Protein transport (PubMed:17329360, PubMed:17827179, PubMed:18833296, PubMed:21835342, PubMed:22928698, PubMed:33704067, PubMed:9685396). Regulator of membrane traffic from the Golgi apparatus towards the endoplasmic reticulum (ER) (PubMed:21795785). Mediates membrane trafficking during egg chamber growth and organization, possibly upstream of exocyst component Sec5. Also during oogenesis, plays a role, together with BicD but independently of Sec5, in the polarization of the oocyte microtubule cytoskeleton, in the localization of oskar mRNA and in the anterodorsal secretion of grk. Required for anterograde opsin transport through the ER-Golgi complex. Plays a role, together with Rich, in regulating CadN transport in photoreceptor cells which is required for the formation of normal synaptic connections between axons from the inner photoreceptor cells in the eye and postsynaptic cells in the brain medulla layer M6 (PubMed:21835342). Necessary for proper development of bristle shafts of macrochaete and microchaete on the head, thorax and scutellum. Modulates Notch signaling (PubMed:10459009). As a key regulator of vesicular traffic, plays a critical role in the regulation of actin organization and is required for normal rates of phagocytic uptake during phagocytosis involved in defense against viral and fungal infection. Interacts with Rich and Act5C (PubMed:21835342, PubMed:22928698). Interacts with BicD (via C-terminal domain) (PubMed:17329360, PubMed:17827179). Interacts (in GTP-bound) with GCC1/CG10703 and cbs (PubMed:19001129). Interacts with Gorab (via C-terminus); binds to a Gorab homodimer, this interaction seems to be required for trans-Golgi localization of Gorab (PubMed:33704067). Colocalizes with Rich at the Golgi apparatus. During oogenesis, first accumulates transiently in a central position during stages 7-8, then is uniformly distributed at the beginning of stage 9 to end up juxtaposed to the entire oocyte cortex. Expressed in larval eye, wing and leg imaginal disks and in salivary gland. Expressed in the larval optic lobe, showing an enrichment in the neuropil. In the adult brain, expressed in photoreceptors and mushroom body. Larval lethal. Belongs to the small GTPase superfamily. Rab family.