Monkey Growth Hormone (GH) Receptor Gene Expression

Abstract

The growth hormone receptor (GHR) cDNA was cloned from the liver of Rhesus macaque using polymerase chain reaction. As deduced from the nucleotide sequence, the mature GHR is a protein of 620 amino acids which presents 94.1% identity with the human receptor. The monkey GHR (mkGHR) expressed in 293 cells presented the expected specificity for a primate GHR and was able to transduce a transcriptional effect of GH. Human GH was able to activate tyrosine phosphorylation of both the tyrosine kinase JAK2 and the receptor in 293 cells co-transfected with mkGHR and JAK2 cDNAs. The GH binding protein (GHBP), the soluble short form of the GHR, was also present in monkey serum. Expression of the GHR cDNA in eucaryotic cells indicated that the GHBP can be produced by proteolytic cleavage of the membrane receptor. Northern blot analysis of GHR gene expression in different tissues allowed us to identify three different transcripts of 5.0 and 2.8 kilobase pairs and a smaller one of 1.7 kilobase pairs which could encode a GHBP. Rapid amplification of cDNA extremities (3-RACE-polymerase chain reaction) was used to identify a cDNA encoding a protein in which the transmembrane and cytoplasmic domains of the receptor are substituted by a short sequence of 9 amino acids. This transcript was present in various tissues and could encode a GHBP as well, suggesting for the first time that two different mechanisms can coexist for the generation of the GHBP: proteolytic cleavage of the membrane receptor and a specific mRNA produced by alternative splicing.

The baboon: a model for the study of primate growth hormone receptor gene expression during development

“…Analysis of the cDNA clones showed that the mature GHR proteins of the baboon and rhesus monkey are extremely well conserved (98·5%), and have a similar degree of variation from the human (baboon 95%, rhesus monkey 94%), with the few amino acid differences dispersed throughout the receptor sequence (present data, Leung et al 1987, Martini et al 1997. This is consistent with the idea that these primates are equi-distant evolutionary ancestors of the human (Pausova et al 1995).…”

“…Evidence for the presence of this V3 subvariant in the baboon was obtained following longer exposure of the Southern blots to X-ray film (data not shown). The baboon V1 sequence was also a perfect match for the 5 UTR sequence of the rhesus monkey GHR cDNA reported by Martini et al (1997) except, surprisingly, for the terminal 3 12 nucleotides representing the splice site in exon 2: these were missing in the rhesus monkey GHR mRNA sequence.…”

“…Since both the human and rhesus receptors are glycosylated at several sites (Leung et al 1987, Martini et al 1997, it is likely that carbohydrate groups are added to the baboon GHR at the conserved asparagine residues. The formation of two extracellular domain disulphide bridges occurs in the GHRs of all species studied to date, and is also a feature of the class I division of the cytokine/GH/prolactin receptor superfamily (Argetsinger & Carter-Su 1996).…”

“…In the present study, human GHR-specific primers were used to clone baboon GHR cDNAs by reverse transcription (RT)-PCR from postnatal baboon liver total RNA. Nucleotide sequencing of multiple clones revealed that the baboon GHR has a high level of sequence identity with the human (95%) and rhesus monkey (98·5%) GHRs (present data, Leung et al 1987, Martini et al 1997. V1, V3 and V4 homologues were also cloned by RT-PCR from postnatal baboon liver.…”

“…The complete nucleotide sequence of the baboon GHR cDNA predicts a 620 amino acid mature protein, with 95% and 98·5% amino acid sequence similarity with the human (Leung et al 1987) and rhesus monkey receptors (Martini et al 1997) respectively (Fig. 3).…”