Impaired cell surface expression and digestive function of sucrase-isomaltase gene variants are associated with reduced efficacy of low FODMAPs diet in patients with IBS-D

Diab M Husein, Hassan Y Naim, Diab M Husein, Hassan Y Naim

No abstract available

Keywords: enzyme function; intestinal function; irritable bowel syndrome; low FODMAP diet; protein trafficking; sucrase-isomaltase gene variants.

Conflict of interest statement

Competing interests: None declared.

Figures

Figure 1

(A) Biosynthetic formsof SI wild type (SI-WT) and SI mutants. SI-WT or SI mutants wereimmunoprecipitated from transfected COS-1 cells, treated or not treated with Endoglycosidase H (Endo H) and subjected to Western blot analysis. 245kDa is mature Endo H-resistant SI; 185 kDa is Endo H product of mannose-rich SI. (B) Cellular localisation of SI-WT and SI mutants in COS-1 cells. SI proteins were labeled with anti-SI antibodies (primary) and goat anti-mouse IgG (secondary) carrying DyLight 488 (green). KDEL-ds Red is the ER marker. DAPI labels the nucleus (blue). Bars=30µm.

Figure 2

(A) Trafficking of SI proteins to the cell surface. SI-WT or SI mutants expressed in COS-1 cells were biotinylated and immunoprecipitated. Biotinylated cell surface SI was quantified versus total cellular SI. SI mutants at the cell surface were quantified versus SI-WT set to 100%. (B) Relative Specific enzyme activities of SI-WT and SI mutants. SI proteins were immunoprecipitated from transfected COS-1 cells and assayed for enzymatic activity versus sucrose or palatinose. Western blotting of similar samples was used to quantify the specific activities compared with SI-WT that was set to 100% for sucrase or palatinase. *p