Loss of Num1-mediated cortical dynein anchoring negatively impacts respiratory growth

Abstract

Num1 is a multifunctional protein that both tethers mitochondria to the plasma membrane and anchors dynein to the cell cortex during nuclear inheritance. Previous work has examined the impact loss of Num1-based mitochondrial tethering has on dynein function in Saccharomyces cerevisiae; here, we elucidate its impact on mitochondrial function. We find that like mitochondria, Num1 is regulated by changes in metabolic state, with the protein levels and cortical distribution of Num1 differing between fermentative and respiratory growth conditions. In cells lacking Num1, we observe a reproducible respiratory growth defect, suggesting a role for Num1 in not only maintaining mitochondrial morphology, but also function. A structure-function approach revealed that, unexpectedly, Num1-mediated cortical dynein anchoring is important for normal growth under respiratory conditions. The severe respiratory growth defect in Δnum1 cells is not specifically due to dynein's canonical function in nuclear migration but is dependent on the presence of dynein, as deletion of DYN1 in Δnum1 cells partially rescues respiratory growth. We hypothesize that misregulated dynein present in cells that lack Num1 negatively impacts mitochondrial function resulting in defects in respiratory growth.

Temporal control of contact site formation reveals a relationship between mitochondrial division and Num1-mediated mitochondrial tethering

“…Our previous study demonstrated that ​​Num1-mediated cortical dynein anchoring is important for normal growth under respiratory conditions ( White et al. , 2022 ).…”

“…We refer to this artificial mitochondria-PM tether as RID-Mdv1 ( Figure 6A ). RID-Mdv1 is an inducible version of a constitutive Mdv1NTE-Pil1 artificial tether we used previously to test whether restoring contact or proximity between mitochondria and the PM was able to rescue the respiratory growth defect of ∆ num1 cells ( White et al. , 2022 ).…”

“…, 2000 ; Farkasovsky and Küntzel, 2001 ; Lammers and Markus, 2015 ). Interestingly, Num1-mediated dynein anchoring is also important for mitochondrial function; when dynein is unable to anchor at cortical Num1 clusters, defects in mitochondrial respiration are observed ( White et al. , 2022 ).…”

Mitochondrial Protease Oct1p Regulates Mitochondrial Homeostasis and Influences Pathogenicity through Affecting Hyphal Growth and Biofilm Formation Activities in Candida albicans

“…C. albicans samples were spotted with 5 μL on plates containing different carbon sources and stress reagents, and then incubated at various temperatures for 48 h to observe growth. In addition, we diluted cells to 300 cells/mL in PBS, applied 100 μL to YPD and YPEG solid medium, and incubated at 30 °C, 35 °C, and 37 °C for 48 h [ 23 ]. Colony size was measured with vernier calipers at the end of the incubation.…”