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Insights to the Structural Basis for the Stereospecificity of the Escherichia coli Phytase, AppA. Int J Mol Sci 2022; 23:ijms23116346. [PMID: 35683026 PMCID: PMC9181005 DOI: 10.3390/ijms23116346] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 05/30/2022] [Accepted: 06/02/2022] [Indexed: 02/01/2023] Open
Abstract
AppA, the Escherichia coli periplasmic phytase of clade 2 of the histidine phosphatase (HP2) family, has been well-characterized and successfully engineered for use as an animal feed supplement. AppA is a 1D-6-phytase and highly stereospecific but transiently accumulates 1D-myo-Ins(2,3,4,5)P4 and other lower phosphorylated intermediates. If this bottleneck in liberation of orthophosphate is to be obviated through protein engineering, an explanation of its rather rigid preference for the initial site and subsequent cleavage of phytic acid is required. To help explain this behaviour, the role of the catalytic proton donor residue in determining AppA stereospecificity was investigated. Four variants were generated by site-directed mutagenesis of the active site HDT amino acid sequence motif containing the catalytic proton donor, D304. The identity and position of the prospective proton donor residue was found to strongly influence stereospecificity. While the wild-type enzyme has a strong preference for 1D-6-phytase activity, a marked reduction in stereospecificity was observed for a D304E variant, while a proton donor-less mutant (D304A) displayed exclusive 1D-1/3-phytase activity. High-resolution X-ray crystal structures of complexes of the mutants with a non-hydrolysable substrate analogue inhibitor point to a crucial role played by D304 in stereospecificity by influencing the size and polarity of specificity pockets A and B. Taken together, these results provide the first evidence for the involvement of the proton donor residue in determining the stereospecificity of HP2 phytases and prepares the ground for structure-informed engineering studies targeting the production of animal feed enzymes capable of the efficient and complete dephosphorylation of dietary phytic acid.
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2
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Zubair M, Hamzah R, Griffin R, Ali N. Identification and functional characterization of multiple inositol polyphosphate phosphatase1 (Minpp1) isoform-2 in exosomes with potential to modulate tumor microenvironment. PLoS One 2022; 17:e0264451. [PMID: 35235602 PMCID: PMC8890658 DOI: 10.1371/journal.pone.0264451] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 02/10/2022] [Indexed: 01/06/2023] Open
Abstract
Inositol polyphosphates (InsPs) play key signaling roles in diverse cellular functions, including calcium homeostasis, cell survival and death. Multiple inositol polyphosphate phosphatase 1 (Minpp1) affects the cellular levels of InsPs and cell functions. The Minpp1 is an endoplasmic reticulum (ER) resident but localizes away from its cytosolic InsPs substrates. The current study examines the heterogeneity of Minpp1 and the potential physiologic impact of Minpp1 isoforms, distinct motifs, subcellular distribution, and enzymatic potential. The NCBI database was used to analyze the proteome diversity of Minpp1 using bioinformatics tools. The analysis revealed that translation of three different Minpp1 variants resulted in three isoforms of Minpp1 of varying molecular weights. A link between the minpp1 variant-2 gene and ER-stress, using real-time PCR, suggests a functional similarity between minpp1 variant-1 and variant-2. A detailed study on motifs revealed Minpp1 isoform-2 is the only other isoform, besides isoform-1, that carries a phosphatase motif for InsPs hydrolysis but no ER-retention signal. The confocal microscopy revealed that the Minpp1 isoform-1 predominantly localized near the nucleus with a GRP-78 ER marker, while Minpp1 isoform-2 was scattered more towards the cell periphery where it co-localizes with the plasma membrane-destined multivesicular bodies biomarker CD63. MCF-7 cells were used to establish that Minpp1 isoform-2 is secreted into exosomes. Brefeldin A treatment resulted in overexpression of the exosome-associated Minpp1 isoform-2, suggesting its secretion via an unconventional route involving endocytic-generated vesicles and a link to ER stress. Results further demonstrated that the exosome-associated Minpp1 isoform-2 was enzymatically active. Overall, the data support the possibility that an extracellular form of enzymatically active Minpp1 isoform-2 mitigates any anti-proliferative actions of extracellular InsPs, thereby also impacting the makeup of the tumor microenvironment.
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Affiliation(s)
- Mohd Zubair
- Department of Biology, University of Arkansas at Little Rock, Little Rock, AR, United States of America
| | - Rabab Hamzah
- Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America
- Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, Little Rock, AR, United States of America
| | - Robert Griffin
- Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America
| | - Nawab Ali
- Department of Biology, University of Arkansas at Little Rock, Little Rock, AR, United States of America
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3
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Pérez-Rodriguez S, Wulff T, Voldborg BG, Altamirano C, Trujillo-Roldán MA, Valdez-Cruz NA. Compartmentalized Proteomic Profiling Outlines the Crucial Role of the Classical Secretory Pathway during Recombinant Protein Production in Chinese Hamster Ovary Cells. ACS OMEGA 2021; 6:12439-12458. [PMID: 34056395 PMCID: PMC8154153 DOI: 10.1021/acsomega.0c06030] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 02/24/2021] [Indexed: 05/11/2023]
Abstract
Different cellular processes that contribute to protein production in Chinese hamster ovary (CHO) cells have been previously investigated by proteomics. However, although the classical secretory pathway (CSP) has been well documented as a bottleneck during recombinant protein (RP) production, it has not been well represented in previous proteomic studies. Hence, the significance of this pathway for production of RP was assessed by identifying its own proteins that were associated to changes in RP production, through subcellular fractionation coupled to shot-gun proteomics. Two CHO cell lines producing a monoclonal antibody with different specific productivities were used as cellular models, from which 4952 protein groups were identified, which represent a coverage of 59% of the Chinese hamster proteome. Data are available via ProteomeXchange with identifier PXD021014. By using SAM and ROTS algorithms, 493 proteins were classified as differentially expressed, of which about 80% was proposed as novel targets and one-third were assigned to the CSP. Endoplasmic reticulum (ER) stress, unfolded protein response, calcium homeostasis, vesicle traffic, glycosylation, autophagy, proteasomal activity, protein synthesis and translocation into ER lumen, and secretion of extracellular matrix components were some of the affected processes that occurred in the secretory pathway. Processes from other cellular compartments, such as DNA replication, transcription, cytoskeleton organization, signaling, and metabolism, were also modified. This study gives new insights into the molecular traits of higher producer cells and provides novel targets for development of new sub-lines with improved phenotypes for RP production.
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Affiliation(s)
- Saumel Pérez-Rodriguez
- Programa
de Investigación de Producción de Biomoléculas,
Departamento de Biología Molecular y Biotecnología,
Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510 Ciudad de
México, México
| | - Tune Wulff
- The
Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby 2800, Denmark
| | - Bjørn G. Voldborg
- The
Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby 2800, Denmark
| | - Claudia Altamirano
- Laboratorio
de Cultivos Celulares, Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2085 Valparaíso, Chile
| | - Mauricio A. Trujillo-Roldán
- Programa
de Investigación de Producción de Biomoléculas,
Departamento de Biología Molecular y Biotecnología,
Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510 Ciudad de
México, México
| | - Norma A. Valdez-Cruz
- Programa
de Investigación de Producción de Biomoléculas,
Departamento de Biología Molecular y Biotecnología,
Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510 Ciudad de
México, México
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4
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Acquistapace IM, Zi Etek MA, Li AWH, Salmon M, Kühn I, Bedford MR, Brearley CA, Hemmings AM. Snapshots during the catalytic cycle of a histidine acid phytase reveal an induced-fit structural mechanism. J Biol Chem 2020; 295:17724-17737. [PMID: 33454010 PMCID: PMC7762957 DOI: 10.1074/jbc.ra120.015925] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 10/10/2020] [Indexed: 11/16/2022] Open
Abstract
Highly engineered phytases, which sequentially hydrolyze the hexakisphosphate ester of inositol known as phytic acid, are routinely added to the feeds of monogastric animals to improve phosphate bioavailability. New phytases are sought as starting points to further optimize the rate and extent of dephosphorylation of phytate in the animal digestive tract. Multiple inositol polyphosphate phosphatases (MINPPs) are clade 2 histidine phosphatases (HP2P) able to carry out the stepwise hydrolysis of phytate. MINPPs are not restricted by a strong positional specificity making them attractive targets for development as feed enzymes. Here, we describe the characterization of a MINPP from the Gram-positive bacterium Bifidobacterium longum (BlMINPP). BlMINPP has a typical HP2P-fold but, unusually, possesses a large α-domain polypeptide insertion relative to other MINPPs. This insertion, termed the U-loop, spans the active site and contributes to substrate specificity pockets underpopulated in other HP2Ps. Mutagenesis of U-loop residues reveals its contribution to enzyme kinetics and thermostability. Moreover, four crystal structures of the protein along the catalytic cycle capture, for the first time in an HP2P, a large ligand-driven α-domain motion essential to allow substrate access to the active site. This motion recruits residues both downstream of a molecular hinge and on the U-loop to participate in specificity subsites, and mutagenesis identified a mobile lysine residue as a key determinant of positional specificity of the enzyme. Taken together, these data provide important new insights to the factors determining stability, substrate recognition, and the structural mechanism of hydrolysis in this industrially important group of enzymes.
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Affiliation(s)
| | - Monika A Zi Etek
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Arthur W H Li
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Melissa Salmon
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | | | | | - Charles A Brearley
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Andrew M Hemmings
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom; School of Chemistry, University of East Anglia, Norwich, United Kingdom.
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5
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Kilaparty SP, Agarwal R, Singh P, Kannan K, Ali N. Endoplasmic reticulum stress-induced apoptosis accompanies enhanced expression of multiple inositol polyphosphate phosphatase 1 (Minpp1): a possible role for Minpp1 in cellular stress response. Cell Stress Chaperones 2016; 21:593-608. [PMID: 27038811 PMCID: PMC4907990 DOI: 10.1007/s12192-016-0684-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 03/16/2016] [Accepted: 03/17/2016] [Indexed: 01/22/2023] Open
Abstract
Inositol polyphosphates represent a group of differentially phosphorylated inositol metabolites, many of which are implicated to regulate diverse cellular processes such as calcium mobilization, vesicular trafficking, differentiation, apoptosis, etc. The metabolic network of these compounds is complex and tightly regulated by various kinases and phosphatases present predominantly in the cytosol. Multiple inositol polyphosphate phosphatase 1 (Minpp1) is the only known endoplasmic reticulum (ER) luminal enzyme that hydrolyzes various inositol polyphosphates in vitro as well as in vivo conditions. However, access of the Minpp1 to cytosolic substrates has not yet been demonstrated clearly and hence its physiological function. In this study, we examined a potential role for Minpp1 in ER stress-induced apoptosis. We generated a custom antibody and characterized its specificity to study the expression of Minpp1 protein in multiple mammalian cells under experimentally induced cellular stress conditions. Our results demonstrate a significant increase in the expression of Minpp1 in response to a variety of cellular stress conditions. The protein expression was corroborated with the expression of its mRNA and enzymatic activity. Further, in an attempt to link the role of Minpp1 to apoptotic stress, we studied the effect of Minpp1 expression on apoptosis following silencing of the Minpp1 gene by its specific siRNA. Our results suggest an attenuation of apoptotic parameters following knockdown of Minpp1. Thus, in addition to its known role in inositol polyphosphate metabolism, we have identified a novel role for Minpp1 as a stress-responsive protein. In summary, our results provide, for the first time, a probable link between ER stress-induced apoptosis and Minpp1 expression.
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Affiliation(s)
- Surya P Kilaparty
- Department of Biology, University of Arkansas at Little Rock, 2801 S University Avenue, Little Rock, AR, 72204, USA
| | - Rakhee Agarwal
- Department of Biology, University of Arkansas at Little Rock, 2801 S University Avenue, Little Rock, AR, 72204, USA
- Alexion Pharmaceuticals, Inc., Cheshire, CT, 06410, USA
| | - Pooja Singh
- Department of Biology, University of Arkansas at Little Rock, 2801 S University Avenue, Little Rock, AR, 72204, USA
| | - Krishnaswamy Kannan
- Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Nawab Ali
- Department of Biology, University of Arkansas at Little Rock, 2801 S University Avenue, Little Rock, AR, 72204, USA.
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6
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Kilaparty SP, Singh A, Baltosser WH, Ali N. Computational analysis reveals a successive adaptation of multiple inositol polyphosphate phosphatase 1 in higher organisms through evolution. Evol Bioinform Online 2014; 10:239-50. [PMID: 25574123 PMCID: PMC4275298 DOI: 10.4137/ebo.s18948] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/29/2014] [Accepted: 10/05/2014] [Indexed: 11/05/2022] Open
Abstract
Multiple inositol polyphosphate phosphatase 1 (Minpp1) in higher organisms dephosphorylates InsP6, the most abundant inositol phosphate. It also dephosphorylates less phosphorylated InsP5 and InsP4 and more phosphorylated InsP7 or InsP8. Minpp1 is classified as a member of the histidine acid phosphatase super family of proteins with functional resemblance to phytases found in lower organisms. This study took a bioinformatics approach to explore the extent of evolutionary diversification in Minpp1 structure and function in order to understand its physiological relevance in higher organisms. The human Minpp1 amino acid (AA) sequence was BLAST searched against available national protein databases. Phylogenetic analysis revealed that Minpp1 was widely distributed from lower to higher organisms. Further, we have identified that there exist four isoforms of Minpp1. Multiple computational tools were used to identify key functional motifs and their conservation among various species. Analyses showed that certain motifs predominant in higher organisms were absent in lower organisms. Variation in AA sequences within motifs was also analyzed. We found that there is diversification of key motifs and thus their functions present in Minpp1 from lower organisms to higher organisms. Another interesting result of this analysis was the presence of a glucose-1-phosphate interaction site in Minpp1; the functional significance of which has yet to be determined experimentally. The overall findings of our study point to an evolutionary adaptability of Minpp1 functions from lower to higher life forms.
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Affiliation(s)
- Surya P Kilaparty
- Department of Biology, University of Arkansas at Little Rock, Arkansas, USA
| | - Awantika Singh
- UAMS/UALR Joint Bioinformatics Program, University of Arkansas at Little Rock, Arkansas, USA
| | | | - Nawab Ali
- Department of Biology, University of Arkansas at Little Rock, Arkansas, USA
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7
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Stentz R, Osborne S, Horn N, Li AWH, Hautefort I, Bongaerts R, Rouyer M, Bailey P, Shears SB, Hemmings AM, Brearley CA, Carding SR. A bacterial homolog of a eukaryotic inositol phosphate signaling enzyme mediates cross-kingdom dialog in the mammalian gut. Cell Rep 2014; 6:646-56. [PMID: 24529702 PMCID: PMC3969271 DOI: 10.1016/j.celrep.2014.01.021] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 12/13/2013] [Accepted: 01/15/2014] [Indexed: 11/25/2022] Open
Abstract
Dietary InsP6 can modulate eukaryotic cell proliferation and has complex nutritive consequences, but its metabolism in the mammalian gastrointestinal tract is poorly understood. Therefore, we performed phylogenetic analyses of the gastrointestinal microbiome in order to search for candidate InsP6 phosphatases. We determined that prominent gut bacteria express homologs of the mammalian InsP6 phosphatase (MINPP) and characterized the enzyme from Bacteroides thetaiotaomicron (BtMinpp). We show that BtMinpp has exceptionally high catalytic activity, which we rationalize on the basis of mutagenesis studies and by determining its crystal structure at 1.9 Å resolution. We demonstrate that BtMinpp is packaged inside outer membrane vesicles (OMVs) protecting the enzyme from degradation by gastrointestinal proteases. Moreover, we uncover an example of cross-kingdom cell-to-cell signaling, showing that the BtMinpp-OMVs interact with intestinal epithelial cells to promote intracellular Ca2+ signaling. Our characterization of BtMinpp offers several directions for understanding how the microbiome serves human gastrointestinal physiology. Bacteroides thetaiotaomicron (Bt) secretes a cell-signaling InsP6 phosphatase MINPP BtMinpp is exceptionally active and rationalized from its crystal structure BtMinpp is secreted in outermembrane vesicles BtMinpp/OMVs promote Ca2+ signaling in intestinal epithelial cells
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Affiliation(s)
- Régis Stentz
- Gut Health and Food Safety Programme, Institute of Food Research, Norwich NR4 7UA, UK
| | - Samantha Osborne
- Gut Health and Food Safety Programme, Institute of Food Research, Norwich NR4 7UA, UK
| | - Nikki Horn
- Gut Health and Food Safety Programme, Institute of Food Research, Norwich NR4 7UA, UK
| | - Arthur W H Li
- School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK
| | - Isabelle Hautefort
- Gut Health and Food Safety Programme, Institute of Food Research, Norwich NR4 7UA, UK
| | - Roy Bongaerts
- Gut Health and Food Safety Programme, Institute of Food Research, Norwich NR4 7UA, UK
| | - Marine Rouyer
- Gut Health and Food Safety Programme, Institute of Food Research, Norwich NR4 7UA, UK
| | - Paul Bailey
- Department of Computational and Systems Biology, John Innes Centre, Norwich NR4 7UH, UK
| | - Stephen B Shears
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Andrew M Hemmings
- School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK; School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
| | - Charles A Brearley
- School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
| | - Simon R Carding
- Gut Health and Food Safety Programme, Institute of Food Research, Norwich NR4 7UA, UK; Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, UK.
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8
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Cho J, Choi K, Darden T, Reynolds PR, Petitte JN, Shears SB. Avian multiple inositol polyphosphate phosphatase is an active phytase that can be engineered to help ameliorate the planet's "phosphate crisis". J Biotechnol 2006; 126:248-59. [PMID: 16759730 PMCID: PMC1892222 DOI: 10.1016/j.jbiotec.2006.04.028] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Revised: 03/24/2006] [Accepted: 04/07/2006] [Indexed: 11/18/2022]
Abstract
Contemporary phytase research is primarily concerned with ameliorating the problem of inadequate digestion of inositol hexakisphosphate (phytate; InsP6) in monogastric farm animal feed, so as to reduce the pollution that results from the high phosphate content of the manure. In the current study we pursue a new, safe and cost-effective solution. We demonstrate that the rate of hydrolysis of InsP6 by recombinant avian MINPP (0.7 micromol/mg protein/min) defines it as by far the most active phytase found to date in any animal cell (the corresponding activity of recombinant mammalian MINPP is only 0.006 micromol/mg protein/min). Although avian MINPP has less than 20% sequence identity with microbial phytases, we create a homology model of MINPP in which it is predicted that the structure of the phytase active site is well-conserved. This model is validated by site-directed mutagenesis and by use of a substrate analogue, scyllo-InsP6, which we demonstrate is only a weak MINPP substrate. In a model chicken cell line, we overexpressed a mutant form of MINPP that is secretion-competent. This version of the enzyme was actively secreted without affecting either cell viability or the cellular levels of any inositol phosphates. Our studies offer a genetic strategy for greatly improving dietary InsP6 digestion in poultry.
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Affiliation(s)
- Jaiesoon Cho
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHSS, Research Triangle Park, P.O. Box 12233, NC 27709, USA
| | - Kuicheon Choi
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHSS, Research Triangle Park, P.O. Box 12233, NC 27709, USA
| | - Thomas Darden
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, NIH, DHSS, Research Triangle Park, P.O. Box 12233, NC 27709, USA
| | - Paul R. Reynolds
- Department of Environmental and Occupational Health, University of Pittsburgh, 3343 Forbes Avenue, Pittsburgh, PA 15260, USA
| | - James N. Petitte
- College of Agriculture and Life Science, NC State University, Raleigh, NC 27695, USA
| | - Stephen B. Shears
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHSS, Research Triangle Park, P.O. Box 12233, NC 27709, USA
- * Corresponding author. Tel.: +1 919 541 0793; fax: +1 919 541 0559. E-mail address: (S.B. Shears)
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9
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Delnatte C, Sanlaville D, Mougenot JF, Vermeesch JR, Houdayer C, Blois MCD, Genevieve D, Goulet O, Fryns JP, Jaubert F, Vekemans M, Lyonnet S, Romana S, Eng C, Stoppa-Lyonnet D. Contiguous gene deletion within chromosome arm 10q is associated with juvenile polyposis of infancy, reflecting cooperation between the BMPR1A and PTEN tumor-suppressor genes. Am J Hum Genet 2006; 78:1066-74. [PMID: 16685657 PMCID: PMC1474102 DOI: 10.1086/504301] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2005] [Accepted: 03/14/2006] [Indexed: 12/24/2022] Open
Abstract
We describe four unrelated children who were referred to two tertiary referral medical genetics units between 1991 and 2005 and who are affected with juvenile polyposis of infancy. We show that these children are heterozygous for a germline deletion encompassing two contiguous genes, PTEN and BMPR1A. We hypothesize that juvenile polyposis of infancy is caused by the deletion of these two genes and that the severity of the disease reflects cooperation between these two tumor-suppressor genes.
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Affiliation(s)
- Capucine Delnatte
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Damien Sanlaville
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Jean-François Mougenot
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Joris-Robert Vermeesch
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Claude Houdayer
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Marie-Christine de Blois
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - David Genevieve
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Olivier Goulet
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Jean-Pierre Fryns
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Francis Jaubert
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Michel Vekemans
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Stanislas Lyonnet
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Serge Romana
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Charis Eng
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
| | - Dominique Stoppa-Lyonnet
- Department of Genetics, Institut Curie, and Departments of Genetics, Pediatrics, and Pathology, Hôpital Necker-Enfants Malades, Assistance Publique–Hôpitaux de Paris, and INSERM Equipe Mixte INSERM E0210, Paris; Center of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; and Cleveland Clinic Genomic Medicine Institute and Department of Genetics, Case Western Reserve University School of Medicine, Cleveland
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10
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Hidaka K, Kanematsu T, Caffrey JJ, Takeuchi H, Shears SB, Hirata M. The importance to chondrocyte differentiation of changes in expression of the multiple inositol polyphosphate phosphatase. Exp Cell Res 2003; 290:254-64. [PMID: 14567985 DOI: 10.1016/s0014-4827(03)00337-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It is important to both physiological and pathological osteogenesis to understand the significance of changes in gene expression in growth-plate chondrocytes that transit between the proliferative and hypertrophic states. MINPP is one such gene of interest. The Minpp protein dephosphorylates highly phosphorylated inositol signaling molecules InsP(5) and InsP(6). We show here that the ATDC5 chondrocyte progenitor cell line can recapitulate developmentally specific changes in MINPP expression previously only seen in longitudinal bone growth plates-both an initial 2-3-fold increase and a subsequent decrease back to initial levels during transition to hypertrophy. The increase in MINPP expression was accompanied by a 40% decrease in InsP(6) levels in ATDC5 cells. However, InsP(5) levels were not modified. Furthermore, throughout the hypertrophic phase, during which MINPP expression decreased, there were no alterations in InsP(5) and InsP(6) levels. We also created an ATDC5 line that stably overexpressed Minpp at 2-fold higher levels than in wild-type cells. This had no significant effect upon cellular levels of InsP(5) and InsP(6). Thus, substantial changes in MINPP expression can occur without a net effect upon InsP(5) and InsP(6) turnover in vivo. On the other hand, Minpp-overexpressing cells showed impaired chondrogenesis. We noted that the expression of alkaline phosphatase activity was inversely correlated with the expression of MINPP. The ATDC5 cells that overexpress Minpp failed to show an insulin-dependent increase in alkaline phosphatase levels, which presumably affects phosphate balance [J. Biol. Chem. 276 (2001) 33995], and may be the reason cellular differentiation was impaired. In any case, we conclude that Minpp is important to chondrocyte differentiation, but in a manner that is, surprisingly, independent of inositol polyphosphate turnover.
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Affiliation(s)
- Kiyoshi Hidaka
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
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11
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Zhang D, Schwarz EM, Rosier RN, Zuscik MJ, Puzas JE, O'Keefe RJ. ALK2 functions as a BMP type I receptor and induces Indian hedgehog in chondrocytes during skeletal development. J Bone Miner Res 2003; 18:1593-604. [PMID: 12968668 DOI: 10.1359/jbmr.2003.18.9.1593] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
UNLABELLED Growth plate chondrocytes integrate multiple signals during normal development. The type I BMP receptor ALK2 is expressed in cartilage and expression of constitutively active (CA) ALK2 and other activated type I BMP receptors results in maturation-independent expression of Ihh in chondrocytes in vitro and in vivo. The findings suggest that BMP signaling modulates the Ihh/PTHrP signaling pathway that regulates the rate of chondrocyte differentiation. INTRODUCTION Bone morphogenetic proteins (BMPs) have an important role in vertebrate limb development. The expression of the BMP type I receptors BMPR-IA (ALK3) and BMPR-IB (ALK6) have been more completely characterized in skeletal development than ALK2. METHODS ALK2 expression was examined in vitro in isolated chick chondrocytes and osteoblasts and in vivo in the developing chick limb bud. The effect of overexpression of CA ALK2 and the other type I BMP receptors on the expression of genes involved in chondrocyte maturation was determined. RESULTS ALK2 was expressed in isolated chick osteoblasts and chondrocytes and specifically mediated BMP signaling. In the developing chick limb bud, ALK2 was highly expressed in mesenchymal soft tissues. In skeletal elements, expression was higher in less mature chondrocytes than in chondrocytes undergoing terminal differentiation. CA ALK2 misexpression in vitro enhanced chondrocyte maturation and induced Ihh. Surprisingly, although parathyroid hormone-related peptide (PTHrP) strongly inhibited CA ALK2 mediated chondrocyte differentiation, Ihh expression was minimally decreased. CA ALK2 viral infection in stage 19-23 limbs resulted in cartilage expansion with joint fusion. Enhanced periarticular expression of PTHrP and delayed maturation of the cartilage elements were observed. In the cartilage element, CA ALK2 misexpression precisely colocalized with the expression with Ihh. These findings were most evident in partially infected limbs where normal morphology was maintained. In contrast, BMP-6 had a normal pattern of differentiation-related expression. CA BMPR-IA and CA BMPR-IB overexpression similarly induced Ihh and PTHrP. CONCLUSIONS The findings show that BMP signaling induces Ihh. Although the colocalization of the activated type I receptors and Ihh suggests a direct BMP-mediated signaling event, other indirect mechanisms may also be involved. Thus, while BMPs act directly on chondrocytes to induce maturation, this effect is counterbalanced in vivo by induction of the Ihh/PTHrP signaling loop. The findings suggest that BMPs are integrated into the Ihh/PTHrP signaling loop and that a fine balance of BMP signaling is essential for normal chondrocyte maturation and skeletal development.
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MESH Headings
- Activin Receptors, Type I/genetics
- Activin Receptors, Type I/metabolism
- Animals
- Animals, Genetically Modified
- Base Sequence
- Bone Development/genetics
- Bone Development/physiology
- Bone Morphogenetic Protein Receptors, Type I
- Cartilage/abnormalities
- Cartilage/embryology
- Cartilage/metabolism
- Cell Differentiation
- Cells, Cultured
- Chick Embryo
- Chondrocytes/cytology
- Chondrocytes/metabolism
- Chondrogenesis
- DNA, Complementary/genetics
- Gene Expression Regulation, Developmental
- Hedgehog Proteins
- In Situ Hybridization
- Parathyroid Hormone-Related Protein/metabolism
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- Proteins
- Receptor, Transforming Growth Factor-beta Type I
- Receptors, Growth Factor/genetics
- Receptors, Growth Factor/metabolism
- Receptors, Transforming Growth Factor beta/genetics
- Receptors, Transforming Growth Factor beta/metabolism
- Signal Transduction
- Trans-Activators/biosynthesis
- Trans-Activators/genetics
- Transfection
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Affiliation(s)
- Donghui Zhang
- Center for Musculoskeletal Research, University of Rochester, Rochester, New York 14642, USA
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12
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Zuscik MJ, Pateder DB, Puzas JE, Schwarz EM, Rosier RN, O'Keefe RJ. Lead alters parathyroid hormone-related peptide and transforming growth factor-beta1 effects and AP-1 and NF-kappaB signaling in chondrocytes. J Orthop Res 2002; 20:811-8. [PMID: 12168672 DOI: 10.1016/s0736-0266(02)00007-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The skeletal system is an important target for lead toxicity. One of the impacts of lead in the skeleton, the inhibition of axial bone development, is likely due to its effect on the normal progression of chondrocyte maturation that is central to the process of endochondral ossification. Since little is known about the effect of lead on chondrocyte function/maturation, its impact on (1) growth factor-induced proliferation, (2) expression of maturation-specific markers type X collagen and BMP-6, and (3) the activity of AP-1 and NF-kappaB was examined in chick growth plate and sternal chondrocyte models. Exposure to lead alone (1-30 microM) resulted in a dose-dependent inhibition of thymidine incorporation in growth plate chondrocytes. Lead also blunted the stimulation of thymidine incorporation by parathyroid hormone-related peptide (PTHrP) and transforming growth factor-beta1 (TGF-beta1), two critical regulators of chondrocyte maturation. Lead (1 and 10 microM), TGF-beta1 (3 ng/ml) and PTHrP (10(-7) M) all significantly inhibited the expression of type X collagen, a marker of chondrocyte terminal differentiation. However, when in combination, lead completely reversed the inhibition of type X collagen by PTHrP and TGF-beta1. The effect of lead on BMP-6. an inducer of terminal differentiation. was also examined. Independently, lead and TGF-beta1 were without effect on BMP-6 expression, but PTHrP significantly suppressed it. Comparatively, lead did not alter PTHrP-mediated suppression of BMP-6, but in combination with TGF-beta1. BMP-6 expression was increased 3-fold. To determine if lead effects on signaling might play a role in facilitating these events, the impact of lead on NF-kappaB and AP-1 signaling was assessed using luciferase reporter constructs in sternal chondrocytes. Lead had no effect on the AP-1 reporter, but it dose-dependently inhibited the NF-kappaB reporter. PTHrP, which signals through AP-1, did not activate the NF-kappaB reporter and did not affect inhibition of this reporter by lead. In contrast, PTHrP activation of the AP-1 reporter was dose-dependently enhanced by lead. These findings, which establish that chondrocytes are important targets for lead toxicity, suggest that the effects of lead on bone growth are derived from its impact on the modulation of chondrocyte maturation by growth factors and second messenger signaling responses.
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Affiliation(s)
- Michael J Zuscik
- Center for Muscluskeletal Research, School of Medicine and Dentistry, University of Rochester, NY 14642, USA
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13
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Zhang D, Ferguson CM, O'Keefe RJ, Puzas JE, Rosier RN, Reynolds PR. A role for the BMP antagonist chordin in endochondral ossification. J Bone Miner Res 2002; 17:293-300. [PMID: 11811560 DOI: 10.1359/jbmr.2002.17.2.293] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Bone morphogenetic proteins (BMPs) are ubiquitous regulators of cellular growth and differentiation. A variety of processes modulate BMP activity, including negative regulation by several distinct binding proteins. One such BMP antagonist chordin has a role in axis determination and neural induction in the early embryo. In this study, a role for chordin during endochondral ossification has been investigated. During limb development, Chordin expression was detected only at the distal ends of the skeletal elements. In cultured embryonic sternal chondrocytes, Chordin expression was related inversely to the stages of maturation. Further, treating cultured chondrocytes with chordin interfered with maturation induced by treatment with BMP-2. These results suggest that chordin may negatively regulate chondrocyte maturation and limb growth in vivo. To address this hypothesis, chordin protein was expressed ectopically in Hamburger-Hamilton (HH) stage 25-27 embryonic chick limbs. The phenotypic changes and alteration of gene expression in treated limbs revealed that overexpression of chordin protein delayed chondrocyte maturation in developing skeletal elements. In summary, these findings strongly support a role for chordin as a negative regulator of endochondral ossification.
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Affiliation(s)
- Donghui Zhang
- Department of Orthopedics, School of Medicine and Dentistry, University of Rochester, New York, USA
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14
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Yu WP, Pallen CJ, Tay A, Jirik FR, Brenner S, Tan YH, Venkatesh B. Conserved synteny between the Fugu and human PTEN locus and the evolutionary conservation of vertebrate PTEN function. Oncogene 2001; 20:5554-61. [PMID: 11571655 DOI: 10.1038/sj.onc.1204679] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2001] [Revised: 05/10/2001] [Accepted: 05/10/2001] [Indexed: 11/08/2022]
Abstract
Mutations of PTEN, which encodes a protein-tyrosine and lipid phosphatase, are prevalent in a variety of human cancers. The human genome 'draft' sequence still lacks organization and much of the PTEN and adjacent loci remain undefined. The pufferfish, Fugu rubripes, by virtue of having a compact genome represents an excellent template for rapid vertebrate gene discovery. Sequencing of 56 kb from the Fugu pten (fpten) locus identified four complete genes and one partial gene homologous to human genes. Genes neighboring fpten include a PAPS synthase (fpapss2) differentially expressed between non-metastatic/metastatic human carcinoma cell lines, an inositol phosphatase (fminpp1) and an omega class glutathione-S-transferase (fgsto). We have determined the order of human BAC clones at the hPTEN locus and that the locus contains hPAPSS2 and hMINPP1 genes oriented as are their Fugu orthologs. Although the human genes span 500 kb, the Fugu genes lie within only 22 kb due to the compressed intronic and intergenic regions that typify this genome. Interestingly, and providing striking evidence of regulatory element conservation between widely divergent vertebrate species, the compact 2.1 kb fpten promoter is active in human cells. Also, like hPTEN, fpten has a growth and tumor suppressor activity in human glioblastoma cells, demonstrating conservation of protein function.
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Affiliation(s)
- W P Yu
- Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609, Republic of Singapore
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15
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Ferguson CM, Schwarz EM, Reynolds PR, Puzas JE, Rosier RN, O'Keefe RJ. Smad2 and 3 mediate transforming growth factor-beta1-induced inhibition of chondrocyte maturation. Endocrinology 2000; 141:4728-35. [PMID: 11108288 DOI: 10.1210/endo.141.12.7848] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Transforming growth factor-beta (TGF-beta) is a multifunctional regulator of a variety of cellular functions, including proliferation, differentiation, matrix synthesis, and apoptosis. In growth plate chondrocytes, TGF-beta slows the rate of maturation. Because the current paradigm of TGF-beta signaling involves Smad proteins as downstream regulators of target genes, we have characterized their role as mediators of TGF-beta effects on chondrocyte maturation. Both Smad2 and 3 translocated to the nucleus upon TGF-beta1 signaling, but not upon BMP-2 signaling. Cotransfection experiments using the TGF-beta responsive and Smad3 sensitive p3TP-Lux luciferase reporter demonstrated that wild-type Smad3 potentiated, whereas dominant negative Smad3 inhibited TGF-beta1 induced luciferase activity. To confirm the role of Smad2 and 3 as essential mediators of TGF-beta1 effects on chondrocyte maturation, we overexpressed both wild-type and dominant negative Smad2 and 3 in virally infected chondrocyte cultures. Overexpression of both wild-type Smad2 and 3 potentiated the inhibitory effect of TGF-beta on chondrocyte maturation, as determined by colx and alkaline phosphatase activity, whereas dominant negative Smad2 and 3 blocked these effects. Wild-type and dominant negative forms of Smad3 had more pronounced effects than Smad2. Our results define Smad2 and 3 as key mediators of the inhibitory effect of TGF-beta1 signaling on chondrocyte maturation.
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Affiliation(s)
- C M Ferguson
- Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, New York 14642, USA
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16
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Chi H, Yang X, Kingsley PD, O'Keefe RJ, Puzas JE, Rosier RN, Shears SB, Reynolds PR. Targeted deletion of Minpp1 provides new insight into the activity of multiple inositol polyphosphate phosphatase in vivo. Mol Cell Biol 2000; 20:6496-507. [PMID: 10938126 PMCID: PMC86124 DOI: 10.1128/mcb.20.17.6496-6507.2000] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Multiple inositol polyphosphate phosphatase (Minpp1) metabolizes inositol 1,3,4,5,6-pentakisphosphate (InsP(5)) and inositol hexakisphosphate (InsP(6)) with high affinity in vitro. However, Minpp1 is compartmentalized in the endoplasmic reticulum (ER) lumen, where access of enzyme to these predominantly cytosolic substrates in vivo has not previously been demonstrated. To gain insight into the physiological activity of Minpp1, Minpp1-deficient mice were generated by homologous recombination. Tissue extracts from Minpp1-deficient mice lacked detectable Minpp1 mRNA expression and Minpp1 enzyme activity. Unexpectedly, Minpp1-deficient mice were viable, fertile, and without obvious defects. Although Minpp1 expression is upregulated during chondrocyte hypertrophy, normal chondrocyte differentiation and bone development were observed in Minpp1-deficient mice. Biochemical analyses demonstrate that InsP(5) and InsP(6) are in vivo substrates for ER-based Minpp1, as levels of these polyphosphates in Minpp1-deficient embryonic fibroblasts were 30 to 45% higher than in wild-type cells. This increase was reversed by reintroducing exogenous Minpp1 into the ER. Thus, ER-based Minpp1 plays a significant role in the maintenance of steady-state levels of InsP(5) and InsP(6). These polyphosphates could be reduced below their natural levels by aberrant expression in the cytosol of a truncated Minpp1 lacking its ER-targeting N terminus. This was accompanied by slowed cellular proliferation, indicating that maintenance of cellular InsP(5) and InsP(6) is essential to normal cell growth. Yet, depletion of cellular inositol polyphosphates during erythropoiesis emerges as an additional physiological activity of Minpp1; loss of this enzyme activity in erythrocytes from Minpp1-deficient mice was accompanied by upregulation of a novel, substitutive inositol polyphosphate phosphatase.
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Affiliation(s)
- H Chi
- Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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17
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Reynolds SD, Zhang D, Puzas JE, O'Keefe RJ, Rosier RN, Reynolds PR. Cloning of the chick BMP1/Tolloid cDNA and expression in skeletal tissues. Gene 2000; 248:233-43. [PMID: 10806368 DOI: 10.1016/s0378-1119(00)00114-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The astacin-related metalloproteases Bone Morphogenetic Protein-1 (BMP1) and Tolloid possess multiple functions in the maturation of extracellular matrices containing fibrillar collagens. We are interested in developing an in-vitro model system to study the role of BMP1 and Tolloid in chondrocytes and osteoblasts. Cloning of the cDNAs for chick BMP1 and Tolloid reveals that the two gene products are more than 80% identical to their human and mouse homologs and are similarly derived from the same genetic locus. Anti-BMP1/Tolloid antibodies have been developed, and detect two proteins of 80 and 116kDa. Chick BMP1 and Tolloid message and proteins are found in a variety of embryonic and juvenile tissues, including chondrocytes and osteoblasts. Tolloid message and protein are generally less abundant than BMP1 message; this discrepancy is greatest in growth plate chondrocytes. Tolloid protein is more tightly bound than BMP1 to the extracellular matrix produced by cultured osteoblasts. The Chordin gene is also expressed in chondrocytes and osteoblasts, suggesting that BMP1 and Tolloid influence BMP signaling as well as matrix maturation during skeletogenesis.
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Affiliation(s)
- S D Reynolds
- Department of Pathology and Laboratory Medicine, University of Rochester, School of Medicine and Dentistry, 601 Elmwood Avenue, Box 665, Rochester, NY 14642, USA
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18
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Farquharson C, Lester D, Seawright E, Jefferies D, Houston B. Microtubules are potential regulators of growth-plate chondrocyte differentiation and hypertrophy. Bone 1999; 25:405-12. [PMID: 10511106 DOI: 10.1016/s8756-3282(99)00187-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Terminal differentiation of growth-plate chondrocytes is accompanied by the acquisition of a spherical morphology and a large increase in cell volume. These changes are likely to be associated with rearrangement of the cytoskeleton, but little information on this aspect of chondrocyte hypertrophy is available. We report a role for microtubules in the control of chondrocyte maturation and hypertrophy. Chick growth-plate chondrocytes were fractionated into five maturationally distinct populations by Percoll density gradient centrifugation, and agarose gel differential display analysis was performed. We identified a 1200 bp cDNA fragment derived from a transcript that was most highly expressed in the hypertrophic chondrocytes. After cloning and sequencing, FASTA and BLAST analysis revealed 100% identity to chick beta7-tubulin. Differential expression was confirmed in a reverse transcription-polymerase chain reaction (RT-PCR) assay using specific primers for a 343 bp fragment from the 3' untranslated region of beta7-tubulin. Beta7-tubulin was upregulated three-fold in fully hypertrophic chondrocytes compared with the other four fractions, which all had similar levels of expression. Immunocytochemical localization of beta-tubulin in chick growth-plate sections demonstrated little staining in the chondrocytes of the proliferating zone, but intense cytoplasmic staining was present in the large hypertrophic chondrocytes. In cell culture studies, the addition of colchicine (10(-6) mol/L) resulted in a higher rate of [3H]-thymidine uptake (36.0%; p < 0.001), but lower amounts of alkaline phosphatase activity (69.1%; p < 0.001), collagen (49.1%; p < 0.01), and glycosaminoglycan (43.3%; p < 0.01) accumulation within the cell-matrix layer. Further evidence for the involvement of microtubules in chondrocyte differentiation and hypertrophy was obtained by morphological assessment of colchicine-treated growth-plate explant cultures. A partial failure of chondrocyte hypertrophy was observed, although collagen type X immunoreactivity was noted within the interstitial matrix. Further studies are required to identify the exact role of microtubules in chondrocyte hypertrophy, but the results presented here suggest that upregulation of beta-tubulin may be required for increased microtubule synthesis during changes in cell size during the hypertrophic process. In addition, as cell-matrix interactions are required for chondrocyte maturation, microtubules may promote the differentiated phenotype as a result of their role in Golgi-mediated secretion of matrix proteins.
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Affiliation(s)
- C Farquharson
- Bone Biology Group, Roslin Institute, Midlothian, Scotland, UK.
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19
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Grimsrud CD, Romano PR, D'Souza M, Puzas JE, Reynolds PR, Rosier RN, O'Keefe RJ. BMP-6 is an autocrine stimulator of chondrocyte differentiation. J Bone Miner Res 1999; 14:475-82. [PMID: 10234567 DOI: 10.1359/jbmr.1999.14.4.475] [Citation(s) in RCA: 150] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
While parathyroid hormone-related protein (PTHrP) has been characterized as an important negative regulator of chondrocyte maturation in the growth plate, the autocrine or paracrine factors that stimulate chondrocyte maturation are not well characterized. Cephalic sternal chondrocytes were isolated from 13-day embryos, and the role of bone morphogenetic protein-6 (BMP-6) as a positive regulator of chondrocyte maturation was examined in monolayer cultures. Progressive maturation, which was accelerated in the presence of ascorbate, occurred in the cultures. During maturation, the cultures expressed high levels of BMP-6 mRNA which preceded the induction of type X collagen mRNA. Treatment of the cultures with PTHrP (10(-7) M) at the time of plating completely abolished BMP-6 and type X collagen mRNA expression. Removal of PTHrP after 6 days was followed by the rapid (within 24 h) expression of BMP-6 and type X collagen mRNA, with BMP-6 again preceding type X collagen expression. The addition of exogenous BMP-6 (100 ng/ml) to the cultures accelerated the maturation process both in the presence and absence of ascorbate and resulted in the highest levels of type X collagen. When exogenous BMP-6 was added to PTHrP containing cultures, maturation occurred with the expression of high levels of type X collagen, despite the presence of PTHrP in the cultures. Furthermore, BMP-6 did not stimulate expression of its own mRNA in the PTHrP treated cultures, but it did stimulate the expression of Indian hedgehog (Ihh) mRNA. These latter findings suggest that while PTHrP directly inhibits BMP-6, it indirectly regulates Ihh expression through BMP-6. Other phenotypic changes associated with chondrocyte differentiation were also stimulated by BMP-6, including increased alkaline phosphatase activity and decreased proliferation. The results suggest that BMP-6 is an autocrine factor that initiates chondrocyte maturation and that PTHrP may prevent maturation by inhibiting the expression of BMP-6.
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Affiliation(s)
- C D Grimsrud
- Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, New York, USA
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20
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Chi H, Tiller GE, Dasouki MJ, Romano PR, Wang J, O'keefe RJ, Puzas JE, Rosier RN, Reynolds PR. Multiple inositol polyphosphate phosphatase: evolution as a distinct group within the histidine phosphatase family and chromosomal localization of the human and mouse genes to chromosomes 10q23 and 19. Genomics 1999; 56:324-36. [PMID: 10087200 DOI: 10.1006/geno.1998.5736] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Multiple inositol polyphosphate phosphatase is the only enzyme known to hydrolyze the abundant metabolites inositol pentakisphosphate and inositol hexakisphosphate. We have previously demonstrated that the chick homolog of multiple inositol polyphosphate phosphatase, designated HiPER1, has a role in growth plate chondrocyte differentiation. The relationship of these enzymes to intracellular signaling is obscure, and as part of our investigation we have examined the murine ((MMU)Minpp1) and human ((HSA)MINPP1) homologs. Northern blot analysis demonstrated expression of ((MMU)Minpp1 in a variety of mouse tissues, comparable to the expression of other mammalian homologs, but less restricted than the expression of HiPER1 in chick. A purified (MMU)Minpp1 fusion protein cleaved phosphate from inositol (1,3,4,5)-tetrakisphosphate and para-nitrophenyl phosphate. When the presumptive active site histidine was altered to alanine by site-directed mutagenesis, enzyme activity was abolished, confirming the classification of (MMU)Minpp1 as a histidine phosphatase. The amino acid sequences of the murine and human MINPP proteins share >80% identity with the rat enzyme and >56% identity with HiPER1, with conservation of the C-terminal consensus sequence that retains proteins in the endoplasmic reticulum. The intron/exon structure of the mammalian (MMU)Minpp1 and (HSA)MINPP1 genes is also conserved compared to the chick HiPER1 gene. Sequence analysis of plant and fruit fly MINPP homologs supports the hypothesis that the MINPP enzymes constitute a distinct evolutionary group within the histidine phosphatase family. We have mapped (HSA)MINPP1 to human chromosome 10q23 by fluorescence in situ hybridization, YAC screening, and radiation hybrid mapping. This assignment places (HSA)MINPP1 in a region of chromosome 10 that is frequently mutated in human cancers and places (HSA)MINPP1 proximal to the tumor suppressor PTEN, which maps to 10q23.3. Using a radiation hybrid panel, we localized (MMU)Minpp1 to a region of mouse chromosome 19 that includes the murine homolog of Pten. The evolutionary conservation of this novel enzyme within the inositol polyphosphate pathway suggests a significant role for multiple inositol polyphosphate phosphatase throughout higher eukaryotes.
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Affiliation(s)
- H Chi
- Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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21
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Houston B, Seawright E, Jefferies D, Hoogland E, Lester D, Whitehead C, Farquharson C. Identification and cloning of a novel phosphatase expressed at high levels in differentiating growth plate chondrocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1448:500-6. [PMID: 9990301 DOI: 10.1016/s0167-4889(98)00153-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Growth plate chondrocytes progress through a proliferative phase before acquiring a terminally-differentiated phenotype. In this study we used Percoll density gradients to separate chick growth plate chondrocytes into populations of different maturational phenotype. By applying agarose gel differential display to these populations we cloned a cDNA encoding a novel 268 amino acid protein (3X11A). 3X11A contains two peptide motifs that are conserved in a recently identified superfamily of phosphotransferases. It is likely that 3X11A is a phosphatase, but its substrate specificity remains uncertain. 3X11A expression is upregulated 5-fold during chondrocyte terminal differentiation and its expression is approximately 100-fold higher in hypertrophic chondrocytes than in non-chondrogenic tissues. This suggests that 3X11A participates in a biochemical pathway that is particularly active in differentiating chondrocytes.
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Affiliation(s)
- B Houston
- Bone Biology Group, Roslin Institute, Midlothian, UK.
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Caffrey JJ, Hidaka K, Matsuda M, Hirata M, Shears SB. The human and rat forms of multiple inositol polyphosphate phosphatase: functional homology with a histidine acid phosphatase up-regulated during endochondral ossification. FEBS Lett 1999; 442:99-104. [PMID: 9923613 DOI: 10.1016/s0014-5793(98)01636-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We have derived the full-length sequences of the human and rat forms of the multiple inositol polyphosphate phosphatase (MIPP); their structural and functional comparison with a chick histidine acid phosphatase (HiPER1) has revealed new information: (1) MIPP is approximately 50% identical to HiPER1, but the ER-targeting domains are divergent; (2) MIPP appears to share the catalytic requirement of histidine acid phosphatases, namely, a C-terminal His residue remote from the RHGxRxP catalytic motif; (3) rat MIPP mRNA is up-regulated during chondrocyte hypertrophy. The latter observation provides a context for proposing that MIPP may aid bone mineralization and salvage the inositol moiety prior to apoptosis.
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Affiliation(s)
- J J Caffrey
- Inositide Signaling Group, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA.
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Shears SB. The versatility of inositol phosphates as cellular signals. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1436:49-67. [PMID: 9838040 DOI: 10.1016/s0005-2760(98)00131-3] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Cells from across the phylogenetic spectrum contain a variety of inositol phosphates. Many different functions have been ascribed to this group of compounds. However, it is remarkable how frequently several of these different inositol phosphates have been linked to various aspects of signal transduction. Therefore, this review assesses the evidence that inositol phosphates have evolved into a versatile family of second messengers.
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Affiliation(s)
- S B Shears
- Inositide Signalling Section, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
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