To understand how CNIH-2 increased the surface population of AMPARs, we analyzed its subcellular distribution upon heterologous expression in HeLa cells and over-expression in dissociated hippocampal neurons and glial cells. Both in HeLa cells and hippocampal neurons (DIV 17), exogenously expressed CNIH-2 accumulated in a perinuclear compartment (Fig. 2A, upper and middle panel), while it exhibited a more punctate peripheral distribution in glial cells (Fig. 2A, lower panel). The compartment, in which CNIH-2 concentrated, could be identified as the Golgi complex by co-localization with the cis- or trans-Golgi marker proteins GM130 or galactosyltransferase (GalTase), respectively. In addition, incubation with the fungal toxin Brefeldin A (10 µg/ml, 30 min), which fuses Golgi membranes with those of the ER, resulted in a reversible redistribution of CNIH-2 into the ER (data not shown). With higher expression levels, we also observed CNIH-2 immunoreactivity that was homogenously distributed throughout the cells in a network-like pattern, most likely resembling the ER.
