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Mac TT, Castinetti F, Bar C, Julia S, Pasquet M, Romanet P, Saveanu A, Mougel G, Fauquier T, Jullien N, Barlier A, Reynaud R, Brue T. Deficient anterior pituitary with common variable immune deficiency (DAVID syndrome): a new case and literature reports. J Neuroendocrinol 2023; 35:e13287. [PMID: 37322808 DOI: 10.1111/jne.13287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 03/29/2023] [Accepted: 04/28/2023] [Indexed: 06/17/2023]
Abstract
Deficient anterior pituitary with common variable immune deficiency (DAVID) syndrome is a rare condition characterized by adrenocorticotropic hormone (ACTH) deficiency and primary hypogammaglobulinemia. It is due to heterozygous mutations of the nuclear factor kappa-B subunit 2 (NFKB2) gene. Only a few isolated cases have been reported since its first description by our team. Through the international multicenter GENHYPOPIT network, we identified a new case of DAVID syndrome. We then conducted an extensive review of the DAVID syndrome cases published from 2012 to 2022. A 7-year-old boy was diagnosed with symptomatic hypoglycemia revealing ACTH deficiency. Laboratory tests showed asymptomatic hypogammaglobulinemia. He harbored a heterozygous point mutation in NFKB2 gene (c.2600C > T, p.Ala867Val). His management included hydrocortisone replacement treatment, and he also received subcutaneous immunoglobulins during the Covid-19 pandemic. We analyzed 28 cases of DAVID syndrome with ACTH deficiency. ACTH deficiency was the only hormone deficiency in 79% of patients, but some patients harbored growth hormone (GH) and thyroid stimulating hormone (TSH) deficiencies. The first presenting symptoms were sinus/pulmonary infections (82%, mean age of 3 years) and alopecia (mean age of 4.7 years). ACTH deficiency was the third presenting condition (mean age at diagnosis of 8.6 years). All patients had hypogammaglobulinemia (decreased IgA and IgM levels), and 57% of patients had at least one autoimmune manifestation. Heterozygous mutations at the 3'end of the NFKB2 gene, coding for the C-terminal domain of the protein, were identified in all cases. Better knowledge of DAVID syndrome will help clinicians make an early diagnosis to avoid life-threatening complications.
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Affiliation(s)
- Thi Thom Mac
- Aix Marseille University, UMR1251, MMG - Marseille Medical Genetics - MarMaRa Institute, Faculty of Medicine, Marseille, France
- Endocrinology Department, Hanoi Medical University Hospital, Hanoi, Vietnam
| | - Frederic Castinetti
- Aix Marseille University, UMR1251, MMG - Marseille Medical Genetics - MarMaRa Institute, Faculty of Medicine, Marseille, France
- Endocrinology Department, Conception Hospital - APHM, Marseille, France
| | - Céline Bar
- Department of Endocrinology and Metabolic Diseases, Children's Hospital, Toulouse Cedex 9, France
| | - Sophie Julia
- Department of Medical Genetics, Purpan Hospital, Pavillon Lefèbvre, Place du Docteur Baylac, Toulouse Cedex 9, France
| | - Marlene Pasquet
- Department of Hematology Oncology Immunology, Children's Hospital, Toulouse Cedex 9, France
| | - Pauline Romanet
- Aix Marseille University, UMR1251, MMG - Marseille Medical Genetics - MarMaRa Institute, Faculty of Medicine, Marseille, France
- Department of Molecular Biology, Conception Hospital - APHM, Marseille, France
| | - Alexandru Saveanu
- Aix Marseille University, UMR1251, MMG - Marseille Medical Genetics - MarMaRa Institute, Faculty of Medicine, Marseille, France
- Department of Molecular Biology, Conception Hospital - APHM, Marseille, France
| | - Gregory Mougel
- Aix Marseille University, UMR1251, MMG - Marseille Medical Genetics - MarMaRa Institute, Faculty of Medicine, Marseille, France
- Department of Molecular Biology, Conception Hospital - APHM, Marseille, France
| | - Teddy Fauquier
- Aix Marseille University, UMR1251, MMG - Marseille Medical Genetics - MarMaRa Institute, Faculty of Medicine, Marseille, France
| | - Nicolas Jullien
- INP - Institute of Neurophysiopathology, UMR 7051, Faculty of Medicine, Marseille, France
| | - Anne Barlier
- Aix Marseille University, UMR1251, MMG - Marseille Medical Genetics - MarMaRa Institute, Faculty of Medicine, Marseille, France
- Department of Molecular Biology, Conception Hospital - APHM, Marseille, France
| | - Rachel Reynaud
- Aix Marseille University, UMR1251, MMG - Marseille Medical Genetics - MarMaRa Institute, Faculty of Medicine, Marseille, France
- Multidisciplinary Pediatrics Department, Timone Hospital, Marseille, France
| | - Thierry Brue
- Aix Marseille University, UMR1251, MMG - Marseille Medical Genetics - MarMaRa Institute, Faculty of Medicine, Marseille, France
- Endocrinology Department, Conception Hospital - APHM, Marseille, France
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Marechal E, Poliard A, Henry K, Moreno M, Legrix M, Macagno N, Mondielli G, Fauquier T, Barlier A, Etchevers HC. Multiple congenital malformations arise from somatic mosaicism for constitutively active Pik3ca signaling. Front Cell Dev Biol 2022; 10:1013001. [PMID: 36353506 PMCID: PMC9637999 DOI: 10.3389/fcell.2022.1013001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Accepted: 10/07/2022] [Indexed: 11/17/2022] Open
Abstract
Recurrent missense mutations of the PIK3CA oncogene are among the most frequent drivers of human cancers. These often lead to constitutive activation of its product p110α, a phosphatidylinositol 3-kinase (PI3K) catalytic subunit. In addition to causing a broad range of cancers, the H1047R mutation is also found in affected tissues of a distinct set of congenital tumors and malformations. Collectively termed PIK3CA-related disorders (PRDs), these lead to overgrowth of brain, adipose, connective and musculoskeletal tissues and/or blood and lymphatic vessel components. Vascular malformations are frequently observed in PRD, due to cell-autonomous activation of PI3K signaling within endothelial cells. These, like most muscle, connective tissue and bone, are derived from the embryonic mesoderm. However, important organ systems affected in PRDs are neuroectodermal derivatives. To further examine their development, we drove the most common post-zygotic activating mutation of Pik3ca in neural crest and related embryonic lineages. Outcomes included macrocephaly, cleft secondary palate and more subtle skull anomalies. Surprisingly, Pik3ca-mutant subpopulations of neural crest origin were also associated with widespread cephalic vascular anomalies. Mesectodermal neural crest is a major source of non-endothelial connective tissue in the head, but not the body. To examine the response of vascular connective tissues of the body to constitutive Pik3ca activity during development, we expressed the mutation by way of an Egr2 (Krox20) Cre driver. Lineage tracing led us to observe new lineages that had normally once expressed Krox20 and that may be co-opted in pathogenesis, including vascular pericytes and perimysial fibroblasts. Finally, Schwann cell precursors having transcribed either Krox20 or Sox10 and induced to express constitutively active PI3K were associated with vascular and other tumors. These murine phenotypes may aid discovery of new candidate human PRDs affecting craniofacial and vascular smooth muscle development as well as the reciprocal paracrine signaling mechanisms leading to tissue overgrowth.
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Affiliation(s)
- Elise Marechal
- INSERM, MMG, U1251, MarMaRa Institute, Aix Marseille University, Marseille, France
| | - Anne Poliard
- URP 2496 Orofacial Pathologies, Imagery and Biotherapies, CNRS, GDR 2031 CREST-NET, Université Paris Cité, Montrouge, France
- School of Dentistry, Université Paris Cité, Montrouge, France
| | - Kilian Henry
- School of Dentistry, Université Paris Cité, Montrouge, France
| | - Mathias Moreno
- INSERM, MMG, U1251, MarMaRa Institute, Aix Marseille University, Marseille, France
| | - Mathilde Legrix
- INSERM, MMG, U1251, MarMaRa Institute, Aix Marseille University, Marseille, France
| | - Nicolas Macagno
- INSERM, MMG, U1251, MarMaRa Institute, Aix Marseille University, Marseille, France
| | - Grégoire Mondielli
- INSERM, MMG, U1251, MarMaRa Institute, Aix Marseille University, Marseille, France
| | - Teddy Fauquier
- INSERM, MMG, U1251, MarMaRa Institute, Aix Marseille University, Marseille, France
| | - Anne Barlier
- INSERM, MMG, U1251, MarMaRa Institute, Aix Marseille University, Marseille, France
- AP-HM, MMG, MarMaRa Institute, La Conception Hospital Laboratory of Molecular Biology, Marseille, France
| | - Heather C. Etchevers
- INSERM, MMG, U1251, CNRS, GDR 2031 CREST-NET, MarMaRa Institute, Aix Marseille University, Marseille, France
- *Correspondence: Heather C. Etchevers,
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Brue T, Saveanu A, Jullien N, Fauquier T, Castinetti F, Enjalbert A, Barlier A, Reynaud R. Lessons from monogenic causes of growth hormone deficiency. Annales d'Endocrinologie 2017; 78:77-79. [DOI: 10.1016/j.ando.2017.04.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Fauquier T, Chatonnet F, Picou F, Richard S, Fossat N, Aguilera N, Lamonerie T, Flamant F. Purkinje cells and Bergmann glia are primary targets of the TRα1 thyroid hormone receptor during mouse cerebellum postnatal development. Development 2014; 141:166-75. [PMID: 24346699 DOI: 10.1242/dev.103226] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Thyroid hormone is necessary for normal development of the central nervous system, as shown by the severe mental retardation syndrome affecting hypothyroid patients with low levels of active thyroid hormone. The postnatal defects observed in hypothyroid mouse cerebellum are recapitulated in mice heterozygous for a dominant-negative mutation of Thra, the gene encoding the ubiquitous TRα1 receptor. Using CRE/loxP-mediated conditional expression approach, we found that this mutation primarily alters the differentiation of Purkinje cells and Bergmann glia, two cerebellum-specific cell types. These primary defects indirectly affect cerebellum development in a global manner. Notably, the inward migration and terminal differentiation of granule cell precursors is impaired. Therefore, despite the broad distribution of its receptors, thyroid hormone targets few cell types that exert a predominant role in the network of cellular interactions that govern normal cerebellum maturation.
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Affiliation(s)
- Teddy Fauquier
- Université de Lyon, CNRS, INRA, Université Claude Bernard Lyon 1, École Normale Supérieure de Lyon, Institut de Génomique Fonctionnelle de Lyon, F-69364 Lyon, Cedex 07, France
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Picou F, Fauquier T, Chatonnet F, Richard S, Flamant F. Deciphering direct and indirect influence of thyroid hormone with mouse genetics. Mol Endocrinol 2014; 28:429-41. [PMID: 24617548 DOI: 10.1210/me.2013-1414] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
T3, the active form of thyroid hormone, binds nuclear receptors that regulate the transcription of a large number of genes in many cell types. Unraveling the direct and indirect effect of this hormonal stimulation, and establishing links between these molecular events and the developmental and physiological functions of the hormone, is a major challenge. New mouse genetics tools, notably those based on Cre/loxP technology, are suitable to perform a multiscale analysis of T3 signaling and achieve this task.
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Affiliation(s)
- Frédéric Picou
- Université de Lyon, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Claude Bernard Lyon 1, École Normale, Supérieure de Lyon, Institut de Génomique Fonctionnelle de Lyon, Lyon, France
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Denholm B, Hu N, Fauquier T, Caubit X, Fasano L, Skaer H. The tiptop/teashirt genes regulate cell differentiation and renal physiology in Drosophila. Development 2013; 140:1100-10. [PMID: 23404107 PMCID: PMC3583044 DOI: 10.1242/dev.088989] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The physiological activities of organs are underpinned by an interplay between the distinct cell types they contain. However, little is known about the genetic control of patterned cell differentiation during organ development. We show that the conserved Teashirt transcription factors are decisive for the differentiation of a subset of secretory cells, stellate cells, in Drosophila melanogaster renal tubules. Teashirt controls the expression of the water channel Drip, the chloride conductance channel CLC-a and the Leukokinin receptor (LKR), all of which characterise differentiated stellate cells and are required for primary urine production and responsiveness to diuretic stimuli. Teashirt also controls a dramatic transformation in cell morphology, from cuboidal to the eponymous stellate shape, during metamorphosis. teashirt interacts with cut, which encodes a transcription factor that underlies the differentiation of the primary, principal secretory cells, establishing a reciprocal negative-feedback loop that ensures the full differentiation of both cell types. Loss of teashirt leads to ineffective urine production, failure of homeostasis and premature lethality. Stellate cell-specific expression of the teashirt paralogue tiptop, which is not normally expressed in larval or adult stellate cells, almost completely rescues teashirt loss of expression from stellate cells. We demonstrate conservation in the expression of the family of tiptop/teashirt genes in lower insects and establish conservation in the targets of Teashirt transcription factors in mouse embryonic kidney.
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Affiliation(s)
- Barry Denholm
- Department of Zoology, Downing Street, Cambridge CB2 3EJ, UK.
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D'Aléo A, Bourdolle A, Brustlein S, Fauquier T, Grichine A, Duperray A, Baldeck PL, Andraud C, Brasselet S, Maury O. Ytterbium-Based Bioprobes for Near-Infrared Two-Photon Scanning Laser Microscopy Imaging. Angew Chem Int Ed Engl 2012; 51:6622-5. [DOI: 10.1002/anie.201202212] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Indexed: 11/08/2022]
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D'Aléo A, Bourdolle A, Brustlein S, Fauquier T, Grichine A, Duperray A, Baldeck PL, Andraud C, Brasselet S, Maury O. Ytterbium-Based Bioprobes for Near-Infrared Two-Photon Scanning Laser Microscopy Imaging. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201202212] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Picou F, Fauquier T, Chatonnet F, Flamant F. A bimodal influence of thyroid hormone on cerebellum oligodendrocyte differentiation. Mol Endocrinol 2012; 26:608-18. [PMID: 22361821 DOI: 10.1210/me.2011-1316] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Thyroid hormone (T(3)) can trigger a massive differentiation of cultured oligodendrocytes precursor cells (OPC) by binding the nuclear T(3) receptor α1 (TRα1). Whether this reflects a physiological function of TRα1 remains uncertain. Using a recently generated mouse model, in which CRE/loxP recombination is used to block its function, we show that TRα1 acts at two levels for the in vivo differentiation of OPC in mouse cerebellum. At the early postnatal stage, it promotes the secretion of several neurotrophic factors by acting in Purkinje neurons and astrocytes, defining an environment suitable for OPC differentiation. At later stages, TRα1 acts in a cell-autonomous manner to ensure the complete arrest of OPC proliferation. These data explain contradictory observations made on various models and outline the importance of T(3) signaling both for synchronizing postnatal neurodevelopment and restraining OPC proliferation in adult brain.
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Affiliation(s)
- Frédéric Picou
- Université Lyon 1, Centre National de la Recherche Scientifique, Institut de la Recherché Agronomique, Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France
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Chatonnet F, Picou F, Fauquier T, Flamant F. Thyroid hormone action in cerebellum and cerebral cortex development. J Thyroid Res 2011; 2011:145762. [PMID: 21765985 PMCID: PMC3134109 DOI: 10.4061/2011/145762] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 04/09/2011] [Indexed: 01/30/2023] Open
Abstract
Thyroid hormones (TH, including the prohormone thyroxine (T4) and its active deiodinated derivative 3,3′,5-triiodo-L-thyronine (T3)) are important regulators of vertebrates neurodevelopment. Specific transporters and deiodinases are required to ensure T3 access to the developing brain. T3 activates a number of differentiation processes in neuronal and glial cell types by binding to nuclear receptors, acting directly on transcription. Only few T3 target genes are currently known. Deeper investigations are urgently needed, considering that some chemicals present in food are believed to interfere with T3 signaling with putative neurotoxic consequences.
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Affiliation(s)
- Fabrice Chatonnet
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Université de Lyon, UMR CNRS 5242, 46 allée d'Italie, 69364 Lyon Cedex 07, France
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Fauquier T, Romero E, Picou F, Chatonnet F, Nguyen XN, Quignodon L, Flamant F. Severe impairment of cerebellum development in mice expressing a dominant-negative mutation inactivating thyroid hormone receptor alpha1 isoform. Dev Biol 2011; 356:350-8. [PMID: 21621530 DOI: 10.1016/j.ydbio.2011.05.657] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Revised: 05/10/2011] [Accepted: 05/13/2011] [Indexed: 01/28/2023]
Abstract
Thyroid hormone deficiency is known to deeply affect cerebellum post-natal development. We present here a detailed analysis of the phenotype of a recently generated mouse model, expressing a dominant-negative TRα1 mutation. Although hormonal level is not affected, the cerebellum of these mice displays profound alterations in neuronal and glial differentiation, which are reminiscent of congenital hypothyroidism, indicating a predominant function of this receptor isoform in normal cerebellum development. Some of the observed effects might result from the cell autonomous action of the mutation, while others are more likely to result from a reduction in neurotrophic factor production.
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Affiliation(s)
- Teddy Fauquier
- Université de Lyon, CNRS, INRA, Université Claude Bernard Lyon 1, École Normale, Supérieure de Lyon, Institut de Génomique Fonctionnelle de Lyon, France
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Chatonnet F, Fauquier T, Picou F, Guyot R, Flamant F. Hormone thyroïdienne et développement du cervelet : effets directs ou indirects ? Annales d'Endocrinologie 2011; 72:99-102. [DOI: 10.1016/j.ando.2011.03.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Abstract
The traditional view holds that the anterior pituitary is an endocrine gland with a complex and heterogeneous distribution of cells throughout the parenchyma. Thus, a long-distance mode of intraorgan communication is not usually taken into account in our understanding of pituitary functioning. However, recent in situ pituitary studies have begun to unveil a hitherto unknown route of large-scale information transfer within the pituitary. Agranular folliculostellate cells - the sixth type of pituitary cell initially discovered almost half a century ago - are the functional units of a dynamically active cell network wiring the whole gland. Because folliculostellate cells communicate with their endocrine neighbors, this opens the door to considering the pituitary as a cellular puzzle more ordered than was first thought. Hence, cell networking within the pituitary gland could have a privileged role in coordinating the activities of distant cells in both physiological and pathological conditions.
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Fauquier T, Guérineau NC, McKinney RA, Bauer K, Mollard P. Folliculostellate cell network: a route for long-distance communication in the anterior pituitary. Proc Natl Acad Sci U S A 2001; 98:8891-6. [PMID: 11438713 PMCID: PMC37531 DOI: 10.1073/pnas.151339598] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.3] [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: 11/18/2022] Open
Abstract
All higher life forms critically depend on hormones being rhythmically released by the anterior pituitary. The proper functioning of this master gland is dynamically controlled by a complex set of regulatory mechanisms that ultimately determine the fine tuning of the excitable endocrine cells, all of them heterogeneously distributed throughout the gland. Here, we provide evidence for an intrapituitary communication system by which information is transferred via the network of nonendocrine folliculostellate (FS) cells. Local electrical stimulation of FS cells in acute pituitary slices triggered cytosolic calcium waves, which propagated to other FS cells by signaling through gap junctions. Calcium wave initiation was because of the membrane excitability of FS cells, hitherto classified as silent cells. FS cell coupling could relay information between opposite regions of the gland. Because FS cells respond to central and peripheral stimuli and dialogue with endocrine cells, the form of large-scale intrapituitary communication described here may provide an efficient mechanism that orchestrates anterior pituitary functioning in response to physiological needs.
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Affiliation(s)
- T Fauquier
- Institut National de la Santé et de la Recherche Médicale Unité 469, Centre National de la Recherche Scientifique-INSERM de Pharmacologie-Endocrinologie, 141 Rue de la Cardonille, 34094 Montpellier Cedex 5, France
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Vallentin A, Prévostel C, Fauquier T, Bonnefont X, Joubert D. Membrane targeting and cytoplasmic sequestration in the spatiotemporal localization of human protein kinase C alpha. J Biol Chem 2000; 275:6014-21. [PMID: 10681596 DOI: 10.1074/jbc.275.8.6014] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [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: 11/06/2022] Open
Abstract
In order to map the molecular determinants that dictate the subcellular localization of human protein kinase C alpha (hPKCalpha), full-length and deletion mutants of hPKCalpha were tagged with the green fluorescent protein (GFP) and transiently expressed in GH3B6 cells. We found that upon thyrotropin-releasing hormone (TRH) or phorbol 12-myristate 13-acetate stimulation, hPKCalpha-GFP was localized exclusively in regions of cell-cell contacts. Surprisingly, PKCalpha failed to translocate in single cells despite the presence of TRH receptors, as attested by the TRH-induced rise in intracellular calcium concentration in these cells. TRH-stimulated translocation of hPKCalpha-GFP from the cytoplasm to cell-cell contacts was a biphasic process: a fast (measured in seconds) and transient phase, followed by a slower (approximately 1 hour) and long lasting phase. The latter and the translocation induced by phorbol 12-myristate 13-acetate absolutely required the N-terminal V1 region. In contrast to the full-length hPKCalpha, the N-terminal regulatory domain alone or associated with the V3 hinge region was spontaneously and uniformly localized at the plasma membrane of single and apposed cells. However, treatment with the calcium chelator BAPTA/AM induced a differential cytoplasmic/nuclear redistribution of the regulatory domain, depending on its association with V3, which suggests the existence of a mechanism controlling the cytoplasmic sequestration of inactive hPKCalpha and involving the V3 region. By using other deletion mutants, we were able to map the sequence required for this sequestration to the C2+V3 regions. This work points to the existence of a complex interplay between membrane targeting and cytoplasmic sequestration in the control of the spatiotemporal localization of hPKCalpha.
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Affiliation(s)
- A Vallentin
- INSERM U469, 141 rue de la Cardonille, 34094 Montpellier cedex 5, France
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