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Avendaño-Monsalve MC, Mendoza-Martínez AE, Ponce-Rojas JC, Poot-Hernández AC, Rincón-Heredia R, Funes S. Positively charged amino acids at the N terminus of select mitochondrial proteins mediate early recognition by import proteins αβ'-NAC and Sam37. J Biol Chem 2022; 298:101984. [PMID: 35487246 PMCID: PMC9136113 DOI: 10.1016/j.jbc.2022.101984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 04/16/2022] [Accepted: 04/19/2022] [Indexed: 11/04/2022] Open
Abstract
A major challenge in eukaryotic cells is the proper distribution of nuclear-encoded proteins to the correct organelles. For a subset of mitochondrial proteins, a signal sequence at the N terminus (matrix-targeting sequence [MTS]) is recognized by protein complexes to ensure their proper translocation into the organelle. However, the early steps of mitochondrial protein targeting remain undeciphered. The cytosolic chaperone nascent polypeptide–associated complex (NAC), which in yeast is represented as the two different heterodimers αβ-NAC and αβ′-NAC, has been proposed to be involved during the early steps of mitochondrial protein targeting. We have previously described that the mitochondrial outer membrane protein Sam37 interacts with αβ′-NAC and together promote the import of specific mitochondrial precursor proteins. In this work, we aimed to detect the region in the MTS of mitochondrial precursors relevant for their recognition by αβ′-NAC during their sorting to the mitochondria. We used targeting signals of different mitochondrial proteins (αβ′-NAC-dependent Oxa1 and αβ′-NAC-independent Mdm38) and fused them to GFP to study their intracellular localization by biochemical and microscopy methods, and in addition followed their import kinetics in vivo. Our results reveal the presence of a positively charged amino acid cluster in the MTS of select mitochondrial precursors, such as Oxa1 and Fum1, which are crucial for their recognition by αβ′-NAC. Furthermore, we explored the presence of this cluster at the N terminus of the mitochondrial proteome and propose a set of precursors whose proper localization depends on both αβ′-NAC and Sam37.
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Affiliation(s)
- Maria Clara Avendaño-Monsalve
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Coyoacán, Cd.Mx., Mexico
| | - Ariann E Mendoza-Martínez
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Coyoacán, Cd.Mx., Mexico
| | - José Carlos Ponce-Rojas
- Department of Molecular, Cellular, and Developmental Biology, University of California at Santa Barbara, Santa Barbara, California, USA
| | - Augusto César Poot-Hernández
- Unidad de Bioinformática y Manejo de la Información, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Coyoacán, Cd.Mx., Mexico
| | - Ruth Rincón-Heredia
- Unidad de Imagenología, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Coyoacán, Cd.Mx., Mexico
| | - Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Coyoacán, Cd.Mx., Mexico.
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Avendaño-Monsalve MC, Ponce-Rojas JC, Funes S. Viaje al centro de la mitocondria: importación de proteínas, sus alteraciones y enfermedades relacionadas. TIP RECQB 2021. [DOI: 10.22201/fesz.23958723e.2021.370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Las mitocondrias son organelos fascinantes, no solo porque son el sitio en donde se genera la energía de las células, sino por su relevancia en procesos y patologías de interés médico. La gran mayoría de las proteínas que constituyen el proteoma mitocondrial están codificadas en el núcleo y se traducen por ribosomas citosólicos, por lo que deben ser identificadas correctamente para ser distribuidas e insertadas en cada uno de los subcompartimentos mitocondriales. En este artículo realizamos una descripción de las las maquinarias de importación mitocondrial, además de las diferentes respuestas celulares que contrarrestan las alteraciones en los procesos de transporte de las proteínas o cuando existe una disfunción mitocondrial. Finalmente, mencionamos las enfermedades causadas por mutaciones en los complejos transportadores y de distribución de las proteínas de este organelo, que se han identificado hasta la fecha.
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Avendaño-Monsalve MC, Ponce-Rojas JC, Funes S. From cytosol to mitochondria: the beginning of a protein journey. Biol Chem 2020; 401:645-661. [DOI: 10.1515/hsz-2020-0110] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 02/24/2020] [Indexed: 01/18/2023]
Abstract
AbstractMitochondrial protein import is one of the key processes during mitochondrial biogenesis that involves a series of events necessary for recognition and delivery of nucleus-encoded/cytosol-synthesized mitochondrial proteins into the organelle. The past research efforts have mainly unraveled how membrane translocases ensure the correct protein sorting within the different mitochondrial subcompartments. However, early steps of recognition and delivery remain relatively uncharacterized. In this review, we discuss our current understanding about the signals on mitochondrial proteins, as well as in the mRNAs encoding them, which with the help of cytosolic chaperones and membrane receptors support protein targeting to the organelle in order to avoid improper localization. In addition, we discuss recent findings that illustrate how mistargeting of mitochondrial proteins triggers stress responses, aiming to restore cellular homeostasis.
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Affiliation(s)
- Maria Clara Avendaño-Monsalve
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n Ciudad Universitaria Coyoacán, México, Cd.Mx. 04510, Mexico
| | - José Carlos Ponce-Rojas
- Department of Molecular, Cellular, and Developmental Biology, University of California at Santa Barbara, Santa Barbara, CA 93106-9625, USA
| | - Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n Ciudad Universitaria Coyoacán, México, Cd.Mx. 04510, Mexico
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Rubalcava-Gracia D, Vázquez-Acevedo M, Funes S, Pérez-Martínez X, González-Halphen D. Mitochondrial versus nuclear gene expression and membrane protein assembly: the case of subunit 2 of yeast cytochrome c oxidase. Mol Biol Cell 2018; 29:820-833. [PMID: 29437907 PMCID: PMC5905295 DOI: 10.1091/mbc.e17-09-0560] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 01/12/2018] [Accepted: 02/01/2018] [Indexed: 12/24/2022] Open
Abstract
Deletion of the yeast mitochondrial gene COX2, encoding subunit 2 (mtCox2) of cytochrome c oxidase (CcO), results in a respiratory-incompetent Δcox2 strain. For a cytosol-synthesized Cox2 to restore respiratory growth, it must carry the W56R mutation (cCox2W56R). Nevertheless, only a fraction of cCox2W56R is matured in mitochondria, allowing ∼60% steady-state accumulation of CcO. This can be attributed either to the point mutation or to an inefficient biogenesis of cCox2W56R. We generated a strain expressing the mutant protein mtCox2W56R inside mitochondria which should follow the canonical biogenesis of mitochondria-encoded Cox2. This strain exhibited growth rates, CcO steady-state levels, and CcO activity similar to those of the wild type; therefore, the efficiency of Cox2 biogenesis is the limiting step for successful allotopic expression. Upon coexpression of cCox2W56R and mtCox2, each protein assembled into CcO independently from its genetic origin, resulting in a mixed population of CcO with most complexes containing the mtCox2 version. Notably, the presence of the mtCox2 enhances cCox2W56R incorporation. We provide proof of principle that an allotopically expressed Cox2 may complement a phenotype due to a mutant mitochondrial COX2 gene. These results are relevant to developing a rational design of genes for allotopic expression intended to treat human mitochondrial diseases.
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Affiliation(s)
- Diana Rubalcava-Gracia
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
| | - Miriam Vázquez-Acevedo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
| | - Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
| | - Xochitl Pérez-Martínez
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
| | - Diego González-Halphen
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
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Aguilar-Lopez JL, Laboy R, Jaimes-Miranda F, Garay E, DeLuna A, Funes S. Slm35 links mitochondrial stress response and longevity through TOR signaling pathway. Aging (Albany NY) 2017; 8:3255-3271. [PMID: 27922823 PMCID: PMC5270667 DOI: 10.18632/aging.101093] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 09/27/2016] [Indexed: 12/20/2022]
Abstract
In most eukaryotic cells mitochondria are essential organelles involved in a great variety of cellular functions. One of the physiological processes linked to mitochondria is aging, a gradual process of damage accumulation that eventually promotes cell death. Aging depends on a balance between mitochondrial biogenesis, function and degradation. It has been previously shown that Tor1, Sch9 and Ras2 are activated in response to nutrient availability and regulate cell growth and division. A deficiency in any of these genes promotes lifespan extension and cell protection during oxidative and heat shock stress. In this work we report that in Saccharomyces cerevisiae, the uncharacterized mitochondrial protein Slm35 is functionally linked with the TOR signaling pathway. A Δtor1Δslm35 strain shows a severe decrease in lifespan and is unable to contend with oxidative and heat shock stresses. Specifically, this mutant shows decreased catalase activity indicating a misregulation of ROS scavenging mechanisms. In this study we show that Slm35 is also relevant for mitochondrial network dynamics and mitophagy. The results presented here suggest that Slm35 plays an important role connecting mitochondrial function with cytosolic responses and cell adaptation to stress and aging.
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Affiliation(s)
- Jose L Aguilar-Lopez
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Cd.Mx. 04510, Mexico
| | - Raymond Laboy
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Cd.Mx. 04510, Mexico
| | - Fabiola Jaimes-Miranda
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Cd.Mx. 04510, Mexico
| | - Erika Garay
- Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del IPN, Irapuato, Guanajuato 36821, Mexico
| | - Alexander DeLuna
- Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del IPN, Irapuato, Guanajuato 36821, Mexico
| | - Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Cd.Mx. 04510, Mexico
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Ponce-Rojas JC, Avendaño-Monsalve MC, Yañez-Falcón AR, Jaimes-Miranda F, Garay E, Torres-Quiroz F, DeLuna A, Funes S. αβ'-NAC cooperates with Sam37 to mediate early stages of mitochondrial protein import. FEBS J 2017; 284:814-830. [PMID: 28109174 DOI: 10.1111/febs.14024] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 12/20/2016] [Accepted: 01/18/2017] [Indexed: 11/30/2022]
Abstract
The mitochondrial proteome is mostly composed of nuclear-encoded proteins. Such polypeptides are synthesized with signals that guide their intracellular transport to the surface of the organelle and later within the different mitochondrial subcompartments until they reach their functional destination. It has been suggested that the nascent-polypeptide associated complex (NAC) - a cytosolic chaperone that recognizes nascent chains on translationally active ribosomes - has a role in the import of nuclear-encoded mitochondrial proteins. However, the molecular mechanisms that regulate the NAC-mediated cotranslational import are still not clear. Here, we show that a particular NAC heterodimer formed by subunits α and β' in Saccharomyces cerevisiae is specifically involved in the process of mitochondrial import and functionally cooperates with Sam37, an outer membrane protein subunit of the sorting and assembly machinery complex. Mutants in both components display growth defects, incorrectly accumulate precursor forms of mitochondrial proteins in the cytosol, and have an altered mitochondrial protein content. We propose that αβ'-NAC and Sam37 are members of the system that recognizes mitochondrial proteins at early stages of their synthesis, escorting them to the import machinery of mitochondria.
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Affiliation(s)
- José Carlos Ponce-Rojas
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Maria Clara Avendaño-Monsalve
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Armando Roberto Yañez-Falcón
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Fabiola Jaimes-Miranda
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Erika Garay
- Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del IPN, Irapuato, Mexico
| | - Francisco Torres-Quiroz
- Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Alexander DeLuna
- Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del IPN, Irapuato, Mexico
| | - Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
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Funes S, Westerburg H, Jaimes-Miranda F, Woellhaf MW, Aguilar-Lopez JL, Janßen L, Bonnefoy N, Kauff F, Herrmann JM. Partial suppression of Oxa1 mutants by mitochondria-targeted signal recognition particle provides insights into the evolution of the cotranslational insertion systems. FEBS J 2013. [PMID: 23198851 DOI: 10.1111/febs.12082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The biogenesis of hydrophobic membrane proteins involves their cotranslational membrane integration in order to prevent their unproductive aggregation. In the cytosol of bacteria and eukaryotes, membrane targeting of ribosomes that synthesize membrane proteins is achieved by signal recognition particles (SRPs) and their cognate membrane-bound receptors. As is evident from the genomes of fully sequenced eukaryotes, mitochondria generally lack an SRP system. Instead, mitochondrial ribosomes are physically associated with the protein insertion machinery in the inner membrane. Accordingly, deletion of ribosome-binding sites on the Oxa1 insertase and the Mba1 ribosome receptor in yeast leads to severe defects in cotranslational protein insertion and results in respiration-deficient mutants. In this study, we expressed mitochondria-targeted versions of the bacterial SRP protein Ffh and its receptor FtsY in these yeast mutants. Interestingly, Ffh was found to bind to the large subunit of mitochondrial ribosomes, and could relieve, to some degree, the defect of these insertion mutants. Although FtsY could also bind to mitochondrial membranes, it did not improve membrane protein biogenesis in this strain, presumably because of its inability to interact with Ffh. Hence, mitochondrial ribosomes are still able to interact physically and functionally with the bacterial SRP system. Our observations are consistent with a model according to which the protein insertion system in mitochondria evolved in three steps. The loss of genes for hydrophilic polypeptides (step 1) allowed the development of ribosome-binding sites on membrane proteins (step 2), which finally made the existence of an SRP-mediated system dispensable (step 3).
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Affiliation(s)
- Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Ciudad Universitaria, Universidad Nacional Autónoma de México, Distrito Federal, Mexico.
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Funes S, Kauff F, van der Sluis EO, Ott M, Herrmann JM. Evolution of YidC/Oxa1/Alb3 insertases: three independent gene duplications followed by functional specialization in bacteria, mitochondria and chloroplasts. Biol Chem 2011; 392:13-9. [PMID: 21194367 DOI: 10.1515/bc.2011.013] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Members of the YidC/Oxa1/Alb3 protein family facilitate the insertion, folding and assembly of proteins of the inner membranes of bacteria and mitochondria and the thylakoid membrane of plastids. All homologs share a conserved hydrophobic core region comprising five transmembrane domains. On the basis of phylogenetic analyses, six subgroups of the family can be distinguished which presumably arose from three independent gene duplications followed by functional specialization. During evolution of bacteria, mitochondria and chloroplasts, subgroup-specific regions were added to the core domain to facilitate the association with ribosomes or other components contributing to the substrate spectrum of YidC/Oxa1/Alb3 proteins.
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Affiliation(s)
- Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Circuito Exterior s/n, Ciudad Universitaria, Universidad Nacional Autónoma de México, Mexico D.F. 04510, Mexico
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Bauerschmitt H, Mick DU, Deckers M, Vollmer C, Funes S, Kehrein K, Ott M, Rehling P, Herrmann JM. Ribosome-binding proteins Mdm38 and Mba1 display overlapping functions for regulation of mitochondrial translation. Mol Biol Cell 2010; 21:1937-44. [PMID: 20427570 PMCID: PMC2883938 DOI: 10.1091/mbc.e10-02-0101] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Biogenesis of respiratory chain complexes depends on the expression of mitochondrial-encoded subunits. Their synthesis occurs on membrane-associated ribosomes and is probably coupled to their membrane insertion. Defects in expression of mitochondrial translation products are among the major causes of mitochondrial disorders. Mdm38 is related to Letm1, a protein affected in Wolf-Hirschhorn syndrome patients. Like Mba1 and Oxa1, Mdm38 is an inner membrane protein that interacts with ribosomes and is involved in respiratory chain biogenesis. We find that simultaneous loss of Mba1 and Mdm38 causes severe synthetic defects in the biogenesis of cytochrome reductase and cytochrome oxidase. These defects are not due to a compromised membrane binding of ribosomes but the consequence of a mis-regulation in the synthesis of Cox1 and cytochrome b. Cox1 expression is restored by replacing Cox1-specific regulatory regions in the mRNA. We conclude, that Mdm38 and Mba1 exhibit overlapping regulatory functions in translation of selected mitochondrial mRNAs.
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Becker T, Bhushan S, Jarasch A, Armache JP, Funes S, Jossinet F, Gumbart J, Mielke T, Berninghausen O, Schulten K, Westhof E, Gilmore R, Mandon EC, Beckmann R. Structure of monomeric yeast and mammalian Sec61 complexes interacting with the translating ribosome. Science 2009; 326:1369-73. [PMID: 19933108 DOI: 10.1126/science.1178535] [Citation(s) in RCA: 221] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The trimeric Sec61/SecY complex is a protein-conducting channel (PCC) for secretory and membrane proteins. Although Sec complexes can form oligomers, it has been suggested that a single copy may serve as an active PCC. We determined subnanometer-resolution cryo-electron microscopy structures of eukaryotic ribosome-Sec61 complexes. In combination with biochemical data, we found that in both idle and active states, the Sec complex is not oligomeric and interacts mainly via two cytoplasmic loops with the universal ribosomal adaptor site. In the active state, the ribosomal tunnel and a central pore of the monomeric PCC were occupied by the nascent chain, contacting loop 6 of the Sec complex. This provides a structural basis for the activity of a solitary Sec complex in cotranslational protein translocation.
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Affiliation(s)
- Thomas Becker
- Gene Center Munich and Center for Integrated Protein Science, Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
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Perez-Martinez X, Funes S, Camacho-Villasana Y, Marjavaara S, Tavares-Carreon F, Shingu-Vazquez M. Protein Synthesis and Assembly in Mitochondrial Disorders. Curr Top Med Chem 2008; 8:1335-50. [DOI: 10.2174/156802608786141124] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Bauerschmitt H, Funes S, Herrmann JM. The membrane-bound GTPase Guf1 promotes mitochondrial protein synthesis under suboptimal conditions. J Biol Chem 2008; 283:17139-46. [PMID: 18442968 DOI: 10.1074/jbc.m710037200] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recently, the bacterial elongation factor LepA was identified as critical for the accuracy of in vitro translation reactions. Extremely well conserved homologues of LepA are present throughout bacteria and eukaryotes, but the physiological relevance of these proteins is unclear. Here we show that the yeast counterpart of LepA, Guf1, is located in the mitochondrial matrix and tightly associated with the inner membrane. It binds to mitochondrial ribosomes in a GTP-dependent manner. Mutants lacking Guf1 show cold- and heat-sensitive growth defects on non-fermentable carbon sources that are especially pronounced under nutrient-limiting conditions. The cold sensitivity is explained by diminished rates of protein synthesis at low temperatures. At elevated temperatures, Guf1-deficient mutants exhibit defects in the assembly of cytochrome oxidase, suggesting that the polypeptides produced are not functional. Moreover, Guf1 mutants exhibit synthetic growth defects with mutations of the protein insertase Oxa1. These observations show a critical role for Guf1 in vivo. The observed defects in Guf1-deficient mitochondria are consistent with a function of Guf1 as a fidelity factor of mitochondrial protein synthesis.
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Affiliation(s)
- Heike Bauerschmitt
- Institute of Physiological Chemistry, University of Munich, 81377 Munich, Germany
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Abstract
Mitochondria are essential organelles of eukaryotic cells. The biogenesis of mitochondria depends on the coordinated function of two separate genetic systems: one in the nucleus and one in the organelle. The study of mitochondria requires the analysis of both genetic systems and their protein products. In this chapter, we focus on the translation and sorting of mitochondrially encoded proteins into the mitochondrial inner membrane in the baker's yeast Saccharomyces cerevisiae. The starting point is the labeling of these proteins, followed by some of the methods developed to investigate their topology and membrane incorporation. The methods described here can be applied also to the study of other aspects of organelle biogenesis such as folding, assembly, and degradation of proteins.
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Affiliation(s)
- Heike Bauerschmitt
- Adolf-Butenandt-Institute of Physiological Chemistry, University of Munich, Munich, Germany
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Storlazzi CT, Albano F, Lo Cunsolo C, Doglioni C, Guastadisegni MC, Impera L, Lonoce A, Funes S, Macrì E, Iuzzolino P, Panagopoulos I, Specchia G, Rocchi M. Upregulation of the SOX5 by promoter swapping with the P2RY8 gene in primary splenic follicular lymphoma. Leukemia 2007; 21:2221-5. [PMID: 17554380 DOI: 10.1038/sj.leu.2404784] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
Mitochondrial biogenesis is an intricate process that requires the coordinated function of two separate genetic systems: one in the organelle and one in the nucleus. The study of mitochondria requires the analysis of both genetic systems and their protein products. We describe the general procedures used to label mitochondrially encoded proteins in the baker's yeast Saccharomyces cerevisiae, a starting point for the investigation of various aspects of organelle biogenesis, such as folding and assembly, sorting, and degradation of proteins.
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Affiliation(s)
- Soledad Funes
- Institut für Physiologische Chemie, Ludwig-Maximilians-Universität München, Germany
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Storlazzi CT, Albano F, Locunsolo C, Lonoce A, Funes S, Guastadisegni MC, Cimarosto L, Impera L, D'Addabbo P, Panagopoulos I, Specchia G, Rocchi M. t(3;12)(q26;q14) in polycythemia vera is associated with upregulation of the HMGA2 gene. Leukemia 2006; 20:2190-2. [PMID: 17024113 DOI: 10.1038/sj.leu.2404418] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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17
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Khalimonchuk O, Ott M, Funes S, Ostermann K, Rödel G, Herrmann JM. Sequential processing of a mitochondrial tandem protein: insights into protein import in Schizosaccharomyces pombe. Eukaryot Cell 2006; 5:997-1006. [PMID: 16835444 PMCID: PMC1489288 DOI: 10.1128/ec.00092-06] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The sequencing of the genome of Schizosaccharomyces pombe revealed the presence of a number of genes encoding tandem proteins, some of which are mitochondrial components. One of these proteins (pre-Rsm22-Cox11) consists of a fusion of Rsm22, a component of the mitochondrial ribosome, and Cox11, a factor required for copper insertion into cytochrome oxidase. Since in Saccharomyces cerevisiae, Cox11 is physically attached to the mitochondrial ribosome, it was suggested that the tandem organization of Rsm22-Cox11 is used to covalently tie the mitochondrial ribosome to Cox11 in S. pombe. We report here that pre-Rsm22-Cox11 is matured in two subsequent processing events. First, the mitochondrial presequence is removed. At a later stage of the import process, the Rsm22 and Cox11 domains are separated by cleavage of the mitochondrial processing peptidase at an internal processing site. In vivo data obtained using a tagged version of pre-Rsm22-Cox11 confirmed the proteolytic separation of Cox11 from the Rsm22 domain. Hence, the tandem organization of pre-Rsm22-Cox11 does not give rise to a persistent fusion protein but rather might be used to increase the import efficiency of Cox11 and/or to coordinate expression levels of Rsm22 and Cox11 in S. pombe.
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Ott M, Prestele M, Bauerschmitt H, Funes S, Bonnefoy N, Herrmann JM. Mba1, a membrane-associated ribosome receptor in mitochondria. EMBO J 2006; 25:1603-10. [PMID: 16601683 PMCID: PMC1440829 DOI: 10.1038/sj.emboj.7601070] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Accepted: 03/09/2006] [Indexed: 11/09/2022] Open
Abstract
The genome of mitochondria encodes a small number of very hydrophobic polypeptides that are inserted into the inner membrane in a cotranslational reaction. The molecular process by which mitochondrial ribosomes are recruited to the membrane is poorly understood. Here, we show that the inner membrane protein Mba1 binds to the large subunit of mitochondrial ribosomes. It thereby cooperates with the C-terminal ribosome-binding domain of Oxa1, which is a central component of the insertion machinery of the inner membrane. In the absence of both Mba1 and the C-terminus of Oxa1, mitochondrial translation products fail to be properly inserted into the inner membrane and serve as substrates of the matrix chaperone Hsp70. We propose that Mba1 functions as a ribosome receptor that cooperates with Oxa1 in the positioning of the ribosome exit site to the insertion machinery of the inner membrane.
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Affiliation(s)
- Martin Ott
- Institut für Physiologische Chemie, Universität München, München, Germany
| | - Martin Prestele
- Institut für Physiologische Chemie, Universität München, München, Germany
| | - Heike Bauerschmitt
- Institut für Physiologische Chemie, Universität München, München, Germany
| | - Soledad Funes
- Institut für Physiologische Chemie, Universität München, München, Germany
| | | | - Johannes M Herrmann
- Institut für Physiologische Chemie, Universität München, München, Germany
- Institut für Physiologische Chemie, Universität München, Butenandtstrasse 5, München 81377, Germany. Tel.: +49 89 2180 77122; Fax: +49 89 2180 77093; E-mail:
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Herrmann JM, Funes S. Biogenesis of cytochrome oxidase—Sophisticated assembly lines in the mitochondrial inner membrane. Gene 2005; 354:43-52. [PMID: 15905047 DOI: 10.1016/j.gene.2005.03.017] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Revised: 02/02/2005] [Accepted: 03/23/2005] [Indexed: 11/18/2022]
Abstract
Biogenesis of the cytochrome oxidase complex in the mitochondrial inner membrane depends on the concerted action of a variety of proteins. Recent studies shed light on this biological assembly process revealing an astonishingly complex procedure by which the different subunits of the enzymes are put together and the required cofactors are supplied. In this review we present a hypothetical model for the assembly process of cytochrome oxidase based on the current knowledge of the functions of specific assembly factors. According to this model the two largest subunits of the complex are first equipped with their respective cofactors on independent assembly lines. Prior to their assembly with the residual subunits that complete the whole complex, these two subcomplexes remain bound to substrate-specific chaperones. We propose that these chaperones, Mss51 for subunit 1 and Cox20 for subunit 2, control the coordinate assembly process to prevent potentially harmful redox reactions of unassembled or misassembled subunits.
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Affiliation(s)
- Johannes M Herrmann
- Institute of Physiological Chemistry, Butenandtstrasse 5, 81377 München, University of Munich, Germany.
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Preuss M, Ott M, Funes S, Luirink J, Herrmann JM. Evolution of mitochondrial oxa proteins from bacterial YidC. Inherited and acquired functions of a conserved protein insertion machinery. J Biol Chem 2005; 280:13004-11. [PMID: 15654078 DOI: 10.1074/jbc.m414093200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the Oxa1/YidC family are involved in the biogenesis of membrane proteins. In bacteria, YidC catalyzes the insertion and assembly of proteins of the inner membrane. Mitochondria of animals, fungi, and plants harbor two distant homologues of YidC, Oxa1 and Cox18/Oxa2. Oxa1 plays a pivotal role in the integration of mitochondrial translation products into the inner membrane of mitochondria. It contains a C-terminal ribosome-binding domain that physically interacts with mitochondrial ribosomes to facilitate the co-translational insertion of nascent membrane proteins. The molecular function of Cox18/Oxa2 is not well understood. Employing a functional complementation approach with mitochondria-targeted versions of YidC we show that YidC is able to functionally replace both Oxa1 and Cox18/Oxa2. However, to integrate mitochondrial translation products into the inner membrane of mitochondria, the ribosome-binding domain of Oxa1 has to be appended onto YidC. On the contrary, the fusion of the ribosome-binding domain onto YidC prevents its ability to complement COX18 mutants suggesting an indispensable post-translational activity of Cox18/Oxa2. Our observations suggest that during evolution of mitochondria from their bacterial ancestors the two descendents of YidC functionally segregated to perform two distinct activities, one co-translational and one post-translational.
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Affiliation(s)
- Marc Preuss
- Institut für Physiologische Chemie, Universität München, Butenandtstrasse 5, 81377 München, Germany
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Funes S, Gerdes L, Inaba M, Soll J, Herrmann JM. TheArabidopsis thalianachloroplast inner envelope protein ARTEMIS is a functional member of the Alb3/Oxa1/YidC family of proteins. FEBS Lett 2004; 569:89-93. [PMID: 15225614 DOI: 10.1016/j.febslet.2004.05.055] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2004] [Revised: 05/12/2004] [Accepted: 05/12/2004] [Indexed: 10/26/2022]
Abstract
The Arabidopsis thaliana protein ARTEMIS is an integral component of the chloroplast inner envelope required for chloroplast division. It contains a domain of significant homology to members of the Alb3/Oxa1/YidC protein family. Here, we show that upon expression in yeast mitochondria, ARTEMIS can partially take over the function of yeast Oxa1 in the insertion and assembly of mitochondrial membrane proteins. This identifies ARTEMIS as a functional member of the Alb3/Oxa1/YidC protein family and suggests the existence of a novel protein sorting pathway in chloroplasts which integrates polypeptides from the stroma into the inner envelope by an evolutionary conserved process.
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Affiliation(s)
- Soledad Funes
- Institut für Physiologische Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5, 81377 München, Germany
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González-Halphen D, Funes S, Pérez-Martínez X, Reyes-Prieto A, Claros MG, Davidson E, King MP. Genetic Correction of Mitochondrial Diseases: Using the Natural Migration of Mitochondrial Genes to the Nucleus in Chlorophyte Algae as a Model System. Ann N Y Acad Sci 2004; 1019:232-9. [PMID: 15247021 DOI: 10.1196/annals.1297.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Mitochondrial diseases display great diversity in clinical symptoms and biochemical characteristics. Although mtDNA mutations have been identified in many patients, there are currently no effective treatments. A number of human diseases result from mutations in mtDNA-encoded proteins, a group of proteins that are hydrophobic and have multiple membrane-spanning regions. One method that has great potential for overcoming the pathogenic consequences of these mutations is to place a wild-type copy of the affected gene in the nucleus, and target the expressed protein to the mitochondrion to function in place of the defective protein. Several respiratory chain subunit genes, which are typically mtDNA encoded, are nucleus encoded in the chlorophyte algae Chlamydomonas reinhardtii and Polytomella sp. Analysis of these genes has revealed adaptations that facilitated their expression from the nucleus. The nucleus-encoded proteins exhibited diminished physical constraints for import as compared to their mtDNA-encoded homologues. The hydrophobicity of the nucleus-encoded proteins is diminished in those regions that are not involved in subunit-subunit interactions or that contain amino acids critical for enzymatic reactions of the proteins. In addition, these proteins have unusually large mitochondrial targeting sequences. Information derived from these studies should be applicable toward the development of genetic therapies for human diseases resulting from mutations in mtDNA-encoded polypeptides.
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Affiliation(s)
- Diego González-Halphen
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Mexico D.F., Mexico
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Funes S, Reyes-Prieto A, Pérez-Martínez X, González-Halphen D. On the evolutionary origins of apicoplasts: revisiting the rhodophyte vs. chlorophyte controversy. Microbes Infect 2004; 6:305-11. [PMID: 15065552 DOI: 10.1016/j.micinf.2003.11.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Apicomplexans are parasites of great medical and veterinary importance. They contain a vestigial plastid, the apicoplast, that originated through the secondary endosymbiosis of the photosynthetic unicellular alga. The nature of this alga remains controversial. Here, we revisit the available evidence and critically summarize the "green vs. red" debate.
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Affiliation(s)
- Soledad Funes
- Institut fur Physiologische Chemie, Ludwig-Maximilians-Universität München, Munich, Germany
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Funes S, Nargang FE, Neupert W, Herrmann JM. The Oxa2 protein of Neurospora crassa plays a critical role in the biogenesis of cytochrome oxidase and defines a ubiquitous subbranch of the Oxa1/YidC/Alb3 protein family. Mol Biol Cell 2004; 15:1853-61. [PMID: 14767059 PMCID: PMC379281 DOI: 10.1091/mbc.e03-11-0789] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Proteins of the Oxa1/YidC/Alb3 family mediate the insertion of proteins into membranes of mitochondria, bacteria, and chloroplasts. Here we report the identification of a second gene of the Oxa1/YidC/Alb3 family in the genome of Neurospora crassa, which we have named oxa2. Its gene product, Oxa2, is located in the inner membrane of mitochondria. Deletion of the oxa2 gene caused a specific defect in the biogenesis of cytochrome oxidase and resulted in induction of the alternative oxidase (AOD), which bypasses the need for complex IV of the respiratory chain. The Oxa2 protein of N. crassa complements Cox18-deficient yeast mutants suggesting a common function for both proteins. The oxa2 sequence allowed the identification of a new subfamily of Oxa1/YidC/Alb3 proteins whose members appear to be ubiquitously present in mitochondria of fungi, plants, and animals including humans.
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Affiliation(s)
- Soledad Funes
- Institut für Physiologische Chemie, Universität München, 81377 München, Germany
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Affiliation(s)
- Soledad Funes
- Instituto de Fisiologia Celular, Universidad Nacional Autónoma de México (UNAM), 04510 D.F., Mexico
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Pérez-Martínez X, Funes S, Tolkunova E, Davidson E, King MP, González-Halphen D. Structure of nuclear-localized cox3 genes in Chlamydomonas reinhardtii and in its colorless close relative Polytomella sp. Curr Genet 2002; 40:399-404. [PMID: 11919679 DOI: 10.1007/s00294-002-0270-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2001] [Accepted: 12/21/2001] [Indexed: 11/30/2022]
Abstract
Several chlorophyte algae do not have the cox3 gene, encoding subunit III of cytochrome c oxidase, in their mitochondrial genomes. The cox3 gene is nuclear-encoded in the photosynthetic alga Chlamydomonas reinhardtii and in the colorless alga Polytomella sp. In this work, the genomic sequences of the cox3 genes of these two closely related algae are reported. The cox3 genes of both C. reinhardtii and Polytomella sp. contain four introns in the region encoding the putative mitochondrial-targeting sequences. These four introns show low sequence identities, but their locations are conserved between these species. The cox3 gene of C. reinhardtii has five additional introns in the region encoding the mature subunit III of cytochrome c oxidase. Sequence analysis of intron 6 of the cox3 gene of C. reinhardtii revealed similarity with two sequence elements present in introns of several other nuclear genes from this green alga. In the majority of the genes, these conserved sequences are located either near the 3' end or near the 5' end of the introns. Based on these data, we propose that the colorless genus Polytomella separated from C. reinhardtii after the cox3 gene was transferred to the nucleus. The data also support the evolutionary hypothesis of a recent acquisition of introns in C. reinhardtii.
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Affiliation(s)
- Xochitl Pérez-Martínez
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, 04510, D.F., Mexico
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Funes S, Davidson E, Claros MG, van Lis R, Pérez-Martínez X, Vázquez-Acevedo M, King MP, González-Halphen D. The typically mitochondrial DNA-encoded ATP6 subunit of the F1F0-ATPase is encoded by a nuclear gene in Chlamydomonas reinhardtii. J Biol Chem 2002; 277:6051-8. [PMID: 11744727 DOI: 10.1074/jbc.m109993200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The atp6 gene, encoding the ATP6 subunit of F(1)F(0)-ATP synthase, has thus far been found only as an mtDNA-encoded gene. However, atp6 is absent from mtDNAs of some species, including that of Chlamydomonas reinhardtii. Analysis of C. reinhardtii expressed sequence tags revealed three overlapping sequences that encoded a protein with similarity to ATP6 proteins. PCR and 5'- and 3'-RACE were used to obtain the complete cDNA and genomic sequences of C. reinhardtii atp6. The atp6 gene exhibited characteristics of a nucleus-encoded gene: Southern hybridization signals consistent with nuclear localization, the presence of introns, and a codon usage and a polyadenylation signal typical of nuclear genes. The corresponding ATP6 protein was confirmed as a subunit of the mitochondrial F(1)F(0)-ATP synthase from C. reinhardtii by N-terminal sequencing. The predicted ATP6 polypeptide has a 107-amino acid cleavable mitochondrial targeting sequence. The mean hydrophobicity of the protein is decreased in those transmembrane regions that are predicted not to participate directly in proton translocation or in intersubunit contacts with the multimeric ring of c subunits. This is the first example of a mitochondrial protein with more than two transmembrane stretches, directly involved in proton translocation, that is nucleus-encoded.
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Affiliation(s)
- Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiologia Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, 04510 México D.F., Mexico
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Pérez-Martínez X, Antaramian A, Vazquez-Acevedo M, Funes S, Tolkunova E, d'Alayer J, Claros MG, Davidson E, King MP, González-Halphen D. Subunit II of cytochrome c oxidase in Chlamydomonad algae is a heterodimer encoded by two independent nuclear genes. J Biol Chem 2001; 276:11302-9. [PMID: 11094061 DOI: 10.1074/jbc.m010244200] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial genomes of Chlamydomonad algae lack the cox2 gene that encodes the essential subunit COX II of cytochrome c oxidase. COX II is normally a single polypeptide encoded by a single mitochondrial gene. In this work we cloned two nuclear genes encoding COX II from both Chlamydomonas reinhardtii and Polytomella sp. The cox2a gene encodes a protein, COX IIA, corresponding to the N-terminal portion of subunit II of cytochrome c oxidase, and the cox2b gene encodes COX IIB, corresponding to the C-terminal region. The cox2a and cox2b genes are located in the nucleus and are independently transcribed into mRNAs that are translated into separate polypeptides. These two proteins assemble with other cytochrome c oxidase subunits in the inner mitochondrial membrane to form the mature multi-subunit complex. We propose that during the evolution of the Chlorophyte algae, the cox2 gene was divided into two mitochondrial genes that were subsequently transferred to the nucleus. This event was evolutionarily distinct from the transfer of an intact cox2 gene to the nucleus in some members the Leguminosae plant family.
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Affiliation(s)
- X Pérez-Martínez
- Departamento de Genética Molecular, Instituto de Fisiologia Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, México 04510, D.F. Mexico
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Szczepanik AM, Funes S, Petko W, Ringheim GE. IL-4, IL-10 and IL-13 modulate A beta(1--42)-induced cytokine and chemokine production in primary murine microglia and a human monocyte cell line. J Neuroimmunol 2001; 113:49-62. [PMID: 11137576 DOI: 10.1016/s0165-5728(00)00404-5] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A hallmark of the immunopathology associated with Alzheimer's disease (AD) is the presence of activated microglia surrounding senile plaque deposits of beta-amyloid (A beta) peptides. A beta peptides have been shown to be potent activators of microglia and macrophages, but little is known about endogenous factors that may modulate their responses to amyloid. We investigated whether the 'anti-inflammatory' cytokines IL-4, IL-10 and IL-13 could regulate A beta-induced production of the inflammatory cytokines IL-1 alpha, IL-1 beta, TNF-alpha, IL-6 and the chemokine MCP-1. A beta(1-42) time- and dose-dependently induced the production and secretion of these inflammatory proteins in the human THP-1 monocyte cell line and in primary murine microglia, similar to what was observed for lipopolysaccharide (LPS) stimulated cells. IL-10 was found to suppress all A beta and LPS-induced inflammatory proteins measured (IL-1 alpha, IL-1 beta, IL-6, TNF-alpha and MCP-1) in both cell types with the exception of LPS-induced MCP-1 in THP-1 cells where no change was observed. In contrast to the inhibition observed for IL-10, both IL-4 and IL-13 enhanced MCP-1 secretion. IL-4 and IL-13 reduced IL-6 secretion, but effects on IL-1 alpha, IL-1 beta or TNF-alpha were dependent on cell type and stimulus conditions. Additional experiments using RT-PCR showed that IL-4, IL-10 and IL-13 mRNA is found to be present in human brain tissue. These results show that IL-4, IL-10, and IL-13 differentially regulate microglial responses to A beta and may play a role in the inflammation pathology observed surrounding senile plaques.
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Affiliation(s)
- A M Szczepanik
- CNS Department, Aventis Pharmaceuticals, Inc., Route 202-206 P.O. Box 6800, Bridgewater, NJ 08807-0800, USA
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Pérez-Martínez X, Vazquez-Acevedo M, Tolkunova E, Funes S, Claros MG, Davidson E, King MP, González-Halphen D. Unusual location of a mitochondrial gene. Subunit III of cytochrome C oxidase is encoded in the nucleus of Chlamydomonad algae. J Biol Chem 2000; 275:30144-52. [PMID: 10899162 DOI: 10.1074/jbc.m003940200] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The algae of the family Chlamydomonadaceae lack the gene cox3 that encodes subunit III of cytochrome c oxidase in their mitochondrial genomes. This observation has raised the question of whether this subunit is present in cytochrome c oxidase or whether the corresponding gene is located in the nucleus. Cytochrome c oxidase was isolated from the colorless chlamydomonad Polytomella spp., and the existence of subunit III was established by immunoblotting analysis with an antibody directed against Saccharomyces cerevisiae subunit III. Based partly upon the N-terminal sequence of this subunit, oligodeoxynucleotides were designed and used for polymerase chain reaction amplification, and the resulting product was used to screen a cDNA library of Chlamydomonas reinhardtii. The complete sequences of the cox3 cDNAs from Polytomella spp. and C. reinhardtii are reported. Evidence is provided that the genes for cox3 are encoded by nuclear DNA, and the predicted polypeptides exhibit diminished physical constraints for import as compared with mitochondrial-DNA encoded homologs. This indicates that transfer of this gene to the nucleus occurred before Polytomella diverged from the photosynthetic Chlamydomonas lineage and that this transfer may have occurred in all chlamydomonad algae.
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Affiliation(s)
- X Pérez-Martínez
- Departamento de Genética Molecular, Instituto de Fisiologia Celular, Universidad Nacional Autónoma de México, 04510
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Antaramian A, Funes S, Vázquez-acevedo M, Atteia A, Coria R, González-Halphen D. Two unusual amino acid substitutions in cytochrome b of the colorless alga Polytomella spp.: correlation with the atypical spectral properties of the bH heme. Arch Biochem Biophys 1998; 354:206-14. [PMID: 9637728 DOI: 10.1006/abbi.1998.0680] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The dithionite-reduced spectra of the purified bc1 complexes from the colorless alga Polytomella spp. and the closely related green alga Chlamydomonas reinhardtii were compared. The spectrum of the bc1 complex from C. reinhardtii showed a profile similar to those of the bc1 complexes from other species. In contrast, the bc1 complex from Polytomella spp. exhibits a double-peak spectrum in the alpha-band region, where the absorption bands of cytochrome c1 and cytochrome b are completely resolved. To further understand the molecular basis of these spectroscopic differences, the mitochondrial gene encoding cytochrome b of Polytomella spp. was cloned, sequenced, and compared with that of C. reinhardtii. The Polytomella spp. cytochrome b gene is 1113 bp long and does not contain introns. The deduced protein sequence exhibits 56% identity and 68% similarity with the cytochrome b of C. reinhardtii, and in a phylogenetic analysis it clearly affiliated with the b-type cytochromes of C. reinhardtii and C. smithii. A comparison of the primary sequences of the Polytomella spp. cytochrome b with other b-type cytochromes, and its analysis based on the structure featuring eight transmembrane stretches, allowed the identification of a tyrosine in position 114, which substitutes for a tryptophan present in all mitochondrial b-type cytochromes sequenced to date. In addition, the primary sequence of the cytochrome b from Polytomella spp. has a serine at position 36, instead of a nonpolar residue (alanine or leucine) found in all other species. In the proposed model for cytochrome b, both residues Tyr114 and Ser36 are in close proximity to the high-potential bH heme. The above data suggest that the polar residues Y114 and S36, each one by itself or in combination, may interact with heme bH of Polytomella spp. and, thus, may be responsible for the unique spectroscopic characteristics of cytochrome b.
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Affiliation(s)
- A Antaramian
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de Mexico, Mexico City, D.F., 04510, Mexico
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Hornsperger JM, Collard JN, Heydt JG, Giacobini E, Funes S, Dow J, Schirlin D. Trimethylsilylated trifluoromethyl ketones, a novel class of acetylcholinesterase inhibitors: biochemical and pharmacological profile of MDL 73,745. Biochem Soc Trans 1994; 22:758-63. [PMID: 7821680 DOI: 10.1042/bst0220758] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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