Involved in maintaining Golgi structure. Stimulates the formation of Golgi stacks and ribbons. Involved in intra-Golgi retrograde transport (By similarity). Homodimer. Interacts with RAB1A that has been activated by GTP-binding. Interacts with isoform CASP of CUX1 (By similarity). Found throughout the Golgi. Highly phosphorylated during mitosis. Phosphorylation is barely detectable during interphase (By similarity).