Previous work has shown that under some conditions C-reactive protein (CRP) can interact with the phosphocholine components of phospholipids, and this results in complement (C) activation. Liposomes consisting of phospholipid, cholesterol (Chol), and either containing or lacking a charged lipid or galactosyl ceramide (Gal Cer), were assayed both for reactivity with CRP, and for C consumption and C-dependent membrane damage.
Adsorption studies showed that CRP bound equally well to positively charged liposomes regardless of the phosphatidylcholine (PC) fatty acyl chain length (dimyristoyl vs distearoyl PC) or of the presence of Gal Cer. Negatively charged liposomes also bound CRP, but to a lesser extent.
Despite the above binding studies, C-dependent membrane damage (resulting in glucose release) mediated by CRP was strongly dependent on charge, phospholipid fatty acyl chain length, Chol concentration, and Gal Cer. C damage resulting in glucose release occurred with liposomes containing a strong positive charge, but not with weakly positive, neutral, or negatively charged liposomes.