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At least 19 recordsLinked to original sources
PubMed1989

Purification and protein sequence analysis of rat liver prolactin receptor.

Prolactin receptors were purified from rat liver membranes by single-step immunoaffinity chromatography using a specific monoclonal antibody to the rat liver prolactin receptor. Scatchard analysis of 125I-human growth hormone binding to the purified receptor revealed two classes of specific binding sites with Ka = 18.5 x 10(9) and 1.2 x 10(9) M-1. Considering that both classes of binding sites are responsible for high affinity prolactin binding, the partially purified receptor preparation had a binding activity of 1.69 nmol/mg protein, representing 1000-fold purification over microsomal receptors with a recovery of 52%. From three separate purifications, 6 mg of partially purified prolactin receptor were obtained with a purity of approximately 4 to 6.5%. Thus, the use of monoclonal antibody for affinity chromatography resulted in a large improvement of prolactin receptor purification compared to previous hormone affinity chromatography (300-fold purification, 15% recovery). The purified receptor was run on preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis, and a homogeneous preparation of prolactin receptor was obtained by electroelution from gel slices corresponding to Mr 38,000-43,000. Immunoblot analysis using a radiolabeled monoclonal antibody revealed two separate but closely located bands of Mr 42,000 and 40,000 in microsomal, partially purified, and electroeluted preparations. The homogeneous receptor protein was extensively digested with L-1-tosylamido-2-phenylethyl chloromethyl ketone trypsin, and 10 internal amino acid sequences of the rat liver prolactin receptor were determined by gas-phase sequence analysis. Oligonucleotide probes were prepared against two of these internal sequences, and a prolactin receptor cDNA was isolated from a rat liver library using one of these probes (Boutin, J. M., Jolicoeur, C., Okamura, H., Gagnon, J., Edery, M., Shirota, M., Banville, D., Dusanter-Fourt, I., Djiane, J., and Kelly, P. A. (1988) Cell 53, 69-77). The amino acid sequence deduced from the cDNA reveals three potential sites of N-linked glycosylation, two of which were confirmed during protein sequencing. The prolactin receptor was characterized by affinity labeling with 125I-human growth hormone. Cross-linking of microsomes revealed a single band for the hormone-receptor complex with Mr 62,000. On the other hand, cross-linking of Triton X-100-solubilized or partially purified receptor with labeled hormone resulted in the appearance of two bands with Mr 62,000 and 102,000, suggesting the existence of a subunit structure of the prolactin receptor, or alternatively, the existence of two types of prolactin receptor.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1998

Selective coupling of STAT factors to the mouse prolactin receptor.

Prolactin has been reported to induce distinct sets of signal transducers and activators of transcription (STAT) in a cell-type-specific fashion. In the mammary epithelium, although STAT1, STAT3, STAT5A, STAT5B and STAT6 are present in a latent form, only STAT5A and STAT5B are activated. This selective activation of STAT5 by prolactin was also observed in COS-7 cells cotransfected with the long form of the mouse prolactin receptor (PRL-R) and expression vectors for STAT1, STAT3, STAT5 and STAT6. Mutated PRL-Rs and chimeric erythropoietin/gp130 (EPO/gp130) receptors with a tyrosine-containing motif attached at the carboxy terminus were employed to determine the sites in the PRL-R required for the specific activation of STAT5. The experiments revealed the importance of two motifs containing Y477 and Y578 in the PRL-R. When linked to the EPO/gp130 receptor, these sequences were sufficient to specifically induce DNA binding of STAT5 and to activate transcription from the beta-casein gene promoter. By contrast, only weakly they induced DNA binding of STAT6 and STAT3 and did not induce STAT1. A synthetic nonapeptide with phosphorylated Y477 was able to disrupt STAT5 DNA binding in vitro. Our results define structural domains within the carboxy terminus of the PRL-R which recruit STAT5 for signalling and which are capable of distinguishing STAT5 from other STAT proteins. The activity of STAT5 forms with deletions of the carboxy terminus was induced more strongly than that of their full-length counterparts 2 min after activation of the PRL-R. This effect was not dependent on the presence of Y477 and Y578 in the PRL-R, indicating that facilitated activation of short STAT5 isoforms relies on mechanisms other than increased coupling to specific regions of the PRL-R.

Animals↗
PubMed2006

The role of the bovine growth hormone receptor and prolactin receptor genes in milk, fat and protein production in Finnish Ayrshire dairy cattle.

We herein report new evidence that the QTL effect on chromosome 20 in Finnish Ayrshire can be explained by variation in two distinct genes, growth hormone receptor (GHR) and prolactin receptor (PRLR). In a previous study in Holstein-Friesian dairy cattle an F279Y polymorphism in the transmembrane domain of GHR was found to be associated with an effect on milk yield and composition. The result of our multimarker regression analysis suggests that in Finnish Ayrshire two QTL segregate on the chromosomal region including GHR and PRLR. By sequencing the coding sequences of GHR and PRLR and the sequence of three GHR promoters from the pooled samples of individuals of known QTL genotype, we identified two substitutions that were associated with milk production traits: the previously reported F-to-Y substitution in the transmembrane domain of GHR and an S-to-N substitution in the signal peptide of PRLR. The results provide strong evidence that the effect of PRLR S18N polymorphism is distinct from the GHR F279Y effect. In particular, the GHR F279Y has the highest influence on protein percentage and fat percentage while PRLR S18N markedly influences protein and fat yield. Furthermore, an interaction between the two loci is suggested.

Amino Acid Substitution↗
PubMed2004

Novel association of Vav2 and Nek3 modulates signaling through the human prolactin receptor.

Prolactin (PRL) receptor activation contributes to the progression and motility of human breast cancer. This event activates multimeric signaling pathways, including the activation of the Vav family of guanine nucleotide exchange factors. To detect novel proteins interacting with Vav, yeast two-hybrid analysis was performed and demonstrated an interaction between the serine/threonine NIMA (never in mitosis A)-related family kinase p56Nek3 and Vav1. The PRL-dependent interaction of Nek3 with Vav1 and Vav2 was confirmed by coimmunoprecipitation analysis. PRL stimulation of T47D cells induced Nek3 kinase activity and the interaction of Vav2/Nek3 with the PRL receptor. Increased Nek3 levels up-regulated Vav2 serine and tyrosine phosphorylation, whereas knockdown of Nek3 resulted in a reduction of Vav2 phosphorylation. Activation of guanosine triphosphatase Rac-1 in Chinese hamster ovary transfectants required both Nek3 and Vav2 and was inhibited by the overexpression of a kinase inactivating Nek3 mutant. However, overexpression of either Nek3 or kinase-inactive Nek3 had no effect on Vav2-potentiated signal transducer and activator of transcription 5-mediated gene expression. Overexpression of kinase inactive Nek3 in T47D cells led to a 50% increase in apoptosis vs. controls. These data suggest that the PRL-mediated activation of Nek3 contributes differentially to Vav2 signaling pathways involving Rac1 and signal transducer and activator of transcription 5 and implicates Nek3 during PRL-mediated actions in breast cancer.

Animals↗
PubMed1987

Partial purification and characterization of bovine mammary gland prolactin receptor.

Prolactin (PRL) receptors from the mammary gland of the lactating cow were solubilized with 3-[(3-cholamidopropyl)dimethylamonio]-1-propane sulfonate (CHAPS). Affinite chromatography on human growth hormone (hGH) coupled to Affi-Gel 10 resulted in over 500-fold purification, as compared to microsomal fractions. Scatchard analysis of the binding of hGH indicated an increase in the affinity constant of 2.5-fold after solubilization and of further 2-fold after the affinity purification. The specific binding activity of the affinity-purified fraction was 9000 fmol hGH/mg protein. Complexes of Triton X-100-solubilized receptors with [125I]hGH were analyzed by gel filtration on Sephadex G-150, in the presence of Triton X-100. A minor fraction of the complexes eluted as high molecular weight (Mr) aggregates, whereas a major fraction eluted as a 150 kDa peak. Assuming a contribution of approximately 30% to the Mr by the bound detergent and a hormone: receptor ratio of 1:1 in the complex, a Mr of 80-85 kDa can be calculated for the receptor molecule. Affinity labelling of the receptor with [125I]hGH revealed a Mr of 37 +/- 0.5 kDa (n = 7) for the binding subunit. Specific high Mr aggregates were also observed after crosslinking; however, the size of the labelled species was not affected by reducing agents. Homologous and heterologous competitive binding studies with ovine PRL (oPRL) or hGH revealed a considerably higher affinity for hGH as compared to oPRL. The competitive displacement patterns obtained with oPRL or hGH as tracers were similar, indicating that both hormones bound to the same receptor sites with different affinities. A similar difference in affinity was retained by the affinity-purified receptors.

Affinity Labels↗
PubMed1996

Cloning and characterization of an ovarian-specific protein that associates with the short form of the prolactin receptor.

Prolactin (PRL) is essential for progesterone biosynthesis and luteal cell hypertrophy of the rat corpus luteum during pregnancy. Both the long and short form of the PRL receptor have been identified in the corpus luteum of pregnant rat. The long form has been shown to transduce PRL signal in other cells, whereas no information is available on the role of the short form, especially in the corpus luteum. In the present study, we have cloned a rat ovarian-specific phosphoprotein, PRAP (PRL Receptor Associated Protein), which has no significant homology to other known proteins. We have demonstrated that this protein is immunoprecipitated by anti-PRL receptor and anti-phosphotyrosine antibodies. To determine whether PRAP associates with either the long or the short form of the PRL receptor, fusion proteins with glutathione S-transferase containing the cytoplasmic domain of the long or short form of the PRL receptor were produced, purified, and incubated with luteal proteins. Our results indicate that PRAP preferentially binds to the short form of the PRL receptor. Thus, the long form and short forms of the PRL receptor may signal through distinct pathways. These data provide evidence for the involvement of a novel protein in PRL signal transduction and suggest that PRAP may contribute to the luteotropic effects of PRL on the corpus luteum during pregnancy.

Amino Acid Sequence↗
PubMed2000

Mammary gland development and the prolactin receptor.

Prolactin (PRL), synthesized by the anterior pituitary and to a lesser extent by numerous extrapituitary tissues, affects more physiological processes than all other pituitary hormones combined. This hormone is involved in > 300 separate effects in various vertebrate species where its role has been well documented. The initial step in its action is the binding to a specific membrane receptor which belongs to the superfamily of class 1 cytokine receptors. The function of this receptor is mediated, at least in part, by two families of signaling molecules: Janus kinases and signal transducers and activators of transcription. PRL-binding sites have been identified in a number of cells and tissues of adult animals. Disruption of the gene for the PRL receptor has provided a new animal model with which to better understand the actions of PRL on mammary morphogenesis and mammary gland gene expression. The recent availability of genetic mouse models provides new insights into mammary developmental biology and how the action of a hormone at specific stages of development can have effects later in life on processes such as mammary development and breast cancer initiation and progression.

Animals↗
PubMed2006

Cloning and functional characterization of allelic variation in the porcine prolactin receptor.

Prolactin (PRL) regulates various functions in pigs including reproduction, mammary development and lactation. We used 5'-rapid amplification of cDNA ends (5'-RACE) to clone three full-length alleles of the porcine PRL receptor (pPRLR) from Landrace (alleles LR2 and LR4) and Yucatan miniature (MP) pigs, corresponding to the A and B alleles previously reported to be associated with reproductive traits. When expressed in Chinese hamster ovary (CHO-K1) cells, all three pPRLRs transduced differentiation signals to a beta-casein promoter with the same effectiveness, where human growth hormone (hGH) and porcine PRL (pPRL) were more effective ligands than ovine PRL (oPRL). The pPRLR had a lower binding affinity for oPRL than pPRL while binding affinity for hGH was not different between the three pPRLR variants. The pPRLRs primarily localized to the cytoplasm with perinuclear concentration. In conclusion, we have cloned three allelic variants of the pPRLR and have functionally characterized these as different from the hPRLR. However, our data do not support the proposal that allelic variation of the pPRLR confers functional differences in vivo.

Alleles↗
PubMed1994

Growth signaling and JAK2 association mediated by membrane-proximal cytoplasmic regions of prolactin receptors.

Prolactin (PRL) has recently been demonstrated to induce tyrosine phosphorylation and activation of the cytoplasmic tyrosine kinase JAK2 in PRL-dependent Nb2 lymphoma cells. The present study represents an initial effort to identify cytoplasmic regions of the PRL receptor (PRLR) that are critical to growth signal generation and JAK2 activation. Variably truncated rat PRLRs were stably expressed in the murine 32D cell line. PRL-induced proliferation was mediated by the full-length receptor and the mutant G328, which contains the membrane-proximal Homology Boxes 1 and 2 characteristic of hematopoietin receptors. In contrast, mutant receptors lacking either Box 2 or both Boxes 1 and 2 were not capable of transmitting a growth signal. The mitogenic capacity of the PRLR variants correlated with JAK2 association and activation, as well as with induction of mRNA levels for the growth-related gene ornithine decarboxylase. We conclude that mitogenic competence of rat PRLRs resides within the first 94 amino acids of the cytoplasmic domain. The data suggest that Homology Box 1/Box 2 region is critical to JAK2 phosphorylation and association with the PRLR. These findings will serve as a basis for more detailed molecular characterization of PRLR domains essential for JAK2 interaction and growth signal generation.

Amino Acid Sequence↗
PubMed1990

Influence of neonatal diethylstilbestrol treatment on prolactin receptor levels in the mouse male reproductive system.

Neonatal exposure to the synthetic estrogen, diethylstilbestrol, is known to affect the structure of the male reproductive system; thus, changes may also occur in the levels of hormone receptors. Prolactin receptor levels from the reproductive systems of male BALB/c mice exposed neonatally to diethylstilbestrol were analyzed. Neonatal exposure to diethylstilbestrol caused significant decreases (i) in prolactin receptor levels in the seminal vesicle, ductus deferens, and anterior and ventral prostates and (ii) in tissue weight and protein content in reproductive organs other than the ventral prostate.

Animals↗
PubMed1984

Structures of the somatotropin receptor and prolactin receptor on rat hepatocytes characterized by affinity labelling.

Human somatotropin competed for 125I-human somatotropin binding to hepatocytes from female or male rats. Bovine somatotropin and prolactin each inhibited part, but not all, of the uptake of 125I-human somatotropin. The binding of 125I-prolactin was inhibited by human somatotropin and prolactin, but not by bovine somatotropin. Bovine somatotropin and human somatotropin, but not prolactin, competed for 125I-bovine somatotropin binding sites. 125I-labelled hormones were covalently coupled to membrane receptors with higher efficiency on hepatocytes from female than from male rats, allowing structural descriptions of lactogenic and somatogenic binding sites that had not been possible previously. Disuccinimidyl suberate covalently coupled 125I-human somatotropin into saturable complexes of Mr 300 000, 220 000, 130 000, 65 000 and 50 000. Bovine somatotropin inhibited the incorporation of 125I-human somatotropin into complexes of Mr 300 000, 220 000 and 130 000, whereas low concentrations of prolactin competed for incorporation into the 65 000- and 50 000-Mr species. 125I-bovine somatotropin was incorporated into complexes of Mr 300 000, 220 000 and 130 000. Human somatotropin and bovine somatotropin, but not prolactin, inhibited the production of these complexes. 125I-prolactin binding produced complexes of Mr 65 000 and 50 000. Native prolactin and human somatotropin, but not bovine somatotropin, inhibited uptake of 125I-prolactin into these species. Thus direct affinity labelling, as well as competition for covalent coupling, suggests that the 300 000-, 220 000- and 130 000-Mr species are components of the somatotropin receptor and that the 65 000- and 50 000-Mr complexes result from hormone binding to the prolactin receptor. By subtracting the Mr of prolactin, it was calculated that the hormone was bound to species of Mr 43 000 and 28 000. These Mr values were not affected by reduction of solubilized membranes, suggesting that the structure of the prolactin receptor is not stabilized by interchain disulphide bonds between subunits. Subtracting the Mr of somatotropin from somatogenic complexes indicated that the hormone had bound to species of Mr 280 000, 200 000 and 100 000. The 300 000- and 220 000-Mr complexes were not isolated from reduced membranes, whereas the amount of the 130 000-Mr species was augmented. These observations could suggest that a major component of the somatotropin receptor is a trimeric aggregate in which some subunits are retained in a larger complex by interchain disulphide bonds.

Affinity Labels↗
PubMed1985

Induction of prolactin receptors by prolactin in the rat lung and liver: demonstration of separate receptor and antibody entities.

This study examined the role of prolactin (PRL) in inducing its own receptors in rat lung and liver beyond the parallel immunological response evoked. Ovine PRL (oPRL), mixed with polyvinylpyrrolidone (PVP) and injected s.c. daily to male rats for 7, 10 and 14 days, was shown to induce specific binding of [125I]iodo-oPRL in the lung and liver crude membrane fractions. Doses as low as 12.5 ng/kg were effective in inducing PRL-binding sites, which, however, differed qualitatively from those found in livers of 17 beta-estrogen-treated male rats. The oPRL-induced sites were highly specific for oPRL and were relatively stable to heat, suggesting the possible participation of antihormone antibodies in the binding observed. Indeed, anti-oPRL antibodies found in sera of oPRL-treated rats increasingly bound oPRL as a function of the duration of treatment. Water-washing of the membrane fraction succeeded in gradually eliminating the loosely bound antibody and in partially restoring the displacing ability of excess (1 micrograms) rat PRL on oPRL-binding sites in the lung (32.3%) and liver membranes (29.3%). Also restored were the heat lability typical of the receptor site, as well as the inhibitory effect of anti-PRL-receptor antiserum (1:100) on PRL binding (50-65% inhibition of total binding). In keeping with these results, in vitro incubation of liver membranes with rat anti-oPRL antiserum greatly reduced the ability of rat PRL to compete for oPRL binding, supporting the findings after in vivo treatment with oPRL.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Developmental aspects of adipose tissue in GH receptor and prolactin receptor gene disrupted mice: site-specific effects upon proliferation, differentiation and hormone sensitivity.

Direct metabolic effects of GH on adipose tissue are well established, but effects of prolactin (PRL) have been more controversial. Recent studies have demonstrated PRL receptors on adipocytes and effects of PRL on adipose tissue in vitro. The role of GH in adipocyte proliferation and differentiation is also controversial, since GH stimulates adipocyte differentiation in cell lines, whereas it stimulates proliferation but inhibits differentiation of adipocytes in primary cell culture. Using female gene disrupted (ko) mice, we showed that absence of PRL receptors (PRLRko) impaired development of both internal and s.c. adipose tissue, due to reduced numbers of adipocytes, an effect differing from that of reduced food intake, where cell volume is decreased. In contrast, GHRko mice exhibited major decreases in the number of internal adipocytes, whereas s.c. adipocyte numbers were increased, even though body weight was decreased by 40-50%. The changes in adipose tissue in PRLRko mice appeared to be entirely due to extrinsic factors since preadipocytes proliferated and differentiated in similar fashion to wild-type animals in vitro and their response to insulin and isoproterenol was similar to wild-type animals. This contrasted with GHRko mice, where s.c. adipocytes proliferated, differentiated, and responded to hormones in identical fashion to controls, whereas parametrial adipocytes exhibited markedly depressed proliferation and differentiation potential and failed to respond to insulin or noradrenaline. Our results provide in vivo evidence that both GH and PRL stimulate differentiation of adipocytes but that the effects of GH are site specific and induce intrinsic changes in the precursor population, which are retained in vitro.

1-Methyl-3-isobutylxanthine↗
PubMed2003

Cytokine induction of prolactin receptors mediates prolactin inhibition of nitric oxide synthesis in pulmonary fibroblasts.

Prolactin (PRL) has been implicated as a modulator of immune function, and some of its actions may be linked to NO synthesis. Because NO acts as a mediator of inflammation, we speculated that an inflammatory milieu could unmask pathways by which PRL could affect NO synthesis. Here, we show that pro-inflammatory cytokines induce the expression of PRL receptors in pulmonary fibroblasts, allowing PRL to inhibit cytokine-induced NO production and the expression of the inducible nitric oxide synthase (iNOS). Inhibition of iNOS expression by PRL correlates with the phosphorylation of STAT-5b (signal transducer and activator of transcription 5b) and the suppression of expression of IRF-1 (interferon regulatory factor 1), a transcription factor for iNOS. These results reveal previously unrecognized mechanisms by which PRL and PRL receptors may play significant modulatory roles during immune-inflammatory processes.

Animals↗
PubMed2000

Suppression of nerve growth factor Trk receptors and prolactin receptors by endocannabinoids leads to inhibition of human breast and prostate cancer cell proliferation.

Anandamide and 2-arachidonoylglycerol (2-AG), two endogenous ligands of the CB1 and CB2 cannabinoid receptor subtypes, inhibit the proliferation of PRL-responsive human breast cancer cells (HBCCs) through down-regulation of the long form of the PRL receptor (PRLr). Here we report that 1) anandamide and 2-AG inhibit the nerve growth factor (NGF)-induced proliferation of HBCCs through suppression of the levels of NGF Trk receptors; 2) inhibition of PRLr levels results in inhibition of the proliferation of other PRL-responsive cells, the prostate cancer DU-145 cell line; and 3) CB1-like cannabinoid receptors are expressed in HBCCs and DU-145 cells and mediate the inhibition of cell proliferation and Trk/PRLr expression. Beta-NGF-induced HBCC proliferation was potently inhibited (IC50 = 50-600 nM) by the synthetic cannabinoid HU-210, 2-AG, anandamide, and its metabolically stable analogs, but not by the anandamide congener, palmitoylethanolamide, or the selective agonist of CB2 cannabinoid receptors, BML-190. The effect of anandamide was blocked by the CB1 receptor antagonist, SR141716A, but not by the CB2 receptor antagonist, SR144528. Anandamide and HU-210 exerted a strong inhibition of the levels of NGF Trk receptors as detected by Western immunoblotting; this effect was reversed by SR141716A. When induced by exogenous PRL, the proliferation of prostate DU-145 cells was potently inhibited (IC50 = 100-300 nM) by anandamide, 2-AG, and HU-210. Anandamide also down-regulated the levels of PRLr in DU-145 cells. SR141716A attenuated these two effects of anandamide. HBCCs and DU-145 cells were shown to contain 1) transcripts for CB1 and, to a lesser extent, CB2 cannabinoid receptors, 2) specific binding sites for [3H]SR141716A that could be displaced by anandamide, and 3) a CB1 receptor-immunoreactive protein. These findings suggest that endogenous cannabinoids and CB1 receptor agonists are potential negative effectors of PRL- and NGF-induced biological responses, at least in some cancer cells.

Arachidonic Acids↗
PubMed1997

Internalization of prolactin receptor and prolactin in transfected cells does not involve nuclear translocation.

Prolactin (PRL) interacts with a specific, well characterized plasma membrane receptor (PRLR) that is coupled to signal transduction pathways involving Jak2, Fyn, and MAP kinases, and signal transducers and activators of transcription (STAT). Although a few previous studies have indicated nuclear translocation of PRL in IL-2 stimulated T lymphocytes, PRL-dependent Nb2 lymphoma cell lines and 235-1 lactotrophs, the mechanisms of nuclear targeting remain unknown and conflicting results have been reported concerning the putative nuclear translocation of the PRLR. We therefore decided to investigate nuclear translocation of PRLR and PRL in various cell lines transfected with an expression plasmid encoding PRLR, using confocal laser microscopy. We have constructed various cDNAs of the long and short forms of the rat PRLR containing an oligonucleotide encoding a Flag epitope inserted either just before the N-terminal amino acid or in the C-terminal end of the mature receptor (named N-terminal or C-terminal Flag-tagged PRLR). The corresponding receptors function as the PRLR in transfected cells: they are expressed at the plasma membrane and in compartments of the secretory pathway, they bind PRL with normal affinity (Kd= 4x10(-10) M) and have the same capacity to stimulate the transcriptional activity of a milk protein (beta-casein) gene as wild-type PRLR. In addition, the tagged receptors are much more efficiently immunodetected using anti-Flag antibodies, as compared to anti-PRL antibodies (U5 or U6). Immunofluorescence combined with detailed confocal laser microscopy showed that addition of PRL (0 to 12 hours) to COS-7, CHO and NIH-3T3 transfected fibroblasts induces rapid internalization of the receptor (long form), without any translocation to the nucleus. Using PRL-R tagged both in the N-terminal or C-terminal regions of the mature receptor excludes the possibility of a cleaved fragment which could have been subsequently imported into the nucleus. An absence of nuclear translocation of PRLR was also observed in a 293 cell line stably expressing the receptor, and in physiological targets for PRL, i.e. in Nb2 lymphoma cells expressing the Nb2 form of the receptor or in BGME mammary gland epithelial cells upon overexpression of a Flag-tagged PRLR. Similarly, the short form of the PRLR was not detected in nuclei of transfected COS cells upon PRL treatment. Clearly, our results provide evidence that internalization of the plasma membrane PRLR does not lead to nuclear translocation of the receptor, or part of it, in most fibroblasts and epithelial cells at physiological concentrations of PRL. Also, in co-localization experiments, PRL was internalized without nuclear translocation. Activation of STATs transcription factors and MAP kinases, as well as translocation of these proteins to the nucleus following their phosphorylation, probably remains the intracellular mechanism coupling stimulation to nuclear events.

3T3 Cells↗
PubMed1982

Intracellular localization of prolactin receptor and prolactin in the rat ovary by immunocytochemistry.

The localization of the PRL receptor as well as of PRL has been studied by immunoperoxidase techniques in the ovaries of cycling, pregnant, and lactating rats. Specific antisera to the receptor and to the hormone were used. By light microscopy, immunostaining for the PRL receptor coincided with that for the hormone. Staining was found intracellularly in most components of the ovary, except the theca, and was most striking in the luteal cells. Both PRL and its receptor were concentrated heavily in the ovum. Beginning 24-36 h postpartum, there was a change in the pattern of luteal cell staining, with a shift in the intensity of staining products to the periphery of the luteal cell, giving a ring appearance to these cells. The results suggest roles for PRL in ovarian function involving both maintenance of the corpus luteum and maturation of the ovum. This study also demonstrates the intracellular localization of a polypeptide hormone in association with its specific receptor.

Animals↗