Cloning and expression of eel natriuretic-peptide receptor B and comparison with its mammalian counterparts.
A comparative study of the natriuretic-peptide receptor NPR-B was performed by cloning and expressing, in COS-1 cells, the NPR-B receptor subtype from the eel gill which exhibited a strong C-type-natriuretic-peptide (CNP)-induced guanylate cyclase activity. Like other mammalian NPR-B receptors, the eel NPR-B receptor consisted of a ligand-binding extracellular domain, a hydrophobic transmembrane domain, a kinase-like domain and a guanylate cyclase domain. Sequence comparison among the eel and mammalian receptors revealed a relatively low similarity (approximately 44%) in the extracellular domain compared to a very high similarity (approximately 84%) in the cytoplasmic regulatory and catalytic domains. This low similarity allowed identification of the amino acid residues or candidate regions important for the ligand-binding activity. RNase protection analysis of the eel NPR-B mRNA demonstrated that the message was predominantly expressed in the liver and atrium as well as in the gill with moderate-to-small amounts in the brain, ventricle, esophageal sphincter, stomach, posterior intestine and kidney. The high NPR-B mRNA levels in the liver, atrium and gill were found to decrease markedly when eels were transferred from fresh water to seawater and kept there for 2 weeks. Since similar changes are known to occur in the ligand CNP levels when eels are facing osmotic challenges, the CNP/NPR-B system appears to play an important role in their successful adaptation to salinity changes.
Katafuchi
T
T
Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan.
Takashima
A
A
Kashiwagi
M
M
Hagiwara
H
H
Takei
Y
Y
Hirose
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000302:isolation & purification; D004524:Eels / Q000235:genetics*; D005618:Fresh Water; D005880:Gills / Q000378:metabolism; D006162:Guanylate Cyclase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000378:metabolism; D008322:Mammals / Q000235:genetics; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D017461:Receptors, Atrial Natriuretic Factor / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D012333:RNA, Messenger; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor; C073616:atrial natriuretic factor receptor C