Retro-2 Alters Golgi Structure and Function

Abstract Retro-2 directly interacts with an ER exit site protein, Sec16A, inhibiting ER exit of a Golgi tSNARE, Syntaxin5, which results in rapid re-distribution of Syntaxin5 to the ER. Recently, it was shown that SARS-CoV-2 infection disrupts the Golgi apparatus within 6–12 hours, while its replication was effectively inhibited by Retro-2 in cultured human lung cells. Yet, exactly how Retro-2 may influence ultrastructure of the Golgi apparatus and its function have not been thoroughly investigated. In this study, we characterized the effect of Retro-2 treatment on Golgi function and its ultrastructure using electron microscopy and EM tomography. Our results indicate that Retro-2 treatment significantly alters protein glycosylation at the Golgi without affecting secretion of either small or large cargos. Ultra-structural study of the Golgi revealed rapid accumulation of COPI-like vesicular profiles in the perinuclear area and a partial disassembly of the Golgi stack under electron microscope within 3–5 hours, suggesting altered Golgi organization in these cells. Retro-2 treatment in cells depleted of GRASP65/55, the two well-known Golgi stacking proteins, induced complete and rapid disassembly of the Golgi into individual cisterna. Taken together, these results suggest that Retro-2 profoundly alters Golgi structure and function to a much greater extent than previously anticipated.