Differential association of the Na+/H+ Exchanger Regulatory Factor (NHERF) family of adaptor proteins with the raft- and the non-raft brush border membrane fractions of NHE3.

Background/aims: Trafficking, brush border membrane (BBM) retention, and signal-specific regulation of the Na+/H+ exchanger NHE3 is regulated by the Na+/H+ Exchanger Regulatory Factor (NHERF) family of PDZ-adaptor proteins, which enable the formation of multiprotein complexes. It is unclear, however, what determines signal specificity of these NHERFs. Thus, we studied the association of NHE3, NHERF1 (EBP50), NHERF2 (E3KARP), and NHERF3 (PDZK1) with lipid rafts in murine small intestinal BBM.

Proteome of murine jejunal brush border membrane vesicles.

The first detailed description of the proteome of the mouse jejunal brush border membrane vesicle is presented here. This was obtained by a combination of purification via divalent (Mg2+) cation precipitation starting with isolated cells plus strong cation exchange chromatography LC-MS/MS. Five-hundred seventy proteins were identified including 45 transport proteins.

Stimulation of salivary secretion in vivo by CFTR potentiators in Cftr+/+ and Cftr-/- mice.

Background: Physiologically, salivary secretion is controlled by cholinergic and adrenergic pathways but the role of ionic channels in this process is not yet clearly understood. In cystic fibrosis (CF), most exocrine glands failed to response to beta-adrenergic agonists.

Methods: To determine the implication of CFTR in this process, we measured in vivo the salivary secretion of Cftr(+/+) and Cftr(-/-) mice in the presence of 2 water-soluble benzo[c]quinolizinium derivatives; MPB-07 a potentiator of CFTR Cl(-) channel and MPB-05 an inactive analogue.

Rescue of functional delF508-CFTR channels in cystic fibrosis epithelial cells by the alpha-glucosidase inhibitor miglustat.

In the disease cystic fibrosis (CF), the most common mutation delF508 results in endoplasmic reticulum retention of misfolded CF gene proteins (CFTR). We show that the alpha-1,2-glucosidase inhibitor miglustat (N-butyldeoxynojirimycin, NB-DNJ) prevents delF508-CFTR/calnexin interaction and restores cAMP-activated chloride current in epithelial CF cells. Moreover, miglustat rescues a mature and functional delF508-CFTR in the intestinal crypts of ileal mucosa from delF508 mice.

Biochemical methods to assess CFTR expression and membrane localization.

Detection of cystic fibrosis transmembrane conductance regulator (CFTR) protein is usually a difficult task to accomplish due to the low levels of expression and high turnover that this membrane protein is submitted to in the cell. Common biochemical methods can be used for the detection of CFTR but several critical points must be taken into account. The scope of this article is to outline biochemical methods commonly used to assess CFTR expression, processing and membrane localization.