Secretion of the galectin family of mammalian carbohydrate-binding proteins.
Galectins are cytosolic proteins that lack any signal sequence for transport into the endoplasmic reticulum and are not glycosylated, although several galectins contain consensus sites for N-glycosylation, indicating that these proteins do not traverse the ER-Golgi network. However, there is abundant evidence for the extracellular localisation of some galectins at cell surfaces, in the extracellular matrix and in cell secretions consistent with other evidence for extracellular roles of galectins as modulators of cell adhesion and signalling. How then are galectins secreted if not through the classical secretory pathway? Do all galectins share the same secretory pathway? Can a particular galectin utilise more than one secretory pathway? If galectins play important extracellular roles how is their secretion regulated in relation to function? These are still largely unanswered questions but recent studies are beginning to give glimpses into some novel aspects of the secretion of these intriguing proteins.
Hughes
R C
RC
National Institute for Medical Research, Mill Hill, London, UK. c-hughes@nimr.mrc.ac.uk
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D001665:Binding Sites; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002448:Cell Adhesion; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity; D003600:Cytosol / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D037502:Galectin 3; D037161:Galectins; D006388:Hemagglutinins / Q000378:metabolism*; D006801:Humans; D019897:Periplasm / Q000378:metabolism; D011956:Receptors, Cell Surface
D018528:ATP-Binding Cassette Transporters; D000943:Antigens, Differentiation; D002352:Carrier Proteins; D037502:Galectin 3; D037161:Galectins; D006388:Hemagglutinins; D011956:Receptors, Cell Surface; C055213:saccharide-binding proteins