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Mechanisms Underlying Modulation of SLC26A3 Activity by Lactobacillus acidophilus‐secreted Soluble Factors
Author(s) -
Borthakur Alip,
Priyamvada Shubha,
Kumar Anoop,
Gujral Tarunmeet,
Natarajan Arivarasu A,
Alrefai Waddah A,
Dudeja Pradeep K
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1162.7
Subject(s) - chemistry , microbiology and biotechnology , lipid raft , dids , apical membrane , biochemistry , biology , cell , membrane
DRA (Down‐Regulated in Adenoma, SLC26A3) mediates apical membrane Cl − /HCO 3 − exchange activity in mammalian intestinal epithelial cells. Our previous studies showed that soluble factor(s) in the bacteria‐free culture supernatant (CS) of the probiotic Lactobacillus acidophilus (LA) stimulated Cl − /HCO 3 − exchange activity in Caco‐2 cells via increasing apical membrane DRA levels. Current studies were undertaken to elucidate the mechanisms of LA‐CS enrichment of functional DRA on the apical cell surface. Post‐confluent Caco‐2 monolayers were treated for 3 h with LA‐CS. DRA function was measured as DIDS‐sensitive 125 I‐uptake, surface DRA assessed by cell‐surface biotinylation/confocal microscopy. Inhibitors of PI3 kinase and Rac1, as well as methyl‐β‐D‐cyclodextran, a lipid raft‐disrupting agent, abrogated LA‐CS effects on DRA function. LA‐CS enhanced DRA levels in the detergent insoluble (DI) fraction in Caco‐2 cells. Silencing the PDZ protein NHERF2 attenuated LA‐CS enhancement of apical membrane DRA. Molecular size fractionation showed that soluble factors in the LA‐CS that enhance functional DRA on the apical membrane are of low molecular mass (3–10 kD) and are heat‐stable. Our results define novel mechanisms involving lipid rafts, NHERF, and PI3K‐Rac1 pathway in altered trafficking of DRA induced by probiotic‐secreted bioactive factor(s) to modulate intestinal chloride absorption. [Grant support: VA/NIDDK/Bill & Melinda Gates Foundation]