Journal Article

ENaC in Cholinergic Brush Cells

Scholz, Paul, Perniss, Alexander, Althaus, Mike, Kandel, Chrissy, Osterloh, Sabrina, Keshavarz, Maryam, Kummer, Wolfgang, Schmidt, Patricia, Deckmann, Klaus

2018

Overview

Cholinergic polymodal chemosensory cells in the mammalian urethra (urethral brush cells = UBC) functionally express the canonical bitter and umami taste transduction signaling cascade. Here, we aimed to determine whether UBC are functionally equipped for the perception of salt through ENaC (epithelial sodium channel). Cholinergic UBC were isolated from ChAT-eGFP reporter mice (ChAT = choline acetyltransferase). RT-PCR showed mRNA expression of ENaC subunits , and in urethral epithelium and isolated UBC. could also be detected by next generation sequencing in 4/6 (66%) single UBC, two of them also expressed the bitter receptor Tas2R108. Strong expression of was seen in some urothelial umbrella cells and in 65% of UBC (30/46 cells) in a reporter mouse strain. Intracellular [Ca ] was recorded in isolated UBC stimulated with the bitter substance denatonium benzoate (25 mM), ATP (0.5 mM) and NaCl (50 mM, on top of 145 mM Na and 153 mM Cl baseline in buffer); mannitol (150 mM) served as osmolarity control. NaCl, but not mannitol, evoked an increase in intracellular [Ca ] in 70% of the tested UBC. The NaCl-induced effect was blocked by the ENaC inhibitor amiloride (IC = 0.47 μM). When responses to both NaCl and denatonium were tested, all three possible positive response patterns occurred in a balanced distribution: 42% NaCl only, 33% denatonium only, 25% to both stimuli. A similar reaction pattern was observed with ATP and NaCl as test stimuli. About 22% of the UBC reacted to all three stimuli. Thus, NaCl evokes calcium responses in several UBC, likely involving an amiloride-sensitive channel containing α-ENaC. This feature does not define a new subpopulation of UBC, but rather emphasizes their polymodal character. The actual function of α-ENaC in cholinergic UBC-salt perception, homeostatic ion transport, mechanoreception-remains to be determined.

• Publisher: Frontiers Media SA,Frontiers Media S.A
• Subject: Acetyltransferase / Amiloride / Animal welfare / Antibodies / Benzoic acid / Bitter taste / Calcium (intracellular) / Cell and Developmental Biology / Chemoreception / chemosensory cells / Choline O-acetyltransferase / cholinergic / ENaC / Epithelium / Gene expression / Immunohistochemistry / Intracellular / Kidney diseases / Kinases / Lasers / Mannitol / Next-generation sequencing / Osmolarity / Proteins / salt / Signal transduction / Sodium / Sodium channels / Sodium chloride / Taste receptors / Taste transduction / Umami / Urethra / urethral brush cells