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1.
Cell ; 181(7): 1566-1581.e27, 2020 06 25.
Artigo em Inglês | MEDLINE | ID: mdl-32531200

RESUMO

The accurate timing and execution of organelle biogenesis is crucial for cell physiology. Centriole biogenesis is regulated by Polo-like kinase 4 (Plk4) and initiates in S-phase when a daughter centriole grows from the side of a pre-existing mother. Here, we show that a Plk4 oscillation at the base of the growing centriole initiates and times centriole biogenesis to ensure that centrioles grow at the right time and to the right size. The Plk4 oscillation is normally entrained to the cell-cycle oscillator but can run autonomously of it-potentially explaining why centrioles can duplicate independently of cell-cycle progression. Mathematical modeling indicates that the Plk4 oscillation can be generated by a time-delayed negative feedback loop in which Plk4 inactivates the interaction with its centriolar receptor through multiple rounds of phosphorylation. We hypothesize that similar organelle-specific oscillations could regulate the timing and execution of organelle biogenesis more generally.


Assuntos
Relógios Biológicos/fisiologia , Centríolos/metabolismo , Proteínas de Drosophila/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Animais , Ciclo Celular/fisiologia , Proteínas de Ciclo Celular/metabolismo , Centrossomo/metabolismo , Proteínas de Drosophila/fisiologia , Drosophila melanogaster/metabolismo , Biogênese de Organelas , Fosforilação , Proteínas Serina-Treonina Quinases/fisiologia
2.
Cell ; 174(6): 1507-1521.e16, 2018 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-30100183

RESUMO

The hetero-oligomeric chaperonin of eukarya, TRiC, is required to fold the cytoskeletal protein actin. The simpler bacterial chaperonin system, GroEL/GroES, is unable to mediate actin folding. Here, we use spectroscopic and structural techniques to determine how TRiC promotes the conformational progression of actin to the native state. We find that actin fails to fold spontaneously even in the absence of aggregation but populates a kinetically trapped, conformationally dynamic state. Binding of this frustrated intermediate to TRiC specifies an extended topology of actin with native-like secondary structure. In contrast, GroEL stabilizes bound actin in an unfolded state. ATP binding to TRiC effects an asymmetric conformational change in the chaperonin ring. This step induces the partial release of actin, priming it for folding upon complete release into the chaperonin cavity, mediated by ATP hydrolysis. Our results reveal how the unique features of TRiC direct the folding pathway of an obligate eukaryotic substrate.


Assuntos
Actinas/metabolismo , Chaperonina 10/metabolismo , Chaperonina 60/metabolismo , Actinas/química , Trifosfato de Adenosina/metabolismo , Animais , Bovinos , Chaperonina 10/química , Chaperonina 60/química , Microscopia Crioeletrônica , Desoxirribonuclease I/química , Desoxirribonuclease I/metabolismo , Medição da Troca de Deutério , Humanos , Ligação Proteica , Dobramento de Proteína , Estrutura Terciária de Proteína
3.
Cell ; 172(3): 605-617.e11, 2018 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-29336887

RESUMO

The bacterial chaperonin GroEL and its cofactor, GroES, form a nano-cage for a single molecule of substrate protein (SP) to fold in isolation. GroEL and GroES undergo an ATP-regulated interaction cycle to close and open the folding cage. GroEL consists of two heptameric rings stacked back to back. Here, we show that GroEL undergoes transient ring separation, resulting in ring exchange between complexes. Ring separation occurs upon ATP-binding to the trans ring of the asymmetric GroEL:7ADP:GroES complex in the presence or absence of SP and is a consequence of inter-ring negative allostery. We find that a GroEL mutant unable to perform ring separation is folding active but populates symmetric GroEL:GroES2 complexes, where both GroEL rings function simultaneously rather than sequentially. As a consequence, SP binding and release from the folding chamber is inefficient, and E. coli growth is impaired. We suggest that transient ring separation is an integral part of the chaperonin mechanism.


Assuntos
Chaperonina 60/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Chaperonina 10/metabolismo , Chaperonina 60/química , Chaperonina 60/genética , Mutação , Ligação Proteica
4.
J Biol Chem ; 299(2): 102896, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36639026

RESUMO

We found previously that nuclear receptors (NRs) compete for heterodimerization with their common partner, retinoid X receptor (RXR), in a ligand-dependent manner. To investigate potential competition in their DNA binding, we monitored the mobility of retinoic acid receptor (RAR) and vitamin D receptor (VDR) in live cells by fluorescence correlation spectroscopy. First, specific agonist treatment and RXR coexpression additively increased RAR DNA binding, while both agonist and RXR were required for increased VDR DNA binding, indicating weaker DNA binding of the VDR/RXR dimer. Second, coexpression of RAR, VDR, and RXR resulted in competition for DNA binding. Without ligand, VDR reduced the DNA-bound fraction of RAR and vice versa, i.e., a fraction of RXR molecules was occupied by the competing partner. The DNA-bound fraction of either RAR or VDR was enhanced by its own and diminished by the competing NR's agonist. When treated with both ligands, the DNA-bound fraction of RAR increased as much as due to its own agonist, whereas that of VDR increased less. RXR agonist also increased DNA binding of RAR at the expense of VDR. In summary, competition between RAR and VDR for RXR is also manifested in their DNA binding in an agonist-dependent manner: RAR dominates over VDR in the absence of agonist or with both agonists present. Thus, side effects of NR-ligand-based (retinoids, thiazolidinediones) therapies may be ameliorated by other NR ligands and be at least partly explained by reduced DNA binding due to competition. Our results also complement the model of NR action by involving competition both for RXR and for DNA sites.


Assuntos
Receptores de Calcitriol , Receptores do Ácido Retinoico , Receptores X de Retinoides , DNA/metabolismo , Ligantes , Receptores de Calcitriol/química , Receptores de Calcitriol/metabolismo , Receptores Citoplasmáticos e Nucleares , Receptores X de Retinoides/química , Receptores X de Retinoides/metabolismo , Tretinoína/farmacologia , Receptores do Ácido Retinoico/química , Receptores do Ácido Retinoico/metabolismo
5.
Chemistry ; 30(53): e202401938, 2024 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-38984590

RESUMO

Nanoparticles (NPs), including perovskite nanocrystals (PNCs) with single photon purity, present challenges in fluorescence correlation spectroscopy (FCS) studies due to their distinct photoluminescence (PL) behaviors. In particular, the zero-time correlation amplitude [g2(0)] and the associated diffusion timescale (τD) of their FCS curves show substantial dependency on pump intensity (IP). Optical saturation inadequately explains the origin of this FCS phenomenon in NPs, thus setting them apart from conventional dye molecules, which do not manifest such behavior. This observation is apparently attributed to either photo-brightening or optical trapping, both lead to increased NP occupancy (N) in the excitation volume, consequently reducing the g2(0) amplitude [since g2(0) α 1/N] at high IP. However, an advanced FCS study utilizing alternating laser excitation at two different intensities dismisses such possibilities. Further investigation into single-particle blinking behaviors as a function of IP reveals that the intensity dependence of g2(0) primarily arises from the brightness heterogeneity prevalent in almost all types of NPs. This report delves into the complexities of the photophysical properties of NPs and their adverse impacts on FCS studies.

6.
Bioessays ; 44(12): e2200149, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36284497

RESUMO

Outer membrane proteins (OMPs) maintain the viability of Gram-negative bacteria by functioning as receptors, transporters, ion channels, lipases, and porins. Folding and assembly of OMPs involves synchronized action of chaperones and multi-protein machineries which escort the highly hydrophobic polypeptides to their target outer membrane in a folding competent state. Previous studies have identified proteins and their involvement along the OMP biogenesis pathway. Yet, the mechanisms of action and the intriguing ability of all these molecular machines to work without the typical cellular energy source of ATP, but solely based on thermodynamic principles, are still not well understood. Here, we highlight how different single-molecule studies can shed additional light on the mechanisms and kinetics of OMP biogenesis.


Assuntos
Proteínas da Membrana Bacteriana Externa , Bactérias Gram-Negativas , Proteínas da Membrana Bacteriana Externa/metabolismo , Chaperonas Moleculares/metabolismo , Porinas/metabolismo , Dobramento de Proteína
7.
Proc Natl Acad Sci U S A ; 118(35)2021 08 31.
Artigo em Inglês | MEDLINE | ID: mdl-34433665

RESUMO

Antigen (Ag) crosslinking of immunoglobulin E-receptor (IgE-FcεRI) complexes in mast cells stimulates transmembrane (TM) signaling, requiring phosphorylation of the clustered FcεRI by lipid-anchored Lyn tyrosine kinase. Previous studies showed that this stimulated coupling between Lyn and FcεRI occurs in liquid ordered (Lo)-like nanodomains of the plasma membrane and that Lyn binds directly to cytosolic segments of FcεRI that it initially phosphorylates for amplified activity. Net phosphorylation above a nonfunctional threshold is achieved in the stimulated state but not in the resting state, and current evidence supports the hypothesis that this relies on Ag crosslinking to disrupt a balance between Lyn and tyrosine phosphatase activities. However, the structural interactions that underlie the stimulation process remain poorly defined. This study evaluates the relative contributions and functional importance of different types of interactions leading to suprathreshold phosphorylation of Ag-crosslinked IgE-FcεRI in live rat basophilic leukemia mast cells. Our high-precision diffusion measurements by imaging fluorescence correlation spectroscopy on multiple structural variants of Lyn and other lipid-anchored probes confirm subtle, stimulated stabilization of the Lo-like nanodomains in the membrane inner leaflet and concomitant sharpening of segregation from liquid disordered (Ld)-like regions. With other structural variants, we determine that lipid-based interactions are essential for access by Lyn, leading to phosphorylation of and protein-based binding to clustered FcεRI. By contrast, TM tyrosine phosphatase, PTPα, is excluded from these regions due to its Ld-preference and steric exclusion of TM segments. Overall, we establish a synergy of lipid-based, protein-based, and steric interactions underlying functional TM signaling in mast cells.


Assuntos
Antígenos/metabolismo , Membrana Celular/metabolismo , Lipídeos/fisiologia , Mastócitos/metabolismo , Receptores de IgE/metabolismo , Transdução de Sinais , Animais , Antígenos/imunologia , Células CHO , Linhagem Celular Tumoral , Células Cultivadas , Cricetulus , Proteínas de Fluorescência Verde/metabolismo , Metabolismo dos Lipídeos , Mastócitos/imunologia , Nanoestruturas , Ratos , Quinases da Família src/metabolismo
8.
Int J Mol Sci ; 25(11)2024 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-38892166

RESUMO

Pertuzumab (Perjeta®), a humanized antibody binding to the dimerization arm of HER2 (Human epidermal growth factor receptor-2), has failed as a monotherapy agent in HER2 overexpressing malignancies. Since the molecular interaction of HER2 with ligand-bound EGFR (epidermal growth factor receptor) has been implied in mitogenic signaling and malignant proliferation, we hypothesized that this interaction, rather than HER2 expression and oligomerization alone, could be a potential molecular target and predictor of the efficacy of pertuzumab treatment. Therefore, we investigated static and dynamic interactions between HER2 and EGFR molecules upon EGF stimulus in the presence and absence of pertuzumab in HER2+ EGFR+ SK-BR-3 breast tumor cells using Förster resonance energy transfer (FRET) microscopy and fluorescence correlation and cross-correlation spectroscopy (FCS/FCCS). The consequential activation of signaling and changes in cell proliferation were measured by Western blotting and MTT assay. The autocorrelation functions of HER2 diffusion were best fitted by a three-component model corrected for triplet formation, and among these components the slowly diffusing membrane component revealed aggregation induced by EGFR ligand binding, as evidenced by photon-counting histograms and co-diffusing fractions. This aggregation has efficiently been prevented by pertuzumab treatment, which also inhibited the post-stimulus interaction of EGFR and HER2, as monitored by changes in FRET efficiency. Overall, the data demonstrated that pertuzumab, by hindering post-stimulus interaction between EGFR and HER2, inhibits EGFR-evoked HER2 aggregation and phosphorylation and leads to a dose-dependent decrease in cell proliferation, particularly when higher amounts of EGF are present. Consequently, we propose that EGFR expression on HER2-positive tumors could be taken into consideration as a potential biomarker when predicting the outcome of pertuzumab treatment.


Assuntos
Anticorpos Monoclonais Humanizados , Neoplasias da Mama , Proliferação de Células , Receptores ErbB , Receptor ErbB-2 , Transdução de Sinais , Humanos , Anticorpos Monoclonais Humanizados/farmacologia , Anticorpos Monoclonais Humanizados/uso terapêutico , Receptores ErbB/metabolismo , Receptor ErbB-2/metabolismo , Linhagem Celular Tumoral , Transdução de Sinais/efeitos dos fármacos , Feminino , Proliferação de Células/efeitos dos fármacos , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Neoplasias da Mama/genética , Transferência Ressonante de Energia de Fluorescência , Ativação Transcricional/efeitos dos fármacos , Antineoplásicos Imunológicos/farmacologia , Antineoplásicos Imunológicos/uso terapêutico
9.
Ecol Food Nutr ; 63(2): 135-159, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38349779

RESUMO

National food insecurity early warning systems and food policy interventions need reliable information concerning the classification of food insecurity. The aim of this paper was to produce an acute food insecurity classification in Mozambique, by: i) analyzing food insecurity indicators individually; ii) comparing it with a new integrated analysis of survey-based indicators called the "Matrix Analysis." The Matrix results show more severe classifications than the single indicators for the analyzed districts. The matrix novelty consists on a cross-tabulation of all indicators, allowing a less subjective analysis. Further research is needed on how the Matrix approach could complement national classification systems.


Assuntos
Características da Família , Abastecimento de Alimentos , Humanos , Moçambique , Inquéritos e Questionários , Insegurança Alimentar
10.
J Struct Biol ; 215(2): 107961, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-37059313

RESUMO

AKT/PKB is a kinase involved in the regulation of a plethora of cell processes. Particularly, in embryonic stem cells (ESCs), AKT is crucial for the maintenance of pluripotency. Although the activation of this kinase relies on its recruitment to the cellular membrane and subsequent phosphorylation, multiple other post-translational modifications (PTMs), including SUMOylation, fine-tune its activity and target specificity. Since this PTM can also modify the localization and availability of different proteins, in this work we explored if SUMOylation impacts on the subcellular compartmentalization and distribution of AKT1 in ESCs. We found that this PTM does not affect AKT1 membrane recruitment, but it modifies the AKT1 nucleus/cytoplasm distribution, increasing its nuclear presence. Additionally, within this compartment, we found that AKT1 SUMOylation also impacts on the chromatin-binding dynamics of NANOG, a central pluripotency transcription factor. Remarkably, the oncogenic E17K AKT1 mutant produces major changes in all these parameters increasing the binding of NANOG to its targets, also in a SUMOylation dependent manner. These findings demonstrate that SUMOylation modulates AKT1 subcellular distribution, thus adding an extra layer of regulation of its function, possibly by affecting the specificity and interaction with its downstream targets.


Assuntos
Proteínas Proto-Oncogênicas c-akt , Sumoilação , Mutação , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Sumoilação/genética , Cromatina/genética , Células-Tronco Embrionárias/metabolismo
11.
J Biol Chem ; 298(11): 102570, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36209827

RESUMO

Dengue virus (DENV) is a flavivirus causing an estimated 390 million infections per year around the world. Despite the immense global health and economic impact of this virus, its true receptor(s) for internalization into live cells has not yet been identified, and no successful antivirals or treatments have been isolated to this date. This study aims to improve our understanding of virus entry routes by exploring the sialic acid-based cell surface molecule GM1a and its role in DENV infection. We studied the interaction of the virus with GM1a using fluorescence correlation spectroscopy, fluorescence crosscorrelation spectroscopy, imaging fluorescence correlation spectroscopy, amide hydrogen/deuterium exchange mass spectrometry, and isothermal titration calorimetry. Additionally, we explored the effect of this interaction on infectivity and movement of the virus during infection was explored using plaque assay and fluorescence-based imaging and single particle tracking. GM1a was deemed to interact with DENV at domain I (DI) and domain II (DII) of the E protein of the protein coat at quaternary contacts of a fully assembled virus, leading to a 10-fold and 7-fold increase in infectivity for DENV1 and DENV2 in mammalian cell systems, respectively. We determined that the interaction of the virus with GM1a triggers a speeding up of virus movement on live cell surfaces, possibly resulting from a reduction in rigidity of cellular rafts during infection. Collectively, our results suggest that GM1a functions as a coreceptor/attachment factor for DENV during infection in mammalian systems.


Assuntos
Vírus da Dengue , Dengue , Flavivirus , Animais , Humanos , Vírus da Dengue/metabolismo , Proteínas do Envelope Viral/metabolismo , Gangliosídeos/metabolismo , Flavivirus/metabolismo , Mamíferos/metabolismo
12.
Anal Biochem ; 660: 114959, 2023 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-36341770

RESUMO

RNA double strand hybridization is a hallmark for gene expression regulation. In this function, single stranded regulatory RNA forms Watson-Crick base pairs with complementary messenger RNA. In the presented work the dissociation constants of complementary equally sized RNA single strands were measured at the single molecule level applying fluorescence correlation spectroscopy (FCS). Dissociation constants of 3.2 nM, 1.4 nM and 1.0 nM were determined for 26 bp, 41 bp and 54 bp dsRNA, respectively. The translational diffusion coefficients of RNA, measured at infinite dilution, could be accurately predicted applying the model D = 4.58 × 10-10 N-0.39 m2s-1.


Assuntos
RNA de Cadeia Dupla , Imagem Individual de Molécula , Hibridização de Ácido Nucleico , RNA Mensageiro/genética , Técnicas de Diluição do Indicador
13.
Mol Pharm ; 20(12): 6151-6161, 2023 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-37906224

RESUMO

Mucus mechanically protects the intestinal epithelium and impacts the absorption of drugs, with a largely unknown role for bile. We explored the impacts of bile on mucosal biomechanics and drug transport within mucus. Bile diffused with square-root-of-time kinetics and interplayed with mucus, leading to transient stiffening captured in Brillouin images and a concentration-dependent change from subdiffusive to Brownian-like diffusion kinetics within the mucus demonstrated by differential dynamic microscopy. Bile-interacting drugs, Fluphenazine and Perphenazine, diffused faster through mucus in the presence of bile, while Metoprolol, a drug with no bile interaction, displayed consistent diffusion. Our findings were corroborated by rat studies, where co-dosing of a bile acid sequestrant substantially reduced the bioavailability of Perphenazine but not Metoprolol. We clustered over 50 drugs based on their interactions with bile and mucin. Drugs that interacted with bile also interacted with mucin but not vice versa. This study detailed the dynamics of mucus biomechanics under bile exposure and linked the ability of a drug to interact with bile to its abbility to interact with mucus.


Assuntos
Bile , Elevadores e Escadas Rolantes , Ratos , Animais , Perfenazina , Muco , Mucinas
14.
Lipids Health Dis ; 22(1): 43, 2023 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-36978188

RESUMO

BACKGROUND AND AIM: Familial chylomicronemia syndrome (FCS) is a rare autosomal recessive metabolic disorder caused by mutations in genes involved in chylomicron metabolism. On the other hand, multifactorial chylomicronemia syndrome (MCS) is a polygenic disorder and the most frequent cause of chylomicronemia, which results from the presence of multiple genetic variants related to chylomicron metabolism, in addition to secondary factors. Indeed, the genetic determinants that predispose to MCS are the presence of a heterozygous rare variant or an accumulation of several SNPs (oligo/polygenic). However, their clinical, paraclinical, and molecular features are not well established in our country. The objective of this study was to describe the development and results of a screening program for severe hypertriglyceridemia in Colombia. METHODS: A cross-sectional study was performed. All patients aged >18 years with triglyceride levels ≥500 mg/dL from 2010 to 2020 were included. The program was developed in three stages: 1. Review of electronic records and identification of suspected cases based on laboratory findings (triglyceride levels ≥500 mg/dL); 2. Identification of suspected cases based on laboratory findings that also allowed us to exclude secondary factors; 3. Patients with FCS scores <8 were excluded. The remaining patients underwent molecular analysis. RESULTS: In total, we categorized 2415 patients as suspected clinical cases with a mean age of 53 years, of which 68% corresponded to male patients. The mean triglyceride levels were 705.37 mg/dL (standard deviation [SD] 335.9 mg/dL). After applying the FCS score, 2.4% (n = 18) of patients met the probable case definition and underwent a molecular test. Additionally, 7 patients had unique variants in the APOA5 gene (c.694 T > C; p. Ser232Pro) or in the GPIHBP1 gene (c.523G > C; p. Gly175Arg), for an apparent prevalence of familial chylomicronemia in the consulting population of 0.41 per 1.000 patients with severe HTG measurement. No previously reported pathogenic variants were detected. CONCLUSION: This study describes a screening program for the detection of severe hypertriglyceridemia. Although we identified seven patients as carriers of a variant in the APOA5 gene, we diagnosed only one patient with FCS. We believe that more programs of these characteristics should be developed in our region, given the importance of early detection of this metabolic disorder.


Assuntos
Hiperlipoproteinemia Tipo IV , Hiperlipoproteinemia Tipo I , Hipertrigliceridemia , Humanos , Masculino , Pessoa de Meia-Idade , Hiperlipoproteinemia Tipo I/diagnóstico , Hiperlipoproteinemia Tipo I/genética , Estudos Transversais , Lipase Lipoproteica/genética , Colômbia/epidemiologia , Hipertrigliceridemia/epidemiologia , Hipertrigliceridemia/genética , Hipertrigliceridemia/complicações , Triglicerídeos , Quilomícrons
15.
Proc Natl Acad Sci U S A ; 117(47): 29435-29441, 2020 11 24.
Artigo em Inglês | MEDLINE | ID: mdl-33168730

RESUMO

Molecular agitation more rapid than thermal Brownian motion is reported for cellular environments, motor proteins, synthetic molecular motors, enzymes, and common chemical reactions, yet that chemical activity coupled to molecular motion contrasts with generations of accumulated knowledge about diffusion at equilibrium. To test the limits of this idea, a critical testbed is the mobility of catalytically active enzymes. Sentiment is divided about the reality of enhanced enzyme diffusion, with evidence for and against. Here a master curve shows that the enzyme diffusion coefficient increases in proportion to the energy release rate-the product of Michaelis-Menten reaction rate and Gibbs free energy change (ΔG)-with a highly satisfactory correlation coefficient of 0.97. For 10 catalytic enzymes (urease, acetylcholinesterase, seven enzymes from the glucose cascade cycle, and one other), our measurements span from a roughly 40% enhanced diffusion coefficient at a high turnover rate and negative ΔG to no enhancement at a slow turnover rate and positive ΔG Moreover, two independent measures of mobility show consistency, provided that one avoids undesirable fluorescence photophysics. The master curve presented here quantifies the limits of both ideas, that enzymes display enhanced diffusion and that they do not within instrumental resolution, and has possible implications for understanding enzyme mobility in cellular environments. The striking linear dependence of ΔG for the exergonic enzymes (ΔG <0), together with the vanishing effect for endergonic enzyme (ΔG >0), are consistent with a physical picture in which the mechanism boosting the diffusion is an active one, utilizing the available work from the chemical reaction.


Assuntos
Biocatálise , Enzimas/química , Modelos Químicos , Animais , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Difusão , Ensaios Enzimáticos , Enzimas/metabolismo , Proteínas de Peixes/química , Proteínas de Peixes/metabolismo , Concentração de Íons de Hidrogênio , Cinética , Coelhos , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/metabolismo , Temperatura
16.
Proc Natl Acad Sci U S A ; 117(35): 21328-21335, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32817484

RESUMO

Theoretical and experimental observations that catalysis enhances the diffusion of enzymes have generated exciting implications about nanoscale energy flow, molecular chemotaxis, and self-powered nanomachines. However, contradictory claims on the origin, magnitude, and consequence of this phenomenon continue to arise. To date, experimental observations of catalysis-enhanced enzyme diffusion have relied almost exclusively on fluorescence correlation spectroscopy (FCS), a technique that provides only indirect, ensemble-averaged measurements of diffusion behavior. Here, using an anti-Brownian electrokinetic (ABEL) trap and in-solution single-particle tracking, we show that catalysis does not increase the diffusion of alkaline phosphatase (ALP) at the single-molecule level, in sharp contrast to the ∼20% enhancement seen in parallel FCS experiments using p-nitrophenyl phosphate (pNPP) as substrate. Combining comprehensive FCS controls, ABEL trap, surface-based single-molecule fluorescence, and Monte Carlo simulations, we establish that pNPP-induced dye blinking at the ∼10-ms timescale is responsible for the apparent diffusion enhancement seen in FCS. Our observations urge a crucial revisit of various experimental findings and theoretical models--including those of our own--in the field, and indicate that in-solution single-particle tracking and ABEL trap are more reliable means to investigate diffusion phenomena at the nanoscale.


Assuntos
Fosfatase Alcalina/química , Difusão , Animais , Catálise , Bovinos , Nitrofenóis , Compostos Organofosforados , Espectrometria de Fluorescência
17.
Int J Mol Sci ; 24(3)2023 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-36768309

RESUMO

Cyanine fluorophores are extensively used in fluorescence spectroscopy and imaging. Upon continuous excitation, especially at excitation conditions used in single-molecule and super-resolution experiments, photo-isomerized states of cyanines easily reach population probabilities of around 50%. Still, effects of photo-isomerization are largely ignored in such experiments. Here, we studied the photo-isomerization of the pentamethine cyanine 5 (Cy5) by two similar, yet complementary means to follow fluorophore blinking dynamics: fluorescence correlation spectroscopy (FCS) and transient-state (TRAST) excitation-modulation spectroscopy. Additionally, we combined TRAST and spectrofluorimetry (spectral-TRAST), whereby the emission spectra of Cy5 were recorded upon different rectangular pulse-train excitations. We also developed a framework for analyzing transitions between multiple emissive states in FCS and TRAST experiments, how the brightness of the different states is weighted, and what initial conditions that apply. Our FCS, TRAST, and spectral-TRAST experiments showed significant differences in dark-state relaxation amplitudes for different spectral detection ranges, which we attribute to an additional red-shifted, emissive photo-isomerized state of Cy5, not previously considered in FCS and single-molecule experiments. The photo-isomerization kinetics of this state indicate that it is formed under moderate excitation conditions, and its population and emission may thus deserve also more general consideration in fluorescence imaging and spectroscopy experiments.


Assuntos
Corantes Fluorescentes , Imagem Óptica , Espectrometria de Fluorescência/métodos , Carbocianinas/química , Corantes Fluorescentes/química
18.
J Biol Chem ; 296: 100565, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33745969

RESUMO

Rhodesain is the lysosomal cathepsin L-like cysteine protease of Trypanosoma brucei rhodesiense, the causative agent of Human African Trypanosomiasis. The enzyme is essential for the proliferation and pathogenicity of the parasite as well as its ability to overcome the blood-brain barrier of the host. Lysosomal cathepsins are expressed as zymogens with an inactivating prodomain that is cleaved under acidic conditions. A structure of the uncleaved maturation intermediate from a trypanosomal cathepsin L-like protease is currently not available. We thus established the heterologous expression of T. brucei rhodesiense pro-rhodesain in Escherichia coli and determined its crystal structure. The trypanosomal prodomain differs from nonparasitic pro-cathepsins by a unique, extended α-helix that blocks the active site and whose side-chain interactions resemble those of the antiprotozoal inhibitor K11777. Interdomain dynamics between pro- and core protease domain as observed by photoinduced electron transfer fluorescence correlation spectroscopy increase at low pH, where pro-rhodesain also undergoes autocleavage. Using the crystal structure, molecular dynamics simulations, and mutagenesis, we identify a conserved interdomain salt bridge that prevents premature intramolecular cleavage at higher pH values and may thus present a control switch for the observed pH sensitivity of proenzyme cleavage in (trypanosomal) CathL-like proteases.


Assuntos
Cisteína Endopeptidases/química , Cisteína Endopeptidases/metabolismo , Precursores Enzimáticos/química , Precursores Enzimáticos/metabolismo , Trypanosoma brucei rhodesiense/enzimologia , Ativação Enzimática , Concentração de Íons de Hidrogênio , Modelos Moleculares , Domínios Proteicos
19.
J Cell Sci ; 133(2)2020 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-31932501

RESUMO

F-actin binding and bundling are crucial to a plethora of cell processes, including morphogenesis, migration, adhesion and many others. SWAP-70 was recently described as an in vitro F-actin-binding and -bundling protein. Fluorescence cross-correlation spectroscopy measurements with purified recombinant SWAP-70 confirmed that it forms stable oligomers that facilitate F-actin bundling. However, it remained unclear how SWAP-70 oligomerization and F-actin binding are controlled in living cells. We addressed this by biophysical approaches, including seFRET, FACS-FRET and FLIM-FRET. PIP3-mediated association with the cytoplasmic membrane and non-phosphorylated Y426 are required for SWAP-70 to dimerize and to bind F-actin. The dimerization region was identified near the C terminus where R546 is required for dimerization and, thus, F-actin bundling. The in vitro and in vivo data presented here reveal the functional relationship between the cytoplasm-to-membrane translocation and dimerization of SWAP-70, and F-actin binding and bundling, and demonstrate that SWAP-70 is a finely controlled modulator of membrane-proximal F-actin dynamics.This article has an associated First Person interview with the first author of the paper.


Assuntos
Actinas/metabolismo , Proteínas de Ligação a DNA/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Antígenos de Histocompatibilidade Menor/metabolismo , Proteínas Nucleares/metabolismo , Animais , Estruturas da Membrana Celular/metabolismo , Células HEK293 , Humanos , Melanoma Experimental , Camundongos , Multimerização Proteica
20.
Andrologia ; 54(10): e14554, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36177792

RESUMO

Sperm processing for assisted reproductive technologies (ART) aims to separate immotile and debris from the motile spermatozoa in the semen. The purpose of this study was to assess the effect of free centrifuge sorting (FCS) approach based on a combination of rheotaxis and swim-up on sperm biological characteristics and ICSI clinical outcomes. Each semen sample was splitted into two equal parts for 67 ICSI cycles with donation oocytes. Parts were processed with the Direct Swim Up (DSU) (control) and with the FCS method (experimental). Sperm quality was assessed in terms of motility, fine morphology, mitochondrial membrane potential, lipid peroxidation and sperm DNA fragmentation. Also Following ICSI, the clinical outcomes were compared between the groups. Sperm progressive motility (93.5 ± 4.1% vs. 78.6 ± 8.2%; p < 0.001), the fraction of Class I (good) morphology (30.2 ± 9.4% vs. 23.7 ± 8.5%; p < 0.0001) and the rate of mitochondrial membrane potential (77.4 ± 7.2% vs. 66.9 ± 5.7%; p < 0.0001) were significantly higher in the FCS compared to DSU groups. The level of lipid peroxidation (0.5 ± 0.05% vs. 0.6 ± 0.06%; p < 0.0001) and concentration of DNA fragmentation (DF) (7.4 ± 1.6% vs. 15.4 ± 2.6%; p < 0.0001) were lower in sperm from the FCS group compared to DSU group. There were higher rates of high-quality embryo formation (p < 0.001), implantation and clinical pregnancy rates (p = 0.03) in the FCS group compared to the control group. The processing of seminal samples using FCS collected spermatozoa with better biological quality and resulted in higher reproductive outcomes in ICSI cycles.


Assuntos
Sêmen , Espermatozoides , Fragmentação do DNA , Feminino , Humanos , Masculino , Oócitos , Gravidez , Taxa de Gravidez , Motilidade dos Espermatozoides
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