A conserved mechanism for mitochondria-dependent dynein anchoring

Abstract

Mitochondrial anchors have functions that extend beyond simply positioning mitochondria. In budding yeast, mitochondria drive the assembly of the mitochondrial anchor protein Num1 into clusters, which serve to anchor mitochondria as well as dynein to the cell cortex. Here, we explore a conserved role for mitochondria in dynein anchoring by examining the tethering functions of the evolutionarily distant Schizosaccharomyces pombe Num1 homologue. In addition to its function in dynein anchoring, we find that S. pombe Num1, also known as Mcp5, interacts with and tethers mitochondria to the plasma membrane in S. pombe and Saccharomyces cerevisiae. Thus, the mitochondria and plasma membrane-binding domains of the Num1 homologues, as well as the membrane features these domains recognize, are conserved. In S. pombe, we find that mitochondria impact the assembly and cellular distribution of Num1 clusters and that Num1 clusters actively engaged in mitochondrial tethering serve as cortical attachment sites for dynein. Thus, mitochondria play a critical and conserved role in the formation and distribution of dynein-anchoring sites at the cell cortex and, as a consequence, impact dynein function. These findings shed light on an ancient mechanism of mitochondria-dependent dynein anchoring that is conserved over more than 450 million years of evolution, raising the intriguing possibility that the role mitochondria play in dynein anchoring and function extends beyond yeast to higher eukaryotes.

Cortical tethering of mitochondria by the anchor protein Mcp5 enables uniparental inheritance

“…Similar to previous observations, we counted 29.8 ± 11.6 Mcp5 spots per zygote (Thankachan et al, 2017), of which 87.9 ± 7.6% (n = 536 Mcp5 spots from 18 cells; Fig. S2 A) colocalized with mitochondria (Kraft and Lackner, 2019). We observed complete colocalization between mitochondria at the cortex and Mcp5 foci (Fig.…”

“…In budding yeast, Num1 cluster formation requires mitochondrial attachment and the resulting clusters of Num1 are required for dynein anchoring (Lammers and Markus, 2015; Kraft and Lackner, 2017; Schmit et al, 2018). A recent study has also established the role of S. pombe Mcp5 and its CC domain in tethering mitochondria during fission yeast meiosis (Kraft and Lackner, 2019). However, contrary to our observations, an individual Mcp5 spot was found to be able to tether mitochondria and dynein simultaneously.…”

The Expanding and Unexpected Functions of Mitochondria Contact Sites

“…Thus, Num1-mediated mitochondria-PM tethering not only impacts the spatial distribution of mitochondria within cells but also when and where dynein anchoring occurs and, consequently, the function of dynein in spindle orientation. This surprising connection between a mitochondria-PM contact site and dynein anchoring was recently shown to be conserved in the evolutionarily distant fission yeast S. pombe [33]. The functional and physiological significance of why mitochondria-PM contacts serve as cortical attachment sites for dynein has yet to be determined.…”

ER-localized phosphatidylethanolamine synthase plays a conserved role in lipid droplet formation

“…To visualize the ER in S. pombe cells, pAV0764 (mCherry-AHDL; kindly provided by Sophie Martin -Addgene # 133520) was linearized with BstZ17I and integrated into the lys3 locus and selected for with blasticidin (Vjestica et al, 2020). To visualize mitochondria in S. pombe cells, mito-mCherry (mitoRED::Hyg; (Kraft and Lackner, 2019)) was linearized with NotI and introduced into the leu1 locus and selected for with hygromycin.…”