68Q) of six months also display mammary tissue with smaller, disorganized fat cells, characteristics of ductal hyperplasia, and areas of cells consistent with ductal carcinoma in situ. This will be the first study characterizing the role of MnSOD-K68-Ac in a murine model suggesting that dysregulated K68-Ac leads to neurological and tumor-permissive phenotypes.