Molecular cloning, identification and characterization of four distinct receptor subtypes for insulin and IGF-I in Japanese
(Requests for offprints should be addressed to K Nakashima) Insulin receptor (IR) and IGF-I receptor (IGF-IR) are structurally and functionally related and belong to the tyrosine kinase receptor family. In teleosti such as salmon-ids and turbot, occurrence of multiple IR and IGF-IR members has been...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.484.6252 http://intl-joe.endocrinology-journals.org/content/173/2/365.full.pdf |
| Summary: | (Requests for offprints should be addressed to K Nakashima) Insulin receptor (IR) and IGF-I receptor (IGF-IR) are structurally and functionally related and belong to the tyrosine kinase receptor family. In teleosti such as salmon-ids and turbot, occurrence of multiple IR and IGF-IR members has been reported, but the structures of a complete set of both IR and IGF-IR members in a single teleost species have not yet been characterized. In this study, we cloned and analysed four distinct cDNA clones for IR and IGF-IR members from the liver and kidney of the Japanese flounder (Paralichthys olivaceus). Deduced amino acid sequence analyses and phylogenetic analysis have revealed that two of them (fIR-1 and fIR-2) belong to IR members and the other two (fIGF-IR-1 and fIGF-IR-2) are IGF-IRs. fIR-1 and fIR-2 comprised 1369 and 1368 amino acid residues respectively, and fIGF-IR-1 and fIGF-IR-2 comprised 1412 and 1418 residues respectively. All the receptor proteins contained cysteine-rich domains in their -subunits, and conserved each transmembrane and tyrosine kinase domains in their -subunits. The amino acid sequences of fIRs and fIGF-IRs showed more than 90 % sequence identity with turbot IR and IGF-IR respectively. When compared with their mammalian homologues, fIGF-IR-1 and fIGF-IR-2 pro-teins contained large insertions at their C-termini, as was observed in the corresponding region of turbot IGF-IR. Occurrence of multiple species of mRNA for each IR and IGF-IR was suggested by Northern blot analyses. A ribonuclease protection assay revealed diverse expressions of four receptor mRNAs in a wide range of tissues |
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