CONICET | Buscador de Institutos y Recursos Humanos

To maintain the position of organelles (and intracellular vesicular transport), cells use molecular motors, including actin-basedmyosins. To determine which myosins participate in the positioning andmorphology of the Golgi apparatus we performed a screening against the 37mammalian members. We took advantage of the ?micropatterning technique?, whichbrings cells to adopt a highly reproducible shape, and probabilistic densitymapping, which quantifies spatial organization of a particular compartment. Ourstudies revealed that the knockdown of MYO1C causes Golgi apparatusfragmentation and changes the positioning of this organelle within the cell.MYO1C is a single-headed class I myosin that is enriched in dynamic regions ofthe plasma membrane (PM) distinguished by the presence of lamellipodia,filopodia, and membrane ruffles. This myosin has been reported to participatein exocytosis and recycling of several raft-associated cargoes. However,its specific functions and partners remain to be elucidated. We confirmed that MYO1C-depletionaffects post-Golgi transport, reflected by a slower movement of Rab6-positive secretory vesicles.Additionally, we found that MYO1C interacts with the Golgi-specific BrefeldinA-resistance factor 1 (GBF1) by mass spectrometry and co-immune precipitation,but this interaction was not direct as shown by the yeast-two-hybrid assay. GBF1is a guanine-nucleotide-exchange factor (GEF) of Arf1 and regulates theER-Golgi interface. The activation of Arf1 by GBF1 promotes the recruitment ofCOP-I at the budding vesicles surface. We observed that MYO1Ccolocalizes with a pool of GBF1 that is found at the PM, and interestingly, thepresence of this PM pool of GBF1 is lost upon depletion of MYO1C. We hypothesize that the absence of MYO1C at the PMinduces changes in GBF1 cellular distribution, modifying Golgi transporthomeostasis, and disrupting Golgi morphology.