Macrophage scavenger receptor A mediates adhesion to apolipoproteins AI and E

C Neyen, A Plüddemann, P Roversi, B Thomas… - Biochemistry, 2009 - ACS Publications
C Neyen, A Plüddemann, P Roversi, B Thomas, L Cai, DR van der Westhuyzen, RB Sim
Biochemistry, 2009ACS Publications
Macrophage scavenger receptor A (SR-A) is a multifunctional, multiligand pattern
recognition receptor with roles in innate immunity, apoptotic cell clearance, and age-related
degenerative pathologies, such as atherosclerosis and Alzheimer's disease. Known
endogenous SR-A ligands are polyanionic and include modified lipoproteins, advanced
glycation end products, and extracellular matrix proteins. No native plasma ligands have
been identified, but it is known that SR-A recognition of unidentified serum components …
Macrophage scavenger receptor A (SR-A) is a multifunctional, multiligand pattern recognition receptor with roles in innate immunity, apoptotic cell clearance, and age-related degenerative pathologies, such as atherosclerosis and Alzheimer’s disease. Known endogenous SR-A ligands are polyanionic and include modified lipoproteins, advanced glycation end products, and extracellular matrix proteins. No native plasma ligands have been identified, but it is known that SR-A recognition of unidentified serum components mediates integrin-independent macrophage adhesion, which may drive chronic local inflammation. In this study, we used a high-throughput fractionation and screening method to identify novel endogenous SR-A ligands that may mediate macrophage adhesion. SR-A was found to recognize the exchangeable apolipoproteins A-I and E (apo A-I and apo E, respectively) in both lipid-free and lipid-associated form, suggesting the shared amphipathic α-helix as a potential recognition motif. Adhesion of RAW 264.7 macrophages to surfaces coated with apo A-I and apo E4 proved to be integrin-independent and could be blocked by anti-SR-A antibodies. The presence of apo A-I and apo E in pathological deposits, such as atherosclerotic lesions and neurotoxic Alzheimer’s plaques, suggests a possible contribution of SR-A-dependent adhesion of macrophages to an inflammatory microenvironment.
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