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Kogure K, Nakamura K, Ikeda S, Kitahara Y, Nishimura T, Iwamune M, Minegishi T. Glucose-Regulated Protein, 78-Kilodalton Is a Modulator of Luteinizing Hormone Receptor Expression in Luteinizing Granulosa Cells in Rats1. Biol Reprod 2013; 88:8. [DOI: 10.1095/biolreprod.112.101873] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Andric N, Ascoli M. Mutations of the lutropin/choriogonadotropin receptor that do not activate the phosphoinositide cascade allow hCG to induce aromatase expression in immature rat granulosa cells. Mol Cell Endocrinol 2008; 285:62-72. [PMID: 18313839 PMCID: PMC2288781 DOI: 10.1016/j.mce.2008.01.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Revised: 01/16/2008] [Accepted: 01/23/2008] [Indexed: 11/28/2022]
Abstract
Using primary cultures of immature rat granulosa cells and adenoviral infections we expressed two mutants of the human lutropin receptor (hLHR) that do not activate the phosphoinositide cascade. One mutant (hLFF) has the extracellular domain of the hLHR and the transmembrane and intracellular domains of the hFSHR. The other (hLHR-L457D) has a leucine to aspartate mutation in residue 457 of transmembrane helix 3. When expressed in immature rat granulosa cells the hLHR stimulates cAMP and inositol phosphate accumulation, transactivates the epidermal growth factor receptor (EGFR), elicits a transient increase in Akt phosphorylation, and a sustained increase in ERK1/2 phosphorylation but aromatase expression is not enhanced. When expressed at comparable densities, hLFF and hLHR-L457D support cAMP accumulation and transient Akt phosphorylation but do not support inositol phosphate accumulation, EGFR transactivation or a sustained phosphorylation of ERK1/2. Cells expressing either of these two mutants respond to hCG with increased aromatase expression. We also show that addition of hCG to cells expressing the hLHR antagonizes the effects of hFSH on aromatase expression whereas addition of hCG to cells expressing the hLHR-L457D mutant does not. These results show that activation of the phosphoinositide cascade is upstream of EGFR transactivation and ERK1/2 phosphorylation and that this pathway is a negative regulator of aromatase expression in granulosa cells.
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Affiliation(s)
- Nebojsa Andric
- Department of Pharmacology, Carver College of Medicine, The University of Iowa, 2-319B BSB, 51 Newton Road, Iowa City, IA 52242, USA
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Abstract
Using biochemical and imaging approaches, we examined the postendocytotic fate of the complex formed by human choriogonadotropin (hCG) and a constitutively active mutant of the human lutropin receptor (hLHR-L457R) found in a boy with precocious puberty and Leydig cell hyperplasia. After internalization, some of the complex formed by the hLHR-wild type (hLHR-wt) and hCG recycles to the cell surface, and some is found in lysosomes where the hormone is degraded. In contrast, the complex formed by the hLHR-L457R and hCG is not routed to the lysosomes, most of it is recycled to the cell surface and hormone degradation is barely detectable. For both, hLHR-wt and -L457R, there is an hCG-induced loss of cell surface receptors that accompanies internalization but this loss cannot be prevented by leupeptin. The removal of recycling motifs of the hLHR by truncation of the C-terminal tail at residue 682 greatly enhances the lysosomal accumulation of the hormone-receptor complexes formed by the hLHR-wt or the L457R mutant, the degradation of the internalized hormone, and the loss of cell surface receptors. The degradation of the hormone internalized by these mutants as well as the loss of cell surface receptors is largely prevented by leupeptin. These results highlight a previously unrecognized complexity in the postendocytotic trafficking of the hLHR and document a clear difference between the properties of the constitutively active mutant and the agonist-activated hLHR-wt. This lack of lysosomal degradation of the L457R mutant could contribute to its constitutive activity by prolonging the duration of signaling.
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Affiliation(s)
- Colette Galet
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, 2-319B Bowen Science Building, 51 Newton Road, Iowa City, Iowa 52242-1109, USA
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Piketty V, Kara E, Guillou F, Reiter E, Crepieux P. Follicle-stimulating hormone (FSH) activates extracellular signal-regulated kinase phosphorylation independently of beta-arrestin- and dynamin-mediated FSH receptor internalization. Reprod Biol Endocrinol 2006; 4:33. [PMID: 16787538 PMCID: PMC1524777 DOI: 10.1186/1477-7827-4-33] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Accepted: 06/20/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The follicle-stimulating hormone receptor (FSH-R) is a seven transmembrane spanning receptor (7TMR) which plays a crucial role in male and female reproduction. Upon FSH stimulation, the FSH-R activates the extracellular signal-regulated kinases (ERK). However, the mechanisms whereby the agonist-stimulated FSH-R activates ERK are poorly understood. In order to activate ERK, some 7 TMRs require beta-arrestin-and dynamin-dependent internalization to occur, whereas some others do not. In the present study, we examined the ability of the FSH-activated FSH-R to induce ERK phosphorylation, in conditions where its beta-arrestin- and dynamin-mediated internalization was impaired. METHODS Human embryonic kidney (HEK) 293 cells were transiently transfected with the rat FSH-R. Internalization of the FSH-R was manipulated by co-expression of either a beta-arrestin (319-418) dominant negative peptide, either an inactive dynamin K44A mutant or of wild-type beta-arrestin 1 or 2. The outcomes on the FSH-R internalization were assayed by measuring 125I-FSH binding at the cell surface when compared to internalized 125I-FSH binding. The resulting ERK phosphorylation level was visualized by Western blot analysis. RESULTS In HEK 293 cells, FSH stimulated ERK phosphorylation in a dose-dependent manner. Co-transfection of the beta- arrestin (319-418) construct, or of the dynamin K44A mutant reduced FSH-R internalization in response to FSH, without affecting ERK phosphorylation. Likewise, overexpression of wild-type beta-arrestin 1 or 2 significantly increased the FSH-R internalization level in response to FSH, without altering FSH-induced ERK phosphorylation. CONCLUSION From these results, we conclude that the FSH-R does not require beta-arrestin- nor dynamin-mediated internalization to initiate ERK phosphorylation in response to FSH.
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Affiliation(s)
- Vincent Piketty
- Laboratoire de Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique/Centre National pour la Recherche Scientifique/Université de Tours/Haras Nationaux/Institut Fédératif de Recherche 135, Centre de Recherches de Tours, 37380 Nouzilly, France
| | - Elodie Kara
- Laboratoire de Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique/Centre National pour la Recherche Scientifique/Université de Tours/Haras Nationaux/Institut Fédératif de Recherche 135, Centre de Recherches de Tours, 37380 Nouzilly, France
| | - Florian Guillou
- Laboratoire de Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique/Centre National pour la Recherche Scientifique/Université de Tours/Haras Nationaux/Institut Fédératif de Recherche 135, Centre de Recherches de Tours, 37380 Nouzilly, France
| | - Eric Reiter
- Laboratoire de Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique/Centre National pour la Recherche Scientifique/Université de Tours/Haras Nationaux/Institut Fédératif de Recherche 135, Centre de Recherches de Tours, 37380 Nouzilly, France
| | - Pascale Crepieux
- Laboratoire de Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique/Centre National pour la Recherche Scientifique/Université de Tours/Haras Nationaux/Institut Fédératif de Recherche 135, Centre de Recherches de Tours, 37380 Nouzilly, France
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Yamashita S, Nakamura K, Omori Y, Tsunekawa K, Murakami M, Minegishi T. Association of human follitropin (FSH) receptor with splicing variant of human lutropin/choriogonadotropin receptor negatively controls the expression of human FSH receptor. Mol Endocrinol 2005; 19:2099-111. [PMID: 15890674 DOI: 10.1210/me.2005-0049] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
A splice variant of human lutropin (LH)/choriogonadotropin (CG)-receptor [hLHR(exon 9)] that lacks exon 9 was previously cloned in the corpus luteum of a woman with a normal menstrual cycle. Supported by a detergent-soluble binding assay and a receptor biotinylation experiment, the receptor binding assay shows hLHR(exon 9) is neither expressed at the cell surface nor has the capability of binding to hCG. In addition, hLHR(exon 9) was confirmed in the endoplasmic reticulum (ER) by endoglycosidase H treatment. A coimmunoprecipitation experiment clearly showed that hLHR(exon 9) and constitutively inactivate mutant-LHRs, which stay in the ER, form an association with the human follitropin (FSH)-receptor (hFSHR). This suggests that in the presence of mutant-LHR, hFSHR, which is trapped in the ER and associated with hLHR(exon 9), is unable to come up to the plasma membrane. This phenomenon is specific among gonadotropin receptors because human TSH receptor failed to be coimmunoprecipitated. Furthermore, this receptor complex attenuated the hFSHR receptor protein level within the cells, which impaired cAMP production. To elucidate the mechanism underlying the decrease in hFSHR protein by this receptor complex, we performed a Percoll fractionation experiment, which indicated that the receptor complex drove hFSHR to the lysosome instead of the plasma membrane. These results reveal a novel mechanism of FSHR expression regulation.
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Affiliation(s)
- Soichi Yamashita
- Department of Obstetrics and Gynecology, School of Medicine, Gunma University, Gunma 371-8511, Japan
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Galet C, Min L, Narayanan R, Kishi M, Weigel NL, Ascoli M. Identification of a transferable two-amino-acid motif (GT) present in the C-terminal tail of the human lutropin receptor that redirects internalized G protein-coupled receptors from a degradation to a recycling pathway. Mol Endocrinol 2003; 17:411-22. [PMID: 12554787 DOI: 10.1210/me.2002-0161] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Although highly homologous in amino acid sequence, the agonist-receptor complexes formed by the human lutropin receptor (hLHR) and rat (r) LHR follow different intracellular routes. The agonist-rLHR complex is routed mostly to a lysosomal degradation pathway whereas a substantial portion of the agonist-hLHR complex is routed to a recycling pathway. In a previous study, we showed that grafting a five-residue sequence (GTALL) present in the C-terminal tail of the hLHR into the equivalent position of the rLHR redirects a substantial portion of the internalized agonist-rLHR complex to a recycling pathway. Using a number of mutations of the GTALL motif, we now show that only the first two residues (GT) of this motif are necessary and sufficient to induce recycling of the internalized agonist-rLHR complex. Phosphoamino acid analysis and mutations of the GT motif show that phosphorylation of the threonine residue is not necessary for recycling. Lastly, we show that addition of portions of the C-terminal tail of the hLHR that include the GT motif to the C-terminal tails of the rat follitropin or murine delta-opioid receptors promotes the post-endocytotic recycling of these G protein-coupled receptors.We conclude that the GT motif present in the C-terminal tail of the hLHR is a transferable motif that promotes the postendocytotic recycling of several G protein-coupled receptors and that the GT-induced recycling does not require the phosphorylation of the threonine residue.
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Affiliation(s)
- Colette Galet
- Department of Pharmacology, The University of Iowa, Iowa City, Iowa 52242-1109, USA
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Sun Y, Gershengorn MC. Correlation between basal signaling and internalization of thyrotropin-releasing hormone receptors: evidence for involvement of similar receptor conformations. Endocrinology 2002; 143:2886-92. [PMID: 12130552 DOI: 10.1210/endo.143.8.8940] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Previous studies have shown that rat thyrotropin-releasing hormone (TRH) receptor type 2 exhibits higher basal signaling activity and internalizes more rapidly upon agonist binding than rat TRH receptor type 1. The mouse TRH receptor type 2 (mR2) was recently cloned and, similar to its rat homolog, shows a higher basal signaling activity than mR1. Taking advantage of the high degree of sequence homology between mR1 and mR2, we used chimeras/mutants of these receptors to gain insight into the properties of the receptors that influence internalization and basal signaling. Chimeric receptors that have the mR1 extracellular and transmembrane domains with the carboxyl terminus and intracellular loops of mR2 (R1/R2-tail; R1/R2-I3,tail; R1/R2-I2,3,tail; R1/R2-I1,2,3,tail) exhibited internalization rates and basal activities that were similar to that of mR1. In contrast, a chimeric receptor with the extracellular and transmembrane domains of mR2 and the carboxyl terminus of mR1 exhibited the more rapid internalization rate and higher basal signaling activity characteristic of mR2. We showed previously that mutation of a highly conserved tryptophan to alanine caused mR1 to exhibit a high basal signaling activity and rapid internalization rate. In contrast, mutation of this tryptophan to alanine in mR2 decreased the rate of internalization and inhibited basal signaling activity. The rates of receptor internalization did not correlate with the binding affinities, coupling efficiencies, or potencies of the receptors. Thus, we observed that receptors with more rapid internalization rates showed relatively higher basal signaling activities, whereas receptors with lower basal signaling activities showed slower internalization rates. These data suggest that similar receptor conformations are required for productive coupling to signaling G proteins and to proteins involved in internalization.
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Affiliation(s)
- Yuhua Sun
- The Division of Molecular Medicine, Department of Medicine, Weill Medical College of Cornell University, New York, NY 10021, USA
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Kishi H, Krishnamurthy H, Galet C, Bhaskaran RS, Ascoli M. Identification of a short linear sequence present in the C-terminal tail of the rat follitropin receptor that modulates arrestin-3 binding in a phosphorylation-independent fashion. J Biol Chem 2002; 277:21939-46. [PMID: 11934883 DOI: 10.1074/jbc.m110894200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The rat follitropin receptor (rFSHR) is an unusual G protein-coupled receptor in that agonist-induced activation leads to the phosphorylation of the first and third intracellular loops instead of the C-terminal tail. To determine regions of G protein-coupled receptors that affect internalization independently of phosphorylation we examined the effects of truncations of the C-terminal tail of the rFSHR on agonist-induced internalization. Our studies show that progressive truncations of a region flanked by residues 642 and 651 enhance the internalization of human follicle-stimulating hormone (hFSH). Further characterization of a mutant truncated at residue 649 (designated rFSHR-t649) and another mutant in which the 642-651 region was deleted in the context of the full-length rFSHR, designated rFSHR(Delta642-651), showed that both of them internalized hFSH at rates that were 2-3 times faster than rFSHR-wild type (wt). Like rFSHR-wt, however, the internalization of hFSH mediated by rFSHR-t649 and rFSHR(Delta642-651) can be inhibited with dominant-negative mutants of the non-visual arrestins or dynamin. Alanine-scanning mutagenesis of the 642-651 region suggests that the effects on internalization are not mediated by a single residue, however. In an attempt to understand the molecular basis of the enhanced internalization of hFSH mediated by these mutants we used an assay that can be readily used to assess the association of the rFSHR with the arrestin-3 in co-transfected cells. Using this assay we were able to show that, when compared with rFSHR-wt, rFSHR(Delta642-651) displays an approximately 4-fold enhancement in binding affinity for arrestin-3 and an approximately 1.7-fold reduction in maximal arrestin-3 binding capacity. We conclude that a short linear sequence present in the C-terminal tail of the rFSHR (642SATHNFHARK651) that is not phosphorylated limits internalization by lowering the affinity of the rFSHR for the endogenous non-visual arrestins.
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Affiliation(s)
- Hiroshi Kishi
- Department of Pharmacology, The University of Iowa College of Medicine, Iowa City, Iowa 52242, USA
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Dias JA, Cohen BD, Lindau-Shepard B, Nechamen CA, Peterson AJ, Schmidt A. Molecular, structural, and cellular biology of follitropin and follitropin receptor. Vitam Horm 2002; 64:249-322. [PMID: 11898394 DOI: 10.1016/s0083-6729(02)64008-7] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Follitropin and the follitropin receptor are essential for normal gamete development in males and females. This review discusses the molecular genetics and structural and cellular biology of the follitropin/follitropin receptor system. Emphasis is placed on the human molecules when possible. The structure and regulation of the genes for the follitropin beta subunit and the follitropin receptor is discussed. Control of systemic and cellular protein levels is explained. The structural biology of each protein is described, including protein structure, motifs, and activity relationships. Finally, the follitropin/follitropin receptor signal transduction system is discussed.
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Affiliation(s)
- James A Dias
- Wadsworth Center, David Axelrod Institute for Public Health, New York State Department of Health, Albany, New York 12208, USA
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Abstract
Reproduction cannot take place without the proper functioning of the lutropin/choriogonadotropin receptor (LHR). When the LHR does not work properly, ovulation does not occur in females and Leydig cells do not develop normally in the male. Also, because the LHR is essential for sustaining the elevated levels of progesterone needed to maintain pregnancy during the first trimester, disruptions in the functions of the LHR during pregnancy have catastrophic consequences. As such, a full understanding of the biology of the LHR is essential to the survival of our species. In this review we summarize our current knowledge of the structure, functions, and regulation of this important receptor.
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Affiliation(s)
- Mario Ascoli
- Department of Pharmacology, The University of Iowa, Iowa City, 52242-1109, USA.
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Min L, Galet C, Ascoli M. The association of arrestin-3 with the human lutropin/choriogonadotropin receptor depends mostly on receptor activation rather than on receptor phosphorylation. J Biol Chem 2002; 277:702-10. [PMID: 11696538 DOI: 10.1074/jbc.m106082200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although the involvement of the nonvisual arrestins in the agonist-induced internalization of the human lutropin receptor (hLHR) has been documented previously with the use of dominant-negative mutants, a physical association of the nonvisual arrestins with the hLHR in intact cells has not been established. In the studies presented herein, we used a cross-linking/coimmunoprecipitation/immunoblotting approach as well as confocal microscopy to document the association of the hLHR with the nonvisual arrestins in co-transfected 293 cells. We also used this approach to examine the relative importance of receptor activation and receptor phosphorylation in the formation of this complex. Using hLHR mutants that impair phosphorylation, activation, or both, we show that the formation of the hLHR-nonvisual arrestin complex depends mostly on the agonist-induced activation of the hLHR rather than on the phosphorylation of the hLHR. These results stand in contrast to those obtained with several other G protein-coupled receptors (i.e. the beta2-adrenergic receptor, the m2 muscarinic receptor, rhodopsin, and the type 1A angiotensin receptor) where arrestin binding depends mostly on receptor phosphorylation rather than on receptor activation. We have also examined the association of the nonvisual arrestins with naturally occurring gain-of-function mutations of the hLHR found in boys with Leydig cell hyperplasia or Leydig cell adenomas. Our results show that these mutants associate with the nonvisual arrestins in an agonist-independent fashion.
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Affiliation(s)
- Le Min
- Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242-1109, USA
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Li S, Liu X, Min L, Ascoli M. Mutations of the second extracellular loop of the human lutropin receptor emphasize the importance of receptor activation and de-emphasize the importance of receptor phosphorylation in agonist-induced internalization. J Biol Chem 2001; 276:7968-73. [PMID: 11118455 DOI: 10.1074/jbc.m010482200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alanine scanning mutagenesis of the second extracellular loop of the human lutropin receptor (hLHR) showed that mutation of most of the residues present in this region either enhance or impair the internalization of agonist. A more complete analysis of four mutants, two that enhanced internalization (F515A and T521A) and two that impaired internalization (S512A and V519A), showed that the two mutants that impaired internalization also show a decrease in the sensitivity for agonist-induced cAMP accumulation, whereas the two mutants that enhanced internalization show an increase in the sensitivity for agonist-induced cAMP accumulation. None of these mutants had an effect on the agonist-induced phosphorylation of the hLHR, however. We conclude that, in contrast to the prevailing view of the relative importance of receptor phosphorylation in the internalization of G protein-coupled receptors, the phosphorylation of the hLHR is less important than the agonist-induced activation of the hLHR in the process of internalization.
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Affiliation(s)
- S Li
- Department of Pharmacology, University of Iowa College of Medicine, Iowa City, Iowa 52242-1109, USA
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Kishi H, Ascoli M. Multiple distant amino acid residues present in the serpentine region of the follitropin receptor modulate the rate of agonist-induced internalization. J Biol Chem 2000; 275:31030-7. [PMID: 10915803 DOI: 10.1074/jbc.m005528200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The amino acid sequences of the human (h) and rat (r) follitropin receptors (FSHR) are approximately 89% identical, but the half-time of internalization of agonist mediated by the rFSHR is approximately 3 times faster than that of the hFSHR. Chimeras of the hFSHR and the rFSHR showed that this difference in rate is dictated mostly by the serpentine domain. Further analysis identified six residues, two non-contiguous residues in the transmembrane helix 4 (Leu/Thr in the rFSHR and Met/Ile in the hFSHR), three non-contiguous residues in the third intracellular loop (Thr/Thr/Lys in the rFSHR and Ile/Asn/Arg in the hFSHR), and one in transmembrane helix 7 (Tyr in the rFSHR and His in the hFSHR) that are fully responsible for the difference in the rates of internalization of the hFSHR and the rFSHR.
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Affiliation(s)
- H Kishi
- Department of Pharmacology, The University of Iowa, Iowa City, Iowa 52242, USA
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Kishi M, Ascoli M. The C-terminal tail of the rat lutropin/choriogonadotropin (CG) receptor independently modulates human (h)CG-induced internalization of the cell surface receptor and the lysosomal targeting of the internalized hCG-receptor complex. Mol Endocrinol 2000; 14:926-36. [PMID: 10847593 DOI: 10.1210/mend.14.6.0475] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The analysis of 21 progressive truncations of the C-terminal tail of the rat LH/CG receptor (rLHR) revealed the presence of a region delineated by residues 628-649 that, when removed, enhanced the degradation of the internalized human (h)CG. The analysis of these truncations also revealed the presence of a region delineated by residues 624-631 that, when removed, enhanced the rate of internalization of hCG. Since there is little overlap between these two regions, we conclude that the structural features of the rLHR that mediate internalization and degradation of the internalized hormone are different. Detailed analyses of cells expressing a truncation at Y637 (designated rLHR-t637) showed that the enhanced degradation of hCG observed in the these cells is due to an increase in the rate of transfer of the internalized hCG-rLHR complex from the endosomes to the lysosomes rather than to the enhanced dissociation of the hCG-rLHR complex in the lysosomes.
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Affiliation(s)
- M Kishi
- Department of Pharmacology, The University of Iowa College of Medicine, Iowa City 52242-1109, USA
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Nakamura K, Liu X, Ascoli M. Seven non-contiguous intracellular residues of the lutropin/choriogonadotropin receptor dictate the rate of agonist-induced internalization and its sensitivity to non-visual arrestins. J Biol Chem 2000; 275:241-7. [PMID: 10617611 DOI: 10.1074/jbc.275.1.241] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The amino acid sequences of the human (h) and rat (r) lutropin/choriogonadotropin receptors (LHR) are 87% identical, but the rate of agonist-induced internalization of the hLHR is approximately 7 times faster than that of the rLHR. Chimeras of the hLHR and the rLHR showed that this rate is dictated by the serpentine domain and the cytoplasmic tail. Further mutational analysis identified seven residues, two adjacent residues in the second intracellular loop (Val/Gln in the rLHR and Ile/His in the hLHR), four non-contiguous residues in the third intracellular loop (Arg/Gln/Thr/Pro in the rLHR and Lys/Arg/Met/Thr in the hLHR), and one in the C-terminal tail (Leu in the rLHR and Phe in the hLHR), that are necessary and sufficient to impart the slow rate of internalization of the rLHR and the fast rate of internalization of the hLHR. The internalization of the rLHR and the hLHR display different sensitivities to the non-visual arrestins. Therefore, we also tested if the simultaneous exchange of these seven residues resulted in the exchange of this property. Since this was found to be the case, we propose that these seven residues identified here form a non-visual arrestin-binding site.
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Affiliation(s)
- K Nakamura
- Department of Pharmacology, The University of Iowa, Iowa City, Iowa 52242, USA
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