SRB1, a class B scavenger receptor, recognizes both negatively charged liposomes and apoptotic cells

Scavenger receptors mediate the recognition of a wide range of negatively charged macromolecules such as acetylated low-density lipoproteins (AcLDL). We previously reported the isolation of CHO cell variants expressing a novel type of scavenger receptor, distinct from type I and II macrophage scavenger receptors, that recognize both AcLDL and negatively charged liposomes. In the present study, we found that these isolated CHO cells express class B scavenger receptors (SRB1), which have recently been identified as a new member of the CD36 family of membrane proteins. The isolated CHO cells and CHO transfectants constitutively expressing SRB1 recognized and mediated the endocytosis of cells undergoing apoptosis as well as that of negatively charged liposomes. In contrast, CHO cells constitutively expressing type I or II scavenger receptors were unable to take up these ligands.