No abstract

Collectins are a family of C-type lectins that have collagen-like sequences and carbohydrate recognition domains (CRD). They are involved in host defense through their ability to bind to carbohydrate antigens of microorganisms. The scavenger receptors type A and MARCO are classical type scavenger receptors that have internal collagen-like domains. Here we describe a new scavenger receptor that is a membrane-type collectin from placenta (collectin placenta 1 (CL-P1)), which has a typical collectin collagen-like domain and a CRD. The cDNA has an insert of about 2.2 kilobases coding for a protein containing 742 amino acid residues. The deduced amino acid sequence shows that CL-P1 is a type II membrane protein, has a coiled-coil region, a collagen-like domain, and a CRD. It resembles type A scavenger receptors because the scavenger receptor cysteine-rich domain is replaced by a CRD. Northern analyses, reverse transcription-polymerase chain reaction, and immunohistochemistry show that CL-P1 is expressed in vascular endothelial cells but not in macrophages. By immunoblotting and flow cytometry CL-P1 appears to be a membrane glycoprotein of about 140 kDa in human umbilical vein or arterial endothelial cells, placental membrane extracts, and CL-P1 transfected Chinese hamster ovary cells. We found that CL-P1 can bind and phagocytose not only bacteria (Escherichia coli and Staphylococcus aureus) but also yeast (Saccharomyces cerevisiae). Furthermore, it reacts with oxidized low density lipoprotein (OxLDL) but not with acetylated LDL (AcLDL). These binding activities are inhibited by polyanionic ligands (polyinosinic acid, polyguanylic acid, dextran sulfate) and OxLDL but not by polycationic ligands (polyadenylic acid or polycytidylic acid), LDL, or AcLDL. These results indicate that CL-P1 might play important roles in host defenses that are different from those of soluble collectins in innate immunity.

Collectins are a family of C‐type lectins with two characteristic structures, collagen like domains and carbohydrate recognition domains. They recognize carbohydrate antigens on microorganisms and act as host‐defense. Here we report the cloning and characterization of a novel collectin CL‐K1. RT‐PCR analyses showed CL‐K1 mRNA is present in all organs. The deduced amino acid sequence and the data from immunostaining of CL‐K1 cDNA expressing CHO cells revealed that CL‐K1 is expressed as a secreted protein. CL‐K1 is found in blood by immunoblotting and partial amino acid analyses. CL‐K1 showed Ca2+‐dependent sugar binding activity of fucose and weakly mannose but not N‐acetyl‐galactosamine, N‐acetyl‐glucosamine, or maltose, though mannose‐binding lectin (MBL) containing similar amino acid motif. CL‐K1 can recognize specially several bacterial saccharides due to specific sugar‐binding character. Elucidation of the role of two ancestor collectins of CL‐K1 and CL‐L1 could lead to see the biological function of collectin family.

The UL41 gene product (vhs) of herpes simplex virus (HSV) is packaged in the virion, and mediates host protein synthesis shutoff at the early stage of the virus replication cycle. In order to clarify the role of vhs in virus replication and virulence, we isolated a completely UL41-deficient mutant (the VR∆41 strain) and its revertant (the VR∆41R strain). In the mouse encephalitis model, the replication of strain VR∆41 was inhibited after 2 days post-infection, resulting in low virulence, by γ-ray-sensitive cells such as lymphocytes and/or neutrophils. The result suggested that some cytokines, produced in VR∆41-inoculated brains, activate and induce the migration of γ-raysensitive cells to the infection site. Therefore, cytokines produced by HSV-1-infected human cells were screened, and potent inductions of interleukin (IL)-1β, IL-8 and macrophage inflammatory protein-1α by VR∆41 infection were observed. Moreover, the VR∆41 strain showed 20-and 5-fold higher sensitivity to interferon-α and -β compared to the wild-type strain, respectively. These results indicate that one important role of vhs in vivo is evasion from non-specific host defence mechanisms during primary infection through suppression of cytokine production in HSV-infected cells and reduction of the anti-HSV activity of interferon-α and -β.

We examined the influence on the interferon (IFN) signaling pathway of infection with herpes simplex virus type 1 (HSV-1) strain VR3. Data from reporter gene assays showed that expression of both type I and type II IFN-inducible genes was dramatically suppressed during the early stage of HSV-1 infection (2 to 3 h postinfection). During these periods, phosphorylation levels of janus kinases (JAKs) and STATs did not increase after treatment of HSV-1-infected FL cells with IFN-alpha or IFN-gamma, although cellular protein levels of the JAKs and the STATs were not significantly changed. In contrast, the inhibitory effect of HSV-1 on phosphorylation of STAT1 was not observed in U937 cells, which show resistance to steady-state accumulation of RNA for HSV-1 immediate-early genes. The phosphorylation of STAT1 in FL cells was not inhibited by infection with a UV-inactivated virus. These results indicate that viral gene expression or viral protein production is necessary for the inhibition of phosphorylation by HSV-1.