title: Rectal epithelial expression of protein kinase A phosphorylation of cystic fibrosis transmembrane conductance regulator.
abstract: OBJECTIVE
  Human rectal epithelium in cystic fibrosis (CF) shows impaired ion transport in response to theophylline or bethanechol, although it possesses regulatory subunits of adenosine cyclic 3',5'-monophosphate (cAMP)-dependent protein kinase (protein kinase A). Protein kinase A-specific phosphorylation of CF transmembrane conductance regulator (CFTR) in rectal tissues of control and CF volunteers was examined in this study.
  
  
  METHODS
  CFTR was evaluated using a polyclonal antiserum (pre-NBF) raised against a peptide corresponding to residues 415-427 of CFTR. Microsomal membranes from normal and CF rectal mucosa and from T-84 cells were incubated with [gamma 32P]-adenosine triphosphate +/- protein kinase A and subjected to immunoblotting with pre-NBF and autoradiography.
  
  
  RESULTS
  Pre-NBF recognized a single band of 180 kilodaltons. Protein kinase A altered phosphorylation of this 180-kilodalton band 1.4-, 2.2- and 0.9-fold in T-84, normal, and CF rectal membranes, respectively. Catalytic activities of protein kinase A, Ca2+ calmodulin protein kinase, or protein kinase C in control and CF tissues were similar.
  
  
  CONCLUSIONS
  cAMP and Ca(2+)-signaling pathways are normal up to the kinases in CF rectal mucosa. Our results suggest differences in CFTR phosphorylation in normal and CF rectal mucosal membranes.
authors.affiliation: Department of Physiology and Biophysics, University of Illinois at Chicago.
authors.forename: M C
authors.initials: MC
authors.lastname: Rao
authors.forename: G B
authors.initials: GB
authors.lastname: Bissonnette
authors.forename: T
authors.initials: T
authors.lastname: Mahaffey
authors.forename: W B
authors.initials: WB
authors.lastname: Guggino
authors.forename: J L
authors.initials: JL
authors.lastname: Goldstein
mesh_terms: D000328:Adult; D015153:Blotting, Western; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D012007:Rectum / Q000378:metabolism*; D012016:Reference Values
chemical_list: C505032:CFTR protein, human; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D011494:Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases