G. Elies et al., Insulin and insulin-like growth factor-1 receptors in an evoluted fish, the turbot: cDNA cloning and mRNA expression, MOL C ENDOC, 158(1-2), 1999, pp. 173-185
The insulin receptor (IR) and the structurally related insulin-like growth
factor type 1 receptor (IGF-IR) belong to the tyrosine kinase (TK) receptor
family. In this study, we have carried out the molecular characterization
of both receptors from turbot (Psetta maxima), an evoluted teleost flatfish
. The cDNA encoding the precursors of IGF-1R and the nearly entire IR (only
the first 16 amino acids of the alpha subunit are missing when compared to
the published human sequence) were cloned from an embryonic cDNA library.
The deduced polypeptides contain all the topological features characterizin
g the insulin/IGF-1 receptor family. They are highly conserved compared to
their mammalian counterparts, particularly within domains involved in the c
atalytic activity and in the transduction pathways. Nevertheless, some diff
erences in the primary sequences, especially in the carboxy-terminal domain
of the precursors, may affect the functions fulfilled by these receptors.
As in mammals, the long IGF-IR 5'-untranslated sequence contains open readi
ng frames and potential Sp1 binding sites. Northern blot analyses have reve
aled a major IR transcript of 11 kb, which is approximately the size of IGF
-1R transcript (Elies, G., Groigno, L., Wolff, J., Boeuf, G., Boujard, D.,
1996. Characterization of the insulin-like growth factor type 1 receptor me
ssenger in two teleost species. Mel. Cell. Endocrinol. 124, 131-140.). If I
R and IGF-1R transcripts are detected by RT-PCR at all developmental stages
and in all tissues examined, in situ hybridization studies have shown that
these mRNA can be visualized as ubiquitous signals only in young larvae, w
hereas IGF-1R and IR expression appears weaker during later development and
in adult tissues. (C) 1998 Elsevier Science Ireland Ltd. All rights reserv
ed.