Human sialidase NEU4 long and short are extrinsic proteins bound to outer mitochondrial membrane and the endoplasmic reticulum, respectively.
Sialidases are widely distributed glycohydrolytic enzymes removing sialic acid residues from glycoconjugates. In mammals, several sialidases with different subcellular localizations and biochemical features have been described. NEU4, the most recently identified member of the human sialidase family, is found in two forms, NEU4 long and NEU4 short, differing in the presence of a 12-amino-acid sequence at the N-terminus. Contradictory data are present in the literature about the subcellular distribution of these enzymes, their membrane anchoring mechanism being still unclear. In this work, we investigate the human NEU4 long and NEU4 short membrane anchoring mechanism and their subcellular localization. Protein extraction with Triton X-114 and sodium carbonate and cross-linking experiments demonstrate that both forms of NEU4 are extrinsic membrane proteins, anchored via protein-protein interactions. Moreover, through confocal microscopy and subcellular fractionation, we show that the long form localizes in mitochondria, while the short form is also associated with the endoplasmic reticulum. Finally, mitochondria subfractionation experiments suggest that NEU4 long is bound to the outer mitochondrial membrane.
Bigi
Alessandra
A
Department of Biotechnologies and Biosciences, University of Milan-Bicocca, Piazza della Scienza, 2, 20126, Milano.
Morosi
Lavinia
L
Pozzi
Chiara
C
Forcella
Matilde
M
Tettamanti
Guido
G
Venerando
Bruno
B
Monti
Eugenio
E
Fusi
Paola
P
D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D051336:Mitochondrial Membranes / Q000378:metabolism*; D009439:Neuraminidase / Q000302:isolation & purification / Q000378:metabolism*; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000737:chemistry; D011485:Protein Binding
D011092:Polyethylene Glycols; D017830:Octoxynol; C010615:Nonidet P-40; C491428:NEU4 protein, human; D009439:Neuraminidase