Conformationally Altered C-Reactive Protein Capable of Binding to Atherogenic Lipoproteins Reduces Atherosclerosis

Abstract

The aim of this study was to test the hypothesis that C-reactive protein (CRP) protects against the development of atherosclerosis and that a conformational alteration of wild-type CRP is necessary for CRP to do so. Atherosclerosis is an inflammatory cardiovascular disease and CRP is a plasma protein produced by the liver in inflammatory states. The co-localization of CRP and low-density lipoproteins (LDL) at atherosclerotic lesions suggests a possible role of CRP in atherosclerosis. CRP binds to phosphocholine-containing molecules but does not interact with LDL unless the phosphocholine groups in LDL are exposed. However, CRP can bind to LDL, without the exposure of phosphocholine groups, if the native conformation of CRP is altered. Previously, we reported a CRP mutant, F66A/T76Y/E81A, generated by site-directed mutagenesis, that did not bind to phosphocholine. Unexpectedly, this mutant CRP, without any more conformational alteration, was found to bind to atherogenic LDL. We hypothesized that this CRP mutant, unlike wild-type CRP, could be anti-atherosclerotic and, accordingly, the effects of mutant CRP on atherosclerosis in atherosclerosis-prone LDL receptor-deficient mice were evaluated. Administration of mutant CRP into mice every other day for a few weeks slowed the progression of atherosclerosis. The size of atherosclerotic lesions in the aorta of mice treated with mutant CRP for 9 weeks was ∼40% smaller than the lesions in the aorta of untreated mice. Thus, mutant CRP conferred protection against atherosclerosis, providing a proof of concept that a local inflammation-induced structural change in wild-type CRP is a prerequisite for CRP to control the development of atherosclerosis.

Treatment of Pneumococcal Infection by Using Engineered Human C-Reactive Protein in a Mouse Model

“…As expected, E-CRP-1 acquired the ability of E42Q CRP to bind to factor H. Unexpectedly, CRP triple mutant, F66A/T76Y/E81A, which was not investigated before for factor H-binding ( 18 ), also bound to factor H, without the E42Q mutation ( 50 ). These results were not available till we generated and tested E-CRP-1 for binding to factor H. Since the expression of E-CRP-1 cDNA was higher than the expression of the triple mutant cDNA, we used E-CRP-1 in this study.…”

“…Thus, both E-CRP-1 and E-CRP-2 had the desired factor H-binding activity. Surprisingly, triple mutant CRP, which was not investigated before for factor H binding ( 18 ), also bound to factor H ( 50 ). If it was known earlier that triple mutant CRP, without the addition of E42Q mutation, would bind to factor H, there would have been no need to generate quadruple mutant CRP.…”

“…Previously, we reported that CRP triple mutant, which does not bind to PCh, protected mice against infection and we interepreted the data to suggest that CRP protects mice against pneumococcal infection without binding to pneumococci. Recent findings that triple mutant CRP can also bind to factor H ( 50 ) and that complement activation is critical for protection ( 31 ) indicate that in previously published experiments employing CRP triple mutant ( 18 , 30 ), endogenous murine CRP had also participated, along with triple mutant CRP, in protecting mice against infection.…”

The Contribution of Endothelial-Mesenchymal Transition to Atherosclerosis

“…An appropriate inflammatory microenvironment at the site of LDL deposition is critical to prevent atherosclerosis. The function of inflammation could be changed by the modification of proteins' structures, including CRP during the atherosclerotic process [77]. Despite current treatments for atherosclerosis being available, much work still needs to be carried out to reduce the cardiovascular risk that remains.…”

C-Reactive Protein-Based Strategy to Reduce Antibiotic Dosing for the Treatment of Pneumococcal Infection

“…E-CRP-1 does not bind to PCh while E-CRP-2, like WT CRP, binds to PCh. Both E-CRP-1 and E-CRP-2 bind to complement inhibitor factor H recruited by pneumococci on their surface in mouse circulation; WT CRP does not bind to immobilized factor H (22)(23)(24)(25). Unlike passively administered WT CRP, both E-CRP-1 and E-CRP-2 protected mice against infection even when E-CRP was administered 12 h after administering pneumococci, indicating that a conformationally altered form of CRP that can bind to immobilized factor H is required for CRP-mediated protection of mice against late-stage pneumococcal infection (1,21).…”