Ca2+-CaM activation of AMP deaminase contributes to adenine nucleotide dysregulation and phosphatidylserine externalization in human sickle erythrocytes. Br J Haematol 2009 Feb;144(3):434-45
Date
11/28/2008Pubmed ID
19036100Pubmed Central ID
PMC2701153DOI
10.1111/j.1365-2141.2008.07473.xScopus ID
2-s2.0-58449110030 (requires institutional sign-in at Scopus site) 20 CitationsAbstract
Ca2+-calmodulin (Ca2+-CaM) activates erythrocyte adenosine monophosphate deaminase (AMPD) in conditions of disturbed calcium homeostasis, prompting us to investigate adenine nucleotide metabolic dysregulation in sickle cell disease (SCD). However, higher ATP concentrations in reticulocytes, compared to erythrocytes, confound a comparative evaluation of SCD and normal RBCs. Therefore, a combination of centrifugation and antiCD71-labelled magnetic bead selection was used to prepare reticulocyte-poor fractions (reticulocytes <4% of total RBCs) of SCD RBCs. ATP and total adenine nucleotide concentrations were 12% lower in sickle erythrocytes compared to normal erythrocytes and inosine monophosphate (IMP) concentrations were threefold elevated (all P < 0.05). Furthermore, preincubation with a diffusible CaM antagonist slowed IMP accumulation in sickle erythrocytes during an experimental period of energy imbalance, thus showing that Ca2+-CaM activates AMPD in SCD. Finally, adenine treatment (100 micromol/l) of ex vivo SCD RBCs significantly expanded ATP levels (16% higher) and reduced phosphatidylserine (PS)-exposure, specifically those cells with the highest levels of PS externalization (46% fewer events) (both P-values <0.05 compared to untreated samples). We conclude that Ca2+-CaM activation of AMPD contributes to increased turnover of the adenine nucleotide pool in sickle erythrocytes and that this metabolic dysregulation promotes PS exposure that may contribute to the pathogenesis of SCD.
Author List
Sabina RL, Wandersee NJ, Hillery CAMESH terms used to index this publication - Major topics in bold
AMP DeaminaseAdenine
Adenine Nucleotides
Adenosine Triphosphate
Anemia, Sickle Cell
Calmodulin
Cells, Cultured
Erythrocytes
Flow Cytometry
Humans
Inosine Monophosphate
Phosphatidylserines
Statistics, Nonparametric
p-Methoxy-N-methylphenethylamine
