Organization of DNA in Mammalian Mitochondria

As with all organisms that must organize and condense their DNA to fit within the limited volume of a cell or a nucleus, mammalian mitochondrial DNA (mtDNA) is packaged into nucleoprotein structures called nucleoids. In this study, we first introduce the general modes of DNA compaction, especially the role of the nucleoid-associated proteins (NAPs) that structure the bacterial chromosome. We then present the mitochondrial nucleoid and the main factors responsible for packaging of mtDNA: ARS- (autonomously replicating sequence-) binding factor 2 protein (Abf2p) in yeast and mitochondrial transcription factor A (TFAM) in mammals. We summarize the single-molecule manipulation experiments on mtDNA compaction and visualization of mitochondrial nucleoids that have led to our current knowledge on mtDNA compaction. Lastly, we discuss the possible regulatory role of DNA packaging by TFAM in DNA transactions such as mtDNA replication and transcription.

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Tetrapeptides Modelled to the Androgen Binding Site of ZIP9 Stimulate Expression of Tight Junction Proteins and Tight Junction Formation in Sertoli Cells

Biology ◽

10.3390/biology11010055 ◽

2021 ◽

Vol 11 (1) ◽

pp. 55

Author(s):

Marie-Louise Möller ◽

Ahmed Bulldan ◽

Georgios Scheiner-Bobis

Keyword(s):

Androgen Receptor ◽

Tight Junction ◽

Binding Site ◽

Sertoli Cells ◽

Alternative Pathway ◽

Tight Junction Formation ◽

Associated Proteins ◽

A Cell ◽

Androgen Binding

Androgens stimulate the expression of tight junction (TJ) proteins and the formation of the blood–testis barrier (BTB). Interactions of testosterone with the zinc transporter ZIP9 stimulate the expression of TJ-forming proteins and promote TJ formation in Sertoli cells. In order to investigate androgenic effects mediated by ZIP9 but not by the nuclear androgen receptor (AR), the effects of three tetrapeptides fitting the androgen binding site of ZIP9 were compared with those induced by testosterone in a Sertoli cell line expressing ZIP9 but not the AR. Three tetrapeptides and testosterone displaced testosterone-BSA-FITC from the surface of 93RS2 cells and stimulated the non-classical testosterone signaling pathway that includes the activation of Erk1/2 kinases and transcription factors CREB and ATF-1. The expression of the TJ-associated proteins ZO-1 and claudin-5 was triggered as was the re-distribution of claudin-1 from the cytosol to the membrane and nucleus. Furthermore, TJ formation was stimulated, indicated by increased transepithelial electrical resistance. Silencing ZIP9 expression by siRNA prevented all of these responses. These results are consistent with an alternative pathway for testosterone action at the BTB that does not involve the nuclear AR and highlight the significant role of ZIP9 as a cell-surface androgen receptor that stimulates TJ formation.

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Tetramethylpyrazine blocks TFAM degradation and up-regulates mitochondrial DNA copy number by interacting with TFAM

Bioscience Reports ◽

10.1042/bsr20170319 ◽

2017 ◽

Vol 37 (3) ◽

Cited By ~ 8

Author(s):

Linhua Lan ◽

Miaomiao Guo ◽

Yong Ai ◽

Fuhong Chen ◽

Ya Zhang ◽

...

Keyword(s):

Cultured Cells ◽

Lon Protease ◽

Mitochondrial Transcription Factor ◽

Mitochondrial Dna Copy Number ◽

Antitumour Agent ◽

Small Molecule Compound ◽

Mtdna Replication ◽

Mitochondrial Transcription Factor A ◽

In Cells

The natural small molecule compound: 2,3,5,6-tetramethylpyrazine (TMP), is a major component of the Chinese medicine Chuanxiong, which has wide clinical applications in dilating blood vessels, inhibiting platelet aggregation and treating thrombosis. Recent work suggests that TMP is also an antitumour agent. Despite its chemotherapeutic potential, the mechanism(s) underlying TMP action are unknown. Herein, we demonstrate that TMP binds to mitochondrial transcription factor A (TFAM) and blocks its degradation by the mitochondrial Lon protease. TFAM is a key regulator of mtDNA replication, transcription and transmission. Our previous work showed that when TFAM is not bound to DNA, it is rapidly degraded by the ATP-dependent Lon protease, which is essential for mitochondrial proteostasis. In cultured cells, TMP specifically blocks Lon-mediated degradation of TFAM, leading to TFAM accumulation and subsequent up-regulation of mtDNA content in cells with substantially low levels of mtDNA. In vitro protease assays show that TMP does not directly inhibit mitochondrial Lon, rather interacts with TFAM and blocks degradation. Pull-down assays show that biotinylated TMP interacts with TFAM. These findings suggest a novel mechanism whereby TMP stabilizes TFAM and confers resistance to Lon-mediated degradation, thereby promoting mtDNA up-regulation in cells with low mtDNA content.

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Role of non-motile microtubule-associated proteins in virus trafficking

BioMolecular Concepts ◽

10.1515/bmc-2016-0018 ◽

2016 ◽

Vol 7 (5-6) ◽

pp. 283-292 ◽

Cited By ~ 3

Author(s):

Débora M. Portilho ◽

Roger Persson ◽

Nathalie Arhel

Keyword(s):

Motor Proteins ◽

Current Knowledge ◽

Cell Entry ◽

Cellular Transport ◽

Microtubule Associated Proteins ◽

Virus Trafficking ◽

Cytoskeletal Dynamics ◽

Associated Proteins ◽

Infected Cells

AbstractViruses are entirely dependent on their ability to infect a host cell in order to replicate. To reach their site of replication as rapidly and efficiently as possible following cell entry, many have evolved elaborate mechanisms to hijack the cellular transport machinery to propel themselves across the cytoplasm. Long-range movements have been shown to involve motor proteins along microtubules (MTs) and direct interactions between viral proteins and dynein and/or kinesin motors have been well described. Although less well-characterized, it is also becoming increasingly clear that non-motile microtubule-associated proteins (MAPs), including structural MAPs of the MAP1 and MAP2 families, and microtubule plus-end tracking proteins (+TIPs), can also promote viral trafficking in infected cells, by mediating interaction of viruses with filaments and/or motor proteins, and modulating filament stability. Here we review our current knowledge on non-motile MAPs, their role in the regulation of cytoskeletal dynamics and in viral trafficking during the early steps of infection.

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Feline Morbillivirus Infection in Domestic Cats: What Have We Learned So Far?

Viruses ◽

10.3390/v13040683 ◽

2021 ◽

Vol 13 (4) ◽

pp. 683

Author(s):

Eliana De Luca ◽

Giuseppe Andrea Sautto ◽

Paolo Emidio Crisi ◽

Alessio Lorusso

Keyword(s):

Current Knowledge ◽

Domestic Cats ◽

Stray Cats ◽

Potential Association ◽

Clinicopathological Findings ◽

A Cell ◽

The Subject ◽

First Time

Feline morbillivirus (FeMV) was identified for the first time in stray cats in 2012 in Hong Kong and, since its discovery, it was reported in domestic cats worldwide. Although a potential association between FeMV infection and tubulointerstitial nephritis (TIN) has been suggested, this has not been proven, and the subject remains controversial. TIN is the most frequent histopathological finding in the context of feline chronic kidney disease (CKD), which is one of the major clinical pathologies in feline medicine. FeMV research has mainly focused on defining the epidemiology, the role of FeMV in the development of CKD, and its in vitro tropism, but the pathogenicity of FeMV is still not clear, partly due to its distinctive biological characteristics, as well as to a lack of a cell culture system for its rapid isolation. In this review, we summarize the current knowledge of FeMV infection, including genetic diversity of FeMV strains, epidemiology, pathogenicity, and clinicopathological findings observed in naturally infected cats.

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MAP7 recruits kinesin-1 to microtubules to direct organelle transport

10.1101/557611 ◽

2019 ◽

Author(s):

Abdullah R. Chaudhary ◽

Hailong Lu ◽

Elena B. Krementsova ◽

Carol S. Bookwalter ◽

Kathleen M. Trybus ◽

...

Keyword(s):

Single Molecule ◽

Organelle Transport ◽

Microtubule Associated Proteins ◽

Microtubule Polymerization ◽

Binding Rate ◽

Associated Proteins ◽

Bidirectional Transport ◽

Directed Motility ◽

Clear Shift

Microtubule-associated proteins (MAPs) play well-characterized roles in regulating microtubule polymerization, dynamics, and organization. In addition, MAPs control trans-port along microtubules by regulating the motility of kinesin and dynein. MAP7 (ensconsin, E-MAP-115) is a ubiquitous MAP that organizes the microtubule cytoskeleton in mitosis and neuronal branching. MAP7 also promotes the interaction of kinesin-1 with microtubules. We expressed and purified full-length kinesin-1 and MAP7 in Sf9 cells. In single-molecule motiity assays, MAP7 recruits kinesin-1 to microtubules, increasing the frequency of both diffusive and processive runs. Optical trapping assays on beads transported by single and teams of kinesin-1 motors indicate that MAP7 increases the relative binding rate of kinesin-1 and the number of motors simultaneously engaged in ensembles. To examine the role of MAP7 in regulating bidirectional transport, we isolated late phagosomes along with their native set of kinesin-1, kinesin-2, and dynein motors. Bidirectional cargoes exhibit a clear shift towards plus-end directed motility on MAP7-decorated microtubules due to increased forces exerted by kinesin teams. Collectively, our results indicate that MAP7 enhances kinesin-1 recruitment to microtubules and targets organelle transport to the plus end.

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Role of ATP-binding Cassette Transporters in Sorafenib Therapy for Hepatocellular Carcinoma: an overview

Current Drug Targets ◽

10.2174/1389450122666210412125018 ◽

2021 ◽

Vol 22 ◽

Author(s):

Maria Manuela Estevinho ◽

Carlos Fernandes ◽

João Carlos Silva ◽

Ana Catarina Gomes ◽

Edgar Afecto ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Multidrug Resistance ◽

Abc Transporters ◽

Current Knowledge ◽

Molecular Therapy ◽

Resistance Factors ◽

Sorafenib Therapy ◽

Online Databases ◽

Associated Proteins

Background: Molecular therapy with sorafenib remains the mainstay for advanced-stage hepatocellular carcinoma. Notwithstanding, treatment efficacy is low, with few patients obtaining long-lasting benefits due to the high chemoresistance rate. Objective: To perform, for the first time, an overview of the literature concerning the role of adenosine triphosphate-binding cassette (ABC) transporters in sorafenib therapy for hepatocellular carcinoma. Methods: Three online databases (PubMed, Web of Science and Scopus) were searched, from inception to October 2020. Studies selection, analysis and data collection was independently performed by two authors. Results: The search yielded 224 results; 29 were selected for inclusion. Most studies were pre-clinical, using HCC cell lines; three used human samples. Studies highlight the effect of sorafenib in decreasing ABC transporters expression. Conversely, it is described the role of ABC transporters, particularly multidrug resistance protein 1 (MDR-1), multidrug resistance-associated proteins 1 and 2 (MRP-1 and MRP-2) and ABC subfamily G member 2 (ABCG2) in sorafenib pharmacokinetics and pharmacodynamics, being key resistance factors. Combination therapy with naturally available or synthetic compounds that modulate ABC transporters may revert sorafenib resistance, by increasing absorption and intracellular concentration. Conclusion: A deeper understanding of ABC transporters’ mechanisms may provide guidance for developing innovative approaches for hepatocellular carcinoma. Further studies are warranted to translate the current knowledge into practice and paving the way to individualized therapy.

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Architectural Role of Mitochondrial Transcription Factor A in Maintenance of Human Mitochondrial DNA

Molecular and Cellular Biology ◽

10.1128/mcb.24.22.9823-9834.2004 ◽

2004 ◽

Vol 24 (22) ◽

pp. 9823-9834 ◽

Cited By ~ 183

Author(s):

Tomotake Kanki ◽

Kippei Ohgaki ◽

Martina Gaspari ◽

Claes M. Gustafsson ◽

Atsushi Fukuoh ◽

...

Keyword(s):

Transcription Factor ◽

Mitochondrial Dna ◽

Rna Interference ◽

Normal Level ◽

Hela Cells ◽

Mitochondrial Transcription ◽

Mitochondrial Transcription Factor ◽

In Organello ◽

Mitochondrial Transcription Factor A

ABSTRACT Mitochondrial transcription factor A (TFAM), a transcription factor for mitochondrial DNA (mtDNA) that also possesses the property of nonspecific DNA binding, is essential for maintenance of mtDNA. To clarify the role of TFAM, we repressed the expression of endogenous TFAM in HeLa cells by RNA interference. The amount of TFAM decreased maximally to about 15% of the normal level at day 3 after RNA interference and then recovered gradually. The amount of mtDNA changed closely in parallel with the daily change in TFAM while in organello transcription of mtDNA at day 3 was maintained at about 50% of the normal level. TFAM lacking its C-terminal 25 amino acids (TFAM-ΔC) marginally activated transcription in vitro. When TFAM-ΔC was expressed at levels comparable to those of endogenous TFAM in HeLa cells, mtDNA increased twofold, suggesting that TFAM-ΔC is as competent in maintaining mtDNA as endogenous TFAM under these conditions. The in organello transcription of TFAM-ΔC-expressing cells was no more than that in the control. Thus, the mtDNA amount is finely correlated with the amount of TFAM but not with the transcription level. We discuss an architectural role for TFAM in the maintenance of mtDNA in addition to its role in transcription activation.

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The mechanism of motor inhibition by microtubule-associated proteins

10.1101/2020.10.22.351346 ◽

2020 ◽

Author(s):

Luke S Ferro ◽

Lisa Eshun-Wilson ◽

Mert Gölcük ◽

Jonathan Fernandes ◽

Teun Huijben ◽

...

Keyword(s):

Binding Site ◽

Single Molecule ◽

Intracellular Transport ◽

List Type ◽

Microtubule Associated Proteins ◽

Associated Proteins ◽

Projection Domain ◽

Electron Imaging

SUMMARYMicrotubule (MT)-associated proteins (MAPs) regulate intracellular transport by selectively recruiting or excluding kinesin and dynein motors from MTs. We used single-molecule and cryo-electron imaging to determine the mechanism of MAP-motor interactions in vitro. Unexpectedly, we found that the regulatory role of a MAP cannot be predicted based on whether it overlaps with the motor binding site or forms liquid condensates on the MT. Although the MT binding domain (MTBD) of MAP7 overlaps with the kinesin-1 binding site, tethering of kinesin-1 by the MAP7 projection domain supersedes this inhibition and results in biphasic regulation of kinesin-1 motility. Conversely, the MTBD of tau inhibits dynein motility without overlapping with the dynein binding site or by forming tau islands on the MT. Our results indicate that MAPs sort intracellular cargos moving in both directions, as neither dynein nor kinesin can walk on a MAP-coated MT without favorably interacting with that MAP.HIGHLIGHTSMAP7 binds to a novel site and can coexist with tau on the MT.Kinesin-1 motility is biphasically regulated by MAP7 accumulation on the microtubule.MT decoration of MAPs inhibits motors even when they do not block the motor binding site.Motors need to interact with a MAP to walk on MAP-decorated MTs

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The Role of Mitochondrial Damage-Associated Molecular Patterns in Chronic Neuroinflammation

Mediators of Inflammation ◽

10.1155/2019/4050796 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11 ◽

Cited By ~ 14

Author(s):

Ekta Bajwa ◽

Caitlin B. Pointer ◽

Andis Klegeris

Keyword(s):

Potential Role ◽

Neuronal Damage ◽

Cellular Energy ◽

Mitochondrial Transcription Factor ◽

Chronic Neuroinflammation ◽

The Central Nervous System ◽

Mitochondrial Transcription Factor A ◽

Molecular Patterns ◽

Damage Associated Molecular Patterns

Mitochondrial dysfunction has been established as a common feature of neurodegenerative disorders that contributes to disease pathology by causing impaired cellular energy production. Mitochondrial molecules released into the extracellular space following neuronal damage or death may also play a role in these diseases by acting as signaling molecules called damage-associated molecular patterns (DAMPs). Mitochondrial DAMPs have been shown to initiate proinflammatory immune responses from nonneuronal glial cells, including microglia and astrocytes; thereby, they have the potential to contribute to the chronic neuroinflammation present in these disorders accelerating the degeneration of neurons. In this review, we highlight the mitochondrial DAMPs cytochrome c (CytC), mitochondrial transcription factor A (TFAM), and cardiolipin and explore their potential role in the central nervous system disorders including Alzheimer’s disease and Parkinson’s disease, which are characterized by neurodegeneration and chronic neuroinflammation.

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