title: RBC-NOS-dependent S-nitrosylation of cytoskeletal proteins improves RBC deformability.
abstract: BACKGROUND
  Red blood cells (RBC) possess a nitric oxide synthase (RBC-NOS) whose activation depends on the PI3-kinase/Akt kinase pathway. RBC-NOS-produced NO exhibits important biological functions like maintaining RBC deformability. Until now, the cellular target structure for NO, to exert its influence on RBC deformability, remains unknown. In the present study we analyzed the modification of RBC-NOS activity by pharmacological treatments, the resulting influence on RBC deformability and provide first evidence for possible target proteins of RBC-NOS-produced NO in the RBC cytoskeletal scaffold.
  
  
  RESULTS
  Blood from fifteen male subjects was incubated with the NOS substrate L-arginine to directly stimulate enzyme activity. Direct inhibition of enzyme activity was induced by L-N5-(1-Iminoethyl)-ornithin (L-NIO). Indirect stimulation and inhibition of RBC-NOS were achieved by applying insulin and wortmannin, respectively, substances known to affect PI3-kinase/Akt kinase pathway. The NO donor sodium nitroprusside (SNP) and the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) were additionally applied as NO positive and negative controls, respectively. Immunohistochemical staining was used to determine phosphorylation and thus activation of RBC-NOS. As a marker for NO synthesis nitrite was measured in plasma and RBCs using chemiluminescence detection. S-nitrosylation of erythrocyte proteins was determined by biotin switch assay and modified proteins were identified using LC-MS. RBC deformability was determined by ektacytometry. The data reveal that activated RBC-NOS leads to increased NO production, S-nitrosylation of RBC proteins and RBC deformability, whereas RBC-NOS inhibition resulted in contrary effects.
  
  
  CONCLUSIONS
  This study first-time provides strong evidence that RBC-NOS-produced NO modifies RBC deformability through direct S-nitrosylation of cytoskeleton proteins, most likely α- and β-spectrins. Our data, therefore, gain novel insights into biological functions of RBC-NOS by connecting impaired RBC deformability abilities to specific posttranslational modifications of RBC proteins. By identifying likely NO-target proteins in RBC, our results will stimulate new therapeutic approaches for patients with microvascular disorders.
authors: Department of Molecular and Cellular Sport Medicine, German Sport University Cologne, Cologne, Germany. m.grau@dshs-koeln.de
authors: Marijke
authors: M
authors: Grau
authors: Sebastian
authors: S
authors: Pauly
authors: Jamal
authors: J
authors: Ali
authors: Katja
authors: K
authors: Walpurgis
authors: Mario
authors: M
authors: Thevis
authors: Wilhelm
authors: W
authors: Bloch
authors: Frank
authors: F
authors: Suhr
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D004907:Erythrocyte Deformability; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000737:chemistry / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D003598:Cytoskeletal Proteins; D009573:Nitrites; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; D012694:Serine; D019001:Nitric Oxide Synthase