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Mimicking phosphorylation at Ser-48 strongly reduces surface expression of human macrophage scavenger receptor class
1Institute of Biochemistry, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland. harald.heider@unibas.it
Abstract:
The role of human macrophage scavenger receptor A1 (SRA1) in the development of atherosclerotic lesions is still scarcely defined. Substituting serine 48 in human SRA1 by an aspartate demonstrated that (1) surface expression of the mutated receptor was 13-fold decreased; (2) the amount of cell-associated Texas red-labeled acetylated low density lipoprotein (LDL) in mutant receptor-expressing cells was almost three-fold reduced; (3) the migration of mutant receptor-transfected cells towards surfaces coated with oxidized LDL decreased by almost 60% compared to cells that were transfected with the wild type receptor. Phosphorylation of the cytoplasmic part of SRA1 may help to modulate the residence time of macrophages in atherosclerotic lesions.
Insights
Altering human macrophage scavenger receptor A1 (SRA1) impacts its surface expression and function. This suggests SRA1 phosphorylation may influence macrophage behavior in atherosclerotic lesions.
Area of Science:
- Cardiovascular Biology
- Immunology
- Molecular Medicine
Background:
- The role of human macrophage scavenger receptor A1 (SRA1) in atherosclerosis pathogenesis is not well understood.
- Macrophage scavenger receptors are critical in lipid uptake and inflammatory processes within atherosclerotic lesions.
Purpose of the Study:
- To investigate the functional impact of specific mutations in human SRA1 on its cell surface expression and interaction with modified lipoproteins.
- To explore the potential role of SRA1 phosphorylation in regulating macrophage behavior in the context of atherosclerosis.
Main Methods:
- Site-directed mutagenesis was used to substitute serine 48 with aspartate in human SRA1.
- Flow cytometry and LDL binding assays were performed to assess receptor expression and acetylated LDL uptake.
- Cell migration assays were conducted using oxidized LDL as a chemoattractant.
Main Results:
- The S48D mutation in SRA1 led to a 13-fold decrease in surface receptor expression.
- Cells expressing the S48D mutant SRA1 showed a nearly three-fold reduction in acetylated LDL uptake.
- Migration of cells expressing the S48D mutant SRA1 towards oxidized LDL was reduced by approximately 60% compared to wild-type SRA1.
Conclusions:
- The serine 48 residue in human SRA1 is crucial for its surface expression and function in mediating LDL binding and cell migration.
- Modulation of SRA1 phosphorylation may represent a therapeutic target for controlling macrophage accumulation in atherosclerotic lesions.