Role of plasma membrane-bound sialidase NEU3 in clathrin-mediated endocytosis

RODRIGUEZ WALKER M.; VILCAES A.; GARBARINO-PICO, E.; DANIOTTI J.L.

BIOCHEMICAL JOURNAL

PORTLAND PRESS LTD

Lugar: London; Año: 2015 vol. 470 p. 131 - 144

0264-6021

Gangliosides are sialic acid containing glycosphingolipids mainly expressed at the outer leaflet of the plasma membrane. Sialidase NEU3 is a key enzyme in the catabolism of gangliosides with its up-regulation having been observed in human cancer cells. In the case of clathrin-mediated endocytosis (CME), although this has been widely studied, the role of NEU3 and gangliosides in this cellular process has not yet been established. Here, we found an increased internalization of transferrin (Tf), the archetypical cargo for CME, in cells expressing complex gangliosides with high levels of sialylation. The ectopic expression of NEU3 led to a drastic decrease in Tf endocytosis, suggesting a participation of gangliosides in this process. However, the reduction of Tf endocytosis caused by NEU3 was still observed in glycosphingolipid-depleted cells, indicating that NEU3 could operate in a way that is independent of its action on gangliosides. Additionally, internalization of α2 macroglobulin and low-density lipoprotein, other typical ligands in CME, was also decreased in NEU3 expressing cells. In contrast, cholera toxin β-subunit internalization, which is endocytosed by both clathrin-dependent and clathrin-independent mechanisms, remained unaltered. Kinetic assays revealed that NEU3 caused a reduction in the sorting of endocytosed Tf to early and recycling endosomes, with the Tf binding at the cell surface being also reduced. NEU3 expressing cells showed an altered subcellular distribution of clathrin adaptor AP-2, but did not reveal any changes in the membrane distribution of clathrin, phosphatidylinositol (4, 5)-bisphosphate or caveolin-1. Overall, these results suggest a specific and novel role of NEU3 in CME.