Characterization of the interaction between hydroxypropyl guar galactomannan and galectin-3.
Multivalent galactose ligands have been proposed for selective targeting of carbohydrate-binding proteins on epithelial cell surfaces, both in normal and pathological conditions. One cellular partner is galectin-3, a β-galactoside-binding protein present on many epithelial linings, such as those of the ocular surface. In this study, we investigated the ability of hydroxypropyl guar galactomannan (HPGG) to bind recombinant galectin-3 and to target the apical surface of differentiated human corneal keratinocytes. Pull-down and slot-blot assays demonstrated that fluorescence-labeled HPGG bound recombinant galectin-3 through a galactose-dependent mechanism. In contrast, no binding of HPGG could be detected towards recombinant galectin-8 or -9. In a cell culture system, HPGG bound weakly to biotinylated cell surface corneal isolates containing endogenous galectin-3, and incubation of HPGG with corneal keratinocytes in culture resulted in discrete, galactose-independent, binding to the cell surface. Moreover, HPGG failed to elute the biological counter-receptor MUC16 from galectin-3 affinity columns. We conclude that HPGG binds galectin-3 through the conventional carbohydrate-recognition domain in vitro, but not in a biological system, suggesting that endogenous carbohydrate ligands on epithelial cell surface glycocalyces impair HPGG biorecognition.
Schepens Eye Research Institute, Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
Ashley M
AM
Woodward
Michelle
M
Senchyna
Ravaughn
R
Williams
Pablo
P
Argüeso
D018394:CA-125 Antigen / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D003315:Cornea / Q000166:cytology / Q000378:metabolism; D005690:Galactose / Q000378:metabolism*; D037502:Galectin 3 / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D008351:Mannans / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism
D018394:CA-125 Antigen; D037502:Galectin 3; C451759:MUC16 protein, human; D008351:Mannans; D008565:Membrane Proteins; D005690:Galactose