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Biomedical subjects

V Goffin

Publications and source records attributed to V Goffin.

At least 73 records · Page 4Linked to original sources
PubMed1997

Prolactin stimulates the JAK2 and focal adhesion kinase pathways in human breast carcinoma T47-D cells.

Treatment of T47-D human breast carcinoma cells with recombinant prolactin (rhPRL) induced a concentration- and time-dependent increase in the phosphotyrosine content of JAK2. rhPRL also stimulated JAK2 tyrosine phosphorylation more weakly in three other breast carcinoma lines, MCF-7, ZR-75-1 and MDA-MB-231. Furthermore it stimulated tyrosine phosphorylation of two isoforms of the transcriptional activator STAT5, STAT5a and STAT5b. Surprisingly, rhPRL treatment of T47-D cells also stimulated tyrosine phosphorylation of focal adhesion kinase (FAK), as determined by immunoprecipitation with anti-phosphotyrosine antibody followed by immunoblotting with a specific FAK antibody. The effect of rhPRL was rapid and concentration-dependent, being maximal at 5 ng/ml. At rhPRL concentrations above 25 ng/ml, FAK tyrosine phosphorylation declined but remained above control levels at 100 ng/ml. rhPRL also stimulated paxillin tyrosine phosphorylation in T47-D cells with similar concentration- and time-dependence. In a second human breast carcinoma cell line, MCF-7, rhPRL produced very similar effects on FAK and paxillin tyrosine phosphorylation. These findings identify a new protein tyrosine kinase pathway in the action of the lactogenic hormone rhPRL and represent the first report that a hormone acting through a member of the haemopoietin receptor superfamily can regulate the FAK/paxillin pathway.

Breast Neoplasms↗
PubMed1997

Identification of cytoplasmic motifs required for short prolactin receptor internalization.

Cloning of rat prolactin receptor (PRLR) cDNAs revealed the existence of two isoforms, termed short and long according to the length of their cytoplasmic domain. Internalization studies show, first, that PRLR internalization is hormone-dependent and, second, that ligand-receptor complexes of the short PRLR are internalized to a larger extent compared to the long form. In order to identify regions within the cytoplasmic domain of the short PRLR required for efficient internalization, serial truncations of the cytoplasmic tail were performed by inserting a stop codon in place of those encoding residues 282, 273, 262, 253, 244, or 237 (wild type short PRLR contains 291 amino acids). Our data show that two motifs, lying within residues 253-261 and 273-281, are involved in internalization. Both regions contain a consensus feature identified within other receptors as internalization signals, namely a di-leucine peptide (amino acids 259-260) and a tetrapeptide predicted to adopt a beta-turn structure (amino acids 276-279). We propose these two motifs are involved in PRLR endocytosis. Finally, we show that alpha-adaptin, a component of adaptor protein AP-2, coprecipitates with short PRLR complexes upon PRL stimulation, which strongly suggests that PRLR internalization is mediated by the clathrin-coated pits endocytotic pathway.

Animals↗
PubMed1997

Sodium hypochlorite, bleaching agents, and the stratum corneum.

Interactions between bleaching agents containing sodium hypochlorite (NaOCl) and human stratum corneum are complex and not fully understood. The same applies when NaOCl is used as a war gas decontaminant. In this study data yielded by in vivo testing and an ex vivo bioassay are compared. Fifteen volunteers received patch tests of a neat proprietary NaOCl bleaching agent for 15, 30, 45, 60, and 90 min. No clinical reaction was seen. Reflectance colorimetry, transepidermal water loss (TEWL), and capacitance were measured for 72 hr after patch removal. Squamometry was also performed using D-Squames and colorimetry of the samples. In addition, the ex vivo corneoxenometry bioassay was conducted on various dilutions of the bleach. Data reveal that conductance and squamometry were more sensitive than TEWL to disclose the action of bleach upon the stratum corneum. Corneoxenometry proved to be a good predictive ex vivo bioassay, indicating the same information as the in vivo tests. Both squamometry and corneoxenometry appear valuable and complementary in assessing infraclinical damages of human skin by a NaOCl bleaching agent.

Adult↗
PubMed1997

The prolactin/growth hormone receptor family: structure/function relationships.

Prolactin (PRL) and growth hormone (GH) receptors are members of the cytokine receptor superfamily that are activated by ligand-induced homodimerization. On the basis of this mechanism of activation, hormone antagonists have been developed that block the receptors in an inactive conformation. PRL and GH receptors are non-kinase receptors whose activation of signaling pathways requires participation of receptor-associated kinases, such as Janus kinases or Src kinases. Signal transduction by these receptors mainly involves the JAK/Stat pathway. In this review, we discuss the mechanism of ligand binding and receptor homodimerization as well as the involvement of molecules transducing the hormonal signal. Whenever possible, we attempt to correlate cytoplasmic features of the receptors with association and/or activation of transducer molecules or with a given biological property.

Animals↗
PubMed1997

Regional differences in stratum corneum reactivity to surfactants. Quantitative assessment using the corneosurfametry bioassay.

The skin does not react similarly to the presence of xenobiotics over all anatomic sites. Distinct regional differences have been described for irritancy and percutaneous absorption. The present study assesses the regional variation of stratum corneum reactivity to surfactants using the corneosurfametry bioassay. Stratum corneum was harvested from 6 body sites in 20 young adults. Corneosurfametry was performed using water, 1% SLS and a 5% soap solution. Data show that the best variable to assess regional variability in irritancy is the overall difference in corneosurfametry (ODC), comparing the effect of a given surfactant with water. The dorsal hand and volar forearm were the least reactive, the neck, forehead, back and dorsal foot the most reactive, sites. It is concluded that the corneosurfametry bioassay, through the ODC variable, is a practically noninvasive tool for the evaluation of regional variation in irritancy at the level of the stratum corneum.

Adult↗
PubMed1997

Topical retinol and the stratum corneum response to an environmental threat.

The functional consequences of using topical retinol on skin have not been thoroughly studied so far. The aim of this open study was to compare two preparations containing either retinol or vitamin E, using biometric evaluations. Three methods, namely the sodium lauryl sulfate (SLS) corneosurfametry bioassay, the ultraviolet (UV) squamometry test and optical profilometry of the UV-induced wrinkling process, were used to assess some properties of the stratum corneum. The retinol preparation achieved better scores than the vitamin-E cream in all three tests and appears to improve the resistance of the stratum corneum against some chemical (SLS) and physical (UV) threats. It also limits UV-induced shallow wrinkling.

Administration, Topical↗
PubMed1997

Effect of organic solvents on normal human stratum corneum: evaluation by the corneoxenometry bioassay.

BACKGROUND: Organic solvents alter the stratum corneum structure and barrier function. OBJECTIVE: To measure the effect of various solvents upon human stratum corneum using the ex vivo corneoxenometry bioassay which is a variant of corneosurfametry. METHODS: Corneoxenometry entails collection of human stratum corneum by cyanoacrylate. The material is immersed in organic solvents for periods ranging from 1 to 120 min. After staining the samples with a toluidine blue-basic fuchsin solution, the color is measured using reflectance colorimetry. Solvent aggressivity to the stratum corneum correlates with the color darkening of the samples. RESULTS: The least aggressive solvent was hexane, followed by ethanol, methanol, hexane-ethanol, chloroform, chloroform-methanol and hexane-methanol. The influence of contact time between solvents and the stratum corneum showed a logarithmic pattern which varied according to the solvent. CONCLUSION: Data are in line with previous experiments conducted in vivo and in vitro, thus indicating the predictive value of corneoxenometry. Such a bioassay may avoid hazards of some in vivo human testings.

Alcohols↗
PubMed1997

Immune function of prolactin (PRL) and signal transduction by PRL/GH/cytokine receptors: specificity, redundancy and lessons from chimaeras.

Although prolactin (PRL) was originally regarded exclusively as a lactogenic hormone, there are a number of observations that suggest a role for this protein in the regulation of immune responses. The first step in understanding this unexpected function came from the cloning of the prolactin receptor, which was later shown to be a member of the cytokine receptor superfamily. The PRL receptor shares structural analogies with receptors for proteins acting on immune cells, the prototype of which is IL-2. Studies of cytokine receptor signalling revealed that all messages are transmitted in the cell through a limited set of transducers, among which the JAK kinases and the Stat transcription factors represent a major cascade. Deciphering the rules allowing a given cytokine receptor, and not another, to activate a particular set of JAK and Stat proteins is a key step in understanding functional specificities within this receptor superfamily. Mutational analyses have provided interesting information about which features are required for which property. Much less data are available from studies using chimaeric receptors, although this strategy is probably more powerful for comparing different receptors and addressing the question of their specificity (or redundancy). As frequently as possible, we shall illustrate our discussions through experimental investigations using the chimaeric approach.

Animals↗
PubMed1996

Antagonistic properties of human prolactin analogs that show paradoxical agonistic activity in the Nb2 bioassay.

Based on the assumption that the prolactin receptor (PRLR) is activated by PRL-induced sequential dimerization, potential human PRL (hPRL) antagonists were designed that sterically interfere with binding site 2. We previously reported the unexpected agonistic properties of these hPRL analogs in the rat Nb2 bioassay (Goffin, V., Struman, I., Mainfroid, V., Kinet, S., and Martial, J. A. (1994) J. Biol. Chem. 269, 32598-32606). In order to investigate whether such paradoxical agonistic behavior might result from characteristic features of the Nb2 assay (e.g. species specificity), we transfected in the same cell system the cDNA encoding the PRLR from rat or human species along with reporter genes containing PRL-responsive DNA sequences. We characterized the agonistic, self-antagonistic and/or antagonistic effects of wild type rat PRL, wild type hPRL, and three hPRL analogs, mutated either at binding site 1 or at binding site 2. Our results clearly show that the agonistic/antagonistic properties of PRLs are species-specific. We thus propose different models of receptor activation, depending on the relative affinities of each hormonal binding site, which is directed by species specificity. Finally, this is the first report of hPRL binding site 2 analogs showing antagonistic properties on human and, to a lesser extent, rat receptors.

Animals↗
PubMed1996

Characterization of lactogen receptor-binding site 1 of human prolactin.

Prolactin (PRL) binds to two molecules of PRL receptor (PRLR) through two regions referred to as binding sites 1 and 2. Although binding site 1 has been generally assigned to the pocket delimited by helix 1, helix 4, and the second half of loop 1, the residues involved in receptor binding have not yet all been precisely identified. In an earlier alanine-scanning mutational study, we identified three major binding determinants in loop 1 of human PRL (hPRL) (Goffin, V., Norman, M. & Martial, J. A.(1992) Mol. Endocrinol. 6, 1381-1392). Here we focus on the two other regions that form binding site 1, namely helices 1 and 4. Putative binding residues, selected on the basis of a three-dimensional model of hPRL constructed in this laboratory, were mutated to alanine, and recombinant hPRL mutants produced in Escherichia coli were tested for their ability to bind to the PRLR and to stimulate Nb2 cell proliferation. We thus identified nine single mutations (three in helix 1 and six in helix 4) whose effect was to reduce both binding and mitogenic activity by more than half as compared with wild-type hPRL, indicating the functional involvement of the corresponding residues. Adding these to the three binding determinants identified in loop 1, we now propose a complete picture of PRLR-binding site 1 of hPRL. As we earlier hypothesized, the binding site 1 determinants of hPRL differ from those of human growth hormone, a hPRL homolog.

Animals↗
PubMed1996

Mechanical properties of skin and liposuction.

BACKGROUND: Liposuction removes fat, setting the skin under tension, and could therefore alter the overall viscoelastic properties of the teguments. OBJECTIVE: To measure in vivo the mechanical properties of skin at the site of liposuction and to compare the viscoelastic values with those of the inner aspect of the forearms. METHODS: The Cutometer SEM 474 equipped with a 8-mm probe was used. RESULTS: Data show that cutaneous laxity, which is characteristic for an aging aspect, is not higher at the liposuction sites than on the reference area. CONCLUSION: Liposuction does not increase the clinical aspects of skin aging.

Adult↗
PubMed1996

Sensitive skin and stratum corneum reactivity to household cleaning products.

Products intended for individuals with sensitive skin are being increasingly developed by formulators of household cleaning products. However, there is currently no consensus about the definition and recognition of the biological basis of sensitive skin. We sought to determine the relation between the nature of environmental threat perceived as aggressive by panelists, and the stratum corneum reactivity to household cleaning products as measured by the corneosurfametry test. Results indicate substantial differences in irritancy potential between proprietary products. Corneosurfametry data show significant differences in stratum corneum reactivity between, on the one hand, individuals with either non-sensitive skin or skin sensitive to climate/fabrics, and, on the other hand, individuals with detergent-sensitive skin. It is concluded that sensitive skin is not one single condition. Sound information in rating detergent-sensitive skin may be gained by corneosurfametry.

Adult↗
PubMed1996

Distribution of prolactin receptors in the rat forebrain. Immunohistochemical study.

The distribution of prolactin receptors (PRL-R) in the rat brain was investigated for the first time with the immunohistochemical technique using monoclonal antibodies raised against PRL-R purified from rat liver. Granular immunostaining was observed in neurons and along their dendritic processes and fibers. PRL-R like immunoreactive neurons were found in a number of brain areas. There was a very dense labelling in the cerebral cortex (pyramidal cell layer), septal nuclei, amygdaloid complex as well as in the hypothalamus (suprachiasmatic, supraoptic, paraventricular and dorsomedial nuclei). A dense staining was seen in the substantia nigra, habenula and in the paraventricular thalamic nucleus. Immunostaining was also found in the choroid plexus and in the subcommissural organ. Comparison between the present distribution and that of PRL-like immunoreactivity indicates that the density of PRL-R generally corresponds to that of the fibers. However, in some regions densely stained by PRL-R antibody, there are very few PRL-immunoreactive fibers. These results are suggestive of different modes of action of PRL in the brain.

Amygdala↗
PubMed1996

Convergence of signaling transduced by prolactin (PRL)/cytokine chimeric receptors on PRL-responsive gene transcription.

Ligand binding to cytokine receptors rapidly triggers tyrosine phosphorylation of Janus family tyrosine kinases (Jaks) and signal transducers and activators of transcription (Stats). Jak2 activation is mediated by PRL receptor homodimers as well as by receptors for the interleukin (IL)-3, IL-5, and granulocyte macrophage-colony stimulating factor, which share the common beta c-subunit. Otherwise, Jak1 and Jak3 are involved in IL-2 signaling through heterodimerization of the IL-2 receptor-beta (IL-2R beta) and gamma c-chains. Stat5, a member of the Stat family, confers the PRL response on milk protein genes. Here we show that chimeric PRL receptors that contain the transmembrane and cytoplasmic domains of the IL-2R beta or beta c-chains transduce in response to PRL tyrosine phosphorylation and activation of Jak1 and Jak2, respectively. Tyrosine phosphorylation of Stat5, activation of its DNA-binding activity assessed in bandshift experiments using a lactogenic hormone responsive region (LHRR) probe, and transcriptional induction of a beta-casein promoter luciferase construct in stably transfected CHO cells are observed with both chimeras upon PRL stimulation. Our results demonstrate that distinct cytoplasmic domains of these cytokine receptors elicit convergent signaling pathways and provide evidence that beta c and IL-2R beta function as a complete signal transducer. Our data strengthen previous observations that Stat5 activation is not dependent on the activation of a specific Jak kinase and also suggest that neither Jak3 nor gamma c have a specific role in this process.

Amino Acid Sequence↗