title: Increased protein kinase A regulatory subunit content and cGMP binding in erythrocyte membranes in liver cirrhosis.
abstract: OBJECTIVE
  Patients with liver disease show increased plasma cGMP and decreased intracellular cGMP in lymphocytes. The initial aim of this work was to assess whether decreased intracellular cGMP and increased plasma cGMP may be due to increased ATP-dependent release of cGMP from cells. The results obtained led to a new aim: to identify and quantify a protein responsible for the increased cGMP binding found in erythrocyte membranes from patients with liver disease.
  
  
  METHODS
  ATP-dependent cGMP transport was determined in inside-out vesicles from erythrocyte membranes. cGMP-binding proteins were isolated from the membranes and identified by MALDI-TOF peptide mass fingerprint. Protein kinase A was quantified by immunoblotting.
  
  
  RESULTS
  ATP-independent cGMP binding is increased in erythrocyte membranes from patients. There is a significant increase in the membrane content of a cGMP-binding protein with Mr 48,000, which was identified as the regulatory subunit of protein kinase A.
  
  
  CONCLUSIONS
  The content of the regulatory subunit of protein kinase A is significantly increased (twice) in erythrocyte membranes from patients with liver cirrhosis. This protein binds cGMP strongly and may be responsible for the decrease in intracellular cGMP in liver disease.
authors.affiliation: Servicio de Hepatología, Hospital Clínico Universitario, Departamento de Medicina, Universidad de Valencia, Valencia, Spain.
authors.forename: Carmina
authors.initials: C
authors.lastname: Montoliu
authors.forename: Elena
authors.initials: E
authors.lastname: Kosenko
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Calvete
authors.forename: Anne T
authors.initials: AT
authors.lastname: Nies
authors.forename: Juan A
authors.initials: JA
authors.lastname: Del Olmo
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Serra
authors.forename: José M
authors.initials: JM
authors.lastname: Rodrigo
authors.forename: Vicente
authors.initials: V
authors.lastname: Felipo
mesh_terms: D000328:Adult; D000368:Aged; D001693:Biological Transport, Active; D016022:Case-Control Studies; D017868:Cyclic AMP-Dependent Protein Kinases / Q000097:blood* / Q000737:chemistry; D006152:Cyclic GMP / Q000097:blood*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008103:Liver Cirrhosis / Q000097:blood* / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D021122:Protein Subunits; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D021122:Protein Subunits; D017868:Cyclic AMP-Dependent Protein Kinases; D006152:Cyclic GMP