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Hertz H, Blancas-Velazquez AS, Rath MF. The role of homeobox gene-encoded transcription factors in regulation of phototransduction: Implementing the primary pinealocyte culture as a photoreceptor model. J Pineal Res 2021; 71:e12753. [PMID: 34129741 DOI: 10.1111/jpi.12753] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 06/14/2021] [Accepted: 06/14/2021] [Indexed: 10/21/2022]
Abstract
Homeobox genes encode transcription factors controlling development; however, a number of homeobox genes are expressed postnatally specifically in melatonin-producing pinealocytes of the pineal gland and photoreceptors of the retina along with transcripts devoted to melatonin synthesis and phototransduction. Homeobox genes regulate melatonin synthesis in pinealocytes, but some homeobox genes also seem to be involved in regulation of retinal phototransduction. Due to the lack of photoreceptor models, we here introduce the rat pinealocyte culture as an in vitro model for studying retinal phototransduction. Systematic qPCR analyses were performed on the rat retina and pineal gland in 24 hour in vivo series and on primary cultures of rat pinealocytes: All homeobox genes and melatonin synthesis components, as well as nine out of ten phototransduction genes, were readily detectable in all three experimental settings, confirming molecular similarity between cultured pinealocytes and in vivo retinal tissue. 24 hours circadian expression was mostly confined to transcripts in the pineal gland, including a novel rhythm in arrestin (Sag). Individual knockdown of the homeobox genes orthodenticle homeobox 2 (Otx2), cone-rod homeobox (Crx) and LIM homeobox 4 (Lhx4) in pinealocyte culture using siRNA resulted in specific downregulation of transcripts representing all levels of phototransduction; thus, all phototransduction genes studied in culture were affected by one or several siRNA treatments. Histological colocalization of homeobox and phototransduction transcripts in the rat retinal photoreceptor was confirmed by RNAscope in situ hybridization, thus suggesting that homeobox gene-encoded transcription factors control postnatal expression of phototransduction genes in the retinal photoreceptor.
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Affiliation(s)
- Henrik Hertz
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Martin Fredensborg Rath
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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2
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Klein DC. The 2004 Aschoff/Pittendrigh Lecture: Theory of the Origin of the Pineal Gland— A Tale of Conflict and Resolution. J Biol Rhythms 2016; 19:264-79. [PMID: 15245646 DOI: 10.1177/0748730404267340] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A theory is presented that explains the evolution of the pinealocyte from the common ancestral photoreceptor of both the pinealocyte and retinal photoreceptor. Central to the hypothesis is the previously unrecognized conflict between the two chemistries that define these cells—melatonin synthesis and retinoid recycling. At the core of the conflict is the formation of adducts composed of two molecules of retinaldehyde and one molecule of serotonin, analogous to formation in the retina of the toxic bis-retinyl ethanolamine (A2E). The hypothesis argues that early in chordate evolution, at a point before the genes required for melatonin synthesis were acquired, retinaldehyde—which is essential for photon capture—was depleted by reacting with naturally occurring arylalkylamines (tyramine, serotonin, tryptamine, phenylethylamine) and xenobiotic arylalkylamines. This generated toxic bis-retinyl arylalkylamines (A2AAs). The acquisition of arylalkylamine N-acetyltransferase (AANAT) prevented this by N-acetylating the arylalkylamines. HydroxyindoleOmethyltransferase enhanced detoxification in the primitive photoreceptor by increasing the lipid solubility of serotonin and bis-retinyl serotonin. After the serotonin. melatonin pathway was established, the next step leading toward the pinealocyte was the evolution of a daily rhythm in melatonin and the capacity to recognize it as a signal of darkness. The shift in melatonin from metabolic garbage to information developed a pressure to improve the reliability of the melatonin signal, which in turn led to higher levels of serotonin in the photodetector. This generated the conflict between serotonin and retinaldehyde, which was resolved by the cellular segregation of the two chemistries. The result, in primates, is a pineal gland that does not detect light and a retinal photodetector that does not make melatonin. High levels of AANAT in the latter tissue might serve the same function AANAT had when first acquired— prevention of A2AA formation.
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Affiliation(s)
- David C Klein
- Section on Neuroendocrinology, Laboratory of Developmental Neurobiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4480, USA.
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3
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Bregier C, Krzemień-Ojak L, Włoga D, Jerka-Dziadosz M, Joachimiak E, Batko K, Filipiuk I, Smietanka U, Gaertig J, Fabczak S, Fabczak H. PHLP2 is essential and plays a role in ciliogenesis and microtubule assembly in Tetrahymena thermophila. J Cell Physiol 2013; 228:2175-89. [PMID: 23588994 DOI: 10.1002/jcp.24384] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 04/04/2013] [Indexed: 01/23/2023]
Abstract
Recent studies have implicated the phosducin-like protein-2 (PHLP2) in regulation of CCT, a chaperonin whose activity is essential for folding of tubulin and actin. However, the exact molecular function of PHLP2 is unclear. Here we investigate the significance of PHLP2 in a ciliated unicellular model, Tetrahymena thermophila, by deleting its single homolog, Phlp2p. Cells lacking Phlp2p became larger and died within 96 h. Overexpressed Phlp2p-HA localized to cilia, basal bodies, and cytosol without an obvious change in the phenotype. Despite similar localization, overexpressed GFP-Phlp2p caused a dominant-negative effect. Cells overproducing GFP-Phlp2p had decreased rates of proliferation, motility and phagocytosis, as compared to wild type cells or cells overproducing a non-tagged Phlp2p. Growing GFP-Phlp2p-overexpressing cells had fewer cilia and, when deciliated, failed to regenerate cilia, indicating defects in cilia assembly. Paclitaxel-treated GFP-Phlp2p cells failed to elongate cilia, indicating a change in the microtubules dynamics. The pattern of ciliary and cytosolic tubulin isoforms on 2D gels differed between wild type and GFP-Phlp2p-overexpressing cells. Thus, in Tetrahymena, PhLP2 is essential and under specific experimental conditions its activity affects tubulin and microtubule-dependent functions including cilia assembly.
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Affiliation(s)
- Cezary Bregier
- Department of Cell Biology, Nencki Institute of Experimental Biology, Warsaw, Poland
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4
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Rath MF, Rohde K, Klein DC, Møller M. Homeobox genes in the rodent pineal gland: roles in development and phenotype maintenance. Neurochem Res 2013; 38:1100-12. [PMID: 23076630 PMCID: PMC3570627 DOI: 10.1007/s11064-012-0906-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 09/19/2012] [Accepted: 10/04/2012] [Indexed: 12/12/2022]
Abstract
The pineal gland is a neuroendocrine gland responsible for nocturnal synthesis of melatonin. During early development of the rodent pineal gland from the roof of the diencephalon, homeobox genes of the orthodenticle homeobox (Otx)- and paired box (Pax)-families are expressed and are essential for normal pineal development consistent with the well-established role that homeobox genes play in developmental processes. However, the pineal gland appears to be unusual because strong homeobox gene expression persists in the pineal gland of the adult brain. Accordingly, in addition to developmental functions, homeobox genes appear to be key regulators in postnatal phenotype maintenance in this tissue. In this paper, we review ontogenetic and phylogenetic aspects of pineal development and recent progress in understanding the involvement of homebox genes in rodent pineal development and adult function. A working model is proposed for understanding the sequential action of homeobox genes in controlling development and mature circadian function of the mammalian pinealocyte based on knowledge from detailed developmental and daily gene expression analyses in rats, the pineal phenotypes of homebox gene-deficient mice and studies on development of the retinal photoreceptor; the pinealocyte and retinal photoreceptor share features not seen in other tissues and are likely to have evolved from the same ancestral photodetector cell.
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Affiliation(s)
- Martin F Rath
- Department of Neuroscience and Pharmacology, Panum Institute 24.2, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, Copenhagen 2200, Denmark.
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5
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Putonti C, Quach B, Kooistra RL, Kanzok SM. The evolution and putative function of phosducin-like proteins in the malaria parasite Plasmodium. INFECTION GENETICS AND EVOLUTION 2012; 13:49-55. [PMID: 22995278 DOI: 10.1016/j.meegid.2012.08.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 08/29/2012] [Accepted: 08/31/2012] [Indexed: 01/12/2023]
Abstract
Ubiquitous to the proteomes of all living species is the presence of proteins containing the thioredoxin (Trx)-domain. The best characterized Trx-domain containing proteins include the enzymes involved in cellular redox metabolism facilitated by their cysteine-containing active site. But not all members of the Trx-fold superfamily exhibit this catalytic motif, e.g., the phosducin-like (PhLP) family of proteins. Genome sequencing efforts have uncovered new Trx-domain containing proteins, and their redox activity and cellular functions have yet to be determined. The genome of the malaria parasite Plasmodium contains multiple thioredoxins and thioredoxin-like proteins which are of considerable interest given their role in the parasite's antioxidant defense. While adaptations within the Trx-domain have been studied, primarily with respect to redox active structures, PhLP proteins have not been examined. Using the uncharacterized phosducin-like protein from Plasmodium berghei PhLP-1, we investigated the evolution of PhLP proteins across all branches of the tree of life. As a result of our analysis, we have discovered the presence of two additional PhLP proteins in Plasmodium, PhLP-2 and PhLP-3. Sequence homology with annotated PhLP proteins in other species confirms that the Plasmodium PhLP-2 and PhLP-3 belong to the PhLP family of proteins. Furthermore, as a result of our analysis we hypothesize that the PhLP-2 thioredoxin was lost over time given its absence from higher-order eukaryotes. Probing deeper into the putative function of these proteins, inspection of the active sites indicate that PbPhLP-1 and PbPhLP-2 may be redox active while PbPhLP-3 is very likely not. The results of this phylogenetic study provide insight into the emergence of this family of Trx-domain containing proteins.
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Affiliation(s)
- Catherine Putonti
- Department of Biology, Loyola University Chicago, 1032 W Sheridan Rd, Chicago, IL 60660, USA.
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6
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Ochocinska MJ, Muñoz EM, Veleri S, Weller JL, Coon SL, Pozdeyev N, Iuvone PM, Goebbels S, Furukawa T, Klein DC. NeuroD1 is required for survival of photoreceptors but not pinealocytes: results from targeted gene deletion studies. J Neurochem 2012; 123:44-59. [PMID: 22784109 DOI: 10.1111/j.1471-4159.2012.07870.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
NeuroD1 encodes a basic helix-loop-helix transcription factor involved in the development of neural and endocrine structures, including the retina and pineal gland. To determine the effect of NeuroD1 knockout in these tissues, a Cre/loxP recombination strategy was used to target a NeuroD1 floxed gene and generate NeuroD1 conditional knockout (cKO) mice. Tissue specificity was conferred using Cre recombinase expressed under the control of the promoter of Crx, which is selectively expressed in the pineal gland and retina. At 2 months of age, NeuroD1 cKO retinas have a dramatic reduction in rod- and cone-driven electroretinograms and contain shortened and disorganized outer segments; by 4 months, NeuroD1 cKO retinas are devoid of photoreceptors. In contrast, the NeuroD1 cKO pineal gland appears histologically normal. Microarray analysis of 2-month-old NeuroD1 cKO retina and pineal gland identified a subset of genes that were affected 2-100-fold; in addition, a small group of genes exhibit altered differential night/day expression. Included in the down-regulated genes are Aipl1, which is necessary to prevent retinal degeneration, and Ankrd33, whose protein product is selectively expressed in the outer segments. These findings suggest that NeuroD1 may act through Aipl1 and other genes to maintain photoreceptor homeostasis.
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Affiliation(s)
- Margaret J Ochocinska
- Section on Neuroendocrinology, Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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7
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The identification of phosducin as a novel candidate gene for hypertension and its role in sympathetic activation. Curr Opin Nephrol Hypertens 2011; 20:118-24. [DOI: 10.1097/mnh.0b013e3283432e05] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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8
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Beetz N, Hein L. The physiological roles of phosducin: from retinal function to stress-dependent hypertension. Cell Mol Life Sci 2011; 68:599-612. [PMID: 21069424 PMCID: PMC11114795 DOI: 10.1007/s00018-010-0550-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 09/09/2010] [Accepted: 09/29/2010] [Indexed: 01/26/2023]
Abstract
In the time since its discovery, phosducin's functions have been intensively studied both in vivo and in vitro. Phosducin's most important biochemical feature in in vitro studies is its binding to heterotrimeric G protein βγ-subunits. Data on phosducin's in vivo relevance, however, have only recently been published but expand the range of biological actions, as shown both in animal models as well as in human studies. This review gives an overview of different aspects of phosducin biology ranging from structure, phylogeny of phosducin family members, posttranscriptional modification, biochemical features, localization and levels of expression to its physiological functions. Special emphasis will be placed on phosducin's function in the regulation of blood pressure. In the second part of this article, findings concerning cardiovascular regulation and their clinical relevance will be discussed on the basis of recently published data from gene-targeted mouse models and human genetic studies.
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Affiliation(s)
- Nadine Beetz
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Albertstrasse 25, 79104 Freiburg, Germany
- Centre for Biological Signaling Studies (bioss), University of Freiburg, Freiburg, Germany
| | - Lutz Hein
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Albertstrasse 25, 79104 Freiburg, Germany
- Centre for Biological Signaling Studies (bioss), University of Freiburg, Freiburg, Germany
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9
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Sobierajska K, Joachimiak E, Bregier C, Fabczak S, Fabczak H. Effect of phosducin silencing on the photokinetic motile response of Blepharisma japonicum. Photochem Photobiol Sci 2010; 10:19-24. [PMID: 20976371 DOI: 10.1039/c0pp00221f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The coloured ciliate Blepharisma japonicum changes swimming velocity (positive photokinesis) and elongates its body in response to a prolonged illumination. We have recently proposed that alterations in the phosphorylation level of the ciliate phosducin (Pdc) may be involved in light-induced cell elongation, which in turn affects the interaction of βγ-dimer of G-proteins (Gβγ) with β-tubulin and subsequent cytoskeletal remodelling. The cellular mechanism that governs the photokinetic effect in this ciliate has not been elucidated. In the present study, we utilise real-time PCR to demonstrate that the levels of ciliate Pdc mRNA are significantly reduced in Pdc-RNAi-treated cells compared to cells fed with bacteria carrying the empty vector (control cells). Using western immunoblotting, we confirmed that these cells treated with Pdc-RNAi expressed a substantially lower level of the Pdc protein. The assay also revealed that in ciliates treated with Pdc-RNAi and exposed to light, the cytosolic level of Gβ (~36 kDa) was reduced, whereas the level of Gβ localized to the membrane (~32 kDa) was increased compared to control cells. In addition, behavioural analysis of the cells indicated a substantial reduction of photokinesis. The findings in this study provide additional characterization of the functional properties of the ciliate Pdc protein and we discuss a likely role for this phosphoprotein in the photokinetic phenomenon of the ciliate protist Blepharisma.
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Affiliation(s)
- Katarzyna Sobierajska
- Department of Cell Biology, Nencki Institute of Experimental Biology, 3 Pasteur Street, 02-093, Warsaw, Poland
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10
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Abstract
The defining feature of the pineal gland is the capacity to function as a melatonin factory that operates on a approximately 24 h schedule, reflecting the unique synthetic capacities of the pinealocyte. Melatonin synthesis is typically elevated at night and serves to provide the organism with a signal of nighttime. Melatonin levels can be viewed as hands of the clock. Issues relating to the evolutionary events leading up to the immergence of this system have not received significant attention. When did melatonin synthesis appear in the evolutionary line leading to vertebrates? When did a distinct pineal gland first appear? What were the forces driving this evolutionary trend? As more knowledge has grown about the pinealocyte and the relationship it has to retinal photoreceptors, it has become possible to generate a plausible hypothesis to explain how the pineal gland and the melatonin rhythm evolved. At the heart of the hypothesis is the melatonin rhythm enzyme arylalkylamine N-acetyltransferase (AANAT). The advances supporting the hypothesis will be reviewed here and expanded beyond the original foundation; the hypothesis and its implications will be addressed.
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Affiliation(s)
- David C Klein
- Department of Health and Human Services, Section on Neuroendocrinology, Office of the Scientific Director, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20893, USA.
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11
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Loring RH. The Molecular Basis of Curaremimetic Snake Neurotoxin Specificity for Neuronal Nicotinic Receptor Subtypes. ACTA ACUST UNITED AC 2008. [DOI: 10.3109/15569549309033109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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12
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Pozdeyev N, Tosini G, Li L, Ali F, Rozov S, Lee RH, Iuvone PM. Dopamine modulates diurnal and circadian rhythms of protein phosphorylation in photoreceptor cells of mouse retina. Eur J Neurosci 2008; 27:2691-700. [PMID: 18547251 DOI: 10.1111/j.1460-9568.2008.06224.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many aspects of photoreceptor metabolism are regulated as diurnal or circadian rhythms. The nature of the signals that drive rhythms in mouse photoreceptors is unknown. Dopamine amacrine cells in mouse retina express core circadian clock genes, leading us to test the hypothesis that dopamine regulates rhythms of protein phosphorylation in photoreceptor cells. To this end we investigated the phosphorylation of phosducin, an abundant photoreceptor-specific phosphoprotein. In mice exposed to a daily light-dark cycle, robust daily rhythms of phosducin phosphorylation and retinal dopamine metabolism were observed. Phospho-phosducin levels were low during the daytime and high at night, and correlated negatively with levels of the dopamine metabolite 3,4-dihydroxyphenylacetic acid. The effect of light on phospho-phosducin levels was mimicked by pharmacological activation of dopamine D4 receptors. The amplitude of the diurnal rhythm of phospho-phosducin was reduced by > 50% in D4 receptor-knockout mice, due to higher daytime levels of phospho-phosducin. In addition, the daytime level of phospho-phosducin was significantly elevated by L-745,870, a dopamine D4 receptor antagonist. These data indicate that dopamine and other light-dependent processes cooperatively regulate the diurnal rhythm of phosducin phosphorylation. Under conditions of constant darkness a circadian rhythm of phosducin phosphorylation was observed, which correlated negatively with the circadian rhythm of 3,4-dihydroxyphenylacetic acid levels. The circadian fluctuation of phospho-phosducin was completely abolished by constant infusion of L-745,870, indicating that the rhythm of phospho-phosducin level is driven by dopamine. Thus, dopamine release in response to light and circadian clocks drives daily rhythms of protein phosphorylation in photoreceptor cells.
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Affiliation(s)
- Nikita Pozdeyev
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, USA
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13
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Willardson BM, Howlett AC. Function of phosducin-like proteins in G protein signaling and chaperone-assisted protein folding. Cell Signal 2007; 19:2417-27. [PMID: 17658730 PMCID: PMC2095786 DOI: 10.1016/j.cellsig.2007.06.013] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Accepted: 06/15/2007] [Indexed: 01/08/2023]
Abstract
Members of the phosducin gene family were initially proposed to act as down-regulators of G protein signaling by binding G protein betagamma dimers (Gbetagamma) and inhibiting their ability to interact with G protein alpha subunits (Galpha) and effectors. However, recent findings have over-turned this hypothesis by showing that most members of the phosducin family act as co-chaperones with the cytosolic chaperonin complex (CCT) to assist in the folding of a variety of proteins from their nascent polypeptides. In fact rather than inhibiting G protein pathways, phosducin-like protein 1 (PhLP1) has been shown to be essential for G protein signaling by catalyzing the folding and assembly of the Gbetagamma dimer. PhLP2 and PhLP3 have no role in G protein signaling, but they appear to assist in the folding of proteins essential in regulating cell cycle progression as well as actin and tubulin. Phosducin itself is the only family member that does not participate with CCT in protein folding, but it is believed to have a specific role in visual signal transduction to chaperone Gbetagamma subunits as they translocate to and from the outer and inner segments of photoreceptor cells during light-adaptation.
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Affiliation(s)
- Barry M Willardson
- Department of Chemistry and Biochemistry, C-100 BNSN, Brigham Young University Provo, Utah 84602, USA.
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14
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Muñoz EM, Bailey MJ, Rath MF, Shi Q, Morin F, Coon SL, Møller M, Klein DC. NeuroD1: developmental expression and regulated genes in the rodent pineal gland. J Neurochem 2007; 102:887-99. [PMID: 17630985 DOI: 10.1111/j.1471-4159.2007.04605.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
NeuroD1/BETA2, a member of the bHLH transcription factor family, is known to influence the fate of specific neuronal, endocrine and retinal cells. We report here that NeuroD1 mRNA is highly abundant in the developing and adult rat pineal gland. Pineal expression begins in the 17-day embryo at which time it is also detectable in other brain regions. Expression in the pineal gland increases during the embryonic period and is maintained thereafter at levels equivalent to those found in the cerebellum and retina. In contrast, NeuroD1 mRNA decreases markedly in non-cerebellar brain regions during development. Pineal NeuroD1 levels are similar during the day and night, and do not appear to be influenced by sympathetic neural input. Gene expression analysis of the pineal glands from neonatal NeuroD1 knockout mice identifies 127 transcripts that are down-regulated (>twofold, p < 0.05) and 16 that are up-regulated (>twofold, p < 0.05). According to quantitative RT-PCR, the most dramatically down-regulated gene is kinesin family member 5C ( approximately 100-fold) and the most dramatically up-regulated gene is glutamic acid decarboxylase 1 ( approximately fourfold). Other impacted transcripts encode proteins involved in differentiation, development, signal transduction and trafficking. These findings represent the first step toward elucidating the role of NeuroD1 in the rodent pinealocyte.
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Affiliation(s)
- Estela M Muñoz
- Section on Neuroendocrinology, Office of the Scientific Director, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
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15
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Spessert R, Heil K, Gupta BB, Vollrath L. Biphasic 24-Hour Variations in Cyclic GMP Accumulation in the Rat Pineal Gland Are Due to Corresponding Changes in the Activity of Cytosolic and Particulate Guanylate Cyclase. J Neurochem 2006; 59:2081-6. [PMID: 1359014 DOI: 10.1111/j.1471-4159.1992.tb10098.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Various parameters of the rat pineal gland display a 24-h rhythm. However, nothing is known about possible 24-h variations in cyclic GMP (cGMP) metabolism. In the present study, 24-h variations in pineal gland cGMP accumulation were investigated by determining the increase in cGMP level with and without inhibitors of phosphodiesterase at different time points over a light/dark cycle (12/12 h). Furthermore, the activity of guanylate cyclase (GC) was determined under substrate-saturated conditions regarding the cytosolic and particulate forms of the enzyme. It has been found that cGMP accumulation and GC activity display biphasic 24-h variations with two peaks--one approximately 7 h after lights "on" and the other approximately 7 h after lights "off." The activity of cytosolic GC remains unchanged in the presence of the nitric oxide (NO) synthesis inhibitor N-monomethyl-L-arginine, indicating that 24-h variations in the activity do not reflect changes in the synthesis of the GC stimulator NO.
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Affiliation(s)
- R Spessert
- Department of Anatomy, Johannes Gutenberg University, Mainz, F.R.G
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Sobierajska K, Fabczak H, Fabczak S. Photosensory transduction in unicellular eukaryotes: A comparison between related ciliates Blepharisma japonicum and Stentor coeruleus and photoreceptor cells of higher organisms. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2006; 83:163-71. [PMID: 16488618 DOI: 10.1016/j.jphotobiol.2006.01.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2005] [Revised: 12/29/2005] [Accepted: 01/07/2006] [Indexed: 11/27/2022]
Abstract
Blepharisma japonicum and Stentor coeruleus are related ciliates, conspicuous by their photosensitivity. They are capable of avoiding illuminated areas in the surrounding medium, gathering exclusively in most shaded places (photodispersal). Such behaviour results mainly from motile photophobic response occurring in ciliates. This light-avoiding response is observed during a relatively rapid increase in illumination intensity (light stimulus) and consists of cessation of cell movement, a period of backward movement (ciliary reversal), followed by a forward swimming, usually in a new direction. The photosensitivity of ciliates is ascribed to their photoreceptor system, composed of pigment granules, containing the endogenous photoreceptor -- blepharismin in Blepharisma japonicum, and stentorin in Stentor coeruleus. A light stimulus, applied to both ciliates activates specific stimulus transduction processes leading to the electrical changes at the plasma membrane, correlated with a ciliary reversal during photophobic response. These data indicate that both ciliates Blepharisma japonicum and Stentor coeruleus, the lower eukaryotes, are capable of transducing the perceived light stimuli in a manner taking place in some photoreceptor cells of higher eukaryotes. Similarities and differences concerning particular stages of light transduction in eukaryotes at different evolutional levels are discussed in this article.
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Affiliation(s)
- Katarzyna Sobierajska
- Department of Cell Biology, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3, Pasteur Street, PL 02-093 Warsaw, Poland
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17
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Seo JA, Yu JH. The phosducin-like protein PhnA is required for Gbetagamma-mediated signaling for vegetative growth, developmental control, and toxin biosynthesis in Aspergillus nidulans. EUKARYOTIC CELL 2006; 5:400-10. [PMID: 16467480 PMCID: PMC1405901 DOI: 10.1128/ec.5.2.400-410.2006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Phosducin or phosducin-like protein (PhLP) is a positive regulator of Gbetagamma activity. The Gbeta (SfaD) and Ggamma (GpgA) subunits function in vegetative growth and developmental control in the model filamentous fungus Aspergillus nidulans. To better understand the nature of Gbetagamma-mediated signaling, phnA, encoding an A. nidulans PhLP, has been studied. Deletion of phnA resulted in phenotypes almost identical to those caused by deletion of sfaD, i.e., reduced biomass, asexual sporulation in liquid submerged culture, and defective fruiting body formation, suggesting that PhnA is necessary for Gbeta function. The requirement for the RGS protein FlbA in asexual sporulation could be bypassed by the DeltaphnA mutation, indicating that PhnA functions in FlbA-controlled vegetative growth signaling, primarily mediated by the heterotrimeric G protein composed of FadA (Galpha), SfaD, and GpgA. However, whereas deletion of fadA restored both asexual sporulation and the production of sterigmatocystin (ST), deletion of sfaD, gpgA, or phnA failed to restore ST production in the DeltaflbA mutant. Further studies revealed that SfaD, GpgA, and PhnA are necessary for the expression of aflR, encoding the transcriptional activator for the ST biosynthetic genes, and subsequent ST biosynthesis. Overexpression of aflR bypassed the need for SfaD in ST production, indicating that the results of SfaD-mediated signaling may include transcriptional activation of aflR. Potential differential roles of FadA, Gbetagamma, and FlbA in controlling ST biosynthesis are further discussed.
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Affiliation(s)
- Jeong-Ah Seo
- Department of Food Microbiology and Toxicology, Food Research Institute, University of Wisconsin, Madison, WI 53706, USA
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Rath MF, Muñoz E, Ganguly S, Morin F, Shi Q, Klein DC, Møller M. Expression of the Otx2 homeobox gene in the developing mammalian brain: embryonic and adult expression in the pineal gland. J Neurochem 2006; 97:556-66. [PMID: 16539656 DOI: 10.1111/j.1471-4159.2006.03773.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Otx2 is a vertebrate homeobox gene, which has been found to be essential for the development of rostral brain regions and appears to play a role in the development of retinal photoreceptor cells and pinealocytes. In this study, the temporal expression pattern of Otx2 was revealed in the rat brain, with special emphasis on the pineal gland throughout late embryonic and postnatal stages. Widespread high expression of Otx2 in the embryonic brain becomes progressively restricted in the adult to the pineal gland. Crx (cone-rod homeobox), a downstream target gene of Otx2, showed a pineal expression pattern similar to that of Otx2, although there was a distinct lag in time of onset. Otx2 protein was identified in pineal extracts and found to be localized in pinealocytes. Total pineal Otx2 mRNA did not show day-night variation, nor was it influenced by removal of the sympathetic input, indicating that the level of Otx2 mRNA appears to be independent of the photoneural input to the gland. Our results are consistent with the view that pineal expression of Otx2 is required for development and we hypothesize that it plays a role in the adult in controlling the expression of the cluster of genes associated with phototransduction and melatonin synthesis.
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Affiliation(s)
- Martin F Rath
- Institute of Medical Anatomy, Panum Institute, University of Copenhagen, Denmark
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19
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Sobierajska K, Fabczak H, Fabczak S. Alterations of ciliate phosducin phosphorylation in Blepharisma japonicum cells. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2005; 79:135-43. [PMID: 15878118 DOI: 10.1016/j.jphotobiol.2004.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Revised: 12/20/2004] [Accepted: 12/28/2004] [Indexed: 10/25/2022]
Abstract
We have previously reported that motile photophobic response in ciliate Blepharisma japonicum correlates with dephosphorylation of a cytosolic 28 kDa phosphoprotein (PP28) exhibiting properties similar to those of phosducin. Here we demonstrate in in vivo phosphorylation assay that the light-elicited dephosphorylation of the PP28 is significantly modified by cell incubation with substances known to modulate protein phosphatase and kinase activities. Immunoblot analyses showed that incubation of ciliates with okadaic acid and calyculin A, potent inhibitors of type 1 or 2A protein phosphatases, distinctly increased phosphorylation of PP28 in dark-adapted cells and markedly weakened dephosphorylation of the ciliate phosducin following cell illumination. An enhancement of PP28 phosphorylation was also observed in dark-adapted ciliates exposed to 8-Br-cAMP and 8-Br-cGMP, slowly hydrolysable cyclic nucleotide analogs and 3-isobutyryl-1-methylxanthine (IBMX), a non-specific cyclic nucleotide phosphodiesterase (PDEs) inhibitor. Only slight changes in light-evoked dephosphorylation levels of PP28 were observed in cells treated with the cyclic nucleotide analogs and IBMX. Incubation of ciliates with H 89 or KT 5823, highly selective inhibitor of cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG), respectively, decreased PP28 phosphorylation levels in dark-adapted cells, whereas the extent of light-evoked dephosphorylation of the phosphoprotein was only slightly influenced. Cell treatment with higher Ca2+ concentration together with ionophore A23187 in culture medium resulted in marked increase in PP28 phosphorylation levels, while quite an opposite effect was observed in cells exposed to Ca2+ chelators, EGTA or BAPTA/AM as well as calmodulin antagonists, such as trifluoperazine (TFP), W-7 or calmidazolium. Light-dependent dephosphorylation was not considerably affected by these treatments. The experimental findings presented here suggest that an endogenous light-dependent protein kinase-phosphatase system may be engaged in the alteration of phosducin phosphorylation in ciliate B. japonicum thereby to modulate the cell motile photophobic behavior.
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Affiliation(s)
- Katarzyna Sobierajska
- Department of Cell Biology, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3, Pasteur Street, PL - 02 093 Warsaw, Poland
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Lee BY, Thulin CD, Willardson BM. Site-specific phosphorylation of phosducin in intact retina. Dynamics of phosphorylation and effects on G protein beta gamma dimer binding. J Biol Chem 2004; 279:54008-17. [PMID: 15485848 DOI: 10.1074/jbc.m405669200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosducin (Pdc) is a G protein beta gamma dimer (G beta gamma) binding protein, highly expressed in retinal photoreceptor and pineal cells, yet whose physiological role remains elusive. Light controls the phosphorylation of Pdc in a cAMP and Ca(2+)-dependent manner, and phosphorylation in turn regulates the binding of Pdc to G(t)beta gamma or 14-3-3 proteins in vitro. To directly examine the phosphorylation of Pdc in intact retina, we prepared antibodies specific to the three principal phosphorylation sites (Ser-54, Ser-73, and Ser-106) and measured the kinetics of phosphorylation/dephosphorylation during light/dark adaptation and the subsequent effects on G(t)beta gamma binding. Ser-54 phosphorylation increased slowly (t((1/2)) approximately 90 min) during dark adaptation to approximately 70% phosphorylated and decreased rapidly (t((1/2)) approximately 2 min) during light adaptation to less than 20% phosphorylated. Ser-73 phosphorylation increased much faster during dark adaptation (t((1/2)) approximately 3 min) to approximately 50% phosphorylated and decreased more slowly during light adaptation (t((1/2)) approximately 9 min) to less than 20% phosphorylated. The Ca(2+) chelator BAPTA-AM blocked Ser-54 phosphorylation during dark adaptation but had no effect on Ser-73 phosphorylation. In contrast, Ser-106 was not phosphorylated in either the light or dark. Importantly, G beta gamma binding to Pdc was enhanced by Ca(2+) chelation and the binding kinetics closely paralleled those of Ser-54 dephosphorylation, indicating that Ser-54 phosphorylation controls G(t)beta gamma binding in vivo. These results suggest a pivotal role of Ser-54 and Ser-73 phosphorylation in determining the interactions of Pdc with its binding partners, G(t)beta gamma and 14-3-3 protein, which may regulate the light-dependent translocation of the photoreceptor G protein.
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Affiliation(s)
- Bruce Y Lee
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, USA
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21
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Willeit M, Praschak-Rieder N, Zill P, Neumeister A, Ackenheil M, Kasper S, Bondy B. C825T polymorphism in the G protein beta3-subunit gene is associated with seasonal affective disorder. Biol Psychiatry 2003; 54:682-6. [PMID: 14512207 DOI: 10.1016/s0006-3223(03)00169-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Heterotrimeric G proteins play a pivotal role in the intracellular transduction of many transmitter-receptor interactions. Alterations in signal transduction and in G protein concentrations have been reported in seasonal and nonseasonal affective disorder. A single-nucleotide polymorphism (C825T) in the G protein beta3-subunit gene has been shown to influence intracellular response to G protein-coupled stimuli, and the T-allele of this polymorphism has been associated with hypertension and major depression. METHODS We genotyped deoxyribonucleic acid from peripheral mononuclear cells of 172 patients with seasonal affective disorder, winter type (SAD), and 143 healthy control subjects. RESULTS Patients with SAD were significantly more likely to be either homo- or heterozygous for the G(beta)3 T-allele when compared with healthy control subjects (p =.001), and they displayed a higher frequency of the G(beta)3 C825T T-allele (p =.021). The polymorphism was not associated with seasonality, which is the tendency to experience variations in mood and behavior with changing of the seasons. CONCLUSIONS The G(beta)3 C825T polymorphism was associated with SAD in our study sample. This finding strengthens the evidence for the involvement of G protein-coupled signal transduction in the pathogenesis of affective disorder.
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Affiliation(s)
- Matthäus Willeit
- Department of General Psychiatry, University Hospital of Psychiatry, Vienna, Austria
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22
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Klein DC, Ganguly S, Coon SL, Shi Q, Gaildrat P, Morin F, Weller JL, Obsil T, Hickman A, Dyda F. 14-3-3 proteins in pineal photoneuroendocrine transduction: how many roles? J Neuroendocrinol 2003; 15:370-7. [PMID: 12622836 DOI: 10.1046/j.1365-2826.2003.01000.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent studies suggest that a common theme links the diverse elements of pineal photoneuroendocrine transduction--regulation via binding to 14-3-3 proteins. The elements include photoreception, neurotransmission, signal transduction and the synthesis of melatonin from tryptophan. We review general aspects of 14-3-3 proteins and their biological function as binding partners, and also focus on their roles in pineal photoneuroendocrine transduction.
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Affiliation(s)
- D C Klein
- Section on Neuroendocrinology, Laboratory of Developmental Neurobiology, National Institute of Child Health and Human Development/NIH 49/6A82, Bethesda, MD 20892-4480, USA.
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McLaughlin JN, Thulin CD, Hart SJ, Resing KA, Ahn NG, Willardson BM. Regulatory interaction of phosducin-like protein with the cytosolic chaperonin complex. Proc Natl Acad Sci U S A 2002; 99:7962-7. [PMID: 12060742 PMCID: PMC123003 DOI: 10.1073/pnas.112075699] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phosducin and phosducin-like protein (PhLP) bind G protein betagamma subunits and regulate their activity. This report describes a previously uncharacterized binding partner unique to PhLP that was discovered by coimmunoprecipitation coupled with mass spectrometric identification. Chaperonin containing tailless complex polypeptide 1 (CCT), a cytosolic chaperone responsible for the folding of many cellular proteins, binds PhLP with a stoichiometry of one PhLP per CCT complex. Unlike protein-folding substrates of CCT, which interact only in their nonnative conformations, PhLP binds in its native state. Native PhLP competes directly for binding of protein substrates of CCT and thereby inhibits CCT activity. Overexpression of PhLP inhibited the ability of CCT to fold newly synthesized beta-actin by 80%. These results suggest that the interaction between PhLP and CCT may be a means to regulate CCT-dependent protein folding or alternatively, to control the availability of PhLP to modulate G protein signaling.
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Affiliation(s)
- Joseph N McLaughlin
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA
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24
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Garzón J, Rodríguez-Díaz M, López-Fando A, García-España A, Sánchez-Blázquez P. Glycosylated phosducin-like protein long regulates opioid receptor function in mouse brain. Neuropharmacology 2002; 42:813-28. [PMID: 12015208 DOI: 10.1016/s0028-3908(02)00027-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Phosducin (Phd), a protein that in retina regulates rhodopsin desensitization by controlling the activity of Gt beta gamma-dependent G-protein-coupled receptor kinases (GRKs), is present in very low levels in the CNS of mammals. However, this tissue contains proteins of related sequence and function. This paper reports the presence of N-glycosylated phosducin-like protein long (PhLP(L)) in all structures of mouse CNS, mainly in synaptic plasma membranes and associated with G beta subunits and 14-3-3 proteins. To analyze the role PhLP(L) in opioid receptor desensitization, its expression was reduced by the use of antisense oligodeoxynucleotides (ODNs). The antinociception induced by morphine, [D-Ala(2), N-MePhe(4),Gly-ol(5)]-enkephalin (DAMGO), beta-endorphin, [D-Ala(2)]deltorphin II, [D-Pen(2,5)]-enkephalin (DPDPE) or clonidine in the tail-flick test was reduced in PhLP(L)-knock-down mice. A single intracerebroventricular (icv)-ED(80) analgesic dose of morphine gave rise to acute tolerance that lasted for 4 days, but which was prevented or reversed by icv-injection of myristoylated (myr(+)) G(i2)alpha subunits. PhLP(L) knock-down brought about a myr(+)-G(i2)alpha subunit-insensitive acute tolerance to morphine that was still present after 8 days. It also diminished the specific binding of (125)I-Tyr(27)-beta-endorphin-(1-31) (human) to mouse periaqueductal gray matter membranes. After being exposed to chronic morphine treatment, post-dependent mice required about 10 days for complete recovery of morphine antinociception. The impairment of PhLP(L) extended this period beyond 17 days. It is concluded that PhLP(L) knock-down facilitates desensitization and uncoupling of opioid receptors.
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Affiliation(s)
- J Garzón
- Neurofarmacología, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Avd Doctor Arce, 37, E-28002 Madrid, Spain.
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25
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Kobayashi Y, Hisatomi O, Satoh T, Tokunaga F. Identification of rod- and cone-specific phosducins in teleost retinas. FEBS Lett 2001; 502:117-21. [PMID: 11583111 DOI: 10.1016/s0014-5793(01)02670-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosducin (PD) is a regulatory protein of vertebrate phototransduction cascades. In mammalian retina, it has been thought that only one kind of PD commonly exists in both rods and cones. However, we have found two kinds of PD (OIPD-R and OIPD-C) in the retina of a teleost, medaka (Oryzias latipes). In situ hybridization and immunohistochemical analysis demonstrated that OIPD-R and -C are selectively expressed in rods and cones, respectively. The antiserum against medaka PDs recognized two kinds of proteins in bluegill (Lepomis macrochirus) retina. These results suggest that rod- and cone-specific PDs exist in teleost retinas, probably creating differences in light adaptation between rods and cones.
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Affiliation(s)
- Y Kobayashi
- Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Japan
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26
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Thulin CD, Savage JR, McLaughlin JN, Truscott SM, Old WM, Ahn NG, Resing KA, Hamm HE, Bitensky MW, Willardson BM. Modulation of the G protein regulator phosducin by Ca2+/calmodulin-dependent protein kinase II phosphorylation and 14-3-3 protein binding. J Biol Chem 2001; 276:23805-15. [PMID: 11331285 DOI: 10.1074/jbc.m101482200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phototransduction is a canonical G protein-mediated cascade of retinal photoreceptor cells that transforms photons into neural responses. Phosducin (Pd) is a Gbetagamma-binding protein that is highly expressed in photoreceptors. Pd is phosphorylated in dark-adapted retina and is dephosphorylated in response to light. Dephosphorylated Pd binds Gbetagamma with high affinity and inhibits the interaction of Gbetagamma with Galpha or other effectors, whereas phosphorylated Pd does not. These results have led to the hypothesis that Pd down-regulates the light response. Consequently, it is important to understand the mechanisms of regulation of Pd phosphorylation. We have previously shown that phosphorylation of Pd by cAMP-dependent protein kinase moderately inhibits its association with Gbetagamma. In this study, we report that Pd was rapidly phosphorylated by Ca(2+)/calmodulin-dependent kinase II, resulting in 100-fold greater inhibition of Gbetagamma binding than cAMP-dependent protein kinase phosphorylation. Furthermore, Pd phosphorylation by Ca(2+)/calmodulin-dependent kinase II at Ser-54 and Ser-73 led to binding of the phosphoserine-binding protein 14-3-3. Importantly, in vivo decreases in Ca(2+) concentration blocked the interaction of Pd with 14-3-3, indicating that Ca(2+) controls the phosphorylation state of Ser-54 and Ser-73 in vivo. These results are consistent with a role for Pd in Ca(2+)-dependent light adaptation processes in photoreceptor cells and also suggest other possible physiological functions.
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Affiliation(s)
- C D Thulin
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, USA
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27
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Abstract
The discovery of phosducin (Phd) in photoreceptor cells of the retina and the further identification of phosducin-like proteins (PhdLP) emphasizes the existence of a family of proteins characterized as cytosolic regulators of G protein functions. The individual members represent phosphoproteins with distinct tissue distributions whose highest concentrations were in the retina and the pineal gland, while lower levels were reported for tissues such as liver, spleen, striated muscle, and the brain. Several functions of Phd and PhdLP have been suggested, but their most important ability appears to be their high affinity sequestration with G betagamma subunits of heterotrimeric G proteins. This finding suggests that neutralization of G betagamma by Phd effectively impedes G protein-mediated signal transmission, since G alpha cannot reassemble with G betagamma to provide a functional G protein trimer (G alphabetagamma). Thus, it is the scavenger quality of Phd that is hypothesized to diminish intracellular communication simply by reducing the number of G proteins. An additional important function of Phd relates to the inhibition of G alpha subunits' inherent GTPase. The ability of Phd to directly bind G alpha subunits is probably of minor significance as the affinity between both proteins is low. In general, similar mechanisms have been reported for PhdLPs. In the majority of investigations concerning the interference of Phd with physiological mechanisms, the dark/light adaptation of retinal photoreceptor cells has been the most frequently studied aspect of Phd. More recently, Phd was associated with the adenylyl cyclase of olfactory cilia, as in the presence of the phosphoprotein an increased concentration of cAMP is observed. This finding is in line with the experimental outcome of permanent cell lines transfected to overexpress Phd, which exhibit sensitization to excitatory acting PGE(1), and isoproterenol, respectively. Furthermore, Phd was found to effectively slow down the mechanism of internalization of G protein-coupled opioid receptors. Pathophysiological processes associated with Phd were found for certain eye diseases. Experimental evidence suggests the development of retinal inflammation as a consequence of an autoimmunization process triggered by Phd or shorter fragments thereof. Thus, our present knowledge regarding the functions of members of the Phd family is limited currently to their control of G protein-mediated intracellular signal transmission, the process of endocytosis, and certain autoimmune diseases of the uvea and the pineal gland. However, recent information regarding the presence of certain members of the Phd family in the cell nucleus may bear new insights into the function of these compounds.
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Affiliation(s)
- R Schulz
- Institute of Pharmacology, Toxicology and Pharmacy, University of Munich, Königinstrasse 16, München, D-80539, Germany.
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Keller C, Schulz R. Nucleotide and deduced amino acid sequence of equine retinal and pineal gland phosducin. Am J Vet Res 2001; 62:61-6. [PMID: 11197562 DOI: 10.2460/ajvr.2001.62.61] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES To determine the full-length complementary DNA (cDNA) sequence of equine retinal and pineal gland phosducin (PHD) and to clone these sequences. SAMPLE POPULATION Samples of equine retinal RNA. PROCEDURE A primer set was designed for use in identifying a fragment of the equine PHD nucleotide sequence, derived from retinal RNA samples, and subsequently for use to deduce specific primers for additional examination. The full-length cDNA was determined by the method of rapid amplification of cDNA ends (RACE). For full-length cDNA, newly designed primers were used. Nucleotide sequences were analyzed by use of computer software. The deduced amino acid sequence was compared with sequences of PHD reported for other species. In addition, the sequence of equine pineal PHD was cloned. RESULTS The cDNA nucleotide sequence for equine PHD was 1,209 base pairs (bp) in length with an open-reading frame encoding a protein of 245 amino acids and a calculated molecular mass of 28.214 kd. Similarity with amino acid sequences of PHD from other species was 89 to 93%. Sequences of equine PHD from retina and pineal gland were identical. Equine PHD contained a peptide sequence with 100% homology to an uveitopathogenic peptide reported for rat PHD. CONCLUSIONS Equine PHD is a highly conserved protein that has homology of immunologic interest with rat PHD. These results establish a basis for studying the role of PHD in ocular inflammation of horses.
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Affiliation(s)
- C Keller
- Institute of Pharmacology, Toxicology, and Pharmacy, University of Munich, Germany
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Savage JR, McLaughlin JN, Skiba NP, Hamm HE, Willardson BM. Functional roles of the two domains of phosducin and phosducin-like protein. J Biol Chem 2000; 275:30399-407. [PMID: 10896945 DOI: 10.1074/jbc.m005120200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosducin and phosducin-like protein regulate G protein signaling pathways by binding the betagamma subunit complex (Gbetagamma) and blocking Gbetagamma association with Galpha subunits, effector enzymes, or membranes. Both proteins are composed of two structurally independent domains, each constituting approximately half of the molecule. We investigated the functional roles of the two domains of phosducin and phosducin-like protein in binding retinal G(t)betagamma. Kinetic measurements using surface plasmon resonance showed that: 1) phosducin bound G(t)betagamma with a 2. 5-fold greater affinity than phosducin-like protein; 2) phosphorylation of phosducin decreased its affinity by 3-fold, principally as a result of a decrease in k(1); and 3) most of the free energy of binding comes from the N-terminal domain with a lesser contribution from the C-terminal domain. In assays measuring the association of G(t)betagamma with G(t)alpha and light-activated rhodopsin, both N-terminal domains inhibited binding while neither of the C-terminal domains had any effect. In assays measuring membrane binding of G(t)betagamma, both the N- and C-terminal domains inhibited membrane association, but much less effectively than the full-length proteins. This inhibition could only be described by models that included a change in G(t)betagamma to a conformation that did not bind the membrane. These models yielded a free energy change of +1.5 +/- 0.25 kcal/mol for the transition from the G(t)alpha-binding to the Pd-binding conformation of G(t)betagamma.
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Affiliation(s)
- J R Savage
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, USA
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Kasahara S, Wang P, Nuss DL. Identification of bdm-1, a gene involved in G protein beta-subunit function and alpha-subunit accumulation. Proc Natl Acad Sci U S A 2000; 97:412-7. [PMID: 10618432 PMCID: PMC26677 DOI: 10.1073/pnas.97.1.412] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Targeted disruption of Galpha and Gbeta genes has established the requirement of an intact G protein signaling pathway for optimal execution of several important physiological processes, including pathogenesis, in the chestnut blight fungus Cryphonectria parasitica. We now report the identification of a G protein signal transduction component, beta disruption mimic factor-1, BDM-1. Disruption of the corresponding gene, bdm-1, resulted in a phenotype indistinguishable from that previously observed after disruption of the Gbeta subunit gene, cpgb-1. The BDM-1 deduced amino acid sequence contained several significant clusters of identity with mammalian phosducin, including a domain corresponding to a highly conserved 11-amino acid stretch that has been implicated in binding to the Gbetagamma dimer and two regions of defined Gbeta/phosducin contact points. Unlike the negative regulatory function proposed for mammalian phosducin, the genetic data presented in this report suggest that BDM-1 is required for or facilitates Gbeta function. Moreover, disruption of either bdm-1 or cpgb-1 resulted in a significant, posttranscriptional reduction in the accumulation of CPG-1, a key Galpha subunit required for a range of vital physiological processes.
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Affiliation(s)
- S Kasahara
- Center for Agricultural Biotechnology, University of Maryland Biotechnology Institute, University of Maryland, College Park, MD 20742-4450, USA
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31
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Abstract
BACKGROUND Phosducin binds tightly to the beta gamma subunits (Gt beta gamma) of the heterotrimeric G protein transducin, preventing Gt beta gamma reassociation with Gt alpha-GDP and thereby inhibiting the G-protein cycle. Phosducin-like proteins appear to be widely distributed and may play important roles in regulating many heterotrimeric G-protein signaling pathways. RESULTS The 2.8 A crystal structure of a complex of bovine retinal phosducin with Gt beta gamma shows how the two domains of phosducin cover one side and the top of the seven-bladed beta propeller of Gt beta gamma. The binding of phosducin induces a distinct structural change in the beta propeller of Gt beta gamma, such that a small cavity opens up between blades 6 and 7. Electron density in this cavity has been assigned to the farnesyl moiety of the gamma subunit. CONCLUSIONS beta gamma subunits of heterotrimeric G proteins can exist in two distinct conformations. In the R (relaxed) state, corresponding to the structure of the free beta gamma or the structure of beta gamma in the alpha beta gamma heterotrimer, the hydrophobic farnesyl moiety of the gamma subunit is exposed, thereby mediating membrane association. In the T (tense) state, as observed in the phosducin-Gt beta gamma structure, the farnesyl moiety of the gamma subunit is effectively buried in the cavity formed between blades 6 and 7 of the beta subunit. Binding of phosducin to Gt beta gamma induces the formation of this cavity, resulting in a switch from the R to the T conformation. This sequesters beta gamma from the membrane to the cytosol and turns off the signal-transduction cascade. Regulation of this membrane association/dissociation switch of Gt beta gamma by phosducin may be a general mechanism for attenuation of G protein coupled signal transduction cascades.
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Affiliation(s)
- A Loew
- Department of Biochemistry and Molecular Biology, University of Illinois at Chicago, IL 60612-7334, USA
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Weng G, Jordan J, Chen Y. Structural Basis for the Function of the Heterotrimeric G-Proteins. ACTA ACUST UNITED AC 1998. [DOI: 10.1006/smns.1998.0125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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33
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Bauer PH, Blüml K, Schröder S, Hegler J, Dees C, Lohse MJ. Interactions of phosducin with the subunits of G-proteins. Binding to the alpha as well as the betagamma subunits. J Biol Chem 1998; 273:9465-71. [PMID: 9545273 DOI: 10.1074/jbc.273.16.9465] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The high affinity interactions of phosducin with G-proteins involve binding of phosducin to the G-protein betagamma subunits. Here we have investigated whether phosducin interacts also with G-protein alpha subunits. Interactions of phosducin with the individual subunits of Go were measured by retaining phosducin-G-protein subunit complexes on columns containing immobilized anti-phosducin antibodies. Both the alpha and the beta subunits of trimeric Go were specifically retained by the antibodies in the presence of phosducin. This binding was almost completely abolished for both subunits following protein kinase A-mediated phosphorylation of phosducin and was reduced, more for alpha than for beta subunits, by the stable GTP analog guanosine 5'-(3-O-thio)triphosphate. Isolated alphao was also retained on the columns in the presence of phosducin but not in the presence of protein kinase A-phosphorylated phosducin. Likewise, purified G-protein betagamma subunit complexes as well as purified alpha subunits of Go and Gt were precipitated together with His6-tagged phosducin with nickel-agarose; this co-precipitation occurred concentration-dependently, with apparent affinities for phosducin of 55 nM (Gbetagamma), 110 nM (alphao), and 200 nM (alphat). In functional experiments, the steady state GTPase activity of isolated alphao was inhibited by phosducin by approximately 60% with an IC50 value of approximately 300 nM, whereas the GTPase activity of trimeric Go was inhibited by approximately 90% with an IC50 value of approximately 10 nM. Phosducin did not inhibit the GTP-hydrolytic activity of isolated alphao as measured by single-turnover assays, but it inhibited the release of GDP from alphao; the rate constant of GDP release was decreased approximately 40% by 500 nM phosducin, and the inhibition occurred with an IC50 value for phosducin of approximately 100 nM. These data suggest that phosducin binds with high affinity to G-protein betagamma subunits and with lower affinity to G-protein alpha subunits. We propose that the alpha subunit-mediated effects of phosducin might increase both the extent and the rapidity of its inhibitory effects compared with an action via the betagamma subunit complex alone.
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Affiliation(s)
- P H Bauer
- Institut für Pharmakologie und Toxikologie der Universität Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
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34
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Abstract
Guanine nucleotide binding (G) proteins relay extracellular signals encoded in light, small molecules, peptides, and proteins to activate or inhibit intracellular enzymes and ion channels. The larger G proteins, made up of G alpha beta gamma heterotrimers, dissociate into G alpha and G beta gamma subunits that separately activate intracellular effector molecules. Only recently has the G beta gamma subunit been recognized as a signal transduction molecule in its own right; G beta gamma is now known to directly regulate as many different protein targets as the G alpha subunit. Recent X-ray crystallography of G alpha, G beta gamma, and G alpha beta gamma subunits will guide the investigation of structure-function relationships.
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Affiliation(s)
- D E Clapham
- Department of Neurobiology and Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
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35
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Gaudet R, Bohm A, Sigler PB. Crystal structure at 2.4 angstroms resolution of the complex of transducin betagamma and its regulator, phosducin. Cell 1996; 87:577-88. [PMID: 8898209 DOI: 10.1016/s0092-8674(00)81376-8] [Citation(s) in RCA: 252] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The crystal structure of transducin's betagamma subunits complexed with phosducin, which regulates Gtbetagamma activity, has been solved to 2.4 angstroms resolution. Phosducin has two domains that wrap around Gtbetagamma to form an extensive interface. The N-terminal domain binds loops on the "top" Gtbeta surface, overlapping the Gtalpha binding surface, explaining how phosducin blocks Gtbetagamma's interaction with Gtalpha. The C-terminal domain shows structural homology to thioredoxin and binds the outer strands of Gtbeta's seventh and first blades in a manner likely to disrupt Gtbetagamma's normal orientation relative to the membrane and receptor. Phosducin's Ser-73, which when phosphorylated inhibits phosducin's function, points away from Gtbetagamma, toward a large flexible loop. Thus phosphorylation is not likely to affect the interface directly, but rather indirectly through an induced conformational change.
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Affiliation(s)
- R Gaudet
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06511, USA
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36
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Helmreich EJ, Hofmann KP. Structure and function of proteins in G-protein-coupled signal transfer. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1286:285-322. [PMID: 8982287 DOI: 10.1016/s0304-4157(96)00013-5] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- E J Helmreich
- Department of Clinical Biochemistry and Pathobiochemistry, University of Würzburg, Germany
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37
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Schulz K, Danner S, Bauer P, Schröder S, Lohse MJ. Expression of phosducin in a phosducin-negative cell line reveals functions of a Gbetagamma-binding protein. J Biol Chem 1996; 271:22546-51. [PMID: 8798422 DOI: 10.1074/jbc.271.37.22546] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Phosducin is a member of the large group of proteins that bind to G-protein betagamma-subunits (Gbetagamma) and whose biological functions are often unknown. Human A431 cells do not contain detectable amounts of phosducin. We generated A431 cells expressing phosducin at a level of approximately 1 pmol/mg of cytosolic protein, which is approximately 10% of the phosducin level in brain. cAMP accumulation in response to beta2-adrenergic receptor agonists was enhanced at early times in phosducin-expressing cells, but reached a lower plateau than in control cells. Permeabilization of the cells with digitonin did not change this pattern, but allowed the introduction of specific inhibitors: antibodies to phosducin abolished all differences between the two cell lines. Inhibitors of the beta-adrenergic receptor kinase abolished the differences at early time points. An almost complete loss of beta2-adrenergic receptor desensitization in the phosducin-expressing cells was also observed when intact cells were desensitized and receptor function was then determined in membrane preparations. Inhibition of protein kinase A accentuated the effects of phosducin, suggesting that also in vivo phosducin is regulated by this kinase. These data indicate that phosducin affects G-protein-mediated signaling in at least two ways: it dampens the overall responsiveness, and it impairs the rapid desensitization mediated by the beta-adrenergic receptor kinase.
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Affiliation(s)
- K Schulz
- Institute for Pharmacology, University of Würzburg, Versbacher Strabetae 9, D-97078 Würzburg, Federal Republic of Germany
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38
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Reddy MA, Shukla SD. Potentiation of mitogen-activated protein kinase by ethanol in embryonic liver cells. Biochem Pharmacol 1996; 51:661-8. [PMID: 8615903 DOI: 10.1016/s0006-2952(95)02239-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Ethanol modulates agonist responses in liver cells, which are the major site of ethanol metabolism. Mitogen-activated protein kinases (MAPKs) are involved in the integration of multiple signaling pathways leading to cellular responses. However, the effect of ethanol on liver MAPK is not known. To this end, we studied the activation of MAPK in a normal mouse embryonic liver cell line (BNLCL2) after acute and chronic exposure to ethanol. Acute exposure to ethanol (0-400 mM) for 1 hr had no effect on either basal or serum- and phorbol-12-myristate-13-acetate (PMA)-stimulated MAPK activity. Chronic exposure to ethanol (0-400 mM) for 24 hr potentiated the stimulation of MAPK by serum, PMA, or thrombin. Maximum potentiation was observed with 200 mM ethanol (2- to 3-fold higher than control cells). Chronic exposure had no significant effect on epidermal growth factor-stimulated MAPK activity. In-gel MAPK assay of cytosolic extracts and of immunoprecipitates obtained with MAPK antibody demonstrated that ethanol potentiated the activation of both p42 and p44 MAPKs. When cells were pretreated with pertussis toxin, the potentiation by ethanol was abolished. It is concluded that ethanol potentiates MAPK in fetal liver cells by a pertussis toxin-sensitive G-protein-dependent mechanism.
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Affiliation(s)
- M A Reddy
- Department of Pharmacology, University of Missouri School of Medicine, Columbia 65212, USA
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39
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Hawes BE, Touhara K, Kurose H, Lefkowitz RJ, Inglese J. Determination of the G beta gamma-binding domain of phosducin. A regulatable modulator of G beta gamma signaling. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)43955-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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40
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Hekman M, Bauer PH, Söhlemann P, Lohse MJ. Phosducin inhibits receptor phosphorylation by the beta-adrenergic receptor kinase in a PKA-regulated manner. FEBS Lett 1994; 343:120-4. [PMID: 8168616 DOI: 10.1016/0014-5793(94)80302-1] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Homologous or receptor-specific desensitization of beta-adrenergic receptors is thought to be triggered by receptor phosphorylation mediated by the beta-adrenergic receptor kinases (beta ARK). Upon receptor activation, cytosolic beta ARK translocates to the membrane, probably by binding to G-protein beta gamma-subunits. Using the purified proteins reconstituted into phospholipid vesicles we show here that this binding process can be inhibited by phosducin, a cytosolic protein that has recently been described as a regulator of G-protein-mediated signalling. Phosducin appears to complete very effectively with beta ARK for the G-protein beta gamma-subunits. These inhibitory effects of phosducin on receptor phosphorylation are antagonized following phosphorylation of phosducin by protein kinase A. It is proposed that phosducin may act as a regulator of homologous beta-adrenergic receptor desensitization.
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Affiliation(s)
- M Hekman
- Laboratory of Molecular Biology, University of Munich, Max-Planck-Institute of Biochemistry, Martinsried, Germany
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41
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Cipolla-Neto J, Abdalla DS, Markus RP, Campa A. Circadian variations of superoxide dismutase activity in the rat pineal gland. J Neural Transm (Vienna) 1993; 92:117-23. [PMID: 8369105 DOI: 10.1007/bf01244871] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The 24 h profile of the activity of the antioxidant enzyme superoxide dismutase (SOD) in the pineal gland of rats was studied. Rhythmic analysis showed a significant 24 h rhythm with an amplitude of oscillation of 25% of the 24 h mean value, that was 100.34 +/- 1.6 U SOD (nitrite). An ultradian rhythm of 9 h was also detected. The diurnal profile of superoxide dismutase activity is discussed in relation to the oxidative metabolism of the pineal gland.
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Affiliation(s)
- J Cipolla-Neto
- Department of Physiology and Biophysics, Universidade de São Paulo, Brazil
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42
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Reig JA, Viniegra S, Ballesta JJ, Palmero M, Guitierrez LM. Naphthalenesulfonamide derivatives ML9 and W7 inhibit catecholamine secretion in intact and permeabilized chromaffin cells. Neurochem Res 1993; 18:317-23. [PMID: 8479600 DOI: 10.1007/bf00969089] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The role of protein phosphorylation in catecholamine secretion from bovine adrenomedullary chromaffin cells was studied using different protein kinase inhibitors. Naphthalenesulfonamide derivatives as ML9 and ML7, more specific for the myosin light chain kinase, and the calmodulin antagonist W7 inhibited catecholamine secretion 20 and 40% respectively in digitonin-permeabilized chromaffin cells. ML9 also decreased calcium evoked protein phosphorylation of different proteins including tyrosine hydroxylase in permeabilized cells. These naphthalenesulfonamide derivatives showed also an effect in intact cells, ML9 and W7 produced 50% inhibition in catecholamine secretion and 45Ca2+ uptake, however H8 had no effect. The partial [3H]nitrendipine binding displacement of these drugs to adrenomedullary membranes suggests that these sulfonamide derivatives could interact directly with L-type calcium channels in intact cells. The results obtained in permeabilized cells suggest a possible role of protein phosphorylation in the regulation of catecholamine secretion in chromaffin cells.
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Affiliation(s)
- J A Reig
- Departamento de Neuroquimica, Facultad de Medicina, Spain
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43
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Lee R, Ting T, Lieberman B, Tobias D, Lolley R, Ho Y. Regulation of retinal cGMP cascade by phosducin in bovine rod photoreceptor cells. Interaction of phosducin and transducin. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)74012-5] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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44
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Babila T, Schaad NC, Simonds WF, Shinohara T, Klein DC. Development of MEKA (phosducin), G beta, G gamma and S-antigen in the rat pineal gland and retina. Brain Res 1992; 585:141-8. [PMID: 1511297 DOI: 10.1016/0006-8993(92)91199-o] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Pinealocytes and retinal photoreceptor cells contain an unusual cytoplasmic complex composed of the G beta gamma dimer of GTP-binding regulatory proteins (G-proteins) tightly bound to an acidic 33 kDa phosphoprotein termed MEKA or phosducin; MEKA is a substrate of cyclic AMP-dependent protein kinase. This study characterized the developmental appearance of these and two related proteins, G gamma and S-antigen, in pineal and retinal tissue. MEKA was absent in the pineal gland prior to birth, at a time when it was possible to detect G beta in pineal cytoplasm, indicating that the appearance of G beta in the cytoplasm precedes that of MEKA and does not appear to require the presence of MEKA. The absence of MEKA at this time indicates that the cyclic AMP stimulation of pineal serotonin N-acetyltransferase activity is not mediated by MEKA, which has been considered as a possible role of MEKA. After postnatal day 7, pineal MEKA and cytoplasmic G beta increased in a parallel manner, with peak values occurring at about postnatal day 21. Thereafter, both proteins in the pineal gland decreased in a parallel fashion to 10 and 35% of their peak values, respectively; in contrast, the cytoplasmic protein S-antigen and membrane associated G beta remained at maximal levels after this time. Whereas both MEKA and G beta decreased late in development in the pineal gland, these proteins either increased or remained constant in the retina. These tissue-specific patterns were found to differ from those of another cytosolic protein found exclusively in the pineal gland and retina, S-antigen, which remained constant after day 21 in the pineal gland but decreased in the retina late in life.
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Affiliation(s)
- T Babila
- Section on Neuroendocrinology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
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45
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Bauer PH, Müller S, Puzicha M, Pippig S, Obermaier B, Helmreich EJ, Lohse MJ. Phosducin is a protein kinase A-regulated G-protein regulator. Nature 1992; 358:73-6. [PMID: 1319556 DOI: 10.1038/358073a0] [Citation(s) in RCA: 202] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Signal transduction by G-protein-coupled receptors is regulated by various mechanisms acting at the receptor level; those studied most thoroughly are from the beta-adrenergic receptor/Gs/adenylyl cyclase system. We report here a regulatory mechanism occurring at the level of the G proteins themselves. A protein with M(r) 33,000 that inhibits Gs-GTPase activity was purified from bovine brain. This protein is very similar or identical to phosducin, a protein previously thought to be specific for retina and pineal gland. Recombinant phosducin inhibited the GTPase activity of several G proteins, and also inhibited Gs-mediated adenylyl cyclase activation. Blockade of its inhibitory effects by protein kinase A suggests that phosducin may be part of a complex regulatory network controlling G-protein-mediated signalling.
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Affiliation(s)
- P H Bauer
- Laboratory of Molecular Biology, University of Munich, Max-Planck-Institute of Biochemistry, Martinsried, Germany
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46
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Lolley RN, Craft CM, Lee RH. Photoreceptors of the retina and pinealocytes of the pineal gland share common components of signal transduction. Neurochem Res 1992; 17:81-9. [PMID: 1538828 DOI: 10.1007/bf00966868] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Light absorbed by retinal photoreceptors triggers a cascade of reactions that initiate cGMP hydrolysis, cation channel closure and membrane hyperpolarization. Down-regulation of the cascade involves additional proteins that interfere with amplification along the cascade. Pinealocytes are activated by norepinephrine during the dark phase of the day/night cycle. Mature pinealocytes of the mammalian pineal express the known photoreceptor proteins that are implicated in down-regulation of the visual cascade, but the cascade components that produce cGMP hydrolysis and membrane hyperpolarization are absent. Pinealocytes accumulate cyclic AMP minimally when norepinephrine activates their beta adrenergic receptors alone, but the response is potentiated by the simultaneous activation of their alpha-1 adrenergic receptors. A model is proposed whereby phosducin, a phosphoprotein that binds the beta,gamma subunit of G-proteins, could modulate the synthesis of cyclic AMP by buffering the amount of beta,gamma G-protein subunits that are available for activating adenylate cyclase.
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Affiliation(s)
- R N Lolley
- Department of Anatomy and Cell Biology, UCLA School of Medicine 90024
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47
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Spiegel AM, Backlund PS, Butrynski JE, Jones TL, Simonds WF. The G protein connection: molecular basis of membrane association. Trends Biochem Sci 1991; 16:338-41. [PMID: 1949155 DOI: 10.1016/0968-0004(91)90139-m] [Citation(s) in RCA: 92] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Two distinct types of lipid modification, myristoylation and isoprenylation, are critical for membrane association of heterotrimeric G proteins. Elucidation of the molecular basis for G protein membrane association has important implications for understanding G protein structure and function, and is relevant to potential therapeutic approaches to AIDS and cancer.
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Affiliation(s)
- A M Spiegel
- Molecular Pathophysiology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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48
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Craft CM, Lolley RN, Seldin MF, Lee RH. Rat pineal gland phosducin: cDNA isolation, nucleotide sequence, and chromosomal assignment in the mouse. Genomics 1991; 10:400-9. [PMID: 2071146 DOI: 10.1016/0888-7543(91)90325-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The pineal gland contains a soluble phosphoprotein, phosducin, which is homologous to that of retinal photoreceptors. Phosducin has been shown to bind the beta, gamma subunits of the retinal G-protein transducin. Retinal phosducin has been cloned and now we report a rat pineal cDNA encoding phosducin. A 1217-nucleotide cDNA was isolated from a rat pineal library by DNA-DNA hybridization with a polymerase chain reaction-amplified cDNA of bovine retina mRNA for phosducin. Northern blot analysis demonstrates that the mRNA for phosducin is approximately 1.3 kb in both rat pineal and rat retina. The translated mRNA from rat pineal encodes a protein with 246 amino acids, compared to the 245 amino acids of bovine retina phosducin. The predicted molecular weight of rat pineal phosducin is 28,201. Immunoblot analysis with affinity-purified antibodies against bovine retina phosducin identify a single immunoreactive protein of approximately 33 kDa in both rat retina and rat pineal. The amino acid sequence of rat pineal phosducin is homologous to that of bovine retina phosducin, revealing 89% identity and another 5.7% similarity. Both rat pineal and bovine retina phosducins are acidic proteins with pIs of 4.3 and 4.5, respectively. The translated protein lacks hydrophobic domains that would suggest an integral membrane protein. Rat pineal phosducin has a single consensus phosphorylation domain for protein kinase A that is nearly identical to that of retinal phosducin, which is phosphorylated by protein kinase A in situ. Rat phosducin also contains three potential phosphorylation domains for protein kinase C and nine for casein kinase II as well as a predicted site for N-glycosylation. The cDNA encoding phosducin was used to localize the gene within a linkage group to a large segment of mouse chromosome 1 in a conserved region with the long arm of human chromosome 1 with a panel of DNA samples from an interspecific cross. In keeping with a proposed role of retinal phosducin in down-regulation of the photo-transduction cascade, a modulatory role in signal transduction is proposed for pineal phosducin.
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Affiliation(s)
- C M Craft
- Department of Psychiatry, University of Texas Southwestern Medical School, Dallas 75235
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49
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Kurstjens NP, Fröhlich M, Dees C, Cantrill RC, Hekman M, Helmreich EJ. Binding of alpha- and beta gamma-subunits of Go to beta 1-adrenoceptor in sealed unilamellar lipid vesicles. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 197:167-76. [PMID: 1849815 DOI: 10.1111/j.1432-1033.1991.tb15895.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
First, we describe a preparation of sealed unilamellar lipid vesicles. When this preparation was subjected to sucrose density gradient centrifugation, two rather uniform fractions emerged, one consisting of lighter lipid-rich vesicles with average diameters ranging over 150-200 nm (fraction I), the other consisting of heavier vesicles with average diameters ranging over 30-70 nm (fraction II). When the lipid mixture containing dimyristoylglycerophosphocholine, cholesterol, dipalmitoylglycerophosphoserine and dipalmitoylglycerophosphoethanolamine at molar ratios of 54:35:10:1 was reconstituted with alpha- and beta gamma-subunits of Go-proteins purified to homogeneity from bovine brain, the lipid-rich lighter vesicle fraction I took up these subunits nearly exclusively. Whereas, when a beta 1-adrenoceptor preparation purified from turkey erythrocyte membranes was reconstituted, it was found nearly completely in the smaller heavier vesicle fraction II where it was incorporated inside-out. On co-reconstitution of either alpha o or beta gamma alone with beta 1-adrenoceptors, some of these subunits appear together with beta 1-adrenoceptors in the small vesicle fraction II, but much more alpha o was bound to the receptor in the presence of beta gamma-subunits. The observations reported are novel and surprising in several respects: firstly, they suggest that beta gamma-subunits can bind to the non-activated beta 1-receptor where they may serve as an anchor for alpha-subunits. Secondly, the binding of alpha o- and beta gamma-subunits to the beta 1-adrenoceptors enhances the basal GTPase activity of alpha o. Thirdly, since the binding domains of the beta 1-adrenoceptor for G-proteins were facing outwards in our sealed vesicle preparations, it follows that interactions of G-proteins with the beta-receptor can occur at the aqueous membrane interface as was postulated originally by M. Chabre [Trends Biochem. Sci. 12, 213-215 (1987)] for the transducin-rhodopsin interactions. Finally, the binding of Go-subunits from bovine brain to a beta 1-adrenoceptor from turkey erythrocytes was not expected, since these polypeptides are not likely to be physiological partners.
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Affiliation(s)
- N P Kurstjens
- Physiologisch-Chemisches Institut der Universität Würzburg, Federal Republic of Germany
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50
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Watanabe Y, Kawasaki K, Miki N, Kuo CH. Isolation and analysis of the human MEKA gene encoding a retina-specific protein. Biochem Biophys Res Commun 1990; 170:951-6. [PMID: 2383274 DOI: 10.1016/0006-291x(90)92183-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We have isolated and sequenced a human gene encoding photoreceptor cell-specific MEKA protein. The protein coding region was separated into three exons, which encoded 246 amino acid residues with a molecular weight of 28,311. The coding region of the human gene exhibited the homologies of 90.7% nucleotides and 88.5% amino acids with those of the bovine cDNA. Southern blot analysis revealed that the human MEKA gene has a single copy number. However, the anti-bovine MEKA stained both rod and cone photoreceptor cells in the human retina.
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Affiliation(s)
- Y Watanabe
- Department of Pharmacology, Kanazawa University, Japan
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