Trafficking of SLC26A3 in Intestinal Epithelial Cells: Effect of Enteropathogenic E. coli Infection

2014-10-28T00:00:00Z (GMT) by Tarunmeet Gujral
Trafficking of SLC26A3 (DRA) in Intestinal Epithelial Cells: Effect of Enteropathogenic E.coli (EPEC) Infection Tarunmeet Gujral, Anoop Kumar, Shubha Priyamvada, Ravinder K Gill, Gail A Hecht, Waddah A Alrefai, & Pradeep K Dudeja Enteropathogenic E.coli. (EPEC) via a type 3-secretion system decreases the activity of apical Cl-/HCO3- exchanger, DRA contributing to the pathophysiology of early diarrhea. Little is known about the mechanisms that regulate the cellular trafficking of DRA. We hypothesized that EPEC modulates endocytic and/or exocytic pathways involved in DRA trafficking. The aim of the current study was to study DRA trafficking events utilizing Caco-2 cells as an in vitro model. Dynasore, a dynamin inhibitor increased function and surface levels of DRA via decreased endocytosis. Disruption of microtubules followed by recovery in the presence or absence of nocodazole suggested that intact microtubules are essential for basal exocytic but not endocytic trafficking of DRA. Further, mice treated with colchicine showed a decrease in apical surface levels and an increase the sub-apical pool of DRA. EPEC deletion mutants EspG1/G2 (unable to disrupt microtubules) prevented both increased DRA endocytosis and decreased DRA exocytosis induced by wild-type EPEC indicating that intact microtubules are essential for surface membrane expression of DRA. EPEC induced decrease in apical Cl-/OH-(HCO3-) exchange activity and DRA association with lipid-rafts was unaltered in the presence of dynasore, suggesting a clathrin independent internalization of surface DRA during EPEC infection. Collectively, these data indicate that EPEC induces decrease in DRA surface levels by i) decreasing its association with rafts, ii) partly increasing endocytosis by clathrin independent mechanisms; and iii) by decreasing exocytosis of DRA via disruption of host microtubular network. In conclusion, our results highlight novel mechanisms of DRA cellular trafficking under physiological conditions and in response to EPEC infection. (Supported by NIDDK and Department of Veterans Affairs)

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