TY - JOUR
T1 - Galectin-2 at the enterocyte brush border of the small intestine
AU - Thomsen, Martha Kampp
AU - Hansen, Gert H
AU - Danielsen, E Michael
PY - 2009
Y1 - 2009
N2 - The brush border of pig small intestine is a local hotspot for beta-galactoside-recognizing lectins, as evidenced by its prominent labeling with fluorescent lectin PNA. Previously, galectins 3-4, intelectin, and lectin-like anti-glycosyl antibodies have been localized to this important body boundary. Together with the membrane glycolipids these lectins form stable lipid raft microdomains that also harbour several of the major digestive microvillar enzymes. In the present work, we identified a lactose-sensitive 14-kDa protein enriched in a microvillar detergent resistant fraction as galectin-2. Its release from closed, right-side-out microvillar membrane vesicles shows that at least some of the galectin-2 resides at the lumenal surface of the brush border, indicating that it plays a role in the organization/stabilization of the lipid raft domains. Galectin-2 was released more effectively from the membrane by lactose than was galectin-4, and surprisingly, it was also released by the noncanonical disaccharides sucrose and maltose. Furthermore, unlike galectin-4, galectin-2 was preferentially co-immunoisolated with sucrase-isomaltase rather than with aminopeptidase N. Together, these results show that the galectins are not simply redundant proteins competing for the same ligands but rather act in concert to ensure an optimal cross-linking of membrane glycolipids and glycoproteins. In this way, they offer a maximal protection of the brush border against exposure to bile, pancreatic enzymes and pathogens.
AB - The brush border of pig small intestine is a local hotspot for beta-galactoside-recognizing lectins, as evidenced by its prominent labeling with fluorescent lectin PNA. Previously, galectins 3-4, intelectin, and lectin-like anti-glycosyl antibodies have been localized to this important body boundary. Together with the membrane glycolipids these lectins form stable lipid raft microdomains that also harbour several of the major digestive microvillar enzymes. In the present work, we identified a lactose-sensitive 14-kDa protein enriched in a microvillar detergent resistant fraction as galectin-2. Its release from closed, right-side-out microvillar membrane vesicles shows that at least some of the galectin-2 resides at the lumenal surface of the brush border, indicating that it plays a role in the organization/stabilization of the lipid raft domains. Galectin-2 was released more effectively from the membrane by lactose than was galectin-4, and surprisingly, it was also released by the noncanonical disaccharides sucrose and maltose. Furthermore, unlike galectin-4, galectin-2 was preferentially co-immunoisolated with sucrase-isomaltase rather than with aminopeptidase N. Together, these results show that the galectins are not simply redundant proteins competing for the same ligands but rather act in concert to ensure an optimal cross-linking of membrane glycolipids and glycoproteins. In this way, they offer a maximal protection of the brush border against exposure to bile, pancreatic enzymes and pathogens.
U2 - 10.1080/09687680903167781
DO - 10.1080/09687680903167781
M3 - Journal article
C2 - 19657968
SN - 0968-7688
VL - 26
SP - 347
EP - 355
JO - Molecular Membrane Biology
JF - Molecular Membrane Biology
IS - 5
ER -