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8‐CPT‐cAMP is a self‐inhibition reliever for ENaC expressed in Xenopus oocytes
Author(s) -
JI HONGLONG,
Molina Raul,
Han DongYun,
Zhao RunZhen
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.611.5
Subject(s) - epithelial sodium channel , xenopus , chemistry , activator (genetics) , microbiology and biotechnology , receptor , biology , biochemistry , sodium , gene , organic chemistry
The epithelial Na + channels (ENaC) are up‐regulated by cAMP/PKA signal pathway to remove luminal fluid and salt in epithelial tissues. As a specific PKA activator, cell permeable 8‐CPT‐cAMP has been broadly applied to stimulate native ENaC activity in epithelial cells. Recently, it has been proposed that 8‐CPT‐cAMP may act as a ligand of ENaC with unknown mechanisms. To examine whether 8‐CPT‐cAMP stimulates ENaC by eliminating self‐inhibition, both wild type and mutated human αβγ ENaC were expressed in oocytes. Acutely perfusion but not cytosolic microinjection of 8‐CPT‐cAMP activated ENaC current in a dose‐dependent manner with an EC 50 value of 49μM (n=5). 8‐CPT‐cAMP reversibly reduced external Na + self‐inhibition (Ipeak/Isustained ratio, P<0.05). Using Zn 2+ ions to modify external histidine residues abolished the eliminating effect of 8‐CPT‐cAMP on self‐inhibition. However, thiol modifying reagent did not exhibit any effect. Furthermore, we identified that γ H233R was required for 8‐CPT‐cAMP induced stimulation of ENaC. In addition, 8‐CPT‐cAMP did not increase the channel activity associated with a high opening time mutant, β S520C . Our results suggest that in addition to serve as a key signal molecule of cGMP/PKA signaling pathway, 8‐CPT‐cAMP may be an ENaC opener by relieving self‐inhibition and increasing open probability. Supported by HL087017 and HL095435.