Cerebellar granule cells in culture exhibit a ganglioside‐sialidase presumably linked to the plasma membrane

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Abstract
Cerebellar granule cells differentiated in culture were incubated with ganglioside [3H‐Sph]GDla in order to have it inserted into the plasma membrane, internalized by endocytosis, and metabolized. The metabolites formed included GMI. product of GDla desialosylation. No GMI or other metabolites were present in the incubation medium, whereas with the lysosomal apparatus blocked by chloroquine. or GDI a endocytosis prevented at 4° C, the only metabolite formed was GMI. These results suggest that GDI a desialosylation did not occur either extracellularly or intracellularly but likely, at the membrane level. Similar results were obtained with [3H‐Gal]GDlb. whereas no degradation of [3H‐NeuAc]GMI took place in the presence of chloroquine or at 4°C. In conclusion, cerebellar granule cells express in vivo a sialidasc, presumably located on the cell surface. that affects GDIa and GDIb but not GMI.