Regulation of epithelial sodium channels by cGMP/PKGII.
Airway and alveolar fluid clearance is mainly governed by vectorial salt movement via apically located rate-limiting Na(+) channels (ENaC) and basolateral Na(+)/K(+)-ATPases. ENaC is regulated by a spectrum of protein kinases, i.e. protein kinase A (PKA), C (PKC), and G (PKG). However, the molecular mechanisms for the regulation of ENaC by cGMP/PKG remain to be elucidated. In the present study, we studied the pharmacological responses of native epithelial Na(+) channels in human Clara cells and human alphabetagammadelta ENaCs expressed in oocytes to cGMP. 8-pCPT-cGMP increased amiloride-sensitive short-circuit current (I(sc)) across H441 monolayers and heterologously expressed alphabetagammadelta ENaC activity in a dose-dependent manner. Similarly, 8-pCPT-cGMP (a PKGII activator) but not 8-Br-cGMP (a PKGI activator) increased amiloride-sensitive whole cell currents in H441 cells in the presence of CFTRinh-172 and diltiazem. In all cases, the cGMP-activated Na(+) channel activity was inhibited by Rp-8-pCPT-cGMP, a specific PKGII inhibitor. This was substantiated by the evidence that PKGII was the sole isoform expressed in H441 cells at the protein level. Importantly, intratracheal instillation of 8-pCPT-cGMP in BALB/c mice increased amiloride-sensitive alveolar fluid clearance by approximately 30%, consistent with the in vitro results. We therefore conclude that PKGII is an activator of lung epithelial Na(+) channels, which may expedite the resolution of oedematous fluid in alveolar sacs.
Departments of Biochemistry, University of Texas Health Science Center at Tyler, Tyler, TX 75708, USA.
Hong-Guang
HG
Nie
Lan
L
Chen
Dong-Yun
DY
Han
Jun
J
Li
Wei-Feng
WF
Song
Shi-Peng
SP
Wei
Xiao-Hui
XH
Fang
Xiu
X
Gu
Sadis
S
Matalon
Hong-Long
HL
Ji
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D062967:Cyclic GMP-Dependent Protein Kinase Type II; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008564:Membrane Potentials; D051379:Mice; D008807:Mice, Inbred BALB C; D009865:Oocytes; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000201:enzymology*; D011817:Rabbits; D020545:Respiratory Mucosa / Q000187:drug effects / Q000201:enzymology*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D014162:Transfection; D014981:Xenopus
C090860:8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphorothioate; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; C507045:SCNN1A protein, human; C507048:SCNN1B protein, human; C507051:SCNN1D protein, human; C507052:SCNN1G protein, human; D026941:Sodium Channel Blockers; D013873:Thionucleotides; C016276:8-bromocyclic GMP; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; D000584:Amiloride; D000242:Cyclic AMP; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D062967:Cyclic GMP-Dependent Protein Kinase Type II; D017869:Cyclic GMP-Dependent Protein Kinases; C569718:PRKG1 protein, human; C569729:PRKG2 protein, human; C569720:Prkg1 protein, mouse; C569730:Prkg2 protein, mouse; D006152:Cyclic GMP