The calcium-activated chloride channel Anoctamin 1 contributes to the regulation of renal function

Abstract

The role of calcium-activated chloride channels for renal function is unknown. By immunohistochemistry we demonstrate dominant expression of the recently identified calcium-activated chloride channels, Anoctamin 1 (Ano1, TMEM16A) in human and mouse proximal tubular epithelial (PTE) cells, with some expression in podocytes and other tubular segments. Ano1-null mice had proteinuria and numerous large reabsorption vesicles in PTE cells. Selective knockout of Ano1 in podocytes (Ano1-/-/Nphs2-Cre) did not impair renal function, whereas tubular knockout in Ano1-/-/Ksp-Cre mice increased urine protein excretion and decreased urine electrolyte concentrations. Purinergic stimulation activated calcium-dependent chloride currents in isolated proximal tubule epithelial cells from wild-type but not from Ano1-/-/Ksp-Cre mice. Ano1 currents were activated by acidic pH, suggesting parallel stimulation of Ano1 chloride secretion with activation of the proton-ATPase. Lack of calcium-dependent chloride secretion in cells from Ano1-/-/Ksp-Cre mice was paralleled by attenuated proton secretion and reduced endosomal acidification, which compromised proximal tubular albumin uptake. Tubular knockout of Ano1 enhanced serum renin and aldosterone concentrations, probably leading to enhanced compensatory distal tubular reabsorption, thus maintaining normal blood pressure levels. Thus, Ano1 has a role in proximal tubular proton secretion and protein reabsorption. The results correspond to regulation of the proton-ATPase by the Ano1-homolog Ist2 in yeast.

Anoctamins support calcium-dependent chloride secretion by facilitating calcium signaling in adult mouse intestine

“…7). A bypass channel function has been described for Ano1 in renal proximal tubular cells, where electrogenic transport by the proton pump (VATPase) is supported by Cl − transport through Ano1 [12].…”

“…Generation of knockout models Generation of the Ano1 fl allele Ano1 Tm2JRR has been described in a previous publication [12]. In brief, to produce the Ano1 fl allele Ano1 Tm2JRR , a portion of BAC bMQ-379H21 (129S7/SvEv Brd-Hprt b-m2, AB2.2 embryonic stem (ES) cell DNA) was subcloned.…”

Anoctamin-6 Controls Bone Mineralization by Activating the Calcium Transporter NCX1

“…We propose that instead of directly transporting Ca ϩ to the tubular lumen by the Ca 2ϩ -activated V-ATPase is an electrogenic process, and accumulation of charge may limit the transport activity of the pump. Parallel activation of Ano1 leads to Cl Ϫ efflux that counterbalances charge movement, thereby facilitating H ϩ secretion (41). The mineralization defect in Ano6-deficient mice has previously been discussed as being linked to the scramblase function of Ano6, which is significantly impaired in osteoblasts (1).…”

Variomics Screen Identifies the Re-entrant Loop of the Calcium-activated Chloride Channel ANO1 That Facilitates Channel Activation

“…ANO1 is widely expressed in secretory epithelia (5)(6)(7)(8), as well as in a variety of other cell types, including smooth muscles and sensory neurons (6,9,10). ANO1 exhibits an important function in regulating airway fluid secretion, gut motility, secretory functions of exocrine glands, renal function, (vascular) smooth muscle contraction, and nociception (8,10,11).…”