Biochemical characterization of three BLT receptors in zebrafish.
The leukotriene B4 (LTB4) receptor 1 (BLT1) is a high affinity receptor for LTB4, a chemotactic and inflammatory eicosanoid. The LTB4 receptor 2 (BLT2) was originally identified as a low affinity receptor for LTB4, and, more recently, as a high affinity receptor for 12-hydroxyheptadecatrienoic acid (12-HHT). The zebrafish BLT receptors have not been previously identified and the in vivo functions of these receptors have been unknown. In this paper, we describe one zebrafish BLT1-like receptor, Blt1, and two zebrafish BLT2-like receptors, Blt2a and Blt2b. Cells expressing Blt1 exhibited LTB4-induced intracellular [Ca2+] increases, inhibition of cAMP production, ligand-dependent [35S]GTPγS binding, and transforming growth factor-α (TGFα) shedding activity in a dose-dependent manner, similar to human BLT1. Cells expressing Blt2a and Blt2b exhibited 12-HHT- and LTB4-induced intracellular [Ca2+] increases, inhibition of cAMP production, [35S]GTPγS binding, and TGFα shedding activity, with a dose-dependency similar to human BLT2. Reverse transcription (RT)-PCR analysis and whole-mount in situ hybridization revealed that blt1, blt2a, blt2b, zebrafish LTA4 hydrolase (lta4h), and zebrafish 5-lipoxiganase (5lo) are expressed in zebrafish embryos. Knockdown of blt1 by morpholino antisense oligonucleotides resulted in delayed epiboly at gastrulation. Consistently, knockdown of lta4h, an enzyme mediating LTB4 production, induced a phenotype similar to knockdown of blt1. These results suggest that the LTB4-BLT1 axis is involved in epiboly in zebrafish development.
Department of Biochemistry, Juntendo University School of Medicine, Tokyo, Japan; Department of Medical Biochemistry, Kyushu University, Fukuoka, Japan.
Toshiaki
T
Okuno
Division of Cell Regulation Systems, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
Tohru
T
Ishitani
Department of Biochemistry, Juntendo University School of Medicine, Tokyo, Japan; Department of Medical Biochemistry, Kyushu University, Fukuoka, Japan.
Takehiko
T
Yokomizo
D000595:Amino Acid Sequence; D000818:Animals; D008969:Molecular Sequence Data; D011485:Protein Binding; D018102:Receptors, Leukotriene B4 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D018102:Receptors, Leukotriene B4; D029961:Zebrafish Proteins