The basic residue cluster 55KKWVR59 in CCL5 is required for in vivo biologic function

Abstract

Chemokine function in vivo depends on the presentation by structures of the extracellular matrix or on
endothelial surfaces. CCL5 contains two clusters of basic amino acid residues (44RKNR47 and 55KKWVR59)
implicated in presentation of the protein. While 44RKNR47 has been shown to moderate CCL5 binding to
glycosaminoglycans (GAGs), no direct role for the basic residues in the so called 50s loop (55KKWVR59)
as a presentation structure has been published to date. In ex vivo studies both regions were found to be
necessary for direct tissue binding suggesting a role for 55KKWVR59. In vitro T lymphocyte and monocyte
induced firm adhesion under flow, as well as leukocyte recruitment to the peritoneal cavity in vivo was
reduced in the 50s mutant. The binding of the 50s mutant to endothelial cells was significantly reduced
as compared to the wild type protein demonstrated by ELISA. The 50s mutant had little impact on GAG
binding in vitro. These data suggest that functional CCL5 presentation is mediated through both the 40s
as well as the 50s loop with differential functions of the two loops of clusters of basic residues.