Role of actin in EGF-induced alterations in enterocyte SGLT1 expression

Abstract

Na+-glucose cotransporter (SGLT1) expression and the role of actin in epidermal growth factor (EGF)-induced alterations in glucose transport and brush-border surface area were examined in New Zealand White rabbit jejunal loops. In separate experiments, EGF or EGF concurrent with cytochalasin D, an inhibitor of actin polymerization, was administered to the experimental loop and compared with its vehicle control. SGLT1 expression was measured by Western blot in brush-border membrane vesicles (BBMV) after 5-min and 1-h exposure. Glucose kinetics were determined by a rapid filtration technique, and brush-border surface area was examined by electron microscopy after 1-h exposure. The effect of cytochalasin D alone on BBMV glucose kinetics and brush-border surface area was also assessed. EGF resulted in a significant increase in BBMV SGLT1 expression ( P < 0.05), glucose maximal uptake ( V max; P < 0.001), and absorptive brush-border surface area ( P < 0.001). These effects were abolished with concurrent cytochalasin D treatment. Cytochalasin D alone had no effect on glucose transport or brush-border surface area. The findings suggest that EGF acutely upregulates jejunal brush-border surface area and the V max for jejunal glucose uptake via the recruitment and insertion of SGLT1 from an internal pool into the brush border by a mechanism that is dependent on actin polymerization.

SGLT-1-mediated glucose uptake protects human intestinal epithelial cells against Giardia duodenalis-induced apoptosis

“…For detection of SGLT-1 expression, a previously validated polyclonal rabbit anti-mouse SGLT-1 antibody that cross-reacts with human SGLT-1 (1:500, Chemicon International, Temecula, CA) was used as the primary antibody ( [Chung et al, 1999] and [Chung et al, 2002a]). Secondary antibodies were goat anti-rabbit conjugated to Alexa 594 or Alexa 488 (1:1000, Molecular Probes, Eugene, OR).…”

Immunopathology of giardiasis: the role of lymphocytes in intestinal epithelial injury and malfunction

“…Conversely, addition of actin monomers to membrane-associated ends of brush border microvillar filaments increases microvillous length (Mooseker et al 1982). Recent observations also suggest that the rapid upregulation of microvillous length by epidermal growth factor may involve an apical translocation of intracellular pools of membrane constituents via actin polymerization (Chung et al 1999). In addition, bacterial pathogens such as Yersinia or enteropathogenic E. coli are known to affect apical distribution of F-actin in enterocytes (Finlay & Cossart 1997), and intestinal infection with these microorganisms causes a diffuse shortening of brush border microvilli (Buret et al 1990(Buret et al , 1998.…”

The Effect of Massive Small Bowel Resection and Oral Epidermal Growth Factor Therapy on SGLT-1 Distribution in Rabbit Distal Remnant

“…We have previously documented the validity of this detection system (10). A standard curve of serial dilutions of the peptide against which the antibody was raised demonstrated that trace OD was linear from 0.25 to 7 pmol of the peptide antigen.…”

“…Aliquots of BBM preparations were assessed for SGLT-1 content by Western immunoblot as previously described (10). The anti-SGLT-1 antibodies used in these studies are described in detail in the section on immunohistochemistry below.…”