scholarly journals Mmi1, the Yeast Ortholog of Mammalian Translationally Controlled Tumor Protein (TCTP), Negatively Affects Rapamycin-Induced Autophagy in Post-Diauxic Growth Phase

Cells ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 138 ◽  
Author(s):  
Jana Vojtova ◽  
Jiri Hasek
Keyword(s):  
Growth Phase ◽  
Nitrogen Starvation ◽  
Model System ◽  
Diauxic Growth ◽  
Oxygen Species ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Selective Autophagy ◽  
Translationally Controlled Tumor Protein

Translationally controlled tumor protein (TCTP) is a multifunctional and highly conserved protein from yeast to humans. Recently, its role in non-selective autophagy has been reported with controversial results in mammalian and human cells. Herein we examine the effect of Mmi1, the yeast ortholog of TCTP, on non-selective autophagy in budding yeast Saccharomyces cerevisiae, a well-established model system to monitor autophagy. We induced autophagy by nitrogen starvation or rapamycin addition and measured autophagy by using the Pho8Δ60 and GFP-Atg8 processing assays in WT, mmi1Δ, and in autophagy-deficient strains atg8Δ or atg1Δ. Our results demonstrate that Mmi1 does not affect basal or nitrogen starvation-induced autophagy. However, an increased rapamycin-induced autophagy is detected in mmi1Δ strain when the cells enter the post-diauxic growth phase, and this phenotype can be rescued by inserted wild-type MMI1 gene. Further, the mmi1Δ cells exhibit significantly lower amounts of reactive oxygen species (ROS) in the post-diauxic growth phase compared to WT cells. In summary, our study suggests that Mmi1 negatively affects rapamycin-induced autophagy in the post-diauxic growth phase and supports the role of Mmi1/TCTP as a negative autophagy regulator in eukaryotic cells.

scholarly journals NBR1 directly promotes the formation of p62 – ubiquitin condensates via its PB1 and UBA domains

2020 ◽  
Author(s):  
Adriana Savova ◽  
Julia Romanov ◽  
Sascha Martens
Keyword(s):  
Phase Separation ◽  
Wild Type ◽  
Selective Autophagy ◽  
Ubiquitinated Proteins ◽  
Cargo Receptor ◽  
Condensate Formation ◽  
Uba Domain ◽  
Reconstituted System ◽  
Pb1 Domain

SummarySelective autophagy removes harmful intracellular structures such as ubiquitinated, aggregated proteins ensuring cellular homeostasis. This is achieved by the encapsulation of this cargo material within autophagosomes. The cargo receptor p62/SQSTM1 mediates the phase separation of ubiquitinated proteins into condensates, which subsequently become targets for the autophagy machinery. NBR1, another cargo receptor, is a crucial regulator of condensate formation. The mechanisms of the interplay between p62 and NBR1 are not well understood. Employing a fully reconstituted system we show that two domains of NBR1, the PB1 domain which binds to p62 and the UBA domain which binds to ubiquitin, are required to promote p62-ubiquitin condensate formation. In cells, acute depletion of endogenous NBR1 reduces formation of p62 condensates, a phenotype that can be rescued by re-expression of wild-type NBR1, but not PB1 or UBA domain mutants. Our results provide mechanistic insights into the role of NBR1 in selective autophagy.

scholarly journals Growth Phase Regulation of flaA Expression in Helicobacter pylori Is luxS Dependent

2004 ◽  
Vol 72 (9) ◽  
pp. 5506-5510 ◽  
Author(s):  
John T. Loh ◽  
Mark H. Forsyth ◽  
Timothy L. Cover
Keyword(s):  
Helicobacter Pylori ◽  
Growth Phase ◽  
Wild Type ◽  
Phase Dependence ◽  
Autoinducer 2 ◽  
Extracellular Signaling ◽  
Reporter Strains ◽  
Phase Regulation ◽  
H Pylori

ABSTRACT LuxS plays a role in the synthesis of an extracellular signaling molecule, autoinducer 2 (AI-2). To analyze a possible role of AI-2 in regulating Helicobacter pylori gene expression, we constructed a panel of transcriptional reporter strains. We show that the expression of H. pylori flaA is growth phase dependent and that flaA transcription increases in association with increased culture density. Mutating the luxS gene eliminates growth-phase-dependent control of flaA, and this growth phase dependence is restored when the luxS mutant strain is complemented with the wild-type luxS gene.

scholarly journals The J-related Segment of Tim44 Is Essential for Cell Viability: A Mutant Tim44 Remains in the Mitochondrial Import Site, but Inefficiently Recruits mtHsp70 and Impairs Protein Translocation

1999 ◽  
Vol 145 (5) ◽  
pp. 961-972 ◽  
Author(s):  
Alessio Merlin ◽  
Wolfgang Voos ◽  
Ammy C. Maarse ◽  
Michiel Meijer ◽  
Nikolaus Pfanner ◽  
...  
Keyword(s):  
Protein Import ◽  
Protein Translocation ◽  
Adaptor Protein ◽  
Dependent Manner ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
J Proteins

Tim44 is a protein of the mitochondrial inner membrane and serves as an adaptor protein for mtHsp70 that drives the import of preproteins in an ATP-dependent manner. In this study we have modified the interaction of Tim44 with mtHsp70 and characterized the consequences for protein translocation. By deletion of an 18-residue segment of Tim44 with limited similarity to J-proteins, the binding of Tim44 to mtHsp70 was weakened. We found that in the yeast Saccharomyces cerevisiae the deletion of this segment is lethal. To investigate the role of the 18-residue segment, we expressed Tim44Δ18 in addition to the endogenous wild-type Tim44. Tim44Δ18 is correctly targeted to mitochondria and assembles in the inner membrane import site. The coexpression of Tim44Δ18 together with wild-type Tim44, however, does not stimulate protein import, but reduces its efficiency. In particular, the promotion of unfolding of preproteins during translocation is inhibited. mtHsp70 is still able to bind to Tim44Δ18 in an ATP-regulated manner, but the efficiency of interaction is reduced. These results suggest that the J-related segment of Tim44 is needed for productive interaction with mtHsp70. The efficient cooperation of mtHsp70 with Tim44 facilitates the translocation of loosely folded preproteins and plays a crucial role in the import of preproteins which contain a tightly folded domain.

scholarly journals Transmission of Functional, Wild-Type Mitochondria and the Fittest mtDNA to the Next Generation: Bottleneck Phenomenon, Balbiani Body, and Mitophagy

Genes ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 104 ◽  
Author(s):  
Waclaw Tworzydlo ◽  
Malgorzata Sekula ◽  
Szczepan M. Bilinski
Keyword(s):  
Membrane Potential ◽  
Respiratory Activity ◽  
Metabolic Energy ◽  
Oxygen Species ◽  
Deleterious Mutations ◽  
Next Generation ◽  
Wild Type ◽  
Female Germline ◽  
Final Effect

The most important role of mitochondria is to supply cells with metabolic energy in the form of adenosine triphosphate (ATP). As synthesis of ATP molecules is accompanied by the generation of reactive oxygen species (ROS), mitochondrial DNA (mtDNA) is highly vulnerable to impairment and, consequently, accumulation of deleterious mutations. In most animals, mitochondria are transmitted to the next generation maternally, i.e., exclusively from female germline cells (oocytes and eggs). It has been suggested, in this context, that a specialized mechanism must operate in the developing oocytes enabling escape from the impairment and subsequent transmission of accurate (devoid of mutations) mtDNA from one generation to the next. Literature survey suggest that two distinct and irreplaceable pathways of mitochondria transmission may be operational in various animal lineages. In some taxa, the mitochondria are apparently selected: functional mitochondria with high inner membrane potential are transferred to the cells of the embryo, whereas those with low membrane potential (overloaded with mutations in mtDNA) are eliminated by mitophagy. In other species, the respiratory activity of germline mitochondria is suppressed and ROS production alleviated leading to the same final effect, i.e., transmission of undamaged mitochondria to offspring, via an entirely different route.

scholarly journals Mitochondrial GrpE modulates the function of matrix Hsp70 in translocation and maturation of preproteins.

1995 ◽  
Vol 15 (12) ◽  
pp. 7098-7105 ◽  
Author(s):  
S Laloraya ◽  
P J Dekker ◽  
W Voos ◽  
E A Craig ◽  
N Pfanner
Keyword(s):  
Proteolytic Processing ◽  
Mitochondrial Proteins ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Conditional Mutant ◽  
The Matrix ◽  
Matrix Heat

Mitochondrial GrpE (Mge1p) is a mitochondrial cochaperone essential for viability of the yeast Saccharomyces cerevisiae. To study the role of Mge1p in the biogenesis of mitochondrial proteins, we isolated a conditional mutant allele of MGE1 which conferred a temperature-sensitive growth phenotype and led to the accumulation of mitochondrial preproteins after shifting of the cells to the restrictive temperature. The mutant Mge1 protein was impaired in its interaction with the matrix heat shock protein mt-Hsp70. The mutant mitochondria showed a delayed membrane translocation of preproteins, and the maturation of imported proteins was impaired, as evidenced by the retarded second proteolytic processing of a preprotein in the matrix. Moreover, the aggregation of imported proteins was decreased in the mutant mitochondria. The mutant Mge1p differentially modulated the interaction of mt-Hsp70 with preproteins compared with the wild type, resulting in decreased binding to preproteins in membrane transit and enhanced binding to fully imported proteins. We conclude that the interaction of Mge1p with mt-Hsp70 promotes the progress of the Hsp70 reaction cycle, which is essential for import and maturation of mitochondrial proteins.

scholarly journals Mitigation of coral bleaching by antioxidants

2018 ◽  
Author(s):  
Guillermo Yudowski ◽  
Loretta Roberson ◽  
Michael Marty-Rivera
Keyword(s):  
Quantum Yield ◽  
Coral Bleaching ◽  
Model System ◽  
Oxygen Species ◽  
Thermally Induced ◽  
Porites Astreoides ◽  
Aiptasia Pallida ◽  
Reef Degradation ◽  
Coral Holobiont

Coral bleaching, loss of symbiotic dinoflagellate algae from the coral holobiont, is a complex phenomenon that can result in coral death and reef degradation. Reactive oxygen species (ROS) have been suggested as a possible mechanism underlying this event. To determine if antioxidants can be used to reduce ROS production and coral bleaching, we tested the effects of thermal stress in Aiptasia pallida a model system for coral bleaching studies, and the scleractinian coral, Porites astreoides. We analyzed host ROS levels, symbiont dark-adapted quantum yield of photosystem II, and symbiont loss in the presence or absence of antioxidants. We found that a single dose of the antioxidant catechin, significantly reduced ROS levels in the hosts, mitigated the degradation of the symbionts quantum yield and reduced the loss of symbionts from thermally stressed P. astreoides but not from A. pallida. Taken together, these results support a key role of ROS and that antioxidants can prevent symbiont degradation and loss during thermally-induced bleaching in P. astreoides.

scholarly journals Dentilisin Activity Affects the Organization of the Outer Sheath of Treponema denticola

1998 ◽  
Vol 180 (15) ◽  
pp. 3837-3844 ◽  
Author(s):  
Kazuyuki Ishihara ◽  
Howard K. Kuramitsu ◽  
Tadashi Miura ◽  
Katsuji Okuda
Keyword(s):  
Fusobacterium Nucleatum ◽  
Model System ◽  
High Molecular Mass ◽  
Treponema Denticola ◽  
Deficient Mutant ◽  
Wild Type ◽  
Outer Sheath ◽  
Oligomeric Protein ◽  
Dna Fragment

ABSTRACT Prolyl-phenylalanine-specific serine protease (dentilisin) is a major extracellular protease produced by Treponema denticola. The gene, prtP, coding for the protease was recently cloned and sequenced (K. Ishihara, T. Miura, H. K. Kuramitsu, and K. Okuda, Infect. Immun. 64:5178–5186, 1996). In order to determine the role of this protease in the physiology and virulence of T. denticola, a dentilisin-deficient mutant, K1, was constructed following electroporation with aprtP-inactivated DNA fragment. No chymotrypsin-like protease activity was detected in the dentilisin-deficient mutant. In addition, the high-molecular-mass oligomeric protein characteristic of the outer sheath of the organism decreased in the mutant. Furthermore, the hydrophobicity of the mutant was decreased, and coaggregation of the mutant with Fusobacterium nucleatum was enhanced compared to that of the wild-type organism. The results obtained with a mouse abscess model system indicated that the virulence of the mutant was attenuated relative to that of the wild-type organism. These results suggest that dentilisin activity plays a major role in the structural organization of the outer sheath of T. denticola. The loss of dentilsin activity and the structural change in the outer sheath affect the pathogenicity of T. denticola.

scholarly journals Genetic dominance governs the evolution and spread of mobile genetic elements in bacteria

2020 ◽  
Vol 117 (27) ◽  
pp. 15755-15762
Author(s):  
Jerónimo Rodríguez-Beltrán ◽  
Vidar Sørum ◽  
Macarena Toll-Riera ◽  
Carmen de la Vega ◽  
Rafael Peña-Miller ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Mobile Genetic Elements ◽  
Model System ◽  
Host Bacterium ◽  
Wild Type ◽  
Bacterial Evolution ◽  
Human Interest ◽  
Genetic Dominance ◽  
Genetic Elements

Mobile genetic elements (MGEs), such as plasmids, promote bacterial evolution through horizontal gene transfer (HGT). However, the rules governing the repertoire of traits encoded on MGEs remain unclear. In this study, we uncovered the central role of genetic dominance shaping genetic cargo in MGEs, using antibiotic resistance as a model system. MGEs are typically present in more than one copy per host bacterium, and as a consequence, genetic dominance favors the fixation of dominant mutations over recessive ones. In addition, genetic dominance also determines the phenotypic effects of horizontally acquired MGE-encoded genes, silencing recessive alleles if the recipient bacterium already carries a wild-type copy of the gene. The combination of these two effects governs the catalog of genes encoded on MGEs. Our results help to understand how MGEs evolve and spread, uncovering the neglected influence of genetic dominance on bacterial evolution. Moreover, our findings offer a framework to forecast the spread and evolvability of MGE-encoded genes, which encode traits of key human interest, such as virulence or antibiotic resistance.

scholarly journals Involvement of glnB, glnZ, and glnD Genes in the Regulation of Poly-3-Hydroxybutyrate Biosynthesis by Ammonia in Azospirillum brasilense Sp7

2002 ◽  
Vol 68 (2) ◽  
pp. 985-988 ◽  
Author(s):  
Jun Sun ◽  
Anne Van Dommelen ◽  
Jan Van Impe ◽  
Jos Vanderleyden
Keyword(s):  
Growth Phase ◽  
Azospirillum Brasilense ◽  
Regulatory Genes ◽  
Wild Type ◽  
Active Growth ◽  
Phb Production ◽  
Azospirillum Brasilense Sp7

ABSTRACT The role of three key nitrogen regulatory genes, glnB (encoding the PII protein), glnZ (encoding the Pz protein), and glnD (encoding the GlnD protein), in regulation of poly-3-hydroxybutyrate (PHB) biosynthesis by ammonia in Azospirillum brasilense Sp7 was investigated. It was observed that glnB glnZ and glnD mutants produce substantially higher amounts of PHB than the wild type produces during the active growth phase. glnB and glnZ mutants have PHB production phenotypes similar to that of the wild type. Our results indicate that the PII-Pz system is apparently involved in nitrogen-dependent regulation of PHB biosynthesis in A. brasilense Sp7.

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