Homologous species restriction in lysis of human erythrocytes: a membrane-derived protein with C8-binding capacity functions as an inhibitor.

Abstract

An intrinsic membrane protein with a m.w. of 65,000 that can bind human C8 has been identified after separation of human erythrocyte membrane proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrotransfer to nitrocellulose sheets. The protein, tentatively designated as the C8-binding protein (C8bp) could be isolated from papain-treated erythrocyte (E) membranes by phenol-water extraction and isoelectric focusing. In a functional assay, with chicken (ch) E as target cells, C8bp inhibited the lysis of ch E C5b67 intermediates by human C8 and C9, whereas the lysis by rabbit C8 and C9 was not affected. Because the decay accelerating factor (DAF) from human erythrocyte membranes also inhibits the activity of C3/C5 convertases in an homologous system, we tested whether or not a DAF activity was present in C8bp. C8bp, however, did not accelerate the decay of the classic C3 convertases. Thus, it appears that C8bp and DAF are two different factors of E membranes with a similar molecular size inhibiting different sites of the activation cascade of complement while they can function synergistically to minimize the self-inflicted damage by complement.

The Prospect of Biomimetic Immune Cell Membrane-Coated Nanomedicines for Treatment of Serious Bacterial Infections and Sepsis

“…CD47 on RBCs binds to signal regulatory protein alpha (SIRPα) on macrophages, effectively inhibiting phagocytosis (Oldenborg et al, 2000). Additionally, RBCs express various complement inactivating proteins including C8 binding protein, (Schönermark et al, 1986) homologous restriction protein, (Zalman et al, 1986) decay-accelerating factor, complement receptor 1, (Kim et al, 2008) and CD59 (Babiker et al, 2002). These proteins prevent the complement aggregation on the surface of RBCs, a process that could lead to the rapid clearance of liposomes (Szebeni et al, 2011).…”

Erythrocyte‐Inspired Functional Materials for Biomedical Applications

“…[ 54 ] C8 binding protein and CD59 on the erythrocyte membrane could inhibit the assembly of the hemolytic pore‐forming membrane attack complex to manage the late‐stage complement cascade. [ 55,56 ] Other less noticed membrane proteins include homologous restriction protein and membrane cofactor protein. These findings inspire researchers to attach extracted self‐marker proteins as the surface decoration of the particles.…”