scholarly journals Evaluation of lamin A/C mechanotransduction under different surface topography in LMNA related muscular dystrophy.

2022 ◽  
Author(s):  
Subarna Dutta ◽  
Madavan Vasudevan ◽  
Muruganandan Thangamuniyandi
Keyword(s):  
Muscular Dystrophy ◽  
Protein Complexes ◽  
Single Point ◽  
Point Mutations ◽  
Biological Response ◽  
Young Modulus ◽  
Muscular Dystrophies ◽  
Lamin A ◽  
Wild Type ◽  
Mutant Cells

Most of the single point mutations of the LMNA gene are associated with distinct muscular dystrophies, marked by heterogenous phenotypes but primarily the loss and symmetric weakness of skeletal muscle tissue. The molecular mechanism and phenotype-genotype relationships in these muscular dystrophies are poorly understood. An effort has been here to delineating the adaptation of mechanical inputs into biological response by mutant cells of lamin A associated muscular dystrophy. In this study we implement engineered smooth and pattern surfaces of particular young modulus to mimic muscle physiological range. Using fluorescence and atomic force microscopy we present distinct architecture of the actin filament along with abnormally distorted cell and nuclear shape in mutants, which showed a tendency to deviate from wild type cells. Topographic features of pattern surface antagonizes the binding of the cell with it. Correspondingly, from the analysis of genome wide expression data in wild type and mutant cells, we report differential expression of the gene products of the structural components of cell adhesion as well as LINC (linkers of nucleoskeleton and cytoskeleton) protein complexes. This study also reveals mis expressed downstream signalling processes in mutant cells, which could potentially lead to onset of the disease upon the application of engineered materials to substitute the role of conventional cues in instilling cellular behaviours in muscular dystrophies. Collectively , these data support the notion that lamin A is essential for proper cellular mechanotransduction from extracellular environment to the genome and impairment of the muscle cell differentiation in the pathogenic mechanism for lamin A associated muscular dystrophy.

scholarly journals Genetic perturbation enhances functional heterogeneity in alkaline phosphatase

2021 ◽  
Author(s):  
Morito Sakuma ◽  
Shingo Honda ◽  
Hiroshi Ueno ◽  
Kentaro Miyazaki ◽  
Nobuhiko Tokuriki ◽  
...  
Keyword(s):  
Alkaline Phosphatase ◽  
Catalytic Activity ◽  
Single Molecule ◽  
Single Point ◽  
Point Mutations ◽  
Clear Correlation ◽  
Wild Type ◽  
Functional Heterogeneity ◽  
Genetic Perturbations ◽  
In The Wild

Enzymes inherently exhibit molecule-to-molecule heterogeneity in catalytic activity or function, which underlies the acquisition of new functions in evolutionary processes. However, correlations between the functional heterogeneity of an enzyme and its multi-functionality or promiscuity remain elusive. In addition, the modulation of functional heterogeneity upon genetic perturbation is currently unexplored. Here, we quantitatively analyzed functional heterogeneity in the wild-type and 69 single-point mutants of Escherichia coli alkaline phosphatase (AP) by employing single-molecule assay with a femtoliter reactor array device. Most mutant enzymes exhibited higher functional heterogeneity than the wild-type enzyme, irrespective of catalytic activity. These results indicated that the wild-type AP minimizes functional heterogeneity, and single-point mutations can significantly expand the span of functional heterogeneity in AP. Moreover, we identified a clear correlation between functional heterogeneity and promiscuous activities. These findings suggest that enzymes can acquire greater functional heterogeneity following marginal genetic perturbations that concomitantly promote catalytic promiscuity.

Nuclear envelope defects associated withLMNAmutations cause dilated cardiomyopathy and Emery-Dreifuss muscular dystrophy

2001 ◽  
Vol 114 (24) ◽  
pp. 4447-4457 ◽  
Author(s):  
Wahyu Hendrati Raharjo ◽  
Paul Enarson ◽  
Teresa Sullivan ◽  
Colin L. Stewart ◽  
Brian Burke
Keyword(s):  
Muscular Dystrophy ◽  
Dilated Cardiomyopathy ◽  
Hela Cells ◽  
Autosomal Dominant ◽  
Nuclear Periphery ◽  
Point Mutations ◽  
Molecular Organization ◽  
Structural Defects ◽  
Lamin A ◽  
Dominant Form

Nuclear lamin A and C alleles that are linked to three distinct human diseases have been expressed both in HeLa cells and in fibroblasts derived from Lmna null mice. Point mutations that cause dilated cardiomyopathy (L85R and N195K) and autosomal dominant Emery-Dreifuss muscular dystrophy (L530P) modify the assembly properties of lamins A and C and cause partial mislocalization of emerin, an inner nuclear membrane protein, in HeLa cells. At the same time, these mutant lamins interfere with the targeting and assembly of endogenous lamins and in this way may cause significant changes in the molecular organization of the nuclear periphery. By contrast, lamin A and C molecules harboring a point mutation (R482W), which gives rise to a dominant form of familial partial lipodystrophy, behave in a manner that is indistinguishable from wild-type lamins A and C, at least with respect to targeting and assembly within the nuclear lamina. Taken together, these results suggest that nuclear structural defects could contribute to the etiology of both dilated cardiomyopathy and autosomal dominant Emery-Dreifuss muscular dystrophy.

The cell cycle dependent mislocalisation of emerin may contribute to the Emery-Dreifuss muscular dystrophy phenotype

2002 ◽  
Vol 115 (2) ◽  
pp. 341-354 ◽  
Author(s):  
Elizabeth A. L. Fairley ◽  
Andrew Riddell ◽  
Juliet A. Ellis ◽  
John Kendrick-Jones
Keyword(s):  
Cell Cycle ◽  
Muscular Dystrophy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Transmembrane Domain ◽  
Nuclear Lamina ◽  
Lamin A ◽  
Wild Type ◽  
Cycle Dependent ◽  
Mutant Forms

Emerin is the nuclear membrane protein defective in X-linked Emery-Dreifuss muscular dystrophy (X-EDMD). The majority of X-EDMD patients have no detectable emerin. However, there are cases that produce mutant forms of emerin, which can be used to study its function. Our previous studies have shown that the emerin mutants S54F, P183T, P183H, Del95-99, Del236-241 (identified in X-EDMD patients) are targeted to the nuclear membrane but to a lesser extent than wild-type emerin. In this paper, we have studied how the mislocalisation of these mutant emerins may affect nuclear functions associated with the cell cycle using flow cytometry and immunofluorescence microscopy. We have established that cells expressing the emerin mutant Del236-241 (a deletion in the transmembrane domain), which was mainly localised in the cytoplasm, exhibited an aberrant cell cycle length. Thereafter, by examining the intracellular localisation of endogenously expressed lamin A/C and exogenously expressed wild-type and mutant forms of emerin after a number of cell divisions, we determined that the mutant forms of emerin redistributed endogenous lamin A/C. The extent of lamin A/C redistribution correlated with the amount of EGFP-emerin that was mislocalised. The amount of EGFP-emerin mislocalized, in turn, was associated with alterations in the nuclear envelope morphology. The nuclear morphology and redistribution of lamin A/C was most severely affected in the cells expressing the emerin mutant Del236-241.It is believed that emerin is part of a novel nuclear protein complex consisting of the barrier-to-autointegration factor (BAF), the nuclear lamina, nuclear actin and other associated proteins. The data presented here show that lamin A/C localisation is dominantly directed by its interaction with certain emerin mutants and perhaps wild-type emerin as well. These results suggest that emerin links A-type lamins to the nuclear envelope and that the correct localisation of these nuclear proteins is important for maintaining cell cycle timing.

scholarly journals Enhancing the Thermostability of Rhizomucor miehei Lipase with a Limited Screening Library by Rational-Design Point Mutations and Disulfide Bonds

2017 ◽  
Vol 84 (2) ◽  
Author(s):  
Guanlin Li ◽  
Xingrong Fang ◽  
Feng Su ◽  
Yuan Chen ◽  
Li Xu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Disulfide Bonds ◽  
Rational Design ◽  
Single Point ◽  
Point Mutations ◽  
Rhizomucor Miehei ◽  
Wild Type ◽  
Content Type ◽  
Eukaryotic Protein ◽  
Screening Library

ABSTRACT Rhizomucor miehei lipase (RML), as a kind of eukaryotic protein catalyst, plays an important role in the food, organic chemical, and biofuel industries. However, RML retains its catalytic activity below 50°C, which limits its industrial applications at higher temperatures. Soluble expression of this eukaryotic protein in Escherichia coli not only helps to screen for thermostable mutants quickly but also provides the opportunity to develop rapid and effective ways to enhance the thermal stability of eukaryotic proteins. Therefore, in this study, RML was engineered using multiple computational design methods, followed by filtration via conservation analysis and functional region assessment. We successfully obtained a limited screening library (only 36 candidates) to validate thermostable single point mutants, among which 24 of the candidates showed higher thermostability and 13 point mutations resulted in an apparent melting temperature ( T m app ) of at least 1°C higher. Furthermore, both of the two disulfide bonds predicted from four rational-design algorithms were further introduced and found to stabilize RML. The most stable mutant, with T18K/T22I/E230I/S56C-N63C/V189C-D238C mutations, exhibited a 14.3°C-higher T m app and a 12.5-fold increase in half-life at 70°C. The catalytic efficiency of the engineered lipase was 39% higher than that of the wild type. The results demonstrate that rationally designed point mutations and disulfide bonds can effectively reduce the number of screened clones to enhance the thermostability of RML. IMPORTANCE R. miehei lipase, whose structure is well established, can be widely applied in diverse chemical processes. Soluble expression of R. miehei lipase in E. coli provides an opportunity to explore efficient methods for enhancing eukaryotic protein thermostability. This study highlights a strategy that combines computational algorithms to predict single point mutations and disulfide bonds in RML without losing catalytic activity. Through this strategy, an RML variant with greatly enhanced thermostability was obtained. This study provides a competitive alternative for wild-type RML in practical applications and further a rapid and effective strategy for thermostability engineering.

scholarly journals Structural elements within the methylation loop (residues 112–117) and EF hands III and IV of calmodulin are required for Lys115 trimethylation

1999 ◽  
Vol 340 (2) ◽  
pp. 417-424 ◽  
Author(s):  
Jennifer A. COBB ◽  
Chang-Hoon HAN ◽  
David M. WILLS ◽  
Daniel M. ROBERTS
Keyword(s):  
Single Point ◽  
Point Mutations ◽  
Site Directed Mutagenesis ◽  
Structural Elements ◽  
Nad Kinase ◽  
Wild Type ◽  
Loop Sequence ◽  
Ef Hand ◽  
Single Point Mutations ◽  
Ef Hands

Calmodulin is trimethylated by a specific methyltransferase on Lys115, a residue located in a six amino acid loop (LGEKLT) between EF hands III and IV. To investigate the structural requirements for methylation, domain exchange mutants as well as single point mutations of conserved methylation loop residues (E114A, Glu114 → Ala; L116T, Leu116 → Thr) were generated. E114A and L116T activated cyclic nucleotide phosphodiesterase (PDE) and NAD+ kinase (NADK) similar to wild-type calmodulin, but lost their ability to be methylated. Domain exchange mutants in which EF hand III or IV was replaced by EF hand I or II respectively (CaM1214 and CaM1232 respectively) showed a modest effect on PDE and NADK activation (50 to 100% of wild-type), but calmodulin methylation was abolished. A third domain exchange mutant, CaMEKL, has the methylation loop sequence placed at a symmetrical position between EF hands I and II in the N-terminal lobe [residues QNP(41-43) replaced by EKL]. CaMEKL activated PDE normally, but did not activate NADK. However, CaMEKL retained the ability to bind to NADK and inhibited activation by wild-type calmodulin. Site-directed mutagenesis of single residues showed that Gln41 and Pro43 substitutions had the strongest effect on NADK activation. Additionally, CaMEKL was not methylated, suggesting that the introduction of the methylation loop between EF hands I and II is not adequate for methyltransferase recognition. Overall the data indicate that residues in the methylation loop are essential but not sufficient for methyltransferase recognition, and that additional residues unique to EF hands III and IV are required. Secondly, the QNP sequence in the loop between EF hands I and II is necessary for NADK activation.

scholarly journals Genotyping of Eight Thiopurine Methyltransferase Mutations: Three-Color Multiplexing, “Two-Color/Shared” Anchor, and Fluorescence-quenching Hybridization Probe Assays Based on Thermodynamic Nearest-Neighbor Probe Design

2000 ◽  
Vol 46 (11) ◽  
pp. 1728-1737 ◽  
Author(s):  
Ekkehard Schütz ◽  
Nicolas von Ahsen ◽  
Michael Oellerich
Keyword(s):  
Nearest Neighbor ◽  
Single Point ◽  
Point Mutations ◽  
Melting Curve ◽  
Resonance Energy ◽  
Probe Design ◽  
Thiopurine Methyltransferase ◽  
Wild Type ◽  
Hybridization Probe ◽  
Labeled Probe

Abstract Background: The inherited deficiency of thiopurine methyltransferase (TPMT) leads to severe myelosuppression in homozygous patients treated with thiopurine derivatives. One in 300 Caucasians has a homozygous TPMT deficiency with no measurable enzyme activity. To date, eight single-point mutations have been characterized; one group (TPMT*3) accounts for 75% of these. Methods: We used four LightCyclerTM capillaries to investigate all eight mutations. The three mutations on exon 10 were detected in one capillary with a single “shared” anchor labeled 5′ with Cy5.5 and 3′ with fluorescein. A wild-type-compatible 3′-fluorescein-labeled probe 5′ adjacent to the anchor covered the TPMT*7 mutation, and a 5′-LC-RED640-labeled probe 3′ adjacent to the anchor covered the TPMT*3C mutation. For TPMT*4, the forward amplification primer was internally labeled with a fluorescence quencher [6-carboxytetramethylrhodamine (TAMRA)], and a 3′-fluorescein-labeled antisense wild-type-compatible probe was placed at the mutation. For TPMT*2 and TPMT*3D, located on exon 5, a shared anchor approach was chosen. TPMT*3B and TPMT*6 were detected in multiplex technique and TPMT*5 in conventional manner. Anchors and probes were designed using a thermodynamic nearest-neighbor model. Results: All mutations were detected using four capillaries with one amplification protocol in 40 min. The concentrations of the shared anchors had to be decreased to reduce their intrinsic fluorescence resonance energy transfer signals. The quenching approach using TAMRA produced a very reproducible upside-down-shaped melting curve in channel 1 of the LightCycler. Deviations from wild type were easily detected because the smallest melting point shift for any possible mutation under the core of the probes was 1.5 °C. Conclusions: This total TPMT genotyping approach shows that it is possible to use double site-labeled anchor oligonucleotides, that channel 1 of the LightCycler can be used as detection channel for mutations using a quenching design, and that the designed probes enable detection of wild types with 100% likelihood.

scholarly journals Modulation of the Mechanisms Driving Transthyretin Amyloidosis

2020 ◽  
Vol 13 ◽  
Author(s):  
Filipa Bezerra ◽  
Maria João Saraiva ◽  
Maria Rosário Almeida
Keyword(s):  
Amyloid Fibrils ◽  
Single Point ◽  
Point Mutations ◽  
Disease Process ◽  
Wild Type ◽  
Transthyretin Amyloidosis ◽  
Natural Ligand ◽  
Single Point Mutations ◽  
Pharmacologic Agents ◽  
Plasma Stabilization

Transthyretin (TTR) amyloidoses are systemic diseases associated with TTR aggregation and extracellular deposition in tissues as amyloid. The most frequent and severe forms of the disease are hereditary and associated with amino acid substitutions in the protein due to single point mutations in the TTR gene (ATTRv amyloidosis). However, the wild type TTR (TTR wt) has an intrinsic amyloidogenic potential that, in particular altered physiologic conditions and aging, leads to TTR aggregation in people over 80 years old being responsible for the non-hereditary ATTRwt amyloidosis. In normal physiologic conditions TTR wt occurs as a tetramer of identical subunits forming a central hydrophobic channel where small molecules can bind as is the case of the natural ligand thyroxine (T4). However, the TTR amyloidogenic variants present decreased stability, and in particular conditions, dissociate into partially misfolded monomers that aggregate and polymerize as amyloid fibrils. Therefore, therapeutic strategies for these amyloidoses may target different steps in the disease process such as decrease of variant TTR (TTRv) in plasma, stabilization of TTR, inhibition of TTR aggregation and polymerization or disruption of the preformed fibrils. While strategies aiming decrease of the mutated TTR involve mainly genetic approaches, either by liver transplant or the more recent technologies using specific oligonucleotides or silencing RNA, the other steps of the amyloidogenic cascade might be impaired by pharmacologic compounds, namely, TTR stabilizers, inhibitors of aggregation and amyloid disruptors. Modulation of different steps involved in the mechanism of ATTR amyloidosis and compounds proposed as pharmacologic agents to treat TTR amyloidosis will be reviewed and discussed.

scholarly journals HIV recombination: what is the impact on antiretroviral therapy?

2005 ◽  
Vol 2 (5) ◽  
pp. 489-503 ◽  
Author(s):  
Christophe Fraser
Keyword(s):  
Antiretroviral Therapy ◽  
Single Point ◽  
Point Mutations ◽  
Wild Type Virus ◽  
Wild Type ◽  
Genetic Barrier ◽  
Resistant Strains ◽  
Single Point Mutations ◽  
The Impact ◽  
Retroviral Recombination

Retroviral recombination is a potential mechanism for the development of multiply drug resistant viral strains but the impact on the clinical outcomes of antiretroviral therapy in HIV-infected patients is unclear. Recombination can favour resistance by combining single-point mutations into a multiply resistant genome but can also hinder resistance by breaking up associations between mutations. Previous analyses, based on population genetic models, have suggested that whether recombination is favoured or hindered depends on the fitness interactions between loci, or epistasis. In this paper, a mathematical model is developed that includes viral dynamics during therapy and shows that population dynamics interact non-trivially with population genetics. The outcome of therapy depends critically on the changes to the frequency of cell co-infection and I review the evidence available. Where recombination does have an effect on therapy, it is always to slow or even halt the emergence of multiply resistant strains. I also find that for patients newly infected with multiply resistant strains, recombination can act to prevent reversion to wild-type virus. The analysis suggests that treatment targeted at multiple parts of the viral life-cycle may be less prone to drug resistance due to the genetic barrier caused by recombination but that, once selected, mutants resistant to such regimens may be better able to persist in the population.

scholarly journals Dinitroanilines Bind α-Tubulin to Disrupt Microtubules

2004 ◽  
Vol 15 (4) ◽  
pp. 1960-1968 ◽  
Author(s):  
Naomi S. Morrissette ◽  
Arpita Mitra ◽  
David Sept ◽  
L. David Sibley
Keyword(s):  
Bos Taurus ◽  
Single Point ◽  
Point Mutations ◽  
Docking Studies ◽  
Chemical Mutagenesis ◽  
Wild Type ◽  
Protozoan Parasites ◽  
Resistant Lines ◽  
Single Point Mutations ◽  
A Site

Protozoan parasites are remarkably sensitive to dinitroanilines such as oryzalin, which disrupt plant but not animal microtubules. To explore the basis of dinitroaniline action, we isolated 49 independent resistant Toxoplasma gondii lines after chemical mutagenesis. All 23 of the lines that we examined harbored single point mutations in α-tubulin. These point mutations were sufficient to confer resistance when transfected into wild-type parasites. Several mutations were in the M or N loops, which coordinate protofilament interactions in the microtubule, but most of the mutations were in the core of α-tubulin. Docking studies predict that oryzalin binds with an average affinity of 23 nM to a site located beneath the N loop of Toxoplasma α-tubulin. This binding site included residues that were mutated in several resistant lines. Moreover, parallel analysis of Bos taurus α-tubulin indicated that oryzalin did not interact with this site and had a significantly decreased, nonspecific affinity for vertebrate α-tubulin. We propose that the dinitroanilines act through a novel mechanism, by disrupting M-N loop contacts. These compounds also represent the first class of drugs that act on α-tubulin function.

scholarly journals Protein flexibility and dissociation pathway differentiation can explain onset of resistance mutations in kinases

2021 ◽  
Author(s):  
Mrinal Shekhar ◽  
Zachary Smith ◽  
Markus Seeliger ◽  
Pratyush Tiwary
Keyword(s):  
Binding Affinity ◽  
Residence Time ◽  
Single Point ◽  
Point Mutations ◽  
Cancer Drug ◽  
Single Point Mutation ◽  
Dissociation Pathway ◽  
Wild Type ◽  
Resistance Mutations ◽  
In The Wild

Understanding how point mutations can render a ligand or a drug ineffective against a given biological target is a problem of immense fundamental and practical relevance. Often the efficacy of such resistance mutations can be explained purely on a thermodynamic basis wherein the mutated system displays a reduced binding affinity for the ligand. However, the more perplexing and harder to explain situation is when two protein sequences have the same binding affinity for a drug. In this work, we demonstrate how all-atom molecular dynamics simulations, specifically using recent developments grounded in statistical mechanics and information theory, can provide a detailed mechanistic rationale for such variances. We establish the dissociation mechanism for the popular anti-cancer drug Imatinib (Gleevec) against wild-type and N387S mutant of Abl kinase. We show how this single point mutation triggers a non-local response in the protein's flexibility and eventually leads to pathway differentiation during dissociation. This pathway differentiation explains why Gleevec has a long residence time in the wild-type Abl, but for the mutant, by opening up a backdoor pathway for ligand exit, an order of magnitude shorter residence time is obtained. We thus believe that this work marks an efficient and scalable approach to pinpoint the molecular determinants of resistance mutations in biomolecular receptors of pharmacological relevance that are hard to explain using a simple structural perspective and require mechanistic and kinetic insights.

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