Optineurin links myosin VI to the Golgi complex and is involved in Golgi organization and exocytosis

Myosin VI plays a role in the maintenance of Golgi morphology and in exocytosis. In a yeast 2-hybrid screen we identified optineurin as a binding partner for Myosin VI at the Golgi complex and confirmed this interaction in a range of protein interaction studies. Both proteins colocalize at the Golgi complex and in vesicles at the plasma membrane. When optineurin is depleted from cells using RNA interference, Myosin VI is lost from the Golgi complex, the Golgi is fragmented and exocytosis of vesicular stomatitis virus G-protein to the plasma membrane is dramatically reduced. Two further binding partners for optineurin have been identified: Huntingtin and Rab8. We show that Myosin VI and Rab8 colocalize around the Golgi complex and in vesicles at the plasma membrane and overexpression of constitutively active Rab8-Q67L recruits Myosin VI onto Rab8-positive structures. These results show that optineurin links Myosin VI to the Golgi complex and plays a central role in Golgi ribbon formation and exocytosis.