Uptake of fibrillar β-amyloid by microglia isolated from MSR-A (type I and type II) knockout mice
To characterize the receptors involved in binding fibrillar amyloid A-beta (fA beta), we compared the uptake of fA beta in microglia from wildtype (MSR-A+/+) and MSR-A knockout (MSR-A-/-) mice. On average, there was a 60% reduction in the uptake of Cy3-fA beta in microglia from the MSR-A-/- mice. Cy3-fA beta uptake in the MSR-A-/- mice was still competable by scavenger receptor ligands, including acetylated low-density lipoprotein (Ac-LDL) and fucoidan. This indicates that uptake by MSR-B and/or other MSRs is also involved in the uptake of fA beta by microglia. However, the significant reduction in the uptake of fA beta in the MSR-A-/- microglia suggests that fA beta gets internalized mostly by MSR-As in microglia. Uptake of modified fA beta (ClqA beta) was similar in the MSR-A-/- microglia as in the wildtype indicating that the uptake of the opsonized fA beta is independent of MSR-A.