Anti-SLC26A6 monoclonal antibody Made to order

The PDZ-binding protein PDZK1 (CAP70/PDZ-dc-1/NHERF3) in vitro binds to cystic fibrosis transmembrane conductance regulator (CFTR), the anion exchangers SLC26A3 and SLC26A6 and the Na+/H+ exchanger NHE3, all of which are major transport proteins for intestinal anion secretion and salt absorption. This study was undertaken to search for a role of PDZK1 in regulating electrolyte transport in native murine small intestine. Short circuit current (I-SC) and and HCO3- secretory rate (J(HCO 3 -)) were measured to assess electrogenic anion secretion; Na-22(+) fluxes to assess sodium absorption in isolated small intestine. NHE3, CFTR, as well as NHERF1, NHERF2, and PDZK1 messenger RNA (mRNA) expression levels, and NHE3 total enterocyte and brush border membrane (BBM) protein abundance were determined by quantitative polymerase chain reaction (PCR) and Western analysis. NHE3 localization was performed by immunohistochemistry. In pdzk1 -/- jejunal mucosa, basal net Na+ absorption as well as the inhibition of Na+ absorption by forskolin was significantly reduced. In pdzk1 -/- duodenal mucosa, identical basal I-SC and J(HCO 3 -), but a significant, yet mild, reduction of forskolin-stimulated Delta(JHCO 3 -) and Delta ISC was observed compared to +/+ tissue. Tissue conductance, morphological features, and the Delta I-SC and increase in Na-22(+) absorption in response to luminal glucose was identical in pdzk1 +/+ and -/- small intestine, ruling out a general absorptive defect. While CFTR mRNA expression levels were unchanged, NHE3 mRNA expression levels were significantly increased in small intestinal mucosa of pdzk1 -/- mice. Total enterocyte and BBM abundance was not significantly different, suggesting an increased NHE3 turnover, possibly due to reduced NHE3 membrane retention time. Lack of the PDZ-adapter protein PDZK1 in murine small intestine causes a mild reduction in maximal CFTR activation, but a severe defect in electroneutral Na+ absorption.

Inorganic sulfate (SO42-) is essential for a multitude of physiological processes. The specific molecular pathway has been identified for uptake from the small intestine but is virtually unknown for the large bowel, although there is evidence for absorption involving Na+-independent anion exchange. A leading candidate is the apical chloride/bicarbonate (Cl-/HCO3-) exchanger DRA (down-regulated in adenoma; Slc26a3), primarily linked to the Cl- transporting defect in congenital chloride diarrhea. The present study set out to characterize transepithelial (SO42-)-S-35 and Cl-36(-) fluxes across the isolated, short-circuited cecum from wild-type (WT) and knockout (KO) mice and subsequently to define the contribution of DRA. The cecum demonstrated simultaneous net SO42- secretion (-8.39 +/- 0.88 nmol.cm(-2).h(-1)) and Cl- absorption (10.85 +/- 1.41 mu mol.cm(-2).h(-1)). In DRA-KO mice, SO42- secretion was reversed to net absorption via a 60% reduction in serosal to mucosal SO42- flux. Similarly, net Cl- absorption was abolished and replaced by secretion, indicating that DRA represents a major pathway for transcellular SO42- secretion and Cl- absorption. Further experiments including the application of DIDS (500 mu M), bumetanide (100 mu M), and substitutions of extracellular Cl- or HCO3-/CO2 helped to identify specific ion dependencies and driving forces and suggested that additional anion exchangers were operating at both apical and basolateral membranes supporting SO42- transport. In conclusion, DRA contributes to SO42- secretion via DIDS-sensitive HCO3-/SO42- exchange, in addition to being the principal DIDS-resistant Cl-/HCO3- exchanger. With DRA linked to the pathogenesis of other gastrointestinal diseases extending its functional characterization offers a more complete picture of its role in the intestine.