SREC-II, a new member of the scavenger receptor type F family, trans-interacts with SREC-I through its extracellular domain.
The scavenger receptor expressed by endothelial cells (SREC) with an extremely large cytoplasmic domain, was originally identified in a human endothelial cell line. In this study, we have cloned a second isoform named SREC-II and shown that there is a heterophilic interaction between SREC-I and -II at their extracellular domains. The cDNA for murine SREC-II encodes an 834-amino acid protein with 35% homology to SREC-I. Similar to SREC-I, SREC-II contains multiple epidermal growth factor-like repeats in its extracellular domain. However, in contrast to SREC-I, SREC-II had little activity to internalize modified low density lipoproteins (LDL). A Northern blot analysis revealed a tissue expression pattern of SREC-II similar to that of SREC-I with predominant expression in human heart, lung, ovary, and placenta. Mouse fibroblast L cells with no tendency to associate showed noticeable aggregation when SREC-I was overexpressed in these cells, whereas overexpression of SREC-II caused only slight aggregation. Remarkably, intense aggregation was observed when SREC-I-expressing cells were mixed with those expressing SREC-II. Deletion of almost all of the cytoplasmic receptor domain had no effect on the receptor expression and cell aggregation, indicating that solely the extracellular domain is involved in cell aggregation. The association of SREC-I and -II was effectively suppressed by the presence of scavenger receptor ligands such as acetylated LDL and oxidized LDL. These findings suggest that SREC-I and -II show weak cell-cell interaction by their extracellular domains (termed homophilic trans-interaction) but display strong heterophilic trans-interaction through the extracellular epidermal growth factor-like repeat domains.
Ishii
Junko
J
Laboratory of Cellular Biochemistry, RIKEN (the Institute of Physical and Chemical Research), 2-1 Wako-shi, Saitama 351-0198, Japan.
Adachi
Hideki
H
Aoki
Junken
J
Koizumi
Hiroyuki
H
Tomita
Susumu
S
Suzuki
Toshiharu
T
Tsujimoto
Masafumi
M
Inoue
Keizo
K
Arai
Hiroyuki
H
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D016466:CHO Cells; D015815:Cell Adhesion Molecules; D002455:Cell Division; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary / Q000378:metabolism; D019992:Databases as Topic; D020224:Expressed Sequence Tags; D017353:Gene Deletion; D006801:Humans; D007962:Leukocytes / Q000378:metabolism; D008074:Lipoproteins / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000378:metabolism*; D011973:Receptors, LDL / Q000737:chemistry* / Q000378:metabolism*; D051116:Receptors, Scavenger; D051128:Scavenger Receptors, Class F; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014162:Transfection
D015815:Cell Adhesion Molecules; D018076:DNA, Complementary; D008074:Lipoproteins; D011956:Receptors, Cell Surface; D011973:Receptors, LDL; D051116:Receptors, Scavenger; C495126:SCARF1 protein, human; C469357:SCARF2 protein, human; D051128:Scavenger Receptors, Class F; D010100:Oxygen