title: Non-neuronal cholinergic system and signal transduction pathways mediated by band 3 in red blood cells.
abstract: BACKGROUND
  Non-neuronal acetylcholine (ACh) and acetylcholinesterase (AChE) have been recognized in the past. Vascular ACh has been associated by us with the regulation of microcirculatory flow by modulating nitric oxide (NO) intracellular mobilization, metabolism (NOx) and release from erythrocytes, as well as the glycolytic flux. Velnacrine maleate is a well-known AChE inhibitor which plays a competitive role by decreasing NO-mediated erythrocyte responses. A plausible hypothesis to explain the mechanisms underlying those events hinges on the NO translocation among nitrosylated molecules and phosphorylated/dephosphorylated states of band 3 protein, processed by major tyrosine-kinases (PTK: p72syk, p53/56lyn and p59/61hck) and phosphotyrosine-phosphatases (PTP).
  
  
  METHODS
  To assess this hypothesis under the influence of AChE effectors (acetylcholine/velnacrine), blood samples from healthy donors were harvested and Western blot analysis was subsequently used to determine the degree of band 3 phosphorylation, in the presence and absence of PTK/PTP inhibitors. NO and nitrites/nitrates were quantified using an amperometric method and the Griess Reaction, respectively, in erythrocyte suspensions. Measurements of erythrocyte metabolites (2,3-bisphosphoglycerate; glyceraldehyde 3-phosphate dehydrogenase; glucose-6-phosphodehydrogenase; lactate), hemoglobin and cyclic nucleotides were conducted afterwards.
  
  
  RESULTS
  Increased levels of phosphorylated-band 3 obtained upon p72syk inhibition suggest p59/61hck and p53/56lyn as secondary involved kinases. As to NO/NOx quantification, in the presence of PTKi we reported higher levels with velnacrine-AChE, as opposed to acetylcholine-AChE. Calpeptin, a PTP inhibitor which triggers full band 3-phosphorylation, led to the opposite NO mobilization, being reinforced by ACh. Oxy-hemoglobin, glyceraldehyde 3-phosphate dehydrogenase and glucose-6-phosphodehydrogenase were found to decrease with ACh, whereas P50, lactate and both cGMP/cAMP happened to increase.
  
  
  CONCLUSIONS
  Changes on human erythrocyte NOx mobilization and metabolic fluxes occur under influence of non-neuronal ACh/AChE, in turn dependent on the degree of band 3-phosphorylation. Since these vascular events may potentially change under pathological conditions, coadjuvant drugs could become accessible in the setting of microcirculation disease.
authors.affiliation: Institute of Biochemistry, Institute of Molecular Medicine, University of Lisbon Medical School, Lisbon, Portugal.
authors.forename: Filomena A
authors.initials: FA
authors.lastname: Carvalho
authors.forename: José Pedro
authors.initials: JP
authors.lastname: Almeida
authors.forename: Isabel O
authors.initials: IO
authors.lastname: Fernandes
authors.forename: Teresa
authors.initials: T
authors.lastname: Freitas-Santos
authors.forename: Carlota
authors.initials: C
authors.lastname: Saldanha
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000110:Acetylcholinesterase / Q000378:metabolism*; D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051572:Proto-Oncogene Proteins c-hck / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000072377:Syk Kinase; D013619:Tacrine / Q000031:analogs & derivatives / Q000494:pharmacology; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D002800:Cholinesterase Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; C454201:SLC4A1 protein, human; D009569:Nitric Oxide; D013619:Tacrine; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D011505:Protein-Tyrosine Kinases; C496631:HCK protein, human; D051572:Proto-Oncogene Proteins c-hck; C000606896:SYK protein, human; D000072377:Syk Kinase; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D000110:Acetylcholinesterase; D000109:Acetylcholine; C056424:velnacrine