Journal article
Regulation of the cystic fibrosis transmembrane conductance regulator Cl- channel by specific protein kinases and protein phosphatases
The Journal of biological chemistry, Vol.268(3), pp.2037-2047
1993
DOI: 10.1016/S0021-9258(18)53959-4
PMID: 7678414
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is a regulated Cl- channel; in secretory epithelia, it is located in the apical membrane where it regulates transepithelial Cl- secretion. Previous studies have shown that cAMP-dependent protein kinase (PKA) can phosphorylate and activate CFTR Cl- channels. We asked whether other kinases would phosphorylate CFTR in vitro and activate CFTR Cl- channels in excised, inside-out patches of membrane from NIH 3T3 fibroblasts stably expressing recombinant CFTR. We found that both Ca(2+)-independent and Ca(2+)-dependent isoforms of protein kinase C (PKC) activated the CFTR Cl- channel. Consistent with this finding, PKC also phosphorylated CFTR in vitro. In contrast, the multifunctional Ca2+/calmodulin-dependent protein kinase failed to either activate or to phosphorylate CFTR Cl- channels, suggesting that this enzyme has no direct effect on CFTR. We found that cGMP-dependent protein kinase (cGK) (purified from bovine lung) phosphorylated CFTR in vitro. However, cGMP failed to increase the apical membrane Cl- permeability in human airway epithelia, and addition of cGMP, ATP, and cGK failed to activate CFTR Cl- channels. These results suggest that if cGK phosphorylates CFTR in vivo, it does so at sites not involved in CFTR Cl- channel activation. Because cAMP-dependent activation of CFTR Cl- channels and Cl- secretion in intact cells is reversible, we asked whether specific phosphatases can dephosphorylate and inactivate CFTR Cl- channels. Addition of protein phosphatase 2A (PP2A) decreased PKA-activated current by 67% within 10 min. The phosphatase inhibitor calyculin-A blocked the effect of PP2A. In contrast, neither protein phosphatases 1, 2B, nor two preparations of alkaline phosphatase inactivated PKA-phosphorylated CFTR Cl- channels. The effects of protein phosphatases on CFTR function were paralleled by their ability to dephosphorylate CFTR in vitro. Our data indicate that CFTR Cl- channels can be phosphorylated and activated by PKA as well as by Ca(2+)-dependent and Ca(2+)-independent isoforms of PKC and can be dephosphorylated and thus inactivated by PP2A.
Details
- Title: Subtitle
- Regulation of the cystic fibrosis transmembrane conductance regulator Cl- channel by specific protein kinases and protein phosphatases
- Creators
- Herbert A Berger - Univ. Iowa coll. medicine, Howard Hughes medical inst., dep. internal medicine, Iowa City IA 52242, United StatesSue M Travis - Univ. Iowa coll. medicine, Howard Hughes medical inst., dep. internal medicine, Iowa City IA 52242, United StatesMichael J Welsh - Univ. Iowa coll. medicine, Howard Hughes medical inst., dep. internal medicine, Iowa City IA 52242, United States
- Resource Type
- Journal article
- Publication Details
- The Journal of biological chemistry, Vol.268(3), pp.2037-2047
- DOI
- 10.1016/S0021-9258(18)53959-4
- PMID
- 7678414
- NLM abbreviation
- J Biol Chem
- ISSN
- 0021-9258
- eISSN
- 1083-351X
- Publisher
- American Society for Biochemistry and Molecular Biology; Bethesda, MD
- Language
- English
- Date published
- 1993
- Academic Unit
- Neurology; Molecular Physiology and Biophysics; Pulmonary, Critical Care, and Occupational Medicine; Fraternal Order of Eagles Diabetes Research Center; Neurosurgery; Internal Medicine
- Record Identifier
- 9984020737502771
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