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M C Postel-Vinay

Publications and source records attributed to M C Postel-Vinay.

At least 73 records · Page 4Linked to original sources
PubMed1994

Distinct cytoplasmic regions of the growth hormone receptor are required for activation of JAK2, mitogen-activated protein kinase, and transcription.

The GH receptor (GHR) is a member of the cytokine/hematopoietic growth factor family, and protein tyrosine phosphorylation has been implicated in the signaling cascade of these receptors. It was recently shown that the tyrosine kinase JAK2 is associated with the GHR. GH induces the activation of JAK2, which phosphorylates itself and the receptor. Mitogen-activated protein (MAP) kinase activation and transcriptional stimulation of specific genes, such as Spi 2.1, have also been reported to be induced by GH. To identify functionally important regions in the cytoplasmic domain of the GHR, we compared the actions of the wild-type receptor, two truncated mutants, and one internal deletion mutant (similar to the intermediate Nb2 form of the PRL receptor) in transfectants of the Chinese hamster ovary cell line. A region of 46 amino acids adjacent to the membrane was found to be sufficient for activation of both JAK2 and MAP kinases. This region contains a proline-rich sequence (box 1) conserved in the cytokine receptor family that is important for signal transduction. For transcriptional activity, the C-terminal region of the GHR is required, and we found that the last 80 terminal residues contain sequences allowing activation of the Spi 2.1 promoter. Tyrosine phosphorylation of the receptor also requires the C-terminal portion of the GHR cytoplasmic domain, and we found that GHR tyrosine phosphorylation appears to be linked to activation of the Spi 2.1 transcription pathway. Thus, the GHR could be composed of at least 2 functional regions: the 46 proximal amino acids required for activation of JAK2 and sufficient to stimulate the MAP kinase pathway, and an additional carboxy-terminal region necessary for transcriptional activation.

Animals↗
PubMed1994

Expression of the growth hormone receptor gene in human digestive tissue.

We have examined the forms and the distribution of the messenger ribonucleic acids (mRNAs) encoding the GH receptor (GHR) in human digestive tissues. GHR mRNAs were identified and characterized by Northern blot, dot blot, and in situ hybridization analyses, using complementary DNAs coding for the extracellular part of the human liver GHR. Amplification using the polymerase chain reaction was also used, as tissues express low levels of GHR mRNAs. Our results demonstrate that the GHR gene is expressed in human liver, pancreas, esophagus, stomach, small intestine, and colon. A single 4.5-kilobase mRNA form, which probably encodes the full-length membrane receptor, was detected. GHR mRNA was visualized by in situ hybridization in hepatocytes, exocrine pancreas, and some islet cells; signal was also present in the mucosa of the digestive tract. No specific GH-binding-protein mRNA was found, suggesting that in man, the soluble form of the receptor is generated through proteolytic cleavage of the membrane receptor.

Adolescent↗
PubMed1994

Receptor domains involved in signal transduction of prolactin and growth hormone.

Prolactin (PRL) and growth hormone (GH) receptors are members of a superfamily that include receptors for a number of cytokines. GH and its receptor form an unusual homodimer consisting of one molecule of GH and two molecules of receptor. A similar homodimer of the PRL receptor is probably required for biological effects to be seen. Using specific assays to measure the functional activity of PRL and GH receptors, a 25 amino acid juxtamembrane region has been identified as essential but not sufficient for normal action. More detailed studies have limited the region to eight amino acids, rich in prolines, that is highly conserved in many members of the receptor superfamily. Finally, GH and PRL have been shown to induce the rapid tyrosine phosphorylation of an associated kinase, Janus kinase 2, and of the receptor itself.

Animals↗
PubMed1993

Lack of hormone binding in COS-7 cells expressing a mutated growth hormone receptor found in Laron dwarfism.

A single point mutation in the growth hormone (GH) receptor gene generating a Phe-->Ser substitution in the extracellular binding domain of the receptor has been identified in one family with Laron type dwarfism. The mutation was introduced by site-directed mutagenesis into cDNAs encoding the full-length rabbit GH receptor and the extracellular domain or binding protein (BP) of the human and rabbit GH receptor, and also in cDNAs encoding the full length and the extracellular domain of the related rabbit prolactin (PRL) receptor. All constructs were transiently expressed in COS-7 cells. Both wild type and mutant full-length rabbit GH and PRL receptors, as well as GH and prolactin BPs (wild type and mutant), were detected by Western blot in cell membranes and concentrated culture media, respectively. Immunofluorescence studies showed that wild type and mutant full-length GH receptors had the same cell surface and intracellular distribution and were expressed with comparable intensities. In contrast, all mutant forms (full-length receptors or BPs), completely lost their modify the synthesis ligand. These results clearly demonstrate that this point mutation (patients with Laron syndrome) does not modify the synthesis or the intracellular pathway of receptor proteins, but rather abolishes ability of the receptor or BP to bind GH and is thus responsible for the extreme GH resistance in these patients.

Animals↗
PubMed1993

Evidence for generation of the growth hormone-binding protein through proteolysis of the growth hormone membrane receptor.

The growth hormone-binding protein (GHBP) which circulates in plasma is a soluble short form of the membrane growth hormone receptor (GHR). In rats and mice, GHR and GHBP originate from two alternatively spliced mRNAs (4.5 and 1.2 kb). In human and rabbit tissues, a single predominant mRNA of 4.5 kb was detected and it was hypothesized that GHBP could be produced by proteolytic cleavage of the GHR. Using gel filtration and HPLC, we have detected a high level of GH binding activity in media of cells transfected with rabbit GHR cDNA. The [125I]hGH-GHBP complex eluted at the same time as the plasma complex and both the binding affinity and specificity of the BP were comparable to that of rabbit plasma. Immunoprecipitation experiments and Western blots confirmed that GHBP in the media of transfected cells was a 55 kDa protein related to the extracellular domain of the GHR. In contrast, no BP was detected in the media of cells transfected with the cDNA encoding the rat GHR. These results strongly suggest that, in rabbit and probably in man, the GHBP could, at least in part, be produced by proteolytic cleavage of the GHR.

Animals↗
PubMed1993

Familial short stature with very high levels of growth hormone binding protein.

We report a familial syndrome of short stature associated with partial GH resistance and very high levels of GH binding protein (GHBP). In three individuals of the same family, presenting with growth failure, high circulating GH levels, both basal and stimulated, were found. Insulin-like growth factor-1 plasma levels were either normal or in the low normal range. GH binding activity was extremely elevated in the plasma of the three subjects, with very high maximum binding capacity (30- to 110-fold higher than that of normal adult plasma) and normal binding affinity (5-7.4 x 10(8) M-1). The cause and the exact consequences of the very high level of plasma GHBP, resulting in a low proportion of free circulating GH, remain to be clarified. The short stature and the partial GH resistance are probably related to high GHBP levels.

Adolescent↗
PubMed1993

Clinical features and endocrine status in patients with growth hormone insensitivity (Laron syndrome).

Twenty-seven patients with GH insensitivity were identified from 44 possible cases, using a scoring system based on height standard deviation score (SDS), basal GH, insulin-like growth factor-I (IGF-I), IGF-I response to IGF-I generation test, and GH-binding protein (GH-BP) determinations. The 27 cases were from 8 European countries and Australia. Clinical features were as follows: age 2.8-22.6 yr; 12 male, 15 female, 19 prepubertal. Birth weight was median -0.72 SDS (1.75(-)-3.29) and birth length, median -1.59 SDS (0.63(-)-3.63). Hypoglycemia had been documented in 33% of the cases, and micropenis was present in 58% of the males. At assessment, height was median -6.1 SDS (-3.8(-)-10.2), weight was median -3.2 SDS (-0.1 to -5.2), and percentage weight for height, median 111.3 (72-271). Puberty was absent in 2 boys aged 15 yr and in 3 girls aged 13 yr. Bone age was delayed in 19 of the 27 patients. Endocrine investigations showed basal serum GH median 17 micrograms/L (0.5-79), IGF-I values less than 5th percentile, and all except 2, age less than 8 yr, less than 0.1 percentile for age. Percentage increment of IGF-I during IGF-I generation test (hGH 0.1 U/kg body weight daily x 4) did not exceed twice the intraassay coefficient of variation, being less than 0.1 percentile for age. IGF-II was median 135.0 micrograms/L (62-232), all values being less than 5th percentile for age. Insulin-like growth factor binding protein-3 (IGFBP-3) values were median 0.53 mg/L (0.10-1.17 mg/L), all being less than 5th percentile for age. IGFBP-3 values after hGH remained less than 5th percentile. IGFBP-1 values showed the normal fall with age, some being above the normal range; IGFBP-2 values were normal. There was a positive correlation between height SDS and IGF-II SDS (r = 0.66, P < 0.001) and IGFBP-3 (r = 0.64, P < 0.001). Specific binding of [125I]hGH to GH-BP was undetectable in 18 patients and extremely low (< or = 5.6%) in 2. GH-BP was normal (14.2-45.9% radioactivity) in 7 subjects, all female, demonstrating that normal GH-BP does not exclude GH insensitivity.

Adolescent↗
PubMed1992

[Determination of growth hormone binding protein in a normal population and in subjects with short stature due to growth hormone resistance].

With the procedure which uses gel-filtration and high pressure liquid chromatography (HPLC) the authors measured the GH-binding proteins in 96 healthy subjects aged 6 months to 40 years. In the blood 45% of the GH is bound to the BP. The diagnosis was confirmed by our method in 13 patients with Laron type dwarfism and in four patients the GH receptor defect had been proved. The parents, the brothers and sisters showed significantly lower GH-BP II (principal GH-BP) levels. Possible regulation of GH-binding proteins in human plasma was examined. Eight children with isolated GH deficiency had a very low level of plasma GH binding activity (mean +/- SEM) (10.2 +/- 1.1% of radioactivity). Under GH treatment the hormone binding to high affinity BP (GH-BP II) increased in every patient to reach the mean value of 18.5 +/- 1.4%. This increase was related to a higher binding capacity without any significant change in the binding affinity. In nine boys with pubertal delay, the GH specific binding to peak II-BP (GH-BP II) was found to be normal (30.6 +/- 3.7%); it decreased significantly following testosterone treatment. In four boys with precocious puberty, the specific GH binding to peak II BP was low (16.6 +/- 1.1%). It increased significantly to 21.6 +/- 1.1% of radioactivity after treatment with LH-RH analogue. GH and testosterone have an opposite role in the regulation of the high affinity GH-BP.

Adolescent↗
PubMed1992

[Analysis of human growth hormone-binding protein in plasma by high pressure liquid chromatography].

A technique using high pressure liquid chromatography gel filtration was used to evaluate GH-binding proteins (GH-BPs) in human plasma; eluate was monitored for radioactivity in a gamma-detection system connected to a computer. Plasma (200 microliters) was incubated with 125I-human (h) GH (200,000 cpm) at 4 degrees C for 20 hours. Our GH binding assay offers important gains in terms of rapidity and resolution; it has permitted a clear separation and characterization of the two GH-binding components present in human plasma.

Carrier Proteins↗
PubMed1992

Effect of growth hormone on the low level of growth hormone binding protein in idiopathic short stature.

OBJECTIVE: Growth hormone receptor status was assessed in children with idiopathic short stature by evaluating plasma growth hormone-binding protein before and under GH therapy. DESIGN: Among 22 children presenting idiopathic short stature, 15 were randomly selected to be treated with GH (1.2 IU/kg/week); they were studied before and under GH therapy. Untreated patients served as a control group for age and GH effect. PATIENTS: Twenty-two prepubertal children, aged 5-11 years, were studied. They presented growth retardation of -2.8 +/- 0.1 SDS (mean +/- SEM). All had normal GH secretion and their mean IGF-I plasma level was normal. MEASUREMENT: Growth hormone-binding protein was measured using high pressure liquid chromatography gel filtration. The specific binding of 125I-hGH to the growth hormone-binding protein was expressed as a percentage of the total radioactivity. RESULTS: Specific binding of 125I-hGH to the high affinity growth hormone-binding protein was low with a mean +/- SEM value of 11.1 +/- 0.9% of radioactivity. In the treated group, growth hormone-binding protein increased significantly after 3 months of treatment; it reached 21.1 +/- 1.0% of radioactivity (mean +/- SEM) in the eight children who have been treated for 18 months. In the seven untreated children, the growth hormone-binding protein value increased to 16.2 +/- 1.1% after 18 months; this value is significantly lower than that found in the GH-treated children, demonstrating that the GH effect is greater than the age-related increase in the growth hormone-binding protein. A positive correlation was found between IGF-I plasma levels and growth hormone-binding protein and also between growth velocity and growth hormone-binding protein. CONCLUSIONS: The low growth hormone-binding protein and the response to high doses of GH suggest partial GH resistance at the receptor level, in this group of children with idiopathic short stature.

Carrier Proteins↗
PubMed1992

Pyruvate dehydrogenase activity is stimulated by growth hormone (GH) in human mononuclear cells: a new tool to measure GH responsiveness in man.

Human peripheral mononuclear cells (PMC) were used to examine the effects of hGH and insulin on the activity of the pyruvate dehydrogenase (PDH) complex. Incubation of PMC with 10(-7) mol/L hGH or insulin increased basal PDH activity. Hormonal effects were maximal (50-60% above control values) at 15 min. Later on, activation progressively decreased and was no longer detectable at 30 min. Total PDH activity was unaffected by hormonal treatment. PMC were subfractionated into lymphocytes and monocytes to assess the sensitivity of each cell types to the hormones. hGH significantly increased basal PDH activity in lymphocytes and monocytes (38% and 70% above control values, respectively), whereas insulin increased basal PDH activity only in monocytes (151% above control value). PMC from healthy subjects aged 1-45 yr were incubated for 15 min with 10(-7) mol/L hGH or insulin before PDH measurement. An increase of enzyme activity higher than 20% was observed in 26 patients out of 29 with hGH, and in 15 out of 18 with insulin. In conclusion, hGH is able to stimulate PDH activity of human mononuclear cells. This hormonal effect allows rapid evaluation of the cellular responsiveness of hGH in various pathophysiologic situations.

Adolescent↗
PubMed1991

Identification of prolactin and growth hormone binding proteins in rabbit milk.

Two distinct soluble proteins that specifically bind 125I-labeled human growth hormone (GH) are identified in the supernatant of ultracentrifuged rabbit milk, using HPLC gel filtration. The higher molecular weight proteins is GH specific, whereas the other one is specific for prolactin (PRL). The PRL-binding protein has a very high affinity for the hormone, almost 10 times higher than the affinity of the mammary gland membrane receptor. The PRL-binding protein is immunoprecipitated by a monoclonal antibody against the PRL receptor; another monoclonal antibody, which inhibits the PRL binding to mammary gland membranes, is a poor competitor for the PRL binding to the milk protein. These findings suggest that the milk PRL-binding protein corresponds to the binding domain of the receptor, but also that the conformation of the receptor and of the binding protein might differ. The milk and the plasma GH-binding proteins have a similar binding affinity. In cross-linking experiments using 125I-labeled human GH, the Mr of the GH-binding protein and of the PRL-binding protein were estimated to be 51,000 and 33,000, respectively. The binding proteins identified in the present work are probably responsible for the transport of their specific ligands in the milk. It is also conceivable that they have a role in the effects of GH and PRL in the mammary gland and/or the intestine of the young.

Animals↗
PubMed1991

Plasma growth hormone-binding activity is low in uraemic children.

Plasma growth hormone-binding protein (GH-BP) activity was evaluated in two groups of prepubertal children with chronic renal failure (CRF) who had been treated with recombinant human GH (rhGH). Group 1 consisted of eight children (mean chronological age 10.8 years) with advanced renal failure; group 2 consisted of nine children (mean chronological age 6 years) presenting with end-stage renal disease, who were on dialysis. Before treatment the specific binding of (125I)hGH to high-affinity GH-BP was low in the two groups (group 1, 17.3 +/- 1.6% of radioactivity; group 2, 14.2 +/- 1.4%) compared with the mean value obtained in normal prepubertal children (24.8 +/- 1.7%). No significant changes in GH-BP activity were found during the 1st year of GH therapy, although growth velocity and plasma levels of insulin-like growth factor-I increased significantly in both groups. The low GH-binding activity found in children with CRF supports the state of GH resistance. The reason for the absence of a GH-BP response to GH therapy has to be clarified.

Carrier Proteins↗
PubMed1991

Specific binding sites for growth hormone in cultured mouse thymic epithelial cells.

Growth Hormones bound specifically to murine Thymic epithelial cells, which represent the major component of thymic micro-environment and can be modulated by pituitary hormones. The Kds found with human growth hormone and bovine growth hormone were 0.14 and 0.27 nM with a Bmax 0.56 and 0.35 fmol/10(6) cells respectively. Competition experiment analysis showed ED50 of 0.24 nM for hGH, 0.46 nM for rGH, 0.71 nM for bGH, 11.8 nM for hPRL and 11.2 nM for oPRL. No specific binding of [125I]-oPRL was observed under the same conditions. Both hPRL and bGH showed a negative regulatory effect on the number of the hGH binding sites when incubated with the culture for three days. The presence of GH receptors on Thymic epithelial cells provides biochemical evidence for the effect of GH on thymic function.

Animals↗
PubMed1991

Recurrent nonsense mutations in the growth hormone receptor from patients with Laron dwarfism.

In addition to its classical effects on growth, growth hormone (GH) has been shown to have a number of other actions, all of which are initiated by an interaction with specific high affinity receptors present in a variety of tissues. Purification of a rabbit liver protein via its ability to bind GH has allowed the isolation of a cDNA encoding a putative human growth hormone receptor that belongs to a new class of transmembrane receptors. We have previously shown that this putative growth hormone receptor gene is genetically linked to Laron dwarfism, a rare autosomal recessive syndrome caused by target resistance to GH. Nevertheless, the inability to express the corresponding full-length coding sequence and the lack of a test for growth-promoting function have hampered a direct confirmation of its role in growth. We have now identified three nonsense mutations within this growth hormone receptor gene, lying at positions corresponding to the amino terminal extremity and causing a truncation of the molecule, thereby deleting a large portion of both the GH binding domain and the full transmembrane and intracellular domains. Three independent patients with Laron dwarfism born of consanguineous parents were homozygous for these defects. Two defects were identical and consisted of a CG to TG transition. Not only do these results confirm the growth-promoting activity of this receptor but they also suggest that CpG doublets may represent hot spots for mutations in the growth hormone receptor gene that are responsible for hereditary dwarfism.

Dwarfism↗
PubMed1991

The prolactin/growth hormone receptor family.

PRL and GH are hormones with a wide spectrum of actions. Specific receptors are widely distributed in a number of classical target organs, but other tissues that are not known targets also contain measurable binding sites or receptor mRNA. The most likely explanation is that PRL and GH cause effects that have not yet been characterized in certain tissues. Cloning of the cDNAs encoding PRL and GH receptors has led to the discovery that the receptors, like the hormones themselves, form a gene family. Multiple receptor forms have been identified, including a short form, which for PRL is a membrane-bound receptor or for GH is a soluble BP, and a long form, which for both PRL and GH is a membrane-bound receptor. PRL and GH receptors, and the mRNAs encoding them, can be up- and down-regulated. GH induces an up-regulation of both GH and PRL receptors, whereas PRL stimulates an increase of only its own receptor. High concentrations of either hormone induce a homologous down-regulation of receptor expression. An assay has been developed to measure the functional activity of different forms of PRL receptor by cotransfecting a milk protein fusion gene specific to PRL coupled to a reporter-gene along with the cDNA of the PRL receptor. Although the short form represents the major form present in rat mammary gland, only the long form of receptor is able to stimulate milk protein gene transcription. For GH, increased expression of the receptor in some target cells is accompanied by a modest enhancement of the response to GH. No single second messenger mediating the action of either PRL or GH has been identified. Several potential components of the signal transduction pathways have been identified, but as yet none has clearly been shown to be able to mimic the effect of PRL or GH. Because of the wide range of biological actions associated with PRL, and the existence of various forms of PRL receptors, it is doubtful that one unifying mechanism of action will be found for this hormone. No human or animal model of a genetic defect of the PRL receptor has thus far been published. Mutations in the GH receptor gene have been demonstrated in Laron type dwarfism. Different exon deletions or point or nonsense mutations resulting in modifications in the extracellular, GH binding region of the GH receptor have been reported.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Human plasma growth hormone (GH)-binding proteins are regulated by GH and testosterone.

Possible regulation of GH-binding proteins (GH-BPs) in human plasma was examined. Eight children with isolated GH deficiency had a very low level of plasma GH-binding activity (10.2 +/- 1.1% of radioactivity). Under GH treatment the hormone binding to the high affinity BP (peak II-BP) increased in every patient to reach the mean value of 18.5 +/- 1.4%. In one patient, Scatchard plot analysis indicated that this increase was related to a higher binding capacity without any significant change in the binding affinity. A positive correlation existed between the GH-binding activity and insulin-like growth factor-I plasma levels. In nine boys with pubertal delay, the GH-specific binding to peak II-BP was normal (30.6 +/- 3.7% of radioactivity); it decreased significantly after testosterone treatment. In four boys with precocious puberty, the specific GH binding to peak II-BP was low (16.6 +/- 1.1%). It increased significantly to 21.6 +/- 1.1% of radioactivity after treatment with a LHRH analog. A negative correlation existed between plasma testosterone levels and GH binding to peak II-BP in boys presenting pubertal delay or precocious puberty. The high affinity GH-BP is regulated, and among the factors that play a role in this regulation, GH and testosterone have opposite effects.

Adolescent↗