Impact of glycosylation and detergent-resistant membranes on the function of intestinal sucrase-isomaltase

Abstract

Sucrase-isomaltase (SI) is a highly N- and O-glycosylated intestinal brush border membrane protein. SI is sorted with high fidelity to the apical membrane via O-linked glycans that mediate its association with lipid rafts or detergent-resistant membranes (DRMs). Here, we show that N- and O-glycosylation and DRMs are implicated in the regulation of the function of SI in intestinal Caco-2 cells. The activities of sucrase (SUC) and isomaltase (IM) increase substantially in DRMs when N- and O-glycosylation patterns are intact. Disruption of DRMs by solubilization with Triton X-100 at 37 degrees C substantially reduces the activities of SUC and IM. Furthermore, modulation of O-glycosylation by benzyl-2-acetamido-2-deoxy-alpha-d-galactopyranoside and N-glycosylation by deoxymannojirimycin is linked to a decreased capacity of SI to associate with DRMs, with a subsequent reduction of the enzymatic activities of SUC and IM. This is the first report that reveals a direct role of N- and O-glycans in association with DRMs in regulating the function of a membrane glycoprotein.

Core2 O-Glycan Structure Is Essential for the Cell Surface Expression of Sucrase Isomaltase and Dipeptidyl Peptidase-IV during Intestinal Cell Differentiation

“…Because there is no high quality antibody commercially available for immunoblotting mouse DPP-IV, we were only able to compare DPP-IV molecular weight differences with and without RNAi treatment. SI and DPP-IV from GalNAc-bn-treated Caco-2 cells showed a decreased molecular weight, as reported previously (23,37), and only DPP-IV showed significant decreases in molecular weight after RNAi treatment (Fig. 4B, right panel).…”

Characteristic Changes in Cell Surface Glycosylation Accompany Intestinal Epithelial Cell (IEC) Differentiation: High Mannose Structures Dominate the Cell Surface Glycome of Undifferentiated Enterocytes

“…As the major changes in the cell surface during IEC differentiation is because of microvilli formation, we propose that the glycan changes are largely microvilli-associated. Indeed, hydrolases such as alkaline phosphatase, which are present on the apical border, are highly glycosylated (53,54), and their function and stability have been shown to be associated with the presented glycans (55,56). Improper glycosylation would result in rapid degra- dation of these brush border enzymes.…”

Lipid rafts: signaling and sorting platforms of cells and their roles in cancer

“…Cell-cell and cell-matrix c [96] CD9 Cell adhesion, cell motility, tumor metastasis c [96] Integrin Cell adhesion, cytoskeletal structure, lipid-raft cluster c [96] ADAM10 Cell adhesion, release of membrane vesicles c [96] Signaling CD81 Regulation of lymphoma cell growth c [96] FAS/CD95 Apotosis c [44] G proteins (Gia, Gib) Transmembrane signaling, modulator, transducer c, m, c [5,93,96] Ras G protein, signaling, modulator, transducer c [44] Ras-related protein G protein, signaling, modulator, transducer c, c [5,44] uPAR Signal transduction activation effects of uPA, plasmin formation c [34] DPPIV Glycoprotein, essential for TCR signaling c [96] Tumor-associated calcium signal transducer Growth factor receptor c [96] Enzymes Sucrose-isomaltase Carbohydrate digestion c [97] Serine protease TADG-15 Degrades extracellular matrix c [96] Na/K-ATPase Ion exchange across membrane c [95] 5-Lipoxygenase Lipid metabolism l [94] BCR: B-cell receptor; c: Carcinoma; Csk: C-src kinase; DPPIV: Review plays a role in localizing and promoting plasmin formation, mediates the proteolysis-independent signal transduction activation effects of uPA, and is subject to negative feedback regulation by uPA, which cleaves it into an inactive form. The expression of uPAR is cancer stage specific [46].…”