Plasma membrane-bound sialidase Neu3 impairs the clathrin-mediated endocytosis

A. ALEJANDRO VILCAES; MACARENA RODRIGUEZ-WALKER; JOSE L. DANIOTTI

PUERTO VARAS

Congreso; CHILEAN SOCIETY FOR CELL BIOLOGY XXVII ANNUAL MEETING; 2013

CHILEAN SOCIETY FOR CELL BIOLOGY

Introduction: Gangliosides (GS) are sialic acid-containing glycolipids expressed on plasma membranes from nearly all vertebrate cells. GS participate in a variety of physiological and pathological processes such as cell adhesion and endocytosis. GS are synthesized at the Golgi complex, but recently a number of enzymes of GS anabolism and catabolism have been shown to be associated with the plasma membrane. Neu3, a GS-specific sialidase, has been implicated in similar cellular processes as GS. However, the precise influence of Neu3 and GS on the endocytic process has not been established. Materials and methods: By biochemical and confocal microscopy techniques, we studied the role of GS and Neu3 in different endocytic processes. Results: We found an increased internalization of transferrin, the archetypical cargo for internalization through clathrin-mediated endocytosis, in cell lines expressing GS with different sialylation level. The ectopic expression of Neu3 led to a drastic decrease in transferrin endocytosis, suggesting a participation of GS in this process. However, the expression of Neu3 in GS-depleted cells maintained its effect on transferrin endocytosis. Clathrin-mediated endocytosis of LDL was also decreased after Neu3 expression. Interestingly, the internalization of Cholera toxin â-subunit, which is internalized via clathrin-independent pathways, was not modified. Furthermore, the intracellular distribution of caveolin-1 remains without changes in cells expressing Neu3, suggesting a close relationship between Neu3 activity and clathrin-mediated endocytosis. Discussion: The results suggest that the effect of Neu3 on the internalization of cargos via clathrin is probably independent of its action on GS, suggesting a novel role of this sialidase on clathrin-mediated endocytosis.