Erythrocyte spectrin alteration induced by low-density lipoprotein.
Addition of human plasma low-density lipoproteins (LDL) to intact human erythrocytes induces the erythrocytes to undergo morphologic transition from biconcave disks to echinocytes and spherocytes. The transformation is time-dependent. Two hours are required before echinocytes are detected by scanning electron microscopy. After two hours, LDL also decrease the phosphate content of spectrin by 40% relative to the control, suggesting that these lipoproteins modulate cell shape by influencing phosphorylation-dephosphorylation of a membrane-associated cytoskeletal protein. LDL do not induce depletion of intracellular adenosine triphosphate (ATP), nor do they inhibit cyclic adenosine monophosphate-independent protein kinases which phosphorylate spectrin. LDL stimulate membrane-bound phosphatases by a factor of two, thereby reducing the amount of phosphate covalently bound to membrane proteins. The observed effects are specific for LDL. High-density lipoproteins (HDL) do not stimulate dephosphorylation of spectrin or alter erythrocyte morphology. However, HDL protect the erythrocytes against LDL-induced alterations. These data suggest that the circulating lipoproteins have a role in maintaining erythrocyte morphology by regulating the extent of phosphorylation of spectrin.
D004910:Erythrocyte Membrane / Q000187:drug effects / Q000648:ultrastructure; D004912:Erythrocytes / Q000187:drug effects / Q000648:ultrastructure*; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood / Q000494:pharmacology*; D008565:Membrane Proteins / Q000032:analysis* / Q000097:blood; D013049:Spectrin / Q000032:analysis*
D008077:Lipoproteins, LDL; D008565:Membrane Proteins; D013049:Spectrin