UC San Diego

The localization of cellular components like organelles or protein complexes must be precisely controlled in living cells. Proper distribution is largely achieved by motor proteins that selectively bind and transport cargo along cytoskeletal tracks. The traditional view of motor-based transport is that cargo move by directly associating with a motor complex. However, a non-canonical form of motor-based transport termed “hitchhiking” was recently co-discovered by the Reck-Peterson lab, whereby “secondary” cargo move by tethering to motile “primary” cargo that are bound to a motor complex. Hitchhiking-like phenomena have been observed in diverse polarized cells such as filamentous fungi and neurons. The goal of my graduate work was to determine the function and mechanism of peroxisome hitchhiking using filamentous fungi as a model for studying this process in vivo. Peroxisomes are organelles ubiquitous to eukaryotic cells that exhibit different long-distance motility characteristics across diverse species and cell types. In the filamentous fungus Aspergillus nidulans, peroxisomes move long distances along microtubules by hitchhiking on motile early endosomes. This requires the fungal-specific protein PxdA. In my doctoral work, I helped identify the fungal-specific phosphatase DipA as an interaction partner of PxdA. I also explored the role of PxdA in different peroxisome functions, notably during the biogenesis and positioning of Woronin bodies and the compartmentalization of secondary metabolism. These findings highlight the molecular mechanisms underlying organelle hitchhiking in fungi and expand our understanding of dynamic peroxisome function.