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Nicklisch SCT, Rees SD, McGrath AP, Gökirmak T, Bonito LT, Vermeer LM, Cregger C, Loewen G, Sandin S, Chang G, Hamdoun A. Global marine pollutants inhibit P-glycoprotein: Environmental levels, inhibitory effects, and cocrystal structure. SCIENCE ADVANCES 2016; 2:e1600001. [PMID: 27152359 PMCID: PMC4846432 DOI: 10.1126/sciadv.1600001] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Accepted: 03/21/2016] [Indexed: 05/05/2023]
Abstract
The world's oceans are a global reservoir of persistent organic pollutants to which humans and other animals are exposed. Although it is well known that these pollutants are potentially hazardous to human and environmental health, their impacts remain incompletely understood. We examined how persistent organic pollutants interact with the drug efflux transporter P-glycoprotein (P-gp), an evolutionarily conserved defense protein that is essential for protection against environmental toxicants. We identified specific congeners of organochlorine pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers that inhibit mouse and human P-gp, and determined their environmental levels in yellowfin tuna from the Gulf of Mexico. In addition, we solved the cocrystal structure of P-gp bound to one of these inhibitory pollutants, PBDE (polybrominated diphenyl ether)-100, providing the first view of pollutant binding to a drug transporter. The results demonstrate the potential for specific binding and inhibition of mammalian P-gp by ubiquitous congeners of persistent organic pollutants present in fish and other foods, and argue for further consideration of transporter inhibition in the assessment of the risk of exposure to these chemicals.
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Bonito LT, Hamdoun A, Sandin SA. Evaluation of the global impacts of mitigation on persistent, bioaccumulative and toxic pollutants in marine fish. PeerJ 2016; 4:e1573. [PMID: 26839747 PMCID: PMC4734435 DOI: 10.7717/peerj.1573] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 12/16/2015] [Indexed: 11/20/2022] Open
Abstract
Although persistent, bioaccumulative and toxic pollutants (PBTs) are well-studied individually, their distribution and variability on a global scale are largely unknown, particularly in marine fish. Using 2,662 measurements collected from peer-reviewed literature spanning 1969-2012, we examined variability of five classes of PBTs, considering effects of geography, habitat, and trophic level on observed concentrations. While we see large-scale spatial patterning in some PBTs (chlordanes, polychlorinated biphenyls), habitat type and trophic level did not contribute to significant patterning, with the exception of mercury. We further examined patterns of change in PBT concentration as a function of sampling year. All PBTs showed significant declines in concentration levels through time, ranging from 15-30% reduction per decade across PBT groups. Despite consistent evidence of reductions, variation in pollutant concentration remains high, indicating ongoing consumer risk of exposure to fish with pollutant levels exceeding EPA screening values. The temporal trends indicate that mitigation programs are effective, but that global levels decline slowly. In order for monitoring efforts to provide more targeted assessments of risk to PBT exposure, these data highlight an urgent need for improved replication and standardization of pollutant monitoring protocols for marine finfish.
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Shipp LE, Hill RZ, Moy GW, Gökırmak T, Hamdoun A. ABCC5 is required for cAMP-mediated hindgut invagination in sea urchin embryos. Development 2015; 142:3537-48. [PMID: 26395488 DOI: 10.1242/dev.126144] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 08/14/2015] [Indexed: 12/31/2022]
Abstract
ATP-binding cassette (ABC) transporters are evolutionarily conserved proteins that pump diverse substrates across membranes. Many are known to efflux signaling molecules and are extensively expressed during development. However, the role of transporters in moving extracellular signals that regulate embryogenesis is largely unexplored. Here, we show that a mesodermal ABCC (MRP) transporter is necessary for endodermal gut morphogenesis in sea urchin embryos. This transporter, Sp-ABCC5a (C5a), is expressed in pigment cells and their precursors, which are a subset of the non-skeletogenic mesoderm (NSM) cells. C5a expression depends on Delta/Notch signaling from skeletogenic mesoderm and is downstream of Gcm in the aboral NSM gene regulatory network. Long-term imaging of development reveals that C5a knockdown embryos gastrulate, but ∼90% develop a prolapse of the hindgut by the late prism stage (∼8 h after C5a protein expression normally peaks). Since C5a orthologs efflux cyclic nucleotides, and cAMP-dependent protein kinase (Sp-CAPK/PKA) is expressed in pigment cells, we examined whether C5a could be involved in gastrulation through cAMP transport. Consistent with this hypothesis, membrane-permeable pCPT-cAMP rescues the prolapse phenotype in C5a knockdown embryos, and causes archenteron hyper-invagination in control embryos. In addition, the cAMP-producing enzyme soluble adenylyl cyclase (sAC) is expressed in pigment cells, and its inhibition impairs gastrulation. Together, our data support a model in which C5a transports sAC-derived cAMP from pigment cells to control late invagination of the hindgut. Little is known about the ancestral functions of ABCC5/MRP5 transporters, and this study reveals a novel role for these proteins in mesoderm-endoderm signaling during embryogenesis.
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Gokirmak T, Hamdoun A. Transport in technicolor: The sea urchin embryo as an epithelial transport model system. Mol Reprod Dev 2014. [DOI: 10.1002/mrd.22383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Gökirmak T, Shipp LE, Campanale JP, Nicklisch SCT, Hamdoun A. Transport in technicolor: mapping ATP-binding cassette transporters in sea urchin embryos. Mol Reprod Dev 2014; 81:778-93. [PMID: 25156004 DOI: 10.1002/mrd.22357] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 06/27/2014] [Indexed: 12/15/2022]
Abstract
One quarter of eukaryotic genes encode membrane proteins. These include nearly 1,000 transporters that translocate nutrients, signaling molecules, and xenobiotics across membranes. While it is well appreciated that membrane transport is critical for development, the specific roles of many transporters have remained cryptic, in part because of their abundance and the diversity of their substrates. Multidrug resistance ATP-binding cassette (ABC) efflux transporters are one example of cryptic membrane proteins. Although most organisms utilize these ABC transporters during embryonic development, many of these transporters have broad substrate specificity, and their developmental functions remain incompletely understood. Here, we review advances in our understanding of ABC transporters in sea urchin embryos, and methods developed to spatially and temporally map these proteins. These studies reveal that multifunctional transporters are required for signaling, homeostasis, and protection of the embryo, and shed light on how they are integrated into ancestral developmental pathways recapitulated in disease.
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Swartz SZ, Reich AM, Oulhen N, Raz T, Milos PM, Campanale JP, Hamdoun A, Wessel GM. Deadenylase depletion protects inherited mRNAs in primordial germ cells. Development 2014; 141:3134-42. [PMID: 25100654 PMCID: PMC4197533 DOI: 10.1242/dev.110395] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 06/22/2014] [Indexed: 12/12/2022]
Abstract
A crucial event in animal development is the specification of primordial germ cells (PGCs), which become the stem cells that create sperm and eggs. How PGCs are created provides a valuable paradigm for understanding stem cells in general. We find that the PGCs of the sea urchin Strongylocentrotus purpuratus exhibit broad transcriptional repression, yet enrichment for a set of inherited mRNAs. Enrichment of several germline determinants in the PGCs requires the RNA-binding protein Nanos to target the transcript that encodes CNOT6, a deadenylase, for degradation in the PGCs, thereby creating a stable environment for RNA. Misexpression of CNOT6 in the PGCs results in their failure to retain Seawi transcripts and Vasa protein. Conversely, broad knockdown of CNOT6 expands the domain of Seawi RNA as well as exogenous reporters. Thus, Nanos-dependent spatially restricted CNOT6 differential expression is used to selectively localize germline RNAs to the PGCs. Our findings support a 'time capsule' model of germline determination, whereby the PGCs are insulated from differentiation by retaining the molecular characteristics of the totipotent egg and early embryo.
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Campanale JP, Gökirmak T, Espinoza JA, Oulhen N, Wessel GM, Hamdoun A. Migration of sea urchin primordial germ cells. Dev Dyn 2014; 243:917-27. [PMID: 24677545 PMCID: PMC4164171 DOI: 10.1002/dvdy.24133] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 03/23/2014] [Accepted: 03/24/2014] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Small micromeres are produced at the fifth cleavage of sea urchin development. They express markers of primordial germ cells (PGCs), and are required for the production of gametes. In most animals, PGCs migrate from sites of formation to the somatic gonad. Here, we investigated whether they also exhibit similar migratory behaviors using live-cell imaging of small micromere plasma membranes. RESULTS Early in gastrulation, small micromeres transition from non-motile epithelial cells, to motile quasi-mesenchymal cells. Late in gastrulation, at 43 hr post fertilization (HPF), they are embedded in the tip of the archenteron, but remain motile. From 43-49 HPF, they project numerous cortical blebs into the blastocoel, and filopodia that contact ectoderm. By 54 HPF, they begin moving in the plane of the blastoderm, often in a directed fashion, towards the coelomic pouches. Isolated small micromeres also produced blebs and filopodia. CONCLUSIONS Previous work suggested that passive translocation governs some of the movement of small micromeres during gastrulation. Here we show that small micromeres are motile cells that can traverse the archenteron, change position along the left-right axis, and migrate to coelomic pouches. These motility mechanisms are likely to play an important role in their left-right segregation.
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Campanale JP, Gökirmak T, Espinoza JA, Oulhen N, Wessel GM, Hamdoun A. Migration of sea urchin primordial germ cells. Dev Dyn 2014. [DOI: 10.1002/dvdy.24049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Nicklisch S, Bonito L, Sandin S, Hamdoun A. Identification and characterization of the molecular interactions of persistent organic pollutants with the multidrug resistance transport protein ABCB1 (974.4). FASEB J 2014. [DOI: 10.1096/fasebj.28.1_supplement.974.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Gokirmak T, Campanale J, Shipp L, Moy G, Hamdoun A. Understanding mechanisms of multidrug resistance with guidance from evolution (994.2). FASEB J 2014. [DOI: 10.1096/fasebj.28.1_supplement.994.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Cole BJ, Hamdoun A, Epel D. Cost, effectiveness and environmental relevance of multidrug transporters in sea urchin embryos. ACTA ACUST UNITED AC 2013; 216:3896-905. [PMID: 23913944 DOI: 10.1242/jeb.090522] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
ATP-binding cassette transporters protect cells via efflux of xenobiotics and endogenous byproducts of detoxification. While the cost of this ATP-dependent extrusion is known at the molecular level, i.e. the ATP used for each efflux event, the overall cost to a cell or organism of operating this defense is unclear, especially as the cost of efflux changes depending on environmental conditions. During prolonged exposure to xenobiotics, multidrug transporter activity could be costly and ineffective because effluxed substrate molecules are not modified in the process and could thus undergo repeated cycles of efflux and re-entry. Here we use embryos of the purple sea urchin, Strongylocentrotus purpuratus, as a model to determine transport costs and benefits under environmentally relevant xenobiotic concentrations. Strikingly, our results show that efflux transporter activity costs less than 0.2% of total ATP usage, as a proportion of oxygen consumption. The benefits of transport, defined as the reduction in substrate accumulation due to transporter activity, depended largely, but not entirely, on the rate of passive flux of each substrate across the plasma membrane. One of the substrates tested exhibited rapid membrane permeation coupled with high rates of efflux, thus inducing rapid and futile cycles of efflux followed by re-entry of the substrate. This combination significantly reduced transporter effectiveness as a defense and increased costs even at relatively low substrate concentrations. Despite these effects with certain substrates, our results show that efflux transporters are a remarkably effective and low-cost first line of defense against exposure to environmentally relevant concentrations of xenobiotics.
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Campanale JP, Hamdoun A. Programmed reduction of ABC transporter activity in sea urchin germline progenitors. Development 2013. [DOI: 10.1242/dev.098830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Gökirmak T, Campanale JP, Shipp LE, Moy GW, Tao H, Hamdoun A. Localization and substrate selectivity of sea urchin multidrug (MDR) efflux transporters. J Biol Chem 2012; 287:43876-83. [PMID: 23124201 DOI: 10.1074/jbc.m112.424879] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this study, we cloned, expressed and functionally characterized Stronglycentrotus purpuratus (Sp) ATP-binding cassette (ABC) transporters. This screen identified three multidrug resistance (MDR) transporters with functional homology to the major types of MDR transporters found in humans. When overexpressed in embryos, the apical transporters Sp-ABCB1a, ABCB4a, and ABCG2a can account for as much as 87% of the observed efflux activity, providing a robust assay for their substrate selectivity. Using this assay, we found that sea urchin MDR transporters export canonical MDR susbtrates such as calcein-AM, bodipy-verapamil, bodipy-vinblastine, and mitoxantrone. In addition, we characterized the impact of nonconservative substitutions in the primary sequences of drug binding domains of sea urchin versus murine ABCB1 by mutation of Sp-ABCB1a and treatment of embryos with stereoisomeric cyclic peptide inhibitors (QZ59 compounds). The results indicated that two substitutions in transmembrane helix 6 reverse stereoselectivity of Sp-ABCB1a for QZ59 enantiomers compared with mouse ABCB1a. This suggests that subtle changes in the primary sequence of transporter drug binding domains could fine-tune substrate specificity through evolution.
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Whalen K, Reitzel AM, Hamdoun A. Actin polymerization controls the activation of multidrug efflux at fertilization by translocation and fine-scale positioning of ABCB1 on microvilli. Mol Biol Cell 2012; 23:3663-72. [PMID: 22855533 PMCID: PMC3442413 DOI: 10.1091/mbc.e12-06-0438] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Multidrug efflux is activated at fertilization in sea urchin eggs, but it is unclear how cortical reorganization initiates transport. Using structured illumination microscopy, we found that the multidrug transporter ABCB1a translocates along polymerizing actin filaments to the microvillar tips. This short-range (micrometer scale) translocation is necessary for up-regulation of efflux activity. Fertilization changes the structure and function of the cell surface. In sea urchins, these changes include polymerization of cortical actin and a coincident, switch-like increase in the activity of the multidrug efflux transporter ABCB1a. However, it is not clear how cortical reorganization leads to changes in membrane transport physiology. In this study, we used three-dimensional superresolution fluorescence microscopy to resolve the fine-scale movements of the transporter along polymerizing actin filaments, and we show that efflux activity is established after ABCB1a translocates to the tips of the microvilli. Inhibition of actin polymerization or bundle formation prevents tip localization, resulting in the patching of ABCB1a at the cell surface and decreased efflux activity. In contrast, enhanced actin polymerization promotes tip localization. Finally, interference with Rab11, a regulator of apical recycling, inhibits activation of efflux activity in embryos. Together our results show that actin-mediated, short-range traffic and positioning of transporters at the cell surface regulates multidrug efflux activity and highlight the multifaceted roles of microvilli in the spatial distribution of membrane proteins.
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Shipp LE, Hamdoun A. ATP-binding cassette (ABC) transporter expression and localization in sea urchin development. Dev Dyn 2012; 241:1111-24. [PMID: 22473856 DOI: 10.1002/dvdy.23786] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/26/2012] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND ATP-binding cassette (ABC) transporters are membrane proteins that regulate intracellular concentrations of myriad compounds and ions. There are >100 ABC transporter predictions in the Strongylocentrotus purpuratus genome, including 40 annotated ABCB, ABCC, and ABCG "multidrug efflux" transporters. Despite the importance of multidrug transporters for protection and signaling, their expression patterns have not been characterized in deuterostome embryos. RESULTS Sea urchin embryos expressed 20 ABCB, ABCC, and ABCG transporter genes in the first 58 hr of development, from unfertilized egg to early prism. We quantified transcripts of ABCB1a, ABCB4a, ABCC1, ABCC5a, ABCC9a, and ABCG2b, and found that ABCB1a mRNA was 10-100 times more abundant than other transporter mRNAs. In situ hybridization showed ABCB1a was expressed ubiquitously in embryos, while ABCC5a was restricted to secondary mesenchyme cells and their precursors. Fluorescent protein fusions showed localization of ABCB1a on apical cell surfaces, and ABCC5a on basolateral surfaces. CONCLUSIONS Embryos use many ABC transporters with predicted functions in cell signaling, lysosomal and mitochondrial homeostasis, potassium channel regulation, pigmentation, and xenobiotic efflux. Detailed characterization of ABCB1a and ABCC5a revealed that they have different temporal and spatial gene expression profiles and protein localization patterns that correlate to their predicted functions in protection and development, respectively.
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Campanale JP, Hamdoun A. Programmed reduction of ABC transporter activity in sea urchin germline progenitors. Development 2012; 139:783-92. [PMID: 22274698 PMCID: PMC3265063 DOI: 10.1242/dev.076752] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2011] [Indexed: 12/15/2022]
Abstract
ATP-binding cassette (ABC) transporters protect embryos and stem cells from mutagens and pump morphogens that control cell fate and migration. In this study, we measured dynamics of ABC transporter activity during formation of sea urchin embryonic cells necessary for the production of gametes, termed the small micromeres. Unexpectedly, we found small micromeres accumulate 2.32 times more of the ABC transporter substrates calcein-AM, CellTrace RedOrange, BoDipy-verapamil and BoDipy-vinblastine, than any other cell in the embryo, indicating a reduction in multidrug efflux activity. The reduction in small micromere ABC transporter activity is mediated by a pulse of endocytosis occurring 20-60 minutes after the appearance of the micromeres--the precursors of the small micromeres. Treating embryos with phenylarsine oxide, an inhibitor of endocytosis, prevents the reduction of transporter activity. Tetramethylrhodamine dextran and cholera toxin B uptake experiments indicate that micromeres have higher rates of bulk and raft-associated membrane endocytosis during the window of transporter downregulation. We hypothesized that this loss of efflux transport could be required for the detection of developmental signaling molecules such as germ cell chemoattractants. Consistent with this hypothesis, we found that the inhibition of ABCB and ABCC-types of efflux transporters disrupts the ordered distribution of small micromeres to the left and right coelomic pouches. These results point to tradeoffs between signaling and the protective functions of the transporters.
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Hamdoun A, Campanale J, Gokirmak T, Shipp L, Whalen K. Abstract C69: Ontogenetic switches in activity and location of multidrug efflux transporters during embryonic development. Cancer Res 2011. [DOI: 10.1158/1538-7445.fbcr11-c69] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Multidrug resistance, mediated by ATP binding cassette (ABC) transporters, is a major obstacle to the treatment of metastatic cancer. This phenomenon has eluded treatment by direct pharmacological inhibition of the multidrug transporters responsible for resistance. An alternative strategy could be to control drug resistance by targeting the cellular regulation of insertion and retrieval of transporters from the plasma membrane. However, the pleiomorphic nature of cancer cells and tumors complicates the identification of core machinery involved in regulation of transporter dynamics. Embryos have natural, rapid switches in multidrug efflux activity, coincident with the normal reorganization of cell surfaces at fertilization and at epithelial to mesenchymal transitions.
We are focusing on two major changes in surface organization and transport activity occurring during the first 24 hours of sea urchin development. As basal deuterostomes, the branch of evolution leading to vertebrates, sea urchins provide a tractable system in which core machinery regulating multidrug efflux transporters can be manipulated and characterized. The first occurs at fertilization and involves the activation of transport by shortrange, actin-dependent translocation of ABCB1a (aka P-gp, MDR1). Super-resolution fluorescence microscopy reveals that transporters move to the to the distal tips of microvilli, possibly to overcome diffusive limits in the boundary layer between microvilli. The second switch in activity is a selective downregulation of multidrug efflux transport that occurs in germline progenitors of these animals and results in long-term reduction of transport. It is mediated by endocytosis of the proteins in those cells coincident with changes in apicobasal cell polarity. We are currently investigating the sequence of events that leads to pump retrieval in these cells. The implications of this work are new insights into the molecular switches that govern acquisition and loss of transporter-mediated drug resistance during differentiation.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr C69.
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Patel S, Ramakrishnan L, Rahman T, Hamdoun A, Marchant JS, Taylor CW, Brailoiu E. The endo-lysosomal system as an NAADP-sensitive acidic Ca(2+) store: role for the two-pore channels. Cell Calcium 2011; 50:157-67. [PMID: 21529939 DOI: 10.1016/j.ceca.2011.03.011] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Accepted: 03/26/2011] [Indexed: 12/22/2022]
Abstract
Accumulating evidence suggests that the endo-lysosomal system provides a substantial store of Ca(2+) that is tapped by the Ca(2+)-mobilizing messenger, NAADP. In this article, we review evidence that NAADP-mediated Ca(2+) release from this acidic Ca(2+) store proceeds through activation of the newly described two-pore channels (TPCs). We discuss recent advances in defining the sub-cellular targeting, topology and biophysics of TPCs. We also discuss physiological roles and the evolution of this ubiquitous ion channel family.
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Swartz SZ, Juliano CE, Raz T, Lipson D, Milos P, Hamdoun A, Wessel GM. An ancient molecular circuit specifying multipotency. Dev Biol 2010. [DOI: 10.1016/j.ydbio.2010.05.368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Elmadani A, Gasmelseed N, Abuidris D, Hamdoun A. Pattern of thyroid diseases in central Sudan: Nuclear medicine perspective. SUDAN JOURNAL OF MEDICAL SCIENCES 2010. [DOI: 10.4314/sjms.v4i4.50999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Bošnjak I, Uhlinger KR, Heim W, Smital T, Franekić-Čolić J, Coale K, Epel D, Hamdoun A. Multidrug efflux transporters limit accumulation of inorganic, but not organic, mercury in sea urchin embryos. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:8374-80. [PMID: 19924972 PMCID: PMC3166226 DOI: 10.1021/es901677r] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Mercuric compounds are persistent global pollutants that accumulate in marine organisms and in humans who consume them. While the chemical cycles and speciation of mercury in the oceans are relatively well described, the cellular mechanisms that govern which forms of mercury accumulate in cells and why they persist are less understood. In this study we examined the role of multidrug efflux transport in the differential accumulation of inorganic (HgCl(2)) and organic (CH(3)HgCl) mercury in sea urchin (Strongylocentrotus purpuratus) embryos. We found that inhibition of MRP/ABCC-type transporters increases intracellular accumulation of inorganic mercury but had no effect on accumulation of organic mercury. Similarly, pharmacological inhibition of metal conjugating enzymes by ligands GST/GSH significantly increases this antimitotic potency of inorganic mercury, but had no effect on the potency of organic mercury. Our results point to MRP-mediated elimination of inorganic mercury conjugates as a cellular basis for differences in the accumulation and potency of the two major forms of mercury found in marine environments.
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Epel D, Luckenbach T, Stevenson CN, Macmanus-Spencer LA, Hamdoun A, Smital T. Efflux transporters: newly appreciated roles in protection against pollutants. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:3914-20. [PMID: 18589945 PMCID: PMC3160781 DOI: 10.1021/es087187v] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
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Abstract
Contrary to the view that embryos and larvae are the most fragile stages of life, development is stable under real-world conditions. Early cleavage embryos are prepared for environmental vagaries by having high levels of cellular defenses already present in the egg before fertilization. Later in development, adaptive responses to the environment either buffer stress or produce alternative developmental phenotypes. These buffers, defenses, and alternative pathways set physiological limits for development under expected conditions; teratology occurs when embryos encounter unexpected environmental changes and when stress exceeds these limits. Of concern is that rapid anthropogenic changes to the environment are beyond the range of these protective mechanisms.
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Goldstone J, Hamdoun A, Cole B, Howard-Ashby M, Nebert D, Scally M, Dean M, Epel D, Hahn M, Stegeman J. The chemical defensome: environmental sensing and response genes in the Strongylocentrotus purpuratus genome. Dev Biol 2006; 300:366-84. [PMID: 17097629 PMCID: PMC3166225 DOI: 10.1016/j.ydbio.2006.08.066] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2006] [Revised: 08/18/2006] [Accepted: 08/28/2006] [Indexed: 01/08/2023]
Abstract
Metazoan genomes contain large numbers of genes that participate in responses to environmental stressors. We surveyed the sea urchin Strongylocentrotus purpuratus genome for homologs of gene families thought to protect against chemical stressors; these genes collectively comprise the 'chemical defensome.' Chemical defense genes include cytochromes P450 and other oxidases, various conjugating enzymes, ATP-dependent efflux transporters, oxidative detoxification proteins, and transcription factors that regulate these genes. Together such genes account for more than 400 genes in the sea urchin genome. The transcription factors include homologs of the aryl hydrocarbon receptor, hypoxia-inducible factor, nuclear factor erythroid-derived 2, heat shock factor, and nuclear hormone receptors, which regulate stress-response genes in vertebrates. Some defense gene families, including the ABCC, the UGT, and the CYP families, have undergone expansion in the urchin relative to other deuterostome genomes, whereas the stress sensor gene families do not show such expansion. More than half of the defense genes are expressed during embryonic or larval life stages, indicating their importance during development. This genome-wide survey of chemical defense genes in the sea urchin reveals evolutionary conservation of this network combined with lineage-specific diversification that together suggest the importance of these chemical stress sensing and response mechanisms in early deuterostomes. These results should facilitate future studies on the evolution of chemical defense gene networks and the role of these networks in protecting embryos from chemical stress during development.
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Sodergren E, Weinstock GM, Davidson EH, Cameron RA, Gibbs RA, Angerer RC, Angerer LM, Arnone MI, Burgess DR, Burke RD, Coffman JA, Dean M, Elphick MR, Ettensohn CA, Foltz KR, Hamdoun A, Hynes RO, Klein WH, Marzluff W, McClay DR, Morris RL, Mushegian A, Rast JP, Smith LC, Thorndyke MC, Vacquier VD, Wessel GM, Wray G, Zhang L, Elsik CG, Ermolaeva O, Hlavina W, Hofmann G, Kitts P, Landrum MJ, Mackey AJ, Maglott D, Panopoulou G, Poustka AJ, Pruitt K, Sapojnikov V, Song X, Souvorov A, Solovyev V, Wei Z, Whittaker CA, Worley K, Durbin KJ, Shen Y, Fedrigo O, Garfield D, Haygood R, Primus A, Satija R, Severson T, Gonzalez-Garay ML, Jackson AR, Milosavljevic A, Tong M, Killian CE, Livingston BT, Wilt FH, Adams N, Bellé R, Carbonneau S, Cheung R, Cormier P, Cosson B, Croce J, Fernandez-Guerra A, Genevière AM, Goel M, Kelkar H, Morales J, Mulner-Lorillon O, Robertson AJ, Goldstone JV, Cole B, Epel D, Gold B, Hahn ME, Howard-Ashby M, Scally M, Stegeman JJ, Allgood EL, Cool J, Judkins KM, McCafferty SS, Musante AM, Obar RA, Rawson AP, Rossetti BJ, Gibbons IR, Hoffman MP, Leone A, Istrail S, Materna SC, Samanta MP, Stolc V, Tongprasit W, Tu Q, Bergeron KF, Brandhorst BP, Whittle J, Berney K, Bottjer DJ, Calestani C, Peterson K, Chow E, Yuan QA, Elhaik E, Graur D, Reese JT, Bosdet I, Heesun S, Marra MA, Schein J, Anderson MK, Brockton V, Buckley KM, Cohen AH, Fugmann SD, Hibino T, Loza-Coll M, Majeske AJ, Messier C, Nair SV, Pancer Z, Terwilliger DP, Agca C, Arboleda E, Chen N, Churcher AM, Hallböök F, Humphrey GW, Idris MM, Kiyama T, Liang S, Mellott D, Mu X, Murray G, Olinski RP, Raible F, Rowe M, Taylor JS, Tessmar-Raible K, Wang D, Wilson KH, Yaguchi S, Gaasterland T, Galindo BE, Gunaratne HJ, Juliano C, Kinukawa M, Moy GW, Neill AT, Nomura M, Raisch M, Reade A, Roux MM, Song JL, Su YH, Townley IK, Voronina E, Wong JL, Amore G, Branno M, Brown ER, Cavalieri V, Duboc V, Duloquin L, Flytzanis C, Gache C, Lapraz F, Lepage T, Locascio A, Martinez P, Matassi G, Matranga V, Range R, Rizzo F, Röttinger E, Beane W, Bradham C, Byrum C, Glenn T, Hussain S, Manning G, Miranda E, Thomason R, Walton K, Wikramanayke A, Wu SY, Xu R, Brown CT, Chen L, Gray RF, Lee PY, Nam J, Oliveri P, Smith J, Muzny D, Bell S, Chacko J, Cree A, Curry S, Davis C, Dinh H, Dugan-Rocha S, Fowler J, Gill R, Hamilton C, Hernandez J, Hines S, Hume J, Jackson L, Jolivet A, Kovar C, Lee S, Lewis L, Miner G, Morgan M, Nazareth LV, Okwuonu G, Parker D, Pu LL, Thorn R, Wright R. The genome of the sea urchin Strongylocentrotus purpuratus. Science 2006; 314:941-52. [PMID: 17095691 PMCID: PMC3159423 DOI: 10.1126/science.1133609] [Citation(s) in RCA: 798] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes.
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Epel D, Cole B, Hamdoun A, Thurber RV. The sea urchin embryo as a model for studying efflux transporters: roles and energy cost. MARINE ENVIRONMENTAL RESEARCH 2006; 62 Suppl:S1-4. [PMID: 16740304 PMCID: PMC3160780 DOI: 10.1016/j.marenvres.2006.04.062] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We describe the use of the sea urchin as a model for studying efflux transporters and estimating energy cost for the cytotoxin protective system provided by these transporters. The unfertilized egg has low transport activity, which increases to a new steady state shortly after fertilization. Activity results from p-glycoprotein (p-gp) and MRP type transporters which protect the embryo from cytotoxic drugs that can disrupt cell division or induce apoptosis. The energy cost is estimated from a novel use of calcein-AM as a substrate; keeping 0.25 microM substrate levels out of the cell utilizes only 0.023% of steady state respiration.
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