Deoxygenation-induced and Ca2+ dependent phosphatidylserine externalisation in red blood cells from normal individuals and sickle cell patients

Erwin Weiss, Urszula M. Cytlak, David C. Rees, Anna Osei, John S. Gibson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Phosphatidylserine (PS) is usually confined to the inner leaflet of the red blood cell (RBC) membrane. It may become externalised in various conditions, however, notably in RBCs from patients with sickle cell disease (SCD) where exposed PS may contribute to anaemic and ischaemic complications. PS externalisation requires both inhibition of the aminophospholipid translocase (or flippase) and activation of the scramblase. Both may follow from elevation of intracellular Ca2+. Flippase inhibition occurs at low [Ca2+]i, about 1μM, but [Ca2+]i required for scrambling is reported to be much higher (around 100μM). In this work, FITC-labelled lactadherin and FACS were used to measure externalised PS, with [Ca2+]i altered using bromo-A23187 and EGTA/Ca2+ mixtures. Two components of Ca2+-induced scrambling were apparent, of high (EC50 1.8±0.3μM) and low (306±123μM) affinity, in RBCs from normal individuals and the commonest SCD genotypes, HbSS and HbSC. The high affinity component was lost in the presence of unphysiologically high [Mg2+] but was unaffected by high K+ (90mM) or vanadate (1mM). The high affinity component accounted for PS scrambling in ≥2/3rd RBCs. It is likely to be most significant in vivo and may be involved in the pathophysiology of SCD or other conditions involving eryptosis.

Original languageEnglish
Pages (from-to)51-56
Number of pages6
JournalCell calcium
Volume51
Issue number1
DOIs
Publication statusPublished - Jan 2012

Keywords

  • Calcium affinity
  • Deoxygenation
  • Magnesium
  • Phosphatidylserine
  • Sickle cell

Research Beacons, Institutes and Platforms

  • Manchester Cancer Research Centre

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