scholarly journals SynCAM1, a Synaptic Adhesion Molecule, Is Expressed in Astrocytes and Contributes to erbB4 Receptor-Mediated Control of Female Sexual Development

Endocrinology ◽  
2011 ◽  
Vol 152 (6) ◽  
pp. 2364-2376 ◽  
Author(s):  
Ursula S. Sandau ◽  
Alison E. Mungenast ◽  
Zefora Alderman ◽  
S. Pablo Sardi ◽  
Adam I. Fogel ◽  
...  
Keyword(s):  
Adhesion Molecule ◽  
Intracellular Signaling ◽  
Reproductive Function ◽  
Receptor Activation ◽  
Dominant Negative ◽  
Normal Female ◽  
Calcium Calmodulin Dependent ◽  
Erbb4 Receptor ◽  
Gnrh Release ◽  
Female Sexual Development

Female sexual maturation requires erythroblastosis B (erbB)4 signaling in hypothalamic astrocytes; however, the mechanisms by which erbB4 contributes to this process are incompletely understood. Here we show that SynCAM1, a synaptic adhesion molecule with signaling capabilities, is not only expressed highly in neurons, but also in hypothalamic astrocytes and is functionally associated with erbB4 receptor activity. Whereas SynCAM1 expression is diminished in astrocytes with impaired erbB4 signaling, ligand-dependent activation of astroglial erbB4 receptors results in rapid association of erbB4 with SynCAM1 and activation of SynCAM1 gene transcription. To determine whether astrocytic SynCAM1-dependent intracellular signaling is required for normal female reproductive function, we generated transgenic mice that express in an astrocyte-specific manner a dominant-negative form of SynCAM1 lacking the intracellular domain. The mutant protein was correctly targeted to the cell membrane and was functionally viable as shown by its ability to block intracellular calcium/calmodulin-dependent serine protein kinase redistribution, a major SynCAM1-mediated event. Dominant-negative-SynCAM1 female mice had a delayed onset of puberty, disrupted estrous cyclicity, and reduced fecundity. These deficits were associated with a reduced capacity of neuregulin-dependent erbB4 receptor activation to elicit prostaglandin E2 release from astrocytes and GnRH release from the hypothalamus. We conclude that one of the mechanisms underlying erbB4 receptor-mediated facilitation of glial-neuronal interactions in the neuroendocrine brain involves SynCAM1-dependent signaling and that this interaction is required for normal female reproductive function.

scholarly journals Distinct Mechanisms Involving Diverse Histone Deacetylases Repress Expression of the Two Gonadotropin β-Subunit Genes in Immature Gonadotropes, and Their Actions Are Overcome by Gonadotropin-Releasing Hormone

2007 ◽  
Vol 27 (11) ◽  
pp. 4105-4120 ◽  
Author(s):  
Stefan Lim ◽  
Min Luo ◽  
Mingshi Koh ◽  
Meng Yang ◽  
Mohammed Nizam bin Abdul Kadir ◽  
...  
Keyword(s):  
Histone Deacetylases ◽  
Reproductive Function ◽  
Gonadotropin Releasing Hormone ◽  
Β Subunit ◽  
Releasing Hormone ◽  
Calcium Calmodulin Dependent ◽  
Gnrh Release ◽  
Dependent Protein ◽  
Reproductive Cycles ◽  
Class Iia Hdacs

ABSTRACT The gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are produced in the embryonic pituitary in response to delivery of the hypothalamic gonadotropin releasing hormone (GnRH). GnRH has a pivotal role in reestablishing gonadotropin levels at puberty in primates, and for many species with extended reproductive cycles, these are reinitiated in response to central nervous system-induced GnRH release. Thus, a clear role is evident for GnRH in overcoming repression of these genes. Although the mechanisms through which GnRH actively stimulates LH and FSH β-subunit (FSHβ) gene transcription have been described in some detail, there is currently no information on how GnRH overcomes repression in order to terminate reproductively inactive stages. We show here that GnRH overcomes histone deacetylase (HDAC)-mediated repression of the gonadotropin β-subunit genes in immature gonadotropes. The repressive factors associated with each of these genes comprise distinct sets of HDACs and corepressors which allow for differentially regulated derepression of these two genes, produced in the same cell by the same regulatory hormone. We find that GnRH activation of calcium/calmodulin-dependent protein kinase I (CaMKI) plays a crucial role in the derepression of the FSHβ gene involving phosphorylation of several class IIa HDACs associated with both the FSHβ and Nur77 genes, and we propose a model for the mechanisms involved. In contrast, derepression of the LH β-subunit gene is not CaMK dependent. This demonstration of HDAC-mediated repression of these genes could explain the temporal shut-down of reproductive function at certain periods of the life cycle, which can easily be reversed by the actions of the hypothalamic regulatory hormone.

scholarly journals erbB-1 and erbB-4 Receptors Act in Concert to Facilitate Female Sexual Development and Mature Reproductive Function

Endocrinology ◽  
2005 ◽  
Vol 146 (3) ◽  
pp. 1465-1472 ◽  
Author(s):  
Vincent Prevot ◽  
Alejandro Lomniczi ◽  
Gabriel Corfas ◽  
Sergio R. Ojeda
Keyword(s):  
Glial Cells ◽  
Sexual Development ◽  
Double Mutant ◽  
Reproductive Function ◽  
Receptor Activation ◽  
Dominant Negative ◽  
Reproductive Capacity ◽  
Erbb Receptor ◽  
Signaling Systems ◽  
Lhrh Release

Glial erbB-1 and erbB-4 receptors are key components of the process by which neuroendocrine glial cells control LHRH secretion and the onset of female puberty. We now provide evidence that these two signaling systems work in a coordinated fashion to control reproductive function. To generate animals carrying functionally impaired erbB-1 and erbB-4 receptors, we crossed Waved 2 (Wa-2+/+) mice harboring a point mutation of the erbB-1 receptor with mice expressing a dominant-negative erbB-4 receptor in astrocytes. In comparison to single-deficient mice, double-mutant animals exhibited a further delay in the onset of puberty and a strikingly diminished adult reproductive capacity. Ligand-dependent erbB receptor phosphorylation and erbB-mediated MAPK (ERK 1/2) phosphorylation were impaired in mutant astrocytes. Wa-2+/+ or double-mutant astrocytes failed to respond to TGFα with production of prostaglandin E2, one of the factors mediating the stimulatory effect of astroglial erbB receptor activation on LHRH release. Medium conditioned by Wa-2+/+ or double-mutant astrocytes treated with TGFα failed to stimulate LHRH release from GT1–7 cells. The LH response to ovariectomy was significantly attenuated in mutant mice in comparison with wild-type controls. Although the Wa-2 mutation affects all cells bearing erbB-1 receptors, these results suggest that a major defect underlying the reproductive defects of animals with impaired erbB signaling is a decreased ability of glial cells to stimulate LHRH release. Thus, a coordinated involvement of erbB-1 and erbB-4 signaling systems is required for the normalcy of sexual development and the maintenance of mature female reproductive function.

scholarly journals The Synaptic Cell Adhesion Molecule, SynCAM1, Mediates Astrocyte-to-Astrocyte and Astrocyte-to-GnRH Neuron Adhesiveness in the Mouse Hypothalamus

Endocrinology ◽  
2011 ◽  
Vol 152 (6) ◽  
pp. 2353-2363 ◽  
Author(s):  
Ursula S. Sandau ◽  
Alison E. Mungenast ◽  
Jack McCarthy ◽  
Thomas Biederer ◽  
Gabriel Corfas ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecule ◽  
Cell Adhesion Molecule ◽  
Genetic Network ◽  
Dominant Negative ◽  
Gnrh Neuron ◽  
Transgenic Expression ◽  
Erbb4 Receptor ◽  
Gnrh Neurons ◽  
Membrane Spanning

We previously identified synaptic cell adhesion molecule 1 (SynCAM1) as a component of a genetic network involved in the hypothalamic control of female puberty. Although it is well established that SynCAM1 is a synaptic adhesion molecule, its contribution to hypothalamic function is unknown. Here we show that, in addition to the expected neuronal localization illustrated by its presence in GnRH neurons, SynCAM1 is expressed in hypothalamic astrocytes. Cell adhesion assays indicated that SynCAM is recognized by both GnRH neurons and astrocytes as an adhesive partner and promotes cell-cell adhesiveness via homophilic, extracellular domain-mediated interactions. Alternative splicing of the SynCAM1 primary mRNA transcript yields four mRNAs encoding membrane-spanning SynCAM1 isoforms. Variants 1 and 4 are predicted to be both N and O glycosylated. Hypothalamic astrocytes and GnRH-producing GT1-7 cells express mainly isoform 4 mRNA, and sequential N- and O-deglycosylation of proteins extracted from these cells yields progressively smaller SynCAM1 species, indicating that isoform 4 is the predominant SynCAM1 variant expressed in astrocytes and GT1-7 cells. Neither cell type expresses the products of two other SynCAM genes (SynCAM2 and SynCAM3), suggesting that SynCAM-mediated astrocyte-astrocyte and astrocyte-GnRH neuron adhesiveness is mostly mediated by SynCAM1 homophilic interactions. When erbB4 receptor function is disrupted in astrocytes, via transgenic expression of a dominant-negative erbB4 receptor form, SynCAM1-mediated adhesiveness is severely compromised. Conversely, SynCAM1 adhesive behavior is rapidly, but transiently, enhanced in astrocytes by ligand-dependent activation of erbB4 receptors, suggesting that erbB4-mediated events affecting SynCAM1 function contribute to regulate astrocyte adhesive communication.

Stimulation of pro-α1(I) collagen by TGF-β1 in mesangial cells: role of the p38 MAPK pathway

2001 ◽  
Vol 280 (3) ◽  
pp. F495-F504 ◽  
Author(s):  
Beek Yoke Chin ◽  
Amir Mohsenin ◽  
Su Xia Li ◽  
Augustine M. K. Choi ◽  
Mary E. Choi
Keyword(s):  
P38 Mapk ◽  
Intracellular Signaling ◽  
Mesangial Cells ◽  
Mapk Pathway ◽  
Dominant Negative ◽  
Glomerular Mesangial Cells ◽  
Mapk Activation ◽  
Mapk Phosphorylation ◽  
Collagen Mrna

Transforming growth factor-β1(TGF-β1) is a potent inducer of extracellular matrix protein synthesis and a key mediator of renal fibrosis. However, the intracellular signaling mechanisms by which TGF-β1stimulates this process remain incompletely understood. In this report, we examined the role of a major stress-activated intracellular signaling cascade, belonging to the mitogen-activated protein kinase (MAPK) superfamily, in mediating TGF-β1 responses in rat glomerular mesangial cells, using dominant-negative inhibition of TGF-β1 signaling receptors. We first stably transfected rat glomerular mesangial cells with a kinase-deleted mutant TGF-β type II receptor (TβR-IIM) designed to inhibit TGF-β1 signaling in a dominant-negative fashion. Next, expression of TβR-IIM mRNA was confirmed by Northern analysis. Cell surface expression and ligand binding of TβR-IIM protein were demonstrated by affinity cross-linking with 125I-labeled-TGF-β1. TGF-β1 rapidly induced p38 MAPK phosphorylation in wild-type and empty vector (pcDNA3)-transfected control mesangial cells. Interestingly, transfection with dominant-negative TβR-IIM failed to block TGF-β1-induced p38 MAPK phosphorylation. Moreover, dominant-negative TβR-IIMfailed to block TGF-β1-stimulated pro-α1(I) collagen mRNA expression and cellular protein synthesis, whereas TGF-β1-induced extracellular signal-regulated kinase (ERK) 1/ERK2 activation and antiproliferative responses were blocked by TβR-IIM. In the presence of a specific inhibitor of p38 MAPK, SB-203580, TGF-β1 was unable to stimulate pro-α1(I) collagen mRNA expression in the control and TβR-IIM-transfected mesangial cells. Finally, we confirmed that both p38 MAPK activation and pro-α1(I) collagen stimulation were TGF-β1 effects that were abrogated by dominant-negative inhibition of TGF-β type I receptor. Thus we show first demonstration of p38 MAPK activation by TGF-β1 in mesangial cells, and, given the rapid kinetics, this TGF-β1 effect is likely a direct one. Furthermore, our findings suggest that the p38 MAPK pathway functions as a component in the signaling of pro-α1(I) collagen induction by TGF-β1 in mesangial cells.

scholarly journals Role of Nectin in Formation of E-Cadherin–based Adherens Junctions in Keratinocytes: Analysis with the N-Cadherin Dominant Negative Mutant

2003 ◽  
Vol 14 (4) ◽  
pp. 1597-1609 ◽  
Author(s):  
Yoshinari Tanaka ◽  
Hiroyuki Nakanishi ◽  
Shigeki Kakunaga ◽  
Noriko Okabe ◽  
Tomomi Kawakatsu ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecule ◽  
Cell Adhesion Molecule ◽  
Adherens Junctions ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Adhesion Activity ◽  
Negative Mutant ◽  
E Cadherin ◽  
Cell Cell

E-Cadherin is a Ca2+-dependent cell-cell adhesion molecule at adherens junctions (AJs) of epithelial cells. A fragment of N-cadherin lacking its extracellular region serves as a dominant negative mutant (DN) and inhibits cell-cell adhesion activity of E-cadherin, but its mode of action remains to be elucidated. Nectin is a Ca2+-independent immunoglobulin-like cell-cell adhesion molecule at AJs and is associated with E-cadherin through their respective peripheral membrane proteins, afadin and catenins, which connect nectin and cadherin to the actin cytoskeleton, respectively. We showed here that overexpression of nectin capable of binding afadin, but not a mutant incapable of binding afadin, reduced the inhibitory effect of N-cadherin DN on the cell-cell adhesion activity of E-cadherin in keratinocytes. Overexpressed nectin recruited N-cadherin DN to the nectin-based cell-cell adhesion sites in an afadin-dependent manner. Moreover, overexpression of nectin enhanced the E-cadherin–based cell-cell adhesion activity. These results suggest that N-cadherin DN competitively inhibits the association of the endogenous nectin-afadin system with the endogenous E-cadherin-catenin system and thereby reduces the cell-cell adhesion activity of E-cadherin. Thus, nectin plays a role in the formation of E-cadherin–based AJs in keratinocytes.

scholarly journals The Hinge-Helix 1 Region of Peroxisome Proliferator-Activated Receptor γ1 (PPARγ1) Mediates Interaction with Extracellular Signal-Regulated Kinase 5 and PPARγ1 Transcriptional Activation: Involvement in Flow-Induced PPARγ Activation in Endothelial Cells

2004 ◽  
Vol 24 (19) ◽  
pp. 8691-8704 ◽  
Author(s):  
Masashi Akaike ◽  
Wenyi Che ◽  
Nicole-Lerner Marmarosh ◽  
Shinsuke Ohta ◽  
Masaki Osawa ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Adhesion Molecule ◽  
Critical Role ◽  
Physiological Role ◽  
Cellular Adhesion ◽  
Dominant Negative ◽  
Peroxisome Proliferator ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Cellular Adhesion Molecule

ABSTRACT Peroxisome proliferator-activated receptors (PPAR) are ligand-activated transcription factors that form a subfamily of the nuclear receptor gene family. Since both flow and PPARγ have atheroprotective effects and extracellular signal-regulated kinase 5 (ERK5) kinase activity is significantly increased by flow, we investigated whether ERK5 kinase regulates PPARγ activity. We found that activation of ERK5 induced PPARγ1 activation in endothelial cells (ECs). However, we could not detect PPARγ phosphorylation by incubation with activated ERK5 in vitro, in contrast to ERK1/2 and JNK, suggesting a role for ERK5 as a scaffold. Endogenous PPARγ1 was coimmunoprecipitated with endogenous ERK5 in ECs. By mammalian two-hybrid analysis, we found that PPARγ1 associated with ERK5a at the hinge-helix 1 region of PPARγ1. Expressing a hinge-helix 1 region PPARγ1 fragment disrupted the ERK5a-PPARγ1 interaction, suggesting a critical role for hinge-helix 1 region of PPARγ in the ERK5-PPARγ interaction. Flow increased ERK5 and PPARγ1 activation, and the hinge-helix 1 region of the PPARγ1 fragment and dominant negative MEK5β significantly reduced flow-induced PPARγ activation. The dominant negative MEK5β also prevented flow-mediated inhibition of tumor necrosis factor alpha-mediated NF-κB activation and adhesion molecule expression, including vascular cellular adhesion molecule 1 and E-selectin, indicating a physiological role for ERK5 and PPARγ activation in flow-mediated antiinflammatory effects. We also found that ERK5 kinase activation was required, likely by inducing a conformational change in the NH2-terminal region of ERK5 that prevented association of ERK5 and PPARγ1. Furthermore, association of ERK5a and PPARγ1 disrupted the interaction of SMRT and PPARγ1, thereby inducing PPARγ activation. These data suggest that ERK5 mediates flow- and ligand-induced PPARγ activation via the interaction of ERK5 with the hinge-helix 1 region of PPARγ.

scholarly journals Neural Cell Adhesion Molecule Induces Intracellular Signaling via Multiple Mechanisms of Ca2+ Homeostasis

2006 ◽  
Vol 17 (5) ◽  
pp. 2278-2286 ◽  
Author(s):  
Darya Kiryushko ◽  
Irina Korshunova ◽  
Vladimir Berezin ◽  
Elisabeth Bock
Keyword(s):  
Cell Adhesion ◽  
Neuronal Differentiation ◽  
Adhesion Molecule ◽  
Intracellular Signaling ◽  
Hippocampal Neurons ◽  
Cell Adhesion Molecule ◽  
Neural Cell Adhesion Molecule ◽  
Neural Cell ◽  
Src Family Kinases ◽  
Neural Cell Adhesion

The neural cell adhesion molecule (NCAM) plays a pivotal role in the development of the nervous system, promoting neuronal differentiation via homophilic (NCAM–NCAM) as well as heterophilic (NCAM-fibroblast growth factor receptor [FGFR]) interactions. NCAM-induced intracellular signaling has been shown to affect and be dependent on the cytoplasmic Ca2+ concentration ([Ca2+]i). However, the molecular basis of this remains unclear. In this study, we determined [Ca2+]i regulating mechanisms involved in intracellular signaling induced by NCAM. To mimic the effect of homophilic NCAM interaction on [Ca2+]i in vitro, we used a peptide derived from a homophilic binding site of NCAM, termed P2, which triggers signaling cascades similar to those activated by NCAM–NCAM interaction. We found that P2 increased [Ca2+]i in primary hippocampal neurons. This effect depended on two signaling pathways. The first pathway was associated with activation of FGFR, phospholipase Cγ, and production of diacylglycerol, and the second pathway involved Src-family kinases. Moreover, NCAM-mediated Ca2+ entry required activation of nonselective cation and T-type voltage-gated Ca2+ channels. These channels, together with the Src-family kinases, were also involved in neuritogenesis induced by physiological, homophilic NCAM interactions. Thus, unanticipated mechanisms of Ca2+ homeostasis are shown to be activated by NCAM and to contribute to neuronal differentiation.

scholarly journals Sphingosine Kinase as a Regulator of Calcium Entry through Autocrine Sphingosine 1-Phosphate Signaling in Thyroid FRTL-5 Cells

Endocrinology ◽  
2009 ◽  
Vol 150 (11) ◽  
pp. 5125-5134 ◽  
Author(s):  
Dan Gratschev ◽  
Christoffer Löf ◽  
Jari Heikkilä ◽  
Anders Björkbom ◽  
Pramod Sukumaran ◽  
...  
Keyword(s):  
Intracellular Signaling ◽  
Sphingosine Kinase ◽  
Calcium Entry ◽  
Dominant Negative ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Entry Pathway ◽  
Sphingosine 1 Phosphate ◽  
S1p Receptor ◽  
In Cells

Calcium entry is one of the main regulators of intracellular signaling. Here, we have described the importance of sphingosine, sphingosine kinase 1 (SK1), and sphingosine 1-phosphate (S1P) in regulating calcium entry in thyroid FRTL-5 cells. In cells incubated with the phosphatase inhibitor calyculin A, which evokes calcium entry without mobilizing sequestered intracellular calcium, sphingosine inhibited calcium entry in a concentration-dependent manner. Furthermore, inhibiting SK1 or the ATP-binding cassette ABCC1 multidrug transporter attenuated calcium entry. The addition of exogenous S1P restored calcium entry. Neither sphingosine nor inhibition of SK1 attenuated thapsigargin-evoked calcium entry. Blocking S1P receptor 2 or phospholipase C attenuated calcium entry, whereas blocking S1P receptor 3 did not. Overexpression of wild-type SK1, but not SK2, enhanced calyculin-evoked calcium entry compared with mock-transfected cells, whereas calcium entry was decreased in cells transfected with the dominant-negative G82D SK1 mutant. Exogenous S1P restored calcium entry in G82D cells. Our results suggest that the calcium entry pathway is blocked by sphingosine and that activation of SK1 and the production of S1P, through an autocrine mechanism, facilitate calcium entry through activation of S1P receptor 2. This is a novel mechanism by which the sphingosine-S1P rheostat regulates cellular calcium homeostasis.

scholarly journals Minireview: GPCR and G Proteins: Drug Efficacy and Activation in Live Cells

2009 ◽  
Vol 23 (5) ◽  
pp. 590-599 ◽  
Author(s):  
Jean-Pierre Vilardaga ◽  
Moritz Bünemann ◽  
Timothy N. Feinstein ◽  
Nevin Lambert ◽  
Viacheslav O. Nikolaev ◽  
...  
Keyword(s):  
Energy Transfer ◽  
G Protein ◽  
G Proteins ◽  
Intracellular Signaling ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Receptor Activation ◽  
Live Cells ◽  
Mechanical Stimuli ◽  
G Protein Coupled

Abstract Many biochemical pathways are driven by G protein-coupled receptors, cell surface proteins that convert the binding of extracellular chemical, sensory, and mechanical stimuli into cellular signals. Their interaction with various ligands triggers receptor activation that typically couples to and activates heterotrimeric G proteins, which in turn control the propagation of secondary messenger molecules (e.g. cAMP) involved in critically important physiological processes (e.g. heart beat). Successful transfer of information from ligand binding events to intracellular signaling cascades involves a dynamic interplay between ligands, receptors, and G proteins. The development of Förster resonance energy transfer and bioluminescence resonance energy transfer-based methods has now permitted the kinetic analysis of initial steps involved in G protein-coupled receptor-mediated signaling in live cells and in systems as diverse as neurotransmitter and hormone signaling. The direct measurement of ligand efficacy at the level of the receptor by Förster resonance energy transfer is also now possible and allows intrinsic efficacies of clinical drugs to be linked with the effect of receptor polymorphisms.

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