Plays an important role in the maintenance of the Golgi complex, in membrane trafficking, in exocytosis, through its interaction with myosin VI and Rab8. Links myosin VI to the Golgi complex and plays an important role in Golgi ribbon formation. Plays a role in the activation of innate immune response during viral infection. Mechanistically, recruits TBK1 at the Golgi apparatus, promoting its trans-phosphorylation after RLR or TLR3 stimulation. In turn, activated TBK1 phosphorylates its downstream partner IRF3 to produce IFN-beta. Plays a neuroprotective role in the eye and optic nerve. May act by regulating membrane trafficking and cellular morphogenesis via a complex that contains Rab8 and hungtingtin (HD). Mediates the interaction of Rab8 with the probable GTPase-activating protein TBC1D17 during Rab8-mediated endocytic trafficking, such as of transferrin receptor (TFRC/TfR); regulates Rab8 recruitnment to tubules emanating from the endocytic recycling compartment. Autophagy receptor that interacts directly with both the cargo to become degraded and an autophagy modifier of the MAP1 LC3 family; targets ubiquitin-coated bacteria (xenophagy), such as cytoplasmic Salmonella enterica, and appears to function in the same pathway as SQSTM1 and CALCOCO2/NDP52. Self-associates (By similarity). Interacts with HD, Rab8 (RAB8A and/or RAB8B) (active GTP-bound form), GTF3A, TRAF3, TBK1, MYO6 and TFRC. Binds to linear ubiquitin chains. Interacts with LC3 family members MAP1LC3A, MAP1LC3B, GABARAP, GABARAPL1 and GABARAPL2; OPTN phosphorylation increases the association (at least with MAP1LC3B). Interacts with RAB12; the interaction may be indirect. Interacts with TBK1; this interaction leads to the Golgi localization of TBK1 and its subsequent activation. Interacts with palmitoyltransferase ZDHHC17/HIP14; the interaction does not lead to palmitoylation of OPTN (By similarity). Interacts with CYLD (By similarity). Found in the perinuclear region and associates with the Golgi apparatus. Colocalizes with MYO6 and RAB8 at the Golgi complex and in vesicular structures close to the plasma membrane. Localizes to LC3-positive cytoplasmic vesicles upon induction of autophagy (By similarity). In eye, it is expressed in anterior segment, retina, and optic nerve blood vessels (at protein level). Highly expressed in adult liver, heart and testis. Expressed from 7-day-old embryos. Ubiquitin-binding motif (UBAN) is essential for its inhibitory function, subcellular localization and interaction with TBK1. The LIR (LC3-interacting region) motif mediates the interaction with ATG8 family proteins. Phosphorylated by TBK1, leading to restrict bacterial proliferation in case of infection. OPTN E59K transgenic mice exhibit profound gliosis in the retina. OPTN-deficient cells display reduced TBK1 activation, IRF3 phosphorylation, and expression of type I IFNs in response to TLR3 and TLR4 stimulation, indicating a role for OPTN in the innate immune response.