Sortase-Modified Cholera Toxoids Show Specific Golgi Localization

Cholera toxoid is an established tool for use in cellular tracing in neuroscience and cell biology. We use a sortase-labelling approach to generate site-specifically N-terminally modified variants of both the A2-B5 heterohexamer and B5 pentamer forms of the toxoid. Both forms of the toxoid are endocytosed by GM1-positive mammalian cells, and while the heterohexameric toxoid was principally localized in the ER, the B5 pentamer showed an unexpected localization in the medial/trans Golgi. This study suggests a future role for specifically-labelled cholera toxoids in live-cell imaging beyond their current applications in neuronal tracing and labelling of lipid-rafts in fixed cells.