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Lapaille M, Escobar-Ramírez A, Degand H, Baurain D, Rodríguez-Salinas E, Coosemans N, Boutry M, Gonzalez-Halphen D, Remacle C, Cardol P. Atypical subunit composition of the chlorophycean mitochondrial F1FO-ATP synthase and role of Asa7 protein in stability and oligomycin resistance of the enzyme. Mol Biol Evol 2010; 27:1630-44. [PMID: 20156838 DOI: 10.1093/molbev/msq049] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In yeast, mammals, and land plants, mitochondrial F(1)F(O)-ATP synthase (complex V) is a remarkable enzymatic machinery that comprises about 15 conserved subunits. Peculiar among eukaryotes, complex V from Chlamydomonadales algae (order of chlorophycean class) has an atypical subunit composition of its peripheral stator and dimerization module, with nine subunits of unknown evolutionary origin (Asa subunits). In vitro, this enzyme exhibits an increased stability of its dimeric form, and in vivo, Chlamydomonas reinhardtii cells are insensitive to oligomycins, which are potent inhibitors of proton translocation through the F(O) moiety. In this work, we showed that the atypical features of the Chlamydomonadales complex V enzyme are shared by the other chlorophycean orders. By biochemical and in silico analyses, we detected several atypical Asa subunits in Scenedesmus obliquus (Sphaeropleales) and Chlorococcum ellipsoideum (Chlorococcales). In contrast, complex V has a canonical subunit composition in other classes of Chlorophytes (Trebouxiophyceae, Prasinophyceae, and Ulvophyceae) as well as in Streptophytes (land plants), and in Rhodophytes (red algae). Growth, respiration, and ATP levels in Chlorophyceae were also barely affected by oligomycin concentrations that affect representatives of the other classes of Chlorophytes. We finally studied the function of the Asa7 atypical subunit by using RNA interference in C. reinhardtii. Although the loss of Asa7 subunit has no impact on cell bioenergetics or mitochondrial structures, it destabilizes in vitro the enzyme dimeric form and renders growth, respiration, and ATP level sensitive to oligomycins. Altogether, our results suggest that the loss of canonical components of the complex V stator happened at the root of chlorophycean lineage and was accompanied by the recruitment of novel polypeptides. Such a massive modification of complex V stator features might have conferred novel properties, including the stabilization of the enzyme dimeric form and the shielding of the proton channel. In these respects, we discuss an evolutionary scenario for F(1)F(O)-ATP synthase in the whole green lineage (i.e., Chlorophyta and Streptophyta).
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Bol VV, Delattre AI, Reusens B, Raes M, Remacle C. Forced catch-up growth after fetal protein restriction alters the adipose tissue gene expression program leading to obesity in adult mice. Am J Physiol Regul Integr Comp Physiol 2009; 297:R291-9. [DOI: 10.1152/ajpregu.90497.2008] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A mismatch between fetal and postnatal environment can permanently alter the body structure and physiology and therefore contribute later to obesity and related disorders, as revealed by epidemiological studies. Early programming of adipose tissue might be central in this observation. Moreover, adipose tissue secretes adipokines that provide a molecular link between obesity and its related disorders. Therefore, our aim was to investigate whether a protein restriction during fetal life, followed by catch-up growth could lead to obesity in 9-mo-old male mice and could alter the adipose tissue gene expression profile. Dams were fed a low-protein (LP) or an isocaloric control (C) diet during gestation. Postnatal catch-up growth was induced in LP offspring by feeding dams with control diet and by culling LP litters to four pups instead of eight in the C group. At weaning, male mice were fed by lab chow alone (C) or supplemented with a hypercaloric diet (HC), to induce obesity (C-C, C-HC, LP-C, and LP-HC groups). At 9 mo, LP offspring featured increased relative fat mass, hyperglycemia, hypercholesterolemia, and hyperleptinemia. Using a microarray designed to study the expression of 89 genes involved in adipose tissue differentiation/function, we demonstrated that the expression profile of several genes were dependent upon the maternal diet. Among the diverse genes showing altered expression, we could identify genes encoding several enzymes involved in lipid metabolism. These results indicated that offspring submitted to early mismatched nutrition exhibited alterations in adipose tissue gene expression that probably increases their susceptibility to overweight when challenged after weaning with a HC diet.
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Dahri S, Gego C, Grégoire F, Reusens B, Remacle C, Hoet JJ. P-94: Effect of isocaloric low protein diet during gestation on IGFBPs content in serum and organs of mother and fetus in rat. Exp Clin Endocrinol Diabetes 2009. [DOI: 10.1055/s-0029-1211639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Nivoit P, Morens C, Van Assche FA, Jansen E, Poston L, Remacle C, Reusens B. Established diet-induced obesity in female rats leads to offspring hyperphagia, adiposity and insulin resistance. Diabetologia 2009; 52:1133-42. [PMID: 19288075 DOI: 10.1007/s00125-009-1316-9] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Accepted: 01/29/2009] [Indexed: 01/21/2023]
Abstract
AIMS/HYPOTHESIS Accumulating evidence suggests that maternal obesity may increase the risk of metabolic disease in the offspring. We investigated the effects of established maternal diet-induced obesity on male and female offspring appetite, glucose homeostasis and body composition in rats. METHODS Female Wistar rats were fed either a standard chow (3% fat, 7% sugar [wt/wt]) or a palatable obesogenic diet (11% fat, 43% sugar [wt/wt]) for 8 weeks before mating and throughout pregnancy and lactation. Male and female offspring of control and obese dams were weaned on to standard chow and assessed until 12 months of age. RESULTS At mating, obese dams were heavier than control with associated hyperglycaemia and hyperinsulinaemia. Male and female offspring of obese dams were hyperphagic (p < 0.0001) and heavier than control (p < 0.0001) until 12 months of age. NEFA were raised at 2 months but not at 12 months. At 3 months, OGTT showed more pronounced alteration of glucose homeostasis in male than in female offspring of obese animals. Euglycaemic-hyperinsulinaemic clamps performed at 8 to 9 months in female and 10 to 11 months in male offspring revealed insulin resistance in male offspring of obese dams (p < 0.05 compared with control). Body compositional analysis at 12 months also showed increased fat pad weights in male and female offspring of obese animals. CONCLUSIONS/INTERPRETATION Diet-induced obesity in female rats leads to a state of insulin resistance in male offspring, associated with development of obesity and increased adiposity. An increase in food intake may play a role.
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Barbieri MR, Larosa V, Cardol P, Remacle C, Hamel P. 31. Molecular Dissection of Mitochondrial Complex I Assembly In a Genetically Tractable Model System. Mitochondrion 2009. [DOI: 10.1016/j.mito.2008.12.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Goosse K, Bouckenooghe T, Balteau M, Reusens B, Remacle C. Implication of nitric oxide in the increased islet-cells vulnerability of adult progeny from protein-restricted mothers and its prevention by taurine. J Endocrinol 2009; 200:177-87. [PMID: 19039096 DOI: 10.1677/joe-08-0234] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
An increased vulnerability of adult beta-cells seems to be programmed in early life as adult islets from the progeny of dams fed a low-protein diet exhibited an increased apoptotic rate after cytokine stimulation. This was prevented by maternal taurine supplementation. Here, we investigated the mechanisms implicated in such an increased vulnerability and how taurine exerts its protective role. Throughout gestation and lactation, Wistar rats were fed a 20% (control (C group)) or an isocaloric 8% protein diet (recovery (R group)) supplemented or not with taurine (control+taurine and recovery+taurine groups respectively). Offspring received a 20% protein diet after weaning. Islets from 3-month-old females were isolated and cultured for 48 h before being incubated with or without cytokines for 24 h. In unstimulated islets, apoptotic rate and NO(.) secretion were higher in R than in C. Both GADD153 mRNA and protein were increased, whereas mRNA of mitochondrial gene ATPase6 was downregulated in R group compared with C. In the RT group, taurine prevented apoptosis and restored a normal NO(.) production in GADD153 as well as ATPase6 mRNA expression. After cytokines-induction, apoptosis and NO(.) secretion were still increased in R compared with C but both parameters were normalized in the RT group. In conclusion, a maternal low-protein diet programmes a different pattern of gene expression in islet-cells of adult progeny. Higher NO(.) production by these islets could be an important factor in the subsequent cell death. The prevention of these events by maternal taurine supplementation emphasizes the importance of taurine during endocrine pancreas development.
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Vinogradova E, Salinas T, Cognat V, Remacle C, Maréchal-Drouard L. Steady-state levels of imported tRNAs in Chlamydomonas mitochondria are correlated with both cytosolic and mitochondrial codon usages. Nucleic Acids Res 2009; 37:1521-8. [PMID: 19139073 PMCID: PMC2655685 DOI: 10.1093/nar/gkn1073] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The mitochondrial genome of Chlamydomonas reinhardtii only encodes three expressed tRNA genes, thus most mitochondrial tRNAs are likely imported. The sharing of tRNAs between chloroplasts and mitochondria has been speculated in this organism. We first demonstrate that no plastidial tRNA is present in mitochondria and that the mitochondrial translation mainly relies on the import of nucleus-encoded tRNA species. Then, using northern analysis, we show that the extent of mitochondrial localization for the 49 tRNA isoacceptor families encoded by the C. reinhardtii nuclear genome is highly variable. Until now the reasons for such variability were unknown. By comparing cytosolic and mitochondrial codon usage with the sub-cellular distribution of tRNAs, we provide unprecedented evidence that the steady-state level of a mitochondrial tRNA is linked not only to the frequency of the cognate codon in mitochondria but also to its frequency in the cytosol, then allowing optimal mitochondrial translation.
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Reusens B, Sparre T, Kalbe L, Bouckenooghe T, Theys N, Kruhøffer M, Orntoft TF, Nerup J, Remacle C. The intrauterine metabolic environment modulates the gene expression pattern in fetal rat islets: prevention by maternal taurine supplementation. Diabetologia 2008; 51:836-45. [PMID: 18311556 DOI: 10.1007/s00125-008-0956-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Accepted: 01/11/2008] [Indexed: 01/14/2023]
Abstract
AIMS/HYPOTHESIS Events during fetal life may in critical time windows programme tissue development leading to organ dysfunction with potentially harmful consequences in adulthood such as diabetes. In rats, the beta cell mass of progeny from dams fed with a low-protein (LP) diet during gestation is decreased at birth and metabolic perturbation lasts through adulthood even though a normal diet is given after birth or after weaning. Maternal and fetal plasma taurine levels are suboptimal. Maternal taurine supplementation prevents these induced abnormalities. In this study, we aimed to reveal changes in gene expression in fetal islets affected by the LP diet and how taurine may prevent these changes. METHODS Pregnant Wistar rats were fed an LP diet (8% [wt/wt] protein) supplemented or not with taurine in the drinking water or a control diet (20% [wt/wt] protein). At 21.5 days of gestation, fetal pancreases were removed, digested and cultured for 7 days. Neoformed islets were collected and transcriptome analysis was performed. RESULTS Maternal LP diet significantly changed the expression of more than 10% of the genes. Tricarboxylic acid cycle and ATP production were highly targeted, but so too were cell proliferation and defence. Maternal taurine supplementation normalised the expression of all altered genes. CONCLUSIONS/INTERPRETATION Development of the beta cells and particularly their respiration is modulated by the intrauterine environment, which may epigenetically modify expression of the genome and programme the beta cell towards a pre-diabetic phenotype. This mis-programming by maternal LP diet was prevented by early taurine intervention.
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Cognat V, Deragon JM, Vinogradova E, Salinas T, Remacle C, Maréchal-Drouard L. On the evolution and expression of Chlamydomonas reinhardtii nucleus-encoded transfer RNA genes. Genetics 2008; 179:113-23. [PMID: 18493044 PMCID: PMC2390591 DOI: 10.1534/genetics.107.085688] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Accepted: 03/18/2008] [Indexed: 11/18/2022] Open
Abstract
In Chlamydomonas reinhardtii, 259 tRNA genes were identified and classified into 49 tRNA isoaccepting families. By constructing phylogenetic trees, we determined the evolutionary history for each tRNA gene family. The majority of the tRNA sequences are more closely related to their plant counterparts than to animals ones. Northern experiments also permitted us to show that at least one member of each tRNA isoacceptor family is transcribed and correctly processed in vivo. A short stretch of T residues known to be a signal for termination of polymerase III transcription was found downstream of most tRNA genes. It allowed us to propose that the vast majority of the tRNA genes are expressed and to confirm that numerous tRNA genes separated by short spacers are indeed cotranscribed. Interestingly, in silico analyses and hybridization experiments show that the cellular tRNA abundance is correlated with the number of tRNA genes and is adjusted to the codon usage to optimize translation efficiency. Finally, we studied the origin of SINEs, short interspersed elements related to tRNAs, whose presence in Chlamydomonas is exceptional. Phylogenetic analysis strongly suggests that tRNA(Asp)-related SINEs originate from a prokaryotic-type tRNA either horizontally transferred from a bacterium or originally present in mitochondria or chloroplasts.
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Cardol P, Boutaffala L, Memmi S, Devreese B, Matagne RF, Remacle C. In Chlamydomonas, the loss of ND5 subunit prevents the assembly of whole mitochondrial complex I and leads to the formation of a low abundant 700 kDa subcomplex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:388-96. [PMID: 18258177 DOI: 10.1016/j.bbabio.2008.01.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 12/26/2007] [Accepted: 01/08/2008] [Indexed: 10/22/2022]
Abstract
In the green alga Chlamydomonas reinhardtii, a mutant deprived of complex I enzyme activity presents a 1T deletion in the mitochondrial nd5 gene. The loss of the ND5 subunit prevents the assembly of the 950 kDa whole complex I. Instead, a low abundant 700 kDa subcomplex, loosely associated to the inner mitochondrial membrane, is assembled. The resolution of the subcomplex by SDS-PAGE gave rise to 19 individual spots, sixteen having been identified by mass spectrometry analysis. Eleven, mainly associated to the hydrophilic part of the complex, are homologs to subunits of the bovine enzyme whereas five (including gamma-type carbonic anhydrase subunits) are specific to green plants or to plants and fungi. None of the subunits typical of the beta membrane domain of complex I enzyme has been identified in the mutant. This allows us to propose that the truncated enzyme misses the membrane distal domain of complex I but retains the proximal domain associated to the matrix arm of the enzyme. A complex I topology model is presented in the light of our results. Finally, a supercomplex most probably corresponding to complex I-complex III association, was identified in mutant mitochondria, indicating that the missing part of the enzyme is not required for the formation of the supercomplex.
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Dumortier O, Blondeau B, Duvillié B, Reusens B, Bréant B, Remacle C. Different mechanisms operating during different critical time-windows reduce rat fetal beta cell mass due to a maternal low-protein or low-energy diet. Diabetologia 2007; 50:2495-503. [PMID: 17882398 DOI: 10.1007/s00125-007-0811-0] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Accepted: 07/23/2007] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS Adverse events during intra-uterine life may programme organ growth and favour disease later in life. In animals, protein or energy restriction during gestation alters the development of the endocrine pancreas, even though the duration of malnutrition is different. Here, we evaluate the specific effects of both diets during different periods of gestation and the mechanisms underlying the decreased beta cell mass. METHODS Pregnant Wistar rats were fed either a low-protein or a low-energy diet during the last week of gestation or throughout gestation. Fetuses and their pancreases were analysed at days 15 and 21 of gestation. RESULTS The low-energy diet reduced the beta cell mass from 21-day-old fetuses by 33 or 56% when administered during the last week or throughout gestation, respectively. Fetal corticosterone levels were increased. At 15 days of fetal age, the number of cells producing neurogenin 3 (NEUROG3) or pancreatic and duodenal homeobox gene 1 (PDX-1) was reduced. Neither islet vascularisation nor beta cell proliferation was affected. The low-protein diet, in contrast, was more efficient in decreasing the fetal beta cell mass when given during the last week of gestation (-53%) rather than throughout gestation (-33%). Beta cell proliferation was decreased by 50% by the low-protein diet, independently of its duration, and islet vascularisation was reduced. This diet did not affect NEUROG3- or PDX-1-positive cell numbers. CONCLUSION/INTERPRETATION Although both diets reduced the fetal beta cell mass, the cellular mechanisms and the sensitivity windows were different. Early alteration of neogenesis due to elevated corticosterone levels is likely to be responsible for the decreased beta cell mass in low-energy fetuses, whereas impaired beta cell proliferation and islet vascularisation at later stages are implicated in low-protein fetuses.
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Remacle C, Dumortier O, Bol V, Goosse K, Romanus P, Theys N, Bouckenooghe T, Reusens B. Intrauterine programming of the endocrine pancreas. Diabetes Obes Metab 2007; 9 Suppl 2:196-209. [PMID: 17919194 DOI: 10.1111/j.1463-1326.2007.00790.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Epidemiological studies have revealed strong relationships between poor foetal growth and subsequent development of the metabolic syndrome. Persisting effects of early malnutrition become translated into pathology, thereby determine chronic risk for developing glucose intolerance and diabetes. These epidemiological observations identify the phenomena of foetal programming without explaining the underlying mechanisms that establish the causal link. Animal models have been established and studies have demonstrated that reduction in the availability of nutrients during foetal development programs the endocrine pancreas and insulin-sensitive tissues. Whatever the type of foetal malnutrition, whether there are not enough calories or protein in food or after placental deficiency, malnourished pups are born with a defect in their beta-cell population that will never completely recover, and insulin-sensitive tissues will be definitively altered. Despite the similar endpoint, different cellular and physiological mechanisms are proposed. Hormones operative during foetal life like insulin itself, insulin-like growth factors and glucocorticoids, as well as specific molecules like taurine, or islet vascularization were implicated as possible factors amplifying the defect. The molecular mechanisms responsible for intrauterine programming of the beta cells are still elusive, but two hypotheses recently emerged: the first one implies programming of mitochondria and the second, epigenetic regulation.
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Morens C, Nivoit P, Piersma A, Reusens B, Remacle C, Van Assche F. Development of metabolic syndrome can be programmed in utero by maternal diet induced obesity. Appetite 2007. [DOI: 10.1016/j.appet.2007.03.141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Kalbe L, Leunda A, Sparre T, Meulemans C, Ahn MT, Orntoft T, Kruhoffer M, Reusens B, Nerup J, Remacle C. Nutritional regulation of proteases involved in fetal rat insulin secretion and islet cell proliferation. Br J Nutr 2007; 93:309-16. [PMID: 15877869 DOI: 10.1079/bjn20041313] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Epidemiological studies have indicated that malnutrition during early life may programme chronic degenerative disease in adulthood. In an animal model of fetal malnutrition, rats received an isoenergetic, low-protein (LP) diet during gestation. This reduced fetal β-cell proliferation and insulin secretion. Supplementation during gestation with taurine prevented these alterations. Since proteases are involved in secretion and proliferation, we investigated which proteases were associated with these alterations and their restoration in fetal LP islets. Insulin secretion and proliferation of fetal control and LP islets exposed to different protease modulators were measured. Lactacystin and calpain inhibitor I, but not isovaleryl-l-carnitine, raised insulin secretion in control islets, indicating that proteasome and cysteinyl cathepsin(s), but not μ-calpain, are involved in fetal insulin secretion. Insulin secretion from LP islets responded normally to lactacystin but was insensitive to calpain inhibitor I, indicating a loss of cysteinyl cathepsin activity. Taurine supplementation prevented this by restoring the response to calpain inhibitor I. Control islet cell proliferation was reduced by calpain inhibitor I and raised by isovaleryl-l-carnitine, indicating an involvement of calpain. Calpain activity appeared to be lost in LP islets and not restored by taurine. Most modifications in the mRNA expression of cysteinyl cathepsins, calpains and calpastatin due to maternal protein restriction were consistent with reduced protease activity and were restored by taurine. Thus, maternal protein restriction affected cysteinyl cathepsins and the calpain–calpastatin system. Taurine normalised fetal LP insulin secretion by protecting cysteinyl cathepsin(s), but the restoration of LP islet cell proliferation by taurine did not implicate calpains.
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Bonnefoy N, Remacle C, Fox TD. Genetic transformation of Saccharomyces cerevisiae and Chlamydomonas reinhardtii mitochondria. Methods Cell Biol 2007; 80:525-48. [PMID: 17445712 DOI: 10.1016/s0091-679x(06)80026-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Vázquez-Acevedo M, Cardol P, Cano-Estrada A, Lapaille M, Remacle C, González-Halphen D. The mitochondrial ATP synthase of chlorophycean algae contains eight subunits of unknown origin involved in the formation of an atypical stator-stalk and in the dimerization of the complex. J Bioenerg Biomembr 2006; 38:271-82. [PMID: 17160464 DOI: 10.1007/s10863-006-9046-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Mitochondrial F(1)F( O )-ATP synthase of Chlamydomonas reinhardtii and Polytomella sp. is a dimer of 1,600,000 Da. In Chlamydomonas the enzyme lacks the classical subunits that constitute the peripheral stator-stalk as well as those involved in the dimerization of the fungal and mammal complex. Instead, it contains eight novel polypeptides named ASA1 to 8. We show that homologs of these subunits are also present in the chlorophycean algae Polytomella sp. and Volvox carterii. Blue Native Gel Electrophoresis analysis of mitochondria from different green algal species also indicates that stable dimeric mitochondrial ATP synthases may be characteristic of all Chlorophyceae. One additional subunit, ASA9, was identified in the purified mitochondrial ATP synthase of Polytomella sp. The dissociation profile of the Polytomella enzyme at high-temperatures and cross-linking experiments finally suggest that some of the ASA polypeptides constitute a stator-stalk with a unique architecture, while others may be involved in the formation of a highly-stable dimeric complex. The algal enzyme seems to have modified the structural features of its surrounding scaffold, while conserving almost intact the structure of its catalytic subunits.
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Cardol P, Lapaille M, Minet P, Franck F, Matagne RF, Remacle C. ND3 and ND4L subunits of mitochondrial complex I, both nucleus encoded in Chlamydomonas reinhardtii, are required for activity and assembly of the enzyme. EUKARYOTIC CELL 2006; 5:1460-7. [PMID: 16963630 PMCID: PMC1563589 DOI: 10.1128/ec.00118-06] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2006] [Accepted: 07/05/2006] [Indexed: 11/20/2022]
Abstract
Made of more than 40 subunits, the rotenone-sensitive NADH:ubiquinone oxidoreductase (complex I) is the most intricate membrane-bound enzyme of the mitochondrial respiratory chain. In vascular plants, fungi, and animals, at least seven complex I subunits (ND1, -2, -3, -4, -4L, -5, and -6; ND is NADH dehydrogenase) are coded by mitochondrial genes. The role of these highly hydrophobic subunits in the enzyme activity and assembly is still poorly understood. In the unicellular green alga Chlamydomonas reinhardtii, the ND3 and ND4L subunits are encoded in the nuclear genome, and we show here that the corresponding genes, called NUO3 and NUO11, respectively, display features that facilitate their expression and allow the proper import of the corresponding proteins into mitochondria. In particular, both polypeptides show lower hydrophobicity compared to their mitochondrion-encoded counterparts. The expression of the NUO3 and NUO11 genes has been suppressed by RNA interference. We demonstrate that the absence of ND3 or ND4L polypeptides prevents the assembly of the 950-kDa whole complex I and suppresses the enzyme activity. The putative role of hydrophobic ND subunits is discussed in relation to the structure of the complex I enzyme. A model for the assembly pathway of the Chlamydomonas enzyme is proposed.
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Zouaoui Boudjeltia K, Gregoir C, Guillaume M, Remacle C, Piro P, Garbar C, Ducobu J, Moguilevsky N, Vanhaeverbeek M, Delree P, Brohee D. Antigens and granularity of blood monocytes in relation to inflammatory markers and lipids in postmenopausal women. Maturitas 2006; 55:132-41. [DOI: 10.1016/j.maturitas.2005.12.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Revised: 12/09/2005] [Accepted: 12/13/2005] [Indexed: 10/25/2022]
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Remacle C, Cardol P, Coosemans N, Gaisne M, Bonnefoy N. High-efficiency biolistic transformation of Chlamydomonas mitochondria can be used to insert mutations in complex I genes. Proc Natl Acad Sci U S A 2006; 103:4771-6. [PMID: 16537419 PMCID: PMC1450245 DOI: 10.1073/pnas.0509501103] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mitochondrial transformation of Chlamydomonas reinhardtii has been optimized by using a particle-gun device and cloned mitochondrial DNA or PCR fragments. A respiratory-deficient strain lacking a 1.2-kb mitochondrial DNA region including the left telomere and part of the cob gene could be rescued as well as a double-frameshift mutant in the mitochondrial cox1 and nd1 genes. High transformation efficiency has been achieved (100-250 transformants per microgram of DNA), the best results being obtained with linearized plasmid DNA. Molecular analysis of the transformants suggests that the right telomere sequence can be copied to reconstruct the left telomere by recombination. In addition, both nondeleterious and deleterious mutations could be introduced. Myxothiazol-resistant transformants have been created by introducing a nucleotide substitution into the cob gene. Similarly, an in-frame deletion of 23 codons has been created in the nd4 mitochondrial gene of both the deleted and frameshift recipient strains. These 23 codons are believed to encode the first transmembrane segment of the ND4 protein. This Deltand4 mutation causes a misassembly of complex I, with the accumulation of a subcomplex that is 250-kDa smaller than the wild-type complex I. The availability of efficient mitochondrial transformation in Chlamydomonas provides an invaluable tool for the study of mitochondrial biogenesis and, more specifically, for site-directed mutagenesis of mitochondrially encoded subunits of complex I, of special interest because the yeast Saccharomyces cerevisiae, whose mitochondrial genome can be manipulated virtually at will, is lacking complex I.
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Bourges I, Ramus C, Mousson de Camaret B, Beugnot R, Remacle C, Cardol P, Hofhaus G, Issartel JP. Structural organization of mitochondrial human complex I: role of the ND4 and ND5 mitochondria-encoded subunits and interaction with prohibitin. Biochem J 2005; 383:491-9. [PMID: 15250827 PMCID: PMC1133742 DOI: 10.1042/bj20040256] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mitochondria-encoded ND (NADH dehydrogenase) subunits, as components of the hydrophobic part of complex I, are essential for NADH:ubiquinone oxidoreductase activity. Mutations or lack of expression of these subunits have significant pathogenic consequences in humans. However, the way these events affect complex I assembly is poorly documented. To understand the effects of particular mutations in ND subunits on complex I assembly, we studied four human cell lines: ND4 non-expressing cells, ND5 non-expressing cells, and rho degrees cells that do not express any ND subunits, in comparison with normal complex I control cells. In control cells, all the seven analysed nuclear-encoded complex I subunits were found to be attached to the mitochondrial inner membrane, except for the 24 kDa subunit, which was nearly equally partitioned between the membranes and the matrix. Absence of a single ND subunit, or even all the seven ND subunits, caused no major changes in the nuclear-encoded complex I subunit content of mitochondria. However, in cells lacking ND4 or ND5, very low amounts of 24 kDa subunit were found associated with the membranes, whereas most of the other nuclear-encoded subunits remained attached. In contrast, membrane association of most of the nuclear subunits was significantly reduced in the absence of all seven ND proteins. Immunopurification detected several subcomplexes. One of these, containing the 23, 30 and 49 kDa subunits, also contained prohibitin. This is the first description of prohibitin interaction with complex I subunits and suggests that this protein might play a role in the assembly or degradation of mitochondrial complex I.
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Abstract
BACKGROUND There is evidence that malnutrition in early life induces a growth retardation leading, in adult life, to manifest components of the metabolic syndrome. However, the impact on obesity seems less clearly established. OBJECTIVE To review the effects of foetal and postnatal malnutrition on the programming of obesity in the context of the metabolic syndrome, as well as the link between central obesity and cardiovascular diseases. METHODS Included in the review were recent papers exploring the mechanisms linking maternal nutrition with impaired foetal growth and later obesity, cardiovascular disease, hypertension and diabetes in humans and animals. RESULTS The programming of obesity during foetal and early postnatal life depends of the timing of maternal malnutrition as well as the postnatal environment. Obesity arises principally in offspring submitted to malnutrition during early stages of gestation and which presented early catch-up growth. The programming may involve the dysregulation of appetite control or the hormonal environment leading to a context favourable to obesity development (hypersecretion of corticosteroids, hyperinsulinaemia and hyperleptinaemia and anomalies in the IGF axis). Adipose tissue secretes actively several factors implicated in inflammation, blood pressure, coagulation and fibrinolysis. The programmed development of intra-abdominal obesity after early growth restriction may thus favour higher prevalence of hypertension and cardiovascular diseases. CONCLUSIONS Abdominal obesity appears in malnourished offspring and is aggravated by early catch-up growth. Higher rates of intra-abdominal obesity observed after growth restriction may participate to hypertension and create atherothrombotic conditions leading to the development of cardiovascular diseases.
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Zouaoui Boudjeltia K, Moguilevsky N, Legssyer I, Babar S, Guillaume M, Delree P, Vanhaeverbeek M, Brohee D, Ducobu J, Remacle C. Oxidation of low density lipoproteins by myeloperoxidase at the surface of endothelial cells: an additional mechanism to subendothelium oxidation. Biochem Biophys Res Commun 2005; 325:434-8. [PMID: 15530411 DOI: 10.1016/j.bbrc.2004.10.049] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Indexed: 11/29/2022]
Abstract
The present paradigm of atherogenesis proposes that low density lipoproteins (LDL) are trapped in subendothelial space of the vascular wall where they are oxidized. Myeloperoxidase (MPO) plays a key role in oxidative damage. We propose that LDL oxidation by myeloperoxidase (Mox-LDL) could occur at the surface of the endothelial cells and not restricted to the subendothelial space. The triad constituted by endothelial cells, circulating LDL and MPO in close interaction, constitutes a synergic mechanism for the genesis of Mox-LDL.
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Cardol P, González-Halphen D, Reyes-Prieto A, Baurain D, Matagne RF, Remacle C. The mitochondrial oxidative phosphorylation proteome of Chlamydomonas reinhardtii deduced from the Genome Sequencing Project. PLANT PHYSIOLOGY 2005; 137:447-59. [PMID: 15710684 PMCID: PMC1065347 DOI: 10.1104/pp.104.054148] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2004] [Revised: 11/25/2004] [Accepted: 11/25/2004] [Indexed: 05/20/2023]
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Tillemans V, Dispa L, Remacle C, Collinge M, Motte P. Functional distribution and dynamics of Arabidopsis SR splicing factors in living plant cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 41:567-82. [PMID: 15686520 DOI: 10.1111/j.1365-313x.2004.02321.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Serine/arginine-rich (SR) proteins constitute an important class of splicing regulators in higher eukaryotes that share a modular structure consisting of one or two N-terminal RNA recognition motif (RRM) domains and a C-terminal RS-rich domain. Herein, we have investigated the in vivo functional distribution of Arabidopsis SR factors. Agrobacterium-mediated transient transformation revealed nuclear speckled distribution and the overall colocalization of fluorescent protein (FP)-tagged SR factors in both tobacco and Arabidopsis cells. Their overall colocalization in larger nucleoplasmic domains was further observed after transcriptional and phosphorylation/dephosphorylation inhibition, indicating a close functional association between SR factors, independent of their phosphorylation state. Furthermore, we demonstrated in vivo the conserved role of the RS and RRM domains in the efficient targeting of Arabidopsis SR proteins to nuclear speckles by using a series of structural domain-deleted mutants of atRSp31 and atRSZp22. We suggest additional roles of RS domain such as the shuttling of atRSZp22 between nucleoplasm and nucleolus through its phosphorylation level. The coexpression of deletion mutants with wild-type SR proteins revealed potential complex associations between them. Fluorescence recovery after photobleaching demonstrated similar dynamic properties of SR factors in both tobacco transiently expressing cells and Arabidopsis transgenics. Cell cycle phase-dependent organization of FP-tagged SR proteins was observed in living tobacco BY-2 cells. We showed that atRSp31 is degraded at metaphase by fluorescence quantification. SR proteins also localized within small foci at anaphase. These results demonstrate interesting related features as well as potentially important differences between plant and animal SR proteins.
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Reusens B, Remacle C. [Development of diabetes, experimental models]. JOURNEES ANNUELLES DE DIABETOLOGIE DE L'HOTEL-DIEU 2005:77-84. [PMID: 16161307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
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