Sec14-like-Lipid-Binding-4 Enables Hemoglobin Clearance By Liver Sinusoidal Endothelial Cells

Abstract

Hemolysis of banked red blood cells (RBC storage lesion) contributes to lack of therapeutic benefit and higher mortality following transfusion therapy in patients. However, the molecular mechanism underlying storage lesion remains poorly understood. Using a multiple-ancestry genome-wide association analysis among blood donors, our group has recently identified Sec14-like-lipid-binding-4 (Sec14L4) protein to be associated with increased rate of hemolysis following blood storage. Although Sec14L4 is highly similar to yeast phosphatidylinositol transfer protein Sec14, which is known to be involved in the synthesis of golgi-derived transport vesicles, the exact function of Sec14L4 and how it promotes RBC storage lesions remains unknown. Our initial studies using fluorescence microscopy in our newly generated Sec14L4 null mice revealed significant enrichment of Sec14L4 in the live sinusoidal endothelial cells (LSECs), which positively correlated with elevated levels of iron in the liver. Scanning and transmission electron micrographs revealed impaired actin cytoskeleton organization in LSECs of Sec14L4 null mice, which was associated with upregulation of major GTPases RhoA, RhoB and Rac1 activity. The impairment of actin cytoskeletal organization in Sec14L4 null mice lead to impaired vesicle trafficking in LSECs and higher retention of RBCs in the liver sinusoids compared to control mice. These data are the first to demonstrate a previously unrecognized role for Sec14L4 protein in LSEC mediated endocytic trafficking by promoting actin polymerization. These findings also suggest that Sec14L4 may regulate RBC storage lesion through impaired hemoglobin clearance by LSECs secondary to cytoskeletal impairment.