Murine CD9 Is the Receptor for Pregnancy-specific Glycoprotein 17

Abstract

Pregnancy-specific glycoproteins (PSGs) are a family of highly similar secreted proteins produced by the placenta. PSG homologs have been identified in primates and rodents. Members of the human and murine PSG family induce secretion of antiinflammatory cytokines in mononuclear phagocytes. For the purpose of cloning the receptor, we screened a RAW 264.7 cell cDNA expression library. The PSG17 receptor was identified as the tetraspanin, CD9. We confirmed binding of PSG17 to CD9 by ELISA, flow cytometry, alkaline phosphatase binding assays, and in situ rosetting. Anti-CD9 monoclonal antibody inhibited binding of PSG17 to CD9-transfected cells and RAW 264.7 cells. Moreover, PSG17 binding to macrophages from CD9-deficient mice was significantly reduced. We then tested whether PSG17 binds to other members of the murine tetraspanin family. PSG17 did not bind to cells transfected with CD53, CD63, CD81, CD82, or CD151, suggesting that PSG17–CD9 binding is a specific interaction. We have identified the first receptor for a murine PSG as well as the first natural ligand for a member of the tetraspanin superfamily.

Regulation of NK cell trafficking by CD81

“…Based on our results, up-regulation of CD44 might be involved in anti-CD81-induced NK cell adherence as this adhesion molecule represents the main receptor of HA and has been reported to participate in matrix-adhesion, activation, and lymph node homing of lymphocytes [34]. A role for CD44 in NK cell adhesion is further supported by the fact that CD44 was found to be redistributed to the uropod where it co-localized with pERM in anti-CD81-activated NK cells as this has been shown to promote HA binding [35].Although no physiological ligand for CD81 has been identified so far, other members of the tetraspanin family such as CD9 and CD63 have recently been reported to act as receptor for pregnancy-specific glycoprotein 17 and TIMP-1, respectively [36,37]. Thus it is conceivable that CD81 may directly interact with as yet unidentified constituents.…”

“…Although no physiological ligand for CD81 has been identified so far, other members of the tetraspanin family such as CD9 and CD63 have recently been reported to act as receptor for pregnancy-specific glycoprotein 17 and TIMP-1, respectively [36,37]. Thus it is conceivable that CD81 may directly interact with as yet unidentified constituents.…”

“…In brief, 2. [36] was evaluated in a cell adhesion assay carried out as follows: 24-well flat-bottom assay plates were coated overnight with HA (1 mg/mL, Sigma-Aldrich) and subsequently rinsed two times with PBS. After cell stimulation cell subsets were rinsed with PBS, resuspended (3.5 Â 10 5 cells in 300 mL) in serum-free L-glutamine-supplemented RPMI 1640 medium (Biochrom, Berlin, Germany), dispensed onto substrate-coated wells and incubated for 60 min at 371C.…”

CD63 as an Activation-Linked T Cell Costimulatory Element

“…First, CD63 could be the receptor of a costimulatory signal provided by DC. Although no ligand for CD63 has been described so far, other members of the tetraspan family have recently been reported to be able to act as receptors (36,37). Therefore it is conceivable that CD63 directly interacts with a yet unidentified ligand on DC.…”

The Tetraspanin CD9 Localizes to Platelet-Platelet Contacts and Regulates Thrombus Stability

“…With specific regard to the tetraspanin CD9, interactions have been shown with the integrins α3β1 (Yanez-Mo 1998)  , α4β1α6β1,α5β1,αIIbβ3 (GPIIb-IIIa), and precursor β1 (Yunta 2002); the growth factor receptors TGF-α and HB-EGF (Lagaudriere-Gesbert 1997); immunoglobulin superfamily members FRPP and EWI-2 (Stipp 2001); CD36 and CD9P-1 (Miao 2001), CD19 (Horvath 1998), and CD46 (Yunta 2002); the signaling molecules PKC and PI4K ; and the soluble ligands FN , and PSG 17 (Waterhouse 2002). Many more protein partners will likely be identified in the future.…”