Investigating the Potential Role of Pic2 protein in Mitochondrial Copper Transport using Saccharomyces cerevisiae

Abstract

Copper (Cu) is an essential metal required for the assembly and activity of two key mitochondrial enzymes: cytochrome c oxidase (COX) and superoxide dismutase (SOD1), which are responsible for energy metabolism and antioxidant defence, respectively. For the past decade, Pic2 has been generally accepted as the main mitochondrial copper transporter, delivering copper to COX and SOD1, both of which cannot function without this essential metal. However, this model of copper transport in mitochondria had many inconsistencies and required revision due to conflicting data in the literature and more recent findings suggesting that Pic2 is not involved in copper transport. In this project, I hypothesized that Pic2 is not the primary copper transporter for COX and SOD1 and used various approaches, comparing wild-type yeast with a Pic2 deletion strain in the W3030 background, to test the role of Pic2 in copper transport. Growth assays under varying copper concentrations revealed no differences in growth phenotypes between strains and enzymatic assays further demonstrated that loss of Pic2 does not lead to reduced COX or SOD1 activity. Considering that the activity of both enzymes depends on sufficient copper levels in mitochondria, these results suggest that Pic2 is not essential for mitochondrial copper transport. Additionally, measurement of aconitase activity showed that Pic2 deletion had no effect on oxidative stress, thus further supporting the notion that copper homeostasis in mitochondria is maintained in the absence of Pic2. Together, my findings show that Pic2 cannot be the main copper transporter and that its role needs to be reevaluated, given that a better understanding of the mechanism of copper transport into mitochondria could provide new insights into both a subset of mitochondrial and copper-dependent disorders.