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Epithelia are positioned at a critical interface to prevent invasion by microorganisms from the environment. Pattern recognition receptors are important components of innate immunity because of their ability to interact with specific microbe-associated structures and initiate immune responses. Several distinct groups of receptors have been recognized. One of these, the scavenger receptors, has been classified into at least eight separate classes. The class A scavenger receptors are characterized by the presence of a collagen-like domain and include macrophage scavenger receptor type A (SR-A1 I/II, SCARA1) and MARCO (SCARA2). These receptors are known to make important contributions to host defense. Here, we identify a novel murine scavenger receptor, SCARA5, which has a structure typical of this class. The cDNA encodes 491 amino acids, which predict a type II protein that contains C-terminal intracellular, transmembrane, extracellular spacer, collagenous, and N-terminal scavenger receptor cysteine rich domains. Expression in Chinese hamster ovary cells confirmed that the receptor assembles as a homotrimer and is expressed at the plasma membrane. SCARA5-transfected cells bound Escherichia coli and Staphylococcus aureus, but not zymosan, in a polyanionic-inhibitable manner. Unlike other class A scavenger receptors, the receptor was unable to endocytose acetylated or oxidized low density lipoprotein. Quantitative RT-PCR and in situ hybridization demonstrate SCARA5 has a tissue and cellular distribution unique among class A scavenger receptors. Because of the restriction of SCARA5 transcripts to populations of epithelial cells, we propose that this receptor may play important roles in the innate immune activities of these cells.

Original publication

DOI

10.1074/jbc.M507599200

Type

Journal article

Journal

J Biol Chem

Publication Date

28/04/2006

Volume

281

Pages

11834 - 11845

Keywords

Amino Acid Sequence, Animals, Base Sequence, CHO Cells, Cell Membrane, Cloning, Molecular, Cricetinae, DNA, Complementary, Epithelial Cells, Escherichia coli, In Situ Hybridization, Mice, Molecular Sequence Data, Reverse Transcriptase Polymerase Chain Reaction, Scavenger Receptors, Class A, Sequence Homology, Amino Acid, Staphylococcus aureus, Transfection, Zymosan