T-state stabilization of hemoglobin by nitric oxide to form alpha-nitrosyl heme causes constitutive release of ATP from human erythrocytes.
Upon hypoxia, erythrocytes utilize hemoglobin (Hb) to trigger activation of glycolysis through its interaction with band 3. This process contributes to maintenance of ATP, a portion of which is released extracellularly to trigger endothelium-dependent vasorelaxation. However, whether the ATP release results either from metabolic activation of the cells secondarily or from direct regulation of the gating through Hb allostery remains unknown. This study aimed to examine if stabilization of T-state Hb could induce steady-state and hypoxia-induced alterations in glycolysis and the ATP release from erythrocytes. Treatment of deoxygenated erythrocytes with a nitric oxide (NO) donor generated alpha-NO Hb that is stabilized T-state allostery. Under these circumstances, the release of ATP was significantly elevated even under normoxia and not further enhanced upon hypoxia. These events did not coincide with activation of glycolysis of the cells, so far as judged by the fact that intracellular ATP was significantly decreased by the NO treatment. Collectively, the present study suggests that hypoxia-induced ATP release is triggered through mechanisms involving R-T transition of Hb, and the gating process might occur irrespective of hypoxia-responsive regulation of glycolysis.
Akatsu
Tomotaka
T
Departments of Surgery, School of Medicine, Keio University, Tokyo, Japan. gi026001@yahoo.co.jp
Tsukada
Kosuke
K
Hishiki
Takako
T
Suga-Numa
Kazuhiro
K
Tanabe
Minoru
M
Shimazu
Motohide
M
Kitagawa
Yuko
Y
Yachie-Kinoshita
Ayako
A
Suematsu
Makoto
M
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000494:Allosteric Regulation / Q000187:drug effects; D004912:Erythrocytes / Q000187:drug effects* / Q000378:metabolism*; D006019:Glycolysis / Q000187:drug effects; D006418:Heme / Q000378:metabolism*; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009569:Nitric Oxide / Q000494:pharmacology*; D011487:Protein Conformation / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects
D006454:Hemoglobins; D009569:Nitric Oxide; D006418:Heme; D000255:Adenosine Triphosphate