scholarly journals Munc18-1 is a molecular chaperone for α-synuclein, controlling its self-replicating aggregation

2016 ◽  
Vol 214 (6) ◽  
pp. 705-718 ◽  
Author(s):  
Ye Jin Chai ◽  
Emma Sierecki ◽  
Vanesa M. Tomatis ◽  
Rachel S. Gormal ◽  
Nichole Giles ◽  
...  
Keyword(s):  
Single Molecule ◽  
Molecular Chaperone ◽  
Neurotransmitter Release ◽  
Lewy Body ◽  
Epileptic Encephalopathy ◽  
Chaperone Activity ◽  
Wild Type ◽  
Developmental Defects ◽  
Single Molecule Analysis

Munc18-1 is a key component of the exocytic machinery that controls neurotransmitter release. Munc18-1 heterozygous mutations cause developmental defects and epileptic phenotypes, including infantile epileptic encephalopathy (EIEE), suggestive of a gain of pathological function. Here, we used single-molecule analysis, gene-edited cells, and neurons to demonstrate that Munc18-1 EIEE-causing mutants form large polymers that coaggregate wild-type Munc18-1 in vitro and in cells. Surprisingly, Munc18-1 EIEE mutants also form Lewy body–like structures that contain α-synuclein (α-Syn). We reveal that Munc18-1 binds α-Syn, and its EIEE mutants coaggregate α-Syn. Likewise, removal of endogenous Munc18-1 increases the aggregative propensity of α-SynWT and that of the Parkinson’s disease–causing α-SynA30P mutant, an effect rescued by Munc18-1WT expression, indicative of chaperone activity. Coexpression of the α-SynA30P mutant with Munc18-1 reduced the number of α-SynA30P aggregates. Munc18-1 mutations and haploinsufficiency may therefore trigger a pathogenic gain of function through both the corruption of native Munc18-1 and a perturbed chaperone activity for α-Syn leading to aggregation-induced neurodegeneration.

scholarly journals Bottom-up single-molecule strategy for understanding subunit function of tetrameric β-galactosidase

2018 ◽  
Vol 115 (33) ◽  
pp. 8346-8351 ◽  
Author(s):  
Xiang Li ◽  
Yu Jiang ◽  
Shaorong Chong ◽  
David R. Walt
Keyword(s):  
Single Molecule ◽  
Wild Type ◽  
Nucleotide Polymorphism ◽  
Single Nucleotide ◽  
Single Molecule Level ◽  
Subunit Function ◽  
Enzyme Molecules ◽  
Individual Enzyme ◽  
Kinetics Of

In this paper, we report an example of the engineered expression of tetrameric β-galactosidase (β-gal) containing varying numbers of active monomers. Specifically, by combining wild-type and single-nucleotide polymorphism plasmids at varying ratios, tetrameric β-gal was expressed in vitro with one to four active monomers. The kinetics of individual enzyme molecules revealed four distinct populations, corresponding to the number of active monomers in the enzyme. Using single-molecule-level enzyme kinetics, we were able to measure an accurate in vitro mistranslation frequency (5.8 × 10−4 per base). In addition, we studied the kinetics of the mistranslated β-gal at the single-molecule level.

scholarly journals Dual inhibition of MDMX and MDM2 as a therapeutic strategy in leukemia

2018 ◽  
Vol 10 (436) ◽  
pp. eaao3003 ◽  
Author(s):  
Luis A. Carvajal ◽  
Daniela Ben Neriah ◽  
Adrien Senecal ◽  
Lumie Benard ◽  
Victor Thiruthuvanathan ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Single Molecule ◽  
Cellular Proliferation ◽  
Wild Type ◽  
Suppressor Activity ◽  
Mouse Double Minute ◽  
Double Minute ◽  
Wild Type P53

The tumor suppressor p53 is often inactivated via its interaction with endogenous inhibitors mouse double minute 4 homolog (MDM4 or MDMX) or mouse double minute 2 homolog (MDM2), which are frequently overexpressed in patients with acute myeloid leukemia (AML) and other cancers. Pharmacological disruption of both of these interactions has long been sought after as an attractive strategy to fully restore p53-dependent tumor suppressor activity in cancers with wild-type p53. Selective targeting of this pathway has thus far been limited to MDM2-only small-molecule inhibitors, which lack affinity for MDMX. We demonstrate that dual MDMX/MDM2 inhibition with a stapled α-helical peptide (ALRN-6924), which has recently entered phase I clinical testing, produces marked antileukemic effects. ALRN-6924 robustly activates p53-dependent transcription at the single-cell and single-molecule levels and exhibits biochemical and molecular biological on-target activity in leukemia cells in vitro and in vivo. Dual MDMX/MDM2 inhibition by ALRN-6924 inhibits cellular proliferation by inducing cell cycle arrest and apoptosis in cell lines and primary AML patient cells, including leukemic stem cell–enriched populations, and disrupts functional clonogenic and serial replating capacity. Furthermore, ALRN-6924 markedly improves survival in AML xenograft models. Our study provides mechanistic insight to support further testing of ALRN-6924 as a therapeutic approach in AML and other cancers with wild-type p53.

scholarly journals 3P314 Single-molecule analysis of the complex formed between molecular chaperone prefoldin and amyloid beta(Bioimaging,Poster Presentations)

2007 ◽  
Vol 47 (supplement) ◽  
pp. S281
Author(s):  
Naofumi Terada ◽  
Tamotsu Zako ◽  
Masafumi Sakono ◽  
Masafumi Yohda ◽  
Mizuo Maeda
Keyword(s):  
Amyloid Beta ◽  
Single Molecule ◽  
Molecular Chaperone ◽  
Poster Presentations ◽  
Single Molecule Analysis

scholarly journals The early-onset torsion dystonia-associated protein, torsinA, displays molecular chaperone activity in vitro

2010 ◽  
Vol 15 (5) ◽  
pp. 605-617 ◽  
Author(s):  
Alexander J. Burdette ◽  
Perry F. Churchill ◽  
Guy A. Caldwell ◽  
Kim A. Caldwell
Keyword(s):  
Molecular Chaperone ◽  
Early Onset ◽  
Chaperone Activity ◽  
Torsion Dystonia

scholarly journals Tyrosine 136 phosphorylation of α-synuclein aggregates in the Lewy body dementia brain: involvement of serine 129 phosphorylation by casein kinase 2

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Kazunori Sano ◽  
Yasushi Iwasaki ◽  
Yuta Yamashita ◽  
Keiichi Irie ◽  
Masato Hosokawa ◽  
...  
Keyword(s):  
Lewy Body ◽  
Cultured Cells ◽  
Lewy Body Dementia ◽  
Casein Kinase ◽  
Casein Kinase 2 ◽  
Central Feature ◽  
Aggregate Formation ◽  
Wild Type ◽  
Brain Involvement

AbstractSerine 129 (S129) phosphorylation of α-synuclein (αSyn) is a central feature of Lewy body (LB) disease pathology. Although the neighboring tyrosine residues Y125, Y133, and Y136 are also phosphorylation sites, little is known regarding potential roles of phosphorylation cross-talk between these sites and its involvement in the pathogenesis of LB disease. Here, we found that αSyn aggregates are predominantly phosphorylated at Y136 in the Lewy body dementia brain, which is mediated by unexpected kinase activity of Casein kinase 2 (CK2). Aggregate formation with S129 and Y136 phosphorylation of recombinant αSyn (r-αSyn) were induced by CK2 but abolished by replacement of S129 with alanine (S129A) in vitro. Mutation of Y136 to alanine (Y136A) promoted aggregate formation and S129 phosphorylation of r-αSyn by CK2 in vitro. Introduction of Y136A r-αSyn oligomers into cultured cells exhibited increased levels of aggregates with S129 phosphorylation compared to wild-type r-αSyn oligomers. In addition, aggregate formation with S129 phosphorylation induced by introduction of wild-type r-αSyn oligomers was significantly attenuated by CK2 inhibition, which resulted in an unexpected increase in Y136 phosphorylation in cultured cells. Our findings suggest the involvement of CK2-related αSyn Y136 phosphorylation in the pathogenesis of LB disease and its potential as a therapeutic target.

scholarly journals Build Your Own Microscope: Step-By-Step Guide for Building a Prism-Based TIRF Microscope

2018 ◽  
Vol 1 (4) ◽  
pp. 40 ◽  
Author(s):  
Dalton Gibbs ◽  
Anisa Kaur ◽  
Anoja Megalathan ◽  
Kumar Sapkota ◽  
Soma Dhakal
Keyword(s):  
Single Molecule ◽  
Total Internal Reflection ◽  
Life Sciences ◽  
Inverted Microscope ◽  
Sophisticated Instrument ◽  
High Level ◽  
Single Molecule Analysis ◽  
Molecule Dynamics ◽  
Vast Range

Prism-based total internal reflection fluorescence (pTIRF) microscopy is one of the most widely used techniques for the single molecule analysis of a vast range of samples including biomolecules, nanostructures, and cells, to name a few. It allows for excitation of surface bound molecules/particles/quantum dots via evanescent field of a confined region of space, which is beneficial not only for single molecule detection but also for analysis of single molecule dynamics and for acquiring kinetics data. However, there is neither a commercial microscope available for purchase nor a detailed guide dedicated for building this microscope. Thus far, pTIRF microscopes are custom-built with the use of a commercially available inverted microscope, which requires high level of expertise in selecting and handling sophisticated instrument-parts. To directly address this technology gap, here we describe a step-by-step guide on how to build and characterize a pTIRF microscope for in vitro single-molecule imaging, nanostructure analysis and other life sciences research.

scholarly journals Single-molecule analysis reveals self assembly and nanoscale segregation of two distinct cavin subcomplexes on caveolae

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Yann Gambin ◽  
Nicholas Ariotti ◽  
Kerrie-Ann McMahon ◽  
Michele Bastiani ◽  
Emma Sierecki ◽  
...  
Keyword(s):  
Single Molecule ◽  
Self Assembly ◽  
Mammalian Cells ◽  
Protein Complexes ◽  
Building Blocks ◽  
Scaffolding Protein ◽  
Cell Extracts ◽  
Single Molecule Analysis ◽  
Exquisite Specificity

In mammalian cells three closely related cavin proteins cooperate with the scaffolding protein caveolin to form membrane invaginations known as caveolae. Here we have developed a novel single-molecule fluorescence approach to directly observe interactions and stoichiometries in protein complexes from cell extracts and from in vitro synthesized components. We show that up to 50 cavins associate on a caveola. However, rather than forming a single coat complex containing the three cavin family members, single-molecule analysis reveals an exquisite specificity of interactions between cavin1, cavin2 and cavin3. Changes in membrane tension can flatten the caveolae, causing the release of the cavin coat and its disassembly into separate cavin1-cavin2 and cavin1-cavin3 subcomplexes. Each of these subcomplexes contain 9 ± 2 cavin molecules and appear to be the building blocks of the caveolar coat. High resolution immunoelectron microscopy suggests a remarkable nanoscale organization of these separate subcomplexes, forming individual striations on the surface of caveolae.

scholarly journals Altered ubiquitin causes perturbed calcium homeostasis, hyperactivation of calpain, dysregulated differentiation, and cataract

2015 ◽  
Vol 112 (4) ◽  
pp. 1071-1076 ◽  
Author(s):  
Ke Liu ◽  
Lei Lyu ◽  
David Chin ◽  
Junyuan Gao ◽  
Xiurong Sun ◽  
...  
Keyword(s):  
Gap Junction ◽  
Model Systems ◽  
Multiple Model ◽  
Wild Type ◽  
Developmental Defects ◽  
Protein Substrates ◽  
Cataractous Lens ◽  
Ubiquitin Proteasome

Although the ocular lens shares many features with other tissues, it is unique in that it retains its cells throughout life, making it ideal for studies of differentiation/development. Precipitation of proteins results in lens opacification, or cataract, the major blinding disease. Lysines on ubiquitin (Ub) determine fates of Ub-protein substrates. Information regarding ubiquitin proteasome systems (UPSs), specifically of K6 in ubiquitin, is undeveloped. We expressed in the lens a mutant Ub containing a K6W substitution (K6W-Ub). Protein profiles of lenses that express wild-type ubiquitin (WT-Ub) or K6W-Ub differ by only ∼2%. Despite these quantitatively minor differences, in K6W-Ub lenses and multiple model systems we observed a fourfold Ca2+ elevation and hyperactivation of calpain in the core of the lens, as well as calpain-associated fragmentation of critical lens proteins including Filensin, Fodrin, Vimentin, β-Crystallin, Caprin family member 2, and tudor domain containing 7. Truncations can be cataractogenic. Additionally, we observed accumulation of gap junction Connexin43, and diminished Connexin46 levels in vivo and in vitro. These findings suggest that mutation of Ub K6 alters UPS function, perturbs gap junction function, resulting in Ca2+ elevation, hyperactivation of calpain, and associated cleavage of substrates, culminating in developmental defects and a cataractous lens. The data show previously unidentified connections between UPS and calpain-based degradative systems and advance our understanding of roles for Ub K6 in eye development. They also inform about new approaches to delay cataract and other protein precipitation diseases.

scholarly journals The α-synuclein hereditary mutation E46K unlocks a more stable, pathogenic fibril structure

2020 ◽  
Vol 117 (7) ◽  
pp. 3592-3602 ◽  
Author(s):  
David R. Boyer ◽  
Binsen Li ◽  
Chuanqi Sun ◽  
Weijia Fan ◽  
Kang Zhou ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Lewy Body ◽  
Lewy Body Dementia ◽  
Salt Bridge ◽  
Wild Type ◽  
Molecular Feature ◽  
Multiple Systems ◽  
Fibril Structure

Aggregation of α-synuclein is a defining molecular feature of Parkinson’s disease, Lewy body dementia, and multiple systems atrophy. Hereditary mutations in α-synuclein are linked to both Parkinson’s disease and Lewy body dementia; in particular, patients bearing the E46K disease mutation manifest a clinical picture of parkinsonism and Lewy body dementia, and E46K creates more pathogenic fibrils in vitro. Understanding the effect of these hereditary mutations on α-synuclein fibril structure is fundamental to α-synuclein biology. We therefore determined the cryo-electron microscopy (cryo-EM) structure of α-synuclein fibrils containing the hereditary E46K mutation. The 2.5-Å structure reveals a symmetric double protofilament in which the molecules adopt a vastly rearranged, lower energy fold compared to wild-type fibrils. We propose that the E46K misfolding pathway avoids electrostatic repulsion between K46 and K80, a residue pair which form the E46-K80 salt bridge in the wild-type fibril structure. We hypothesize that, under our conditions, the wild-type fold does not reach this deeper energy well of the E46K fold because the E46-K80 salt bridge diverts α-synuclein into a kinetic trap—a shallower, more accessible energy minimum. The E46K mutation apparently unlocks a more stable and pathogenic fibril structure.

scholarly journals BLM helicase facilitates telomere replication during leading strand synthesis of telomeres

2015 ◽  
Vol 210 (2) ◽  
pp. 191-208 ◽  
Author(s):  
William C. Drosopoulos ◽  
Settapong T. Kosiyatrakul ◽  
Carl L. Schildkraut
Keyword(s):  
Single Molecule ◽  
Werner Syndrome ◽  
Telomeric Dna ◽  
G4 Dna ◽  
Genome Wide ◽  
Blm Helicase ◽  
Telomere Replication ◽  
Leading Strand ◽  
Single Molecule Analysis

Based on its in vitro unwinding activity on G-quadruplex (G4) DNA, the Bloom syndrome–associated helicase BLM is proposed to participate in telomere replication by aiding fork progression through G-rich telomeric DNA. Single molecule analysis of replicated DNA (SMARD) was used to determine the contribution of BLM helicase to telomere replication. In BLM-deficient cells, replication forks initiating from origins within the telomere, which copy the G-rich strand by leading strand synthesis, moved slower through the telomere compared with the adjacent subtelomere. Fork progression through the telomere was further slowed in the presence of a G4 stabilizer. Using a G4-specific antibody, we found that deficiency of BLM, or another G4-unwinding helicase, the Werner syndrome-associated helicase WRN, resulted in increased G4 structures in cells. Importantly, deficiency of either helicase led to greater increases in G4 DNA detected in the telomere compared with G4 seen genome-wide. Collectively, our findings are consistent with BLM helicase facilitating telomere replication by resolving G4 structures formed during copying of the G-rich strand by leading strand synthesis.

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