Molecular cloning and functional analysis of scavenger receptor zebrafish CL-P1

Abstract

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.

Soluble Collectin-12 (CL-12) Is a Pattern Recognition Molecule Initiating Complement Activation via the Alternative Pathway

“…Intriguingly, recent findings in zebrafish embryo models have shown that knockdown of zebrafish COLEC12 expression causes severe defects in vasculogenesis and development during the early embryogenic stages (22). These results suggest a pivotal role for CL-12 not only in innate immune defense, but also in fundamental developmental processes.…”

Class-A scavenger receptor function and expression in the rainbow trout (Oncorhynchus mykiss) epithelial cell lines RTgutGC and RTgill-W1

“…SR-A sequences are beginning to be identified in teleost fish. A SCARA4 (CL-P1) homolog has been cloned in zebrafish, Danio rerio, [11] and a SCARA5 homolog has been cloned in puffer fish, Tetraodon nigroviridis [12]. Zebrafish SCARA4 binds both mLDLs and bacteria and is involved in vasculogenesis [11], while puffer fish SCARA5 is able to bind LPS and negatively affect the pro-inflammatory response [12].…”

Scavenger Receptors: Structure, Function and Diversity

“…There is no evidence linking SRCL to disease initiation and progression but the fact that this SR member specifically binds OxLDL but not unmodified LDL or AcLDL particles suggests that the cellular context of binding could be important (Fukuda et al, 2011;Ohtani et al, 2001). Although murine MARCO binds AcLDL, the human orthologue does not recognise either AcLDL or OxLDL (Elshourbagy et al, 2000;Elomaa et al, 1995).…”

“…The SRCL (SCARA4, colec12) gene is located on human and mouse chromosome 18 and has a C-type lectin domain (SRCL II mRNA transcript lacks the C-type lectin domain) and is expressed in many tissues including placenta, umbilical cord, lung, skeletal muscle and heart. SRCL binds to modified LDL and glycans and is involved in the innate immune response; gene expression can be elevated by oxidative and hypoxic stress (Nakamura et al, 2001;Feinberg et al, 2007;Selman et al, 2008;Fukuda et al, 2011). MARCO (SCARA2) is located on human chromosome 2 or mouse chromosome 1 (Kangas et al, 1999) and lacks the a-helical coiled-coil domain present in other class A members (Ojala et al, 2007).…”

“…Antibodies to CD36 or SR-A can reduce cholesterol accumulation in macrophages (Guest et al, 2007). SRCL is involved in embryonic development in zebrafish (Fukuda et al, 2011). Mutations in SCARB2 can also lead to action myoclonus renal failure syndrome (AMRF) and allelic polymorphisms may contribute to Parkinson's disease (Rubboli et al, 2011;Michelakakis et al, 2012).…”