Percifull, L. | bioRxiv Science

bioRxiv2025

The Myo2 adaptor Ldm1 and its receptor Ldo16 mediate actin-dependent lipid droplet motility

Organelle motility enables strategic cellular reorganizations. In yeast, this process depends on the actin cytoskeleton, type V myosin motor proteins, and organelle-specific myosin adaptor proteins. While the myosin adaptors for most organelles are known, the coupling of myosin to lipid droplets (LDs), the cellular lipid storage organelles, remained enigmatic. Using genome-wide screening, we identified Ldm1 (Lipid Droplet Motility 1/Yer085c) as a myosin adaptor. Ldm1 binds to the globular tail domain of the myosin Myo2 and to the LD surface protein Ldo16 to enable actin-dependent LD motility. Ldo16 has additional roles in LD contact sites to the vacuole and the ER, suggesting a coordination of LD motility and organelle tethering. Ldm1 has a second role in mitochondrial transport and elevated Ldm1 levels rescue defects of the mitochondrial Myo2-adaptors Mmr1/Ypt11. Our work identifies the molecular machinery for LD motility and contributes to a comprehensive understanding of acto-myosin-based cellular reorganization.

cell biology↗

bioRxiv2024

Pex3 promotes formation of peroxisome-peroxisome and peroxisome-lipid droplet contact sites

Peroxisomes are ubiquitous organelles that mediate central metabolic functions, such as fatty acid {beta}-oxidation, as well as diverse tissue- and organism-specific processes. Membrane contact sites, regions of close apposition with other organelles for direct communication, are central to several aspects of their life cycle. Pex3 is a conserved multifunctional peroxisomal transmembrane protein involved in the insertion of peroxisomal membrane proteins, in pexophagy, and in the formation of membrane contact sites. Here, we show that elevated Pex3 levels in Saccharomyces cerevisiae induce the formation of peroxisome clusters surrounded by lipid droplets, mediated by peroxisome-peroxisome and peroxisome-lipid droplet contact sites. This clustering occurs independently of Pex3 partners in other processes, Pex19, Inp1, and Atg36. The cytosolic domain of Pex3 binds peroxisomes, suggesting a direct role in homotypic contact site formation. Lipid droplet-peroxisome contact sites require the lipid droplet-localized triacylglycerol lipase Tgl4, which is enriched along with other lipases at this interface. Pex3 overexpression in Drosophila melanogaster similarly alters peroxisome and lipid droplet morphology and promotes contact site formation. Together, our results offer novel molecular insights into homotypic peroxisome contact sites and peroxisome-lipid droplet contact sites across species.

cell biology↗