Role of Akaps in BCAM/Lu Receptor Activation on Normal and Sickle Erythrocytes

Abstract

Background: Human normal and sickle red blood cells (RBCs) adhere with high affinity to laminin-5 via the basal cell adhesion molecule/Lutheran (BCAM/Lu) receptor which is implicated in vasoocclusive episodes (VOEs) in sickle cell disease (SCD). BCAM/Lu is activated through the cyclic adenosine monophosphate (cAMP) signaling pathway.Methods and Results: We established an in vitro technique, based on atomic force microscopy, to detect single BCAM/Lu proteins on the RBC surface and measure the binding force between BCAM/Lu and laminin-5. Importantly, we illustrated that AKAPs are crucial for BCAM/Lu receptor activation. To detect the presence of AKAPs on normal and SS-RBCs, cells were treated with St-Ht31 peptide (5μM), which inhibits binding of PKA to AKAPs. Following pretreatment with St-Ht31, the frequency of active BCAM/Lu receptors decreased significantly in normal RBCs (Figure 1A; 5.71±1.23% to 3.15±1.09%; n=15; p<0.05) and SS-RBCs (Figure 1B; 7.19±1.42% to 2.02±0.37%; n=12; p<0.005). Pretreatment with a control peptide showed no change in receptor frequency (not shown).Conclusions: By using single-molecule measurements, we demonstrated that AKAPs mediate the activation of BCAM/Lu receptors in normal and SS-RBCs. These findings may lead to novel anti-adhesive targets for VOEs in SCD.View Large Image | View Hi-Res Image | Download PowerPoint Slide