Erythrocyte membrane proteins in sickle cell disease (598.1)

Abstract

Sickle cell disease (SCD) is a common inherited hematological disorder where mutation causes substitution of valine for glutamate in β‐globin, giving hemoglobin S (HbS). HbS polymerization and cell dehydration cause cell distortion (sickling) at low oxygen tension, often leading to microvascular occlusion. Membrane changes are found in SCD, and increased Na+/H+ exchange activity mediated by NHE‐1 transporter has been reported. This study assayed levels of key nutrient (GLUT‐1 and hENT‐1) and ion (AE‐1 and NHE‐1) transporters to better understand pathophysiological changes in SCD.Membrane protein levels were examined by SDS‐PAGE and quantitative immunoblot analysis (against a common standard arbitrarily set as 100%). Sodium pump (Na/K ATPase) activity was followed by surrogate assay of p‐nitrophenylphosphatase (PNPase) activity.HPLC analysis confirmed HbSS and control phenotypes. SCD showed decreased expression of hENT‐1 (75.33 ± 3.75 n=11 vs. 98.09 ± 7.67 n=11; p < 0.05), elevation of NHE‐1 (108.92 ± 5.01 vs. 93.19 ± 4.90; p < 0.05) and GLUT‐1 (116.92 ± 5.45 vs. 90.94 ± 2.55; p < 0.05) but no significant change in AE‐1 (96.89 ± 2.99 vs. 95.55 ± 2.48) between normal and SCD samples. PNPase activity was increased in SCD (1.303 ± 0. 211 vs. 0.729 ± 0.137 µmole/mg/ml, n= 7; p < 0.05).NHE‐1 increase is consistent with reported Na‐H exchange and decreased hENT‐1 may affect plasma and intracellular purine levels in SCD.Grant Funding Source: Supported by the College of Graduate Studies, Kuwait University, Research Sector Kuwait University R