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.

Collectin placenta 1 (CL-P1), a recently discovered scavenger receptor, mediates the uptake of oxidized low density lipoprotein and microbes. In this study, we investigated CL-P1-mediated binding and ingestion of yeast-derived zymosan bioparticles using Chinese hamster ovary (CHO) cells stably expressing human CL-P1 (CHO/CL-P1) and human vascular endothelial cells constitutively expressed CL-P1. The uptake of zymosan by CHO/CL-P1 was dependent upon the level of CL-P1 expressed on the membrane and was inhibited by cytochalasin D and wortmannin. The binding of zymosan was also inhibited by ligands of other scavenger receptors such as poly(I) and dextran sulfate. Real time reverse transcription-PCR analyses showed that other scavenger receptors, namely LOX-1, Stabilin-2, or macrophage receptor with collagenous structure (MARCO), were not expressed in human umbilical vein endothelial cells isolated from different individuals. Nonopsonic zymosan ingestion was inhibited in three primary cultured vascular endothelial cells, including different human umbilical vein endothelial cells from nine individuals treated with CL-P1 small interfering RNAs, although small interfering RNAs of other scavenger receptors had no effect on zymosan uptake in these cells. Furthermore, we confirmed that CL-P1 is expressed in human and murine vascular endothelial layers. Our results demonstrated that CL-P1 predominantly mediated phagocytosis for fungi in vascular endothelia.Scavenger receptors are integral membrane proteins consisting at least eight different subclasses (Class A to Class H), with little amino acid sequence homology, that bind to a wide variety of ligands, including modified or oxidized low density lipoproteins (oxLDLs), 2 apoptotic cells, and microbial pathogens (1). Among these ligands, oxLDLs are considered to have an important role in interactions with endothelial cells, macrophages, and smooth muscle cells in the development of atherosclerosis according to Ross's response-to-injury hypothesis (2, 3). Vascular endothelial cells express several distinct scavenger receptors, such as SR-BI (4 -6), LOX-1 (7), SREC (8), FEEL-1/stabilin-1, and FEEL-2/stabilin-2 (9).Using placental cDNA, we recently identified CL-P1 (10), a type II transmembrane protein with a coiled-coil, a collagenlike domain, and a carbohydrate recognition domain (CRD) and showed it to be a scavenger receptor, in addition to its role as a collectin (Colec12). This molecule resembles a Class A scavenger receptor (SR-A) in its structure except for the replacement of the cysteine-rich domain by a CRD (11). CL-P1 can bind to oxLDL without interacting with other modified LDLs such as acetyl-LDL. Interestingly, we found that CL-P1 expression in HUVECs was up-regulated after the induction of oxidative stress in vitro and was increased in aortic endothelia in a rat ischemia-reperfusion model (12). Another reported finding on the ability of CL-P1 to mediate the binding of yeast, as well as Gram-negative and -positive bacteria in CL-P1-transfected CHO cells, strongly ...

LPS induces transient lipid accumulation and expression of ADRP in the liver through inhibition of fatty acid oxidation by downregulation of the PPARalpha-related transcriptional mechanism.

Background: Scavenger receptors are generally expressed in macrophages and vascular endothelial cells and some scavenger receptors are thought to contribute to the development of atherosclerosis. Methods: We cloned the cDNA of a zebrafish CL-P1 (collectin placenta 1) and performed a knockdown study using its antisense morpholino oligonucleotides (MO). Results: Zebrafish CL-P1 (zCL-P1) is 51% identical to human CL-P1 in its amino acid sequence. Microbes and OxLDL bound to zCL-P1 cDNA transfected cells. zCL-P1 mRNA expression gradually increased after 6 hours post-fertilization (hpf), reached its highest level at 24 hpf, and then decreased, which is similar to the gene expression pattern of Tie-2. The knockdown of zCL-P1 led to an increase in the number of zebrafish embryos with severe morphological abnormalities such as short body lengths and defects in the dorsal aorta at 48 hpf. Simultaneous injection of both MO and synthetic zCL-P1 or zVEGF mRNA rescued the abnormal phenotype. Conclusions: In vivo knockdown study shows that zCL-P1 is implicated in vasculogenesis and those of our in vitro study support its role as a scavenger receptor. General Significance: These results suggest that zCL-P1 might be essential for vasculogenesis during the early embryonic phase in bone fish.

In the present study, we examined a role of mitogen-activated protein kinases (MAPKs), extracellular signal-related kinase (ERK), c-Jun N-terminal protein kinase, and p38 MAPK in troglitazone-induced inhibition of cell growth in human pancreatic cancer cells. Among the three kinases, troglitazone specifically inhibited the phosphorylation of ERK1/2 in a dose- and time-dependent manner. Troglitazone also down-regulated the protein expression of mitogen-activated protein kinase kinase (MEK)1/2, an upstream molecule that regulates ERK phosphorylation. Treatment of human pancreatic cancer cells with specific MEK inhibitor, PD98059 or U0126, inhibited ERK1/2 phosphorylation and cell growth. These results suggest for the first time that the inhibition of the MEK1/2-ERK1/2 signaling pathway may be implicated in the growth inhibitory effect by troglitazone in human pancreatic cancer cells.