TY  - JOUR
U1  - Zeitschriftenartikel, wissenschaftlich - begutachtet (reviewed)
A1  - Wichmann, Lukas
A1  - Vowinkel, Kirsty Sophia
A1  - Perniss, Alexander
A1  - Manzini, Ivan
A1  - Althaus, Mike
T1  - Incorporation of the -subunit into the epithelial sodium channel (ENaC) generates protease-resistant ENaCs in Xenopus laevis
JF  - The Journal of Biological Chemistry
N2  - The epithelial sodium channel (ENaC) is a critical regulator of vertebrate electrolyte homeostasis. ENaC is the only constitutively open ion channel in the degenerin/ENaC protein family, and its expression, membrane abundance, and open probability therefore are tightly controlled. The canonical ENaC is composed of three subunits (, , and ), but a fourth -subunit may replace and form atypical -ENaCs. Using Xenopus laevis as a model, here we found that mRNAs of the - and -subunits are differentially expressed in different tissues and that -ENaC predominantly is present in the urogenital tract. Using whole-cell and single-channel electrophysiology of oocytes expressing Xenopus - or -ENaC, we demonstrate that the presence of the -subunit enhances the amount of current generated by ENaC due to an increased open probability, but also changes current into a transient form. Activity of canonical ENaCs is critically dependent on proteolytic processing of the - and -subunits, and immunoblotting with epitope-tagged ENaC subunits indicated that, unlike -ENaC, the -subunit does not undergo proteolytic maturation by the endogenous protease furin. Furthermore, currents generated by -ENaC were insensitive to activation by extracellular chymotrypsin, and presence of the -subunit prevented cleavage of -ENaC at the cell surface. Our findings suggest that subunit composition constitutes an additional level of ENaC regulation, and we propose that the Xenopus -ENaC subunit represents a functional example that demonstrates the importance of proteolytic maturation during ENaC evolution.
KW  - protease
KW  - epithelial sodium channel (ENaC)
KW  - patch clamp
KW  - electrophysiology
KW  - delta-subunit
KW  - Xenopus laevis
KW  - furin
KW  - chymotrypsin
SN  - 0021-9258
SS  - 0021-9258
U6  - https://doi.org/10.1074/jbc.RA118.002543
DO  - https://doi.org/10.1074/jbc.RA118.002543
PM  - 29576549
VL  - 293
IS  - 18
SP  - 6647
EP  - 6658
S1  - 12
PB  - Elsevier
ER  -