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V Goffin

Publications and source records attributed to V Goffin.

At least 91 records · Page 5Linked to original sources
PubMed1995

A single phosphotyrosine residue of the prolactin receptor is responsible for activation of gene transcription.

Members of the cytokine/growth hormone/prolactin (PRL) receptor superfamily are associated with cytoplasmic tyrosine kinases of the Jak family. For the PRL receptor (PRLR), after PRL stimulation, both the kinase Jak2 and the receptor undergo tyrosine phosphorylation. To assess the role of tyrosine phosphorylation of the PRLR in signal transduction, several mutant forms of the PRLR in which various tyrosine residues were changed to phenylalanine were constructed and their functional properties were investigated. We identified a single tyrosine residue located at the C terminus of the PRLR to be necessary for in vivo activation of PRL-responsive gene transcription. This clearly indicates that a phosphotyrosine residue in the cytoplasmic domain of a member of the cytokine/growth hormone/PRL receptor superfamily is directly involved in signal transduction.

Caseins↗
PubMed1995

A double-blind controlled evaluation of the sebosuppressive activity of topical erythromycin-zinc complex.

In a double-blind randomised study, 14 volunteers applied 4% erythromycin plus 1.2% zinc (Zineryt lotion) and 4% erythromycin lotions, each on half of the forehead twice daily for 3 months. The sebum output was evaluated at 3-week intervals using the photometric and the lipid-sensitive film methods. Evaluations of casual level (CL) and sebum excretion rate (SER) were made with a Sebumeter, and total area of lipid spots (TAS) was measured on Sebutapes. Compared to baseline values, the formulation of the erythromycin-zinc complex induced significant reductions in SER after 6 and 9 weeks, and in CL and TAS at 3, 6, 9 and 12 weeks. The mean reduction in TAS was over 20% for four successive 1-h samplings on completion of the study. Significant reductions in CL, SER and TAS were observed for the erythromycin-zinc formulation compared to the control lotion at 6 and 9 weeks, and also at 3 weeks for SER and TAS, and at 12 weeks for CL and TAS. This study indicates that sebum output is significantly reduced by the erythromycin-zinc complex. This reduction is theoretically beneficial for the acneic patient.

Acetates↗
PubMed1995

Surfactant-induced dermatitis: comparison of corneosurfametry with predictive testing on human and reconstructed skin.

BACKGROUND: Surfactants elicit alterations in the stratum corneum. Predictive tests that avoid animal experimentation are needed. OBJECTIVE: This study compares three methods of rating and predicting shampoo-induced irritation. METHODS: Corneosurfametry entails collection of stratum corneum followed by brief contact with diluted surfactants and measurement of variations in staining of samples. RESULTS: Corneosurfametry appears to correlate well with in vivo testing in volunteers with sensitive skin. However, corneosurfametry presents less interindividual variability than in vivo testing and allows better discrimination among mild products. Morphologic information about surfactant-induced loosening of corneocytes may be increased by testing surfactants on human skin equivalent. Results are similar to those provided by specimens used for corneosurfametry. CONCLUSION: The corneosurfametric prediction of surfactant irritancy correlates with in vivo testing and with in vitro evaluation on human skin equivalent.

Adult↗
PubMed1995

Skin water-holding capacity and transdermal estrogen therapy for menopause: a pilot study.

The effects of menopause and hormone replacement therapy (HRT) on the epidermis are largely unknown. The aim of this study was to model and measure the influence of estrogen-transdermal HRT on subtle physiological changes taking place in the epidermis during the perimenopause. Skin capacitance and transepidermal water loss were measured both on normal-looking skin and at the site of a plastic occlusion stress test (POST). Two groups of 15 menopausal women were enrolled. One group was untreated and the other received transdermal estrogen. The water-holding capacity of the stratum corneum was significantly increased at the POST site in women receiving transdermal estrogen. The improvement in the skin water-holding capacity, which is known to be associated with a beneficial effect on the skin barrier function, may contribute to the prevention of several dermatoses.

Administration, Cutaneous↗
PubMed1995

Use of a model to understand prolactin and growth hormone specificities.

A human prolactin (hPRL) model based on a 2.1 A resolution X-ray refinement of porcine growth hormone is reported. Only regions clearly defined in the growth hormone template (the four-helix bundle) or previously assumed to be involved in hPRL-receptor binding (the bundle and the binding site loop) are included. A description of the model construction is provided and the resulting hPRL structure is used to interpret mutation/activity data for the cross-reactivity of human growth hormone (hGH) with the lactogenic receptor and the binding of human and bovine prolactin to the lactogenic receptor. The recognition of hPRL by its receptor unexpectedly appears to resemble more closely the interaction of hGH with the somatogenic receptor than with the lactogenic receptor. Each hGH binds to two receptor molecules, and an essential second messenger mediated by correct formation of the receptor-receptor interface has been proposed. The absence of receptor cross-reactivity for hPRL is linked to key sequence changes in hPRL which could disrupt hPRL-somatogenic receptor binding at the second site. A number of previous experiments have relied on the assumption that bioactivity is mediated by homologous residues at topologically equivalent positions. According to the model, this does not appear to be strictly true at either binding site. Good correlation at equivalent positions may be restricted to residues that are important for maintaining binding site shape as well as providing complementary stabilizing interactions between the hormone and receptor. Experiments are proposed to test our hypotheses.

Algorithms↗
PubMed1995

Comparison of in vitro predictive tests for irritation induced by anionic surfactants.

Skin compatibility of anionic surfactants may often but not always be predicted by in vitro tests. For instance, the correlation between in vivo and in vitro data is classically hampered in the presence of magnesium. This ion is known to interfere with in vitro skin irritation predictive tests based on protein denaturation. This study was conducted to compare a recently introduced assay, corneosurfametry, with other in vitro tests including the pH-rise of bovine serum albumin, collagen swelling, and zein solubilization tests. Corneosurfametry entails collection of cyanoacrylate skin surface strippings and short contact time with surfactants, followed by staining samples with toluidine blue and basic fuchsin dyes. Measurements are made by reflectance colorimetry. Data show that irritation potentials predicted by corneosurfametry agree with those obtained by established in vivo and in vitro irritation tests. Moreover, corneosurfametry data are not artificially lowered by addition of magnesium in surfactant solutions. In conclusion, corneosurfametry should be viewed as one of the realistic predictive tests for surfactant irritancy.

Collagen↗
PubMed1995

Digital image analysis of microcomedones.

OBJECTIVE: Developing a technique for quantifying the number and size of follicular casts and microcomedones. BACKGROUND: There is no human testing that is validated up to now to predict comedogenesis and comedolysis following topical applications of drugs or cosmetics. DESIGN: Evaluations are performed by digital image analysis of cyanoacrylate follicular biopsies. The effects of two topical products are compared. RESULTS: Microcomedogenesis was disclosed after a 2-month period of application of a cosmetic product aimed at treating acne. Microcomedolysis occurred following usage of a topical preparation containing benzoyl peroxide 5% and miconazole nitrate 2%. CONCLUSION: Digital image analysis of skin surface biopsies is a sensitive method documenting microcomedo formation and dissolution.

Acne Vulgaris↗
PubMed1995

Biological activity and immunological reactivity of human prolactin mutants.

We examined the biological activity and immunological reactivity of four mutants of human PRL. Two were mutants that changed the ability of human PRL to inhibit rat PRL storage when transfected into a rat pituitary cell line:mutations S34A and N31T. Two mutations were in regions of PRL that are highly conserved. One, des(3-11)-PRL, removed the N-terminal cystine loop that most PRLs, except those from certain fish, have, and no GHs have. The other, S90A, mutated a serine that is present in all PRLs but those from some fish and in all GHs. The immunological properties of des(3-11)-PRL were reduced 10-fold compared to those of wildtype human PRL in a RIA using NIH antihuman PRL-3, AFP C11580; the others were similar to those of wild-type PRL. The biological activity of des(3-11)-PRL was the most affected; activity was reduced about 8-fold compared to that of wild-type PRL in the Nb2 cell assay. The activities of the others were similar to that of the wild type. Serine 90 may be partially buried by loops connecting the alpha-helixes. The mutation of serine 90 did not affect the stability of the molecule in vitro, determined by comparing the red shift in tryptophan fluorescence that occurs with increasing concentrations of urea in S90A and wild-type PRL. The activity of S34A and N31T mutations indicates there is no correlation between biological activity and ability to affect storage. The N-terminal cystine loop may be conserved because it is needed for biological activity, but the conservation of serine 90 in GH and PRL must be determined by other properties, such as spacial requirements.

Amino Acid Sequence↗
PubMed1994

Evidence for a second receptor binding site on human prolactin.

The existence of a second receptor binding site on human prolactin (hPRL) was investigated by site-directed mutagenesis. First, 12 residues of helices 1 and 3 were mutated to alanine. Since none of the resulting mutants exhibit reduced bioactivity in the Nb2 cell proliferation bioassay, the mutated residues do not appear to be functionally necessary. Next, small residues surrounding the helix 1-helix 3 interface were replaced with Arg and/or Trp, the aim being to sterically hinder the second binding site. Several of these mutants exhibit only weak agonistic properties, supporting our hypothesis that the channel between helices 1 and 3 is involved in a second receptor binding site. We then analyzed the antagonistic and self-antagonistic properties of native hPRL and of several hPRLs analogs altered at binding site 1 or 2. Even at high concentrations (approximately 10 microM), no self-inhibition was observed with native hPRL; site 2 hPRL mutants self-antagonized while site 1 mutants did not. From these data, we propose a model of hPRL-PRL receptor interaction which slightly differs from that proposed earlier for the homologous human growth hormone (hGH) (Fuh, G., Cunningham, B. C., Fukunaga, R., Nagata, S., and Goeddel, D. V., and Well, J. A. (1992) Science 256, 1677-1680). Like hGH, hPRL would bind sequentially to two receptor molecules, first through site 1, then through site 2, but we would expect the two sites of hPRL to display, unlike the two binding sites of hGH, about the same binding affinity, thus preventing self-antagonism at high concentrations.

Animals↗
PubMed1994

Corneosurfametry: a predictive assessment of the interaction of personal-care cleansing products with human stratum corneum.

OBJECTIVE: Corneosurfametry is introduced as a noninvasive quantitative test rating the interaction between surfactants and human stratum corneum. It may be used as a predictive irritancy test. BACKGROUND: Surfactants present in personal-care products elicit multiple effects on the stratum corneum. With upcoming regulations avoiding animal experiments and ethical considerations for human testing, there is a need for new in vitro methods evaluating irritancy. DESIGN: Corneosurfametry entails collection of cyanoacrylate skin surface strippings and short contact time with surfactants followed by staining samples with toluidine blue and basic fuchsin dyes. Measurements are made by reading the color of samples using reflectance colorimetry. RESULTS: The intensity of color increases with irritancy potential of the surfactant. Results are reproducible, and great differences are noted among a series of diluted shampoos, shower gels and facial cleansing gels. CONCLUSION: Corneosurfametry is proposed as a rapid in vitro method allowing a predictive grading of surfactants related to irritancy.

Adult↗
PubMed1993

The addition of nine residues at the C-terminus of human prolactin drastically alters its biological properties.

We have added nine extra residues to the C-terminal of human prolactin and analysed the effect of this mutation on the ability of the hormone to bind to its lactogenic receptor and to induce Nb2 cell division. Both properties are markedly affected when compared to the natural 23-kDa human prolactin. Since no alteration of the global protein folding was detected either by circular dichroism or by infrared spectroscopy, the decrease in biological potency can be exclusively attributed to an effect of the nine additional residues on their near environment. From infrared analysis and secondary structure prediction, the elongated tail is assumed to be involved in a beta-sheet with a few residues initially belonging to the fourth helix. Moreover, from the X-ray structures of porcine and human growth hormones, two proteins homologous to prolactins, the nine extra residues are likely to fold within a concave pocket delimited by helices 1 and 4, and the second half of the loop connecting helices 1 and 2 (loop 1). Thereby, we suggest that the additional residues prevent some residues belonging to this pocket from interacting with the lactogenic receptor. This is in perfect agreement with our earlier proposal that the binding site of prolactin to the lactogenic receptor is homologous to that of growth hormone to the somatogenic receptor, i.e. essentially composed of residues belonging to this concave pocket.

Amino Acid Sequence↗
PubMed1992

Alanine-scanning mutagenesis of human prolactin: importance of the 58-74 region for bioactivity.

We have generated 10 alanine mutants of human PRL (hPRL), a member of the PRL/GH family, to investigate the involvement of the highly conserved 58-74 region in the biological behavior of the protein. When treated with polyclonal anti-hPRL antibodies, all mutants were immunologically indistinguishable from the unmodified hPRL, and circular dichroism analyses indicated that their alpha-helix content was similar to that of the unmodified hormone. Mutations C58A, K69A, and, to a lesser extent, P66A affected drastically the ability of hPRL first to bind to the lactogenic receptor and second to stimulate the proliferation of Nb2 lymphoma cells, proving the importance of the 58-74 peptide segment for hPRL bioactivity. Binding affinities of these mutants to the Nb2 lactogenic receptor have been compared to lactogenic binding data previously obtained for several mutants of hGH. The comparison reveals that the residues involved in the biological properties of the two proteins are not at topologically equivalent positions. Hence, we suggest that the binding of these hormones to the lactogenic receptors occurs through a different molecular mechanism having distinct requirements at the residue level.

Alanine↗
PubMed1991

Spectroscopic investigation of structure in octarellin (a de novo protein designed to adopt the alpha/beta-barrel packing).

We present here a spectroscopic structural characterization of octarellin, a recently reported de novo protein modelled on alpha/beta-barrel proteins [K. Goraj, A. Renard and J.A. Martial (1990) Protein Engng, 3, 259-266]. Infrared and Raman spectra analyses of octarellin's secondary structure reveal the expected percentage of alpha-helices (30%) and a higher beta-sheet content (40%) than predicted from the design. When the Raman spectra obtained with octarellin and native triosephosphate isomerase (a natural alpha/beta-barrel) are compared, similar percentages of secondary structures are found. Thermal denaturation of octarellin monitored by CD confirms that its secondary structures are quite stable, whereas its native-like tertiary fold is not. Tyrosine residues, predicted to be partially hidden from solvent, are actually exposed as revealed by Raman and UV absorption spectra. We conclude that the attempted alpha/beta-barrel conformation in octarellin may be loosely packed. The criteria used to design octarellin are discussed and improvements suggested.

Circular Dichroism↗
PubMed1990

Bacterial production and purification of recombinant human prolactin.

Escherichia coli cells transformed with a recombinant plasmid (pT7L) containing the coding sequence of human prolactin (hPrl) expressed a new protein. This protein, comigrating with human Prl on sodium dodecyl sulfate (SDS)-polyacrylamide gels, represented 50% of the total bacterial extract. Immunoprecipitation of [35S]methionine-labeled bacterial lysate with a rabbit antiserum to hPrl followed by SDS-polyacrylamide gel electrophoresis (PAGE) analysis showed that the major component had a Mr identical to that of standard hPrl. The majority of the recombinant hPrl (r-hPrl) accumulated in inclusion bodies. Analysis of these inclusion bodies by SDS-PAGE under nonreducing conditions showed that they are composed mostly of fully reduced monomers. Solubilization of the inclusion bodies and protein denaturation were performed in 8 M urea. Refolding during the renaturation procedure was confirmed by SDS-PAGE under nonreducing conditions. r-hPrl was further purified by gel permeation chromatography on a fast protein liquid chromatography column. More than 95% of the molecules were recovered as oxidized monomeric forms. The refolded molecule was tested for its bioactivity in the Nb2 lymphoma mitogenic assay. The dose-response curves obtained with either r-hPrl or pituitary-derived hPrl showed a complete parallelism. Furthermore, Nb2 cell proliferation was completely blocked by addition of hPrl antiserum to both preparations. Recombinant hPrl is identical to natural hPrl except for an additional methionine group at the amino terminal end.

Amino Acid Sequence↗