Role of MYO1C in Golgi apparatus morphology and function

CAPMANY A; GOUD B; SCHAUER K

La Serena

Workshop; Actualizations in membrane trafficking in health and disease; 2016

EMBO

To maintain the position of organelles (and intracellular vesicular transport), cells use molecular motors, including actin-based myosins. To determine which myosins participate in the positioning and morphology of the Golgi apparatus we performed a screening against the 37 mammalian members. We took advantage of the ?micropatterning technique?, which brings cells to adopt a highly reproducible shape, and probabilistic density mapping, which quantifies spatial organization of a particular compartment. Our studies revealed that the knockdown of MYO1C causes Golgi apparatus fragmentation and changes the positioning of this organelle within the cell. MYO1C is a single-headed class I myosin that is enriched in dynamic regions of the plasma membrane (PM) distinguished by the presence of lamellipodia, filopodia, and membrane ruffles. This myosin has been reported to participate in exocytosis and recycling of several raft-associated cargoes. However, its specific functions and partners remain to be elucidated. We confirmed that MYO1C-depletion affects post-Golgi transport, reflected by a slower movement of Rab6-positive secretory vesicles. Additionally, we found that MYO1C interacts with the Golgi-specific Brefeldin A-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. GBF1 is a guanine-nucleotide-exchange factor (GEF) of Arf1 and regulates the ER-Golgi interface. The activation of Arf1 by GBF1 promotes the recruitment of COP-I at the budding vesicles surface. We observed that MYO1C colocalizes with a pool of GBF1 that is found at the PM, and interestingly, the presence of this PM pool of GBF1 is lost upon depletion of MYO1C. We hypothesize that the absence of MYO1C at the PM induces changes in GBF1 cellular distribution, modifying Golgi transport homeostasis, and disrupting Golgi morphology.