title: Regulation of erythrocyte survival by AMP-activated protein kinase.
abstract: AMP-activated protein kinase (AMPK), an energy-sensing enzyme, counteracts energy depletion by stimulation of energy production and limitation of energy utilization. On energy depletion, erythrocytes undergo suicidal death or eryptosis, triggered by an increase in cytosolic Ca(2+) activity ([Ca(2+)](i)) and characterized by cell shrinkage and phosphatidylserine (PS) exposure at the erythrocyte surface. The present study explored whether AMPK participates in the regulation of eryptosis. Western blotting and confocal microscopy disclosed AMPK expression in erythrocytes. [Ca(2+)](i) (Fluo3 fluorescence), cell volume (forward scatter), and PS exposure (annexin V binding) were determined by fluorescence-activated cell sorting (FACS) analysis. Glucose removal increased [Ca(2+)](i), decreased cell volume, and increased PS exposure. The AMPK-inhibitor compound C (20 microM) did not significantly modify eryptosis under glucose-replete conditions but significantly augmented the eryptotic effect of glucose withdrawal. An increase in [Ca(2+)](i) by Ca(2+) ionophore ionomycin triggered eryptosis, an effect blunted by the AMPK activator 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR; 1 mM). As compared with erythrocytes from wild-type littermates (ampk(+/+)), erythrocytes from AMPKalpha1-deficient mice (ampk(-/-)) were significantly more susceptible to the eryptotic effect of energy depletion. The ampk(-/-) mice were anemic despite excessive reticulocytosis, and they suffered from severe splenomegaly, again pointing to enhanced erythrocyte turnover. The observations disclose a critical role of AMPK in the survival of circulating erythrocytes.
authors.affiliation: Department of Physiology, University of Tübingen, Tübingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Föller
authors.forename: Mentor
authors.initials: M
authors.lastname: Sopjani
authors.forename: Saisudha
authors.initials: S
authors.lastname: Koka
authors.forename: Shuchen
authors.initials: S
authors.lastname: Gu
authors.forename: Hasan
authors.initials: H
authors.lastname: Mahmud
authors.forename: Kan
authors.initials: K
authors.lastname: Wang
authors.forename: Elisa
authors.initials: E
authors.lastname: Floride
authors.forename: Erwin
authors.initials: E
authors.lastname: Schleicher
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schulz
authors.forename: Thomas
authors.initials: T
authors.lastname: Münzel
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004905:Erythrocyte Aging / Q000187:drug effects / Q000502:physiology*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D005947:Glucose / Q000172:deficiency; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D010718:Phosphatidylserines / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D012265:Ribonucleotides / Q000494:pharmacology
chemical_list: D017304:Annexin A5; D005456:Fluorescent Dyes; D007476:Ionophores; D010718:Phosphatidylserines; D011720:Pyrazoles; D011743:Pyrimidines; D012265:Ribonucleotides; C516138:dorsomorphin; D000620:Aminoimidazole Carboxamide; D015759:Ionomycin; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide; D016650:Fluorescein-5-isothiocyanate; D005947:Glucose; D002118:Calcium