Dynamic localization of αB-crystallin at the microtubule cytoskeleton network in beating heart cells

2020 ◽  
Vol 168 (2) ◽  
pp. 125-137 ◽  
Author(s):  
Eri Ohto-Fujita ◽  
Saaya Hayasaki ◽  
Aya Atomi ◽  
Soichiro Fujiki ◽  
Toshiyuki Watanabe ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Resonance Energy Transfer ◽  
Focal Adhesions ◽  
Resonance Energy ◽  
Heart Cells ◽  
Striated Muscles ◽  
Slow Skeletal Muscle ◽  
Αb Crystallin ◽  
Cardiac Muscles ◽  
Myoblast Cells

Abstract αB-crystallin is highly expressed in the heart and slow skeletal muscle; however, the roles of αB-crystallin in the muscle are obscure. Previously, we showed that αB-crystallin localizes at the sarcomere Z-bands, corresponding to the focal adhesions of cultured cells. In myoblast cells, αB-crystallin completely colocalizes with microtubules and maintains cell shape and adhesion. In this study, we show that in beating cardiomyocytes α-tubulin and αB-crystallin colocalize at the I- and Z-bands of the myocardium, where it may function as a molecular chaperone for tubulin/microtubules. Fluorescence recovery after photobleaching (FRAP) analysis revealed that the striated patterns of GFP-αB-crystallin fluorescence recovered quickly at 37°C. FRAP mobility assay also showed αB-crystallin to be associated with nocodazole-treated free tubulin dimers but not with taxol-treated microtubules. The interaction of αB-crystallin and free tubulin was further confirmed by immunoprecipitation and microtubule sedimentation assay in the presence of 1–100 μM calcium, which destabilizes microtubules. Förster resonance energy transfer analysis showed that αB-crystallin and tubulin were at 1–10 nm apart from each other in the presence of colchicine. These results suggested that αB-crystallin may play an essential role in microtubule dynamics by maintaining free tubulin in striated muscles, such as the soleus or cardiac muscles.

scholarly journals Focal adhesions are sites of integrin extension

2010 ◽  
Vol 188 (6) ◽  
pp. 891-903 ◽  
Author(s):  
Janet A. Askari ◽  
Christopher J. Tynan ◽  
Stephen E.D. Webb ◽  
Marisa L. Martin-Fernandez ◽  
Christoph Ballestrem ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Resonance Energy Transfer ◽  
Focal Adhesions ◽  
Resonance Energy ◽  
Cell Spreading ◽  
Integrin Subunit ◽  
Adherent Cells ◽  
Extended Form ◽  
Integrin Α5β1 ◽  
Mediate Cell

Integrins undergo global conformational changes that specify their activation state. Current models portray the inactive receptor in a bent conformation that upon activation converts to a fully extended form in which the integrin subunit leg regions are separated to enable ligand binding and subsequent signaling. To test the applicability of this model in adherent cells, we used a fluorescent resonance energy transfer (FRET)–based approach, in combination with engineered integrin mutants and monoclonal antibody reporters, to image integrin α5β1 conformation. We find that restricting leg separation causes the integrin to adopt a bent conformation that is unable to respond to agonists and mediate cell spreading. By measuring FRET between labeled α5β1 and the cell membrane, we find extended receptors are enriched in focal adhesions compared with adjacent regions of the plasma membrane. These results demonstrate definitely that major quaternary rearrangements of β1-integrin subunits occur in adherent cells and that conversion from a bent to extended form takes place at focal adhesions.

scholarly journals Fluorescence lifetime imaging for studying DNA compaction and gene activities

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Svitlana M. Levchenko ◽  
Artem Pliss ◽  
Xiao Peng ◽  
Paras N. Prasad ◽  
Junle Qu
Keyword(s):  
Fluorescence Lifetime ◽  
Cultured Cells ◽  
Genomic Structure ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Fluorescence Probes ◽  
Fluorescence Lifetime Imaging ◽  
Dna Compaction ◽  
Lifetime Imaging ◽  
Significant Difference

AbstractOptical imaging is a most useful and widespread technique for the investigation of the structure and function of the cellular genomes. However, an analysis of immensely convoluted and irregularly compacted DNA polymer is highly challenging even by modern super-resolution microscopy approaches. Here we propose fluorescence lifetime imaging (FLIM) for the advancement of studies of genomic structure including DNA compaction, replication as well as monitoring of gene expression. The proposed FLIM assay employs two independent mechanisms for DNA compaction sensing. One mechanism relies on the inverse quadratic relation between the fluorescence lifetimes of fluorescence probes incorporated into DNA and their local refractive index, variable due to DNA compaction density. Another mechanism is based on the Förster resonance energy transfer (FRET) process between the donor and the acceptor fluorophores, both incorporated into DNA. Both these proposed mechanisms were validated in cultured cells. The obtained data unravel a significant difference in compaction of the gene-rich and gene-poor pools of genomic DNA. We show that the gene-rich DNA is loosely compacted compared to the dense DNA domains devoid of active genes.

scholarly journals Dual-color metal-induced and Förster resonance energy transfer for cell nanoscopy

2018 ◽  
Vol 29 (7) ◽  
pp. 846-851 ◽  
Author(s):  
Anna M. Chizhik ◽  
Carina Wollnik ◽  
Daja Ruhlandt ◽  
Narain Karedla ◽  
Alexey I. Chizhik ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Resonance Energy Transfer ◽  
Focal Adhesions ◽  
Resonance Energy ◽  
Forster Resonance Energy Transfer ◽  
Förster Resonance Energy Transfer ◽  
Fluorescence Lifetime Imaging ◽  
Dual Color ◽  
Structural Details ◽  
Förster Resonance

We report a novel method, dual-color axial nanometric localization by metal-­induced energy transfer, and combine it with Förster resonance energy transfer (FRET) for resolving structural details in cells on the molecular level. We demonstrate the capability of this method on cytoskeletal elements and adhesions in human mesenchymal stem cells. Our approach is based on fluorescence-lifetime-imaging microscopy and allows for precise determination of the three-dimensional architecture of stress fibers anchoring at focal adhesions, thus yielding crucial information to understand cell–matrix mechanics. In addition to resolving nanometric structural details along the z-axis, we use FRET to gain precise information on the distance between actin and vinculin at focal adhesions.

scholarly journals GnT1IP-L specifically inhibits MGAT1 in the Golgi via its luminal domain

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Hung-Hsiang Huang ◽  
Antti Hassinen ◽  
Subha Sundaram ◽  
Andrej-Nikolai Spiess ◽  
Sakari Kellokumpu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Inhibitory Activity ◽  
Secretory Pathway ◽  
Cultured Cells ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Bimolecular Fluorescence Complementation ◽  
Invariant Chain ◽  
Fluorescent Resonance Energy Transfer ◽  
Membrane Bound

Mouse GnT1IP-L, and membrane-bound GnT1IP-S (MGAT4D) expressed in cultured cells inhibit MGAT1, the N-acetylglucosaminyltransferase that initiates the synthesis of hybrid and complex N-glycans. However, it is not known where in the secretory pathway GnT1IP-L inhibits MGAT1, nor whether GnT1IP-L inhibits other N-glycan branching N-acetylglucosaminyltransferases of the medial Golgi. We show here that the luminal domain of GnT1IP-L contains its inhibitory activity. Retention of GnT1IP-L in the endoplasmic reticulum (ER) via the N-terminal region of human invariant chain p33, with or without C-terminal KDEL, markedly reduced inhibitory activity. Dynamic fluorescent resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC) assays revealed homomeric interactions for GnT1IP-L in the ER, and heteromeric interactions with MGAT1 in the Golgi. GnT1IP-L did not generate a FRET signal with MGAT2, MGAT3, MGAT4B or MGAT5 medial Golgi GlcNAc-tranferases. GnT1IP/Mgat4d transcripts are expressed predominantly in spermatocytes and spermatids in mouse, and are reduced in men with impaired spermatogenesis.

Mapping of adherens junction components using microscopic resonance energy transfer imaging

1995 ◽  
Vol 108 (3) ◽  
pp. 1051-1062 ◽  
Author(s):  
Z. Kam ◽  
T. Volberg ◽  
B. Geiger
Keyword(s):  
Energy Transfer ◽  
High Resolution ◽  
Resonance Energy Transfer ◽  
Focal Adhesions ◽  
Resonance Energy ◽  
Ccd Camera ◽  
The Other ◽  
Molecular Organization ◽  
Other Hand ◽  
Immunofluorescence Labeling

Quantitative microscopic imaging of resonance energy transfer (RET) was applied for immunological high resolution proximity mapping of several cytoskeletal components of cell adhesions. To conduct this analysis, a microscopic system was developed, consisting of a highly stable field illuminator, computer-controlled filter wheels for rapid multiple-color imaging and a sensitive, high resolution CCD camera, enabling quantitative data recording and processing. Using this system, we have investigated the spatial inter-relationships and organization of four adhesion-associated proteins, namely vinculin, talin, alpha-actinin and actin. Cultured chick lens cells were double labeled for each of the junctional molecules, using fluorescein- and rhodamine-conjugated antibodies or phalloidin. RET images were acquired with fluorescein excitation and rhodamine emission filter setting, corrected for fluorescein and rhodamine fluorescence, and normalized to the fluorescein image. The results pointed to high local densities of vinculin, talin and F-actin in focal adhesions, manifested by mean RET values of 15%, 12% and 10%, respectively. On the other hand, relatively low values (less than 1%) were observed following double immunofluorescence labeling of the same cells for alpha-actinin. Double indirect labeling for pairs of these four proteins (using fluorophore-conjugated antibodies or phalloidin) resulted in RET values of 5% or lower, except for the pair alpha-actinin and actin, which yielded significantly higher values (13-15%). These results suggest that despite their overlapping staining patterns, at the level of resolution of the light microscope, the plaque proteins vinculin and talin are not homogeneously interspersed at the molecular level but form segregated clusters. alpha-Actinin, on the other hand, does not appear to form such clusters but, rather, closely interacts with actin. We discuss here the conceptual and applicative aspects of RET measurements and the implications of the results on the subcellular molecular organization of adherens-type junctions.

scholarly journals Spatial distribution and functional significance of activated vinculin in living cells

2005 ◽  
Vol 169 (3) ◽  
pp. 459-470 ◽  
Author(s):  
Hui Chen ◽  
Daniel M. Cohen ◽  
Dilshad M. Choudhury ◽  
Noriyuki Kioka ◽  
Susan W. Craig
Keyword(s):  
Conformational Change ◽  
Direct Evidence ◽  
Resonance Energy Transfer ◽  
Focal Adhesions ◽  
Resonance Energy ◽  
Time Lapse ◽  
Living Cells ◽  
Actin Binding ◽  
Binding Conformation ◽  
Time Lapse Imaging

Conformational change is believed to be important to vinculin's function at sites of cell adhesion. However, nothing is known about vinculin's conformation in living cells. Using a Forster resonance energy transfer probe that reports on changes in vinculin's conformation, we find that vinculin is in the actin-binding conformation in a peripheral band of adhesive puncta in spreading cells. However, in fully spread cells with established polarity, vinculin's conformation is variable at focal adhesions. Time-lapse imaging reveals a gradient of conformational change that precedes loss of vinculin from focal adhesions in retracting regions. At stable or protruding regions, recruitment of vinculin is not necessarily coupled to the actin-binding conformation. However, a different measure of vinculin conformation, the recruitment of vinexin β by activated vinculin, shows that autoinhibition of endogenous vinculin is relaxed at focal adhesions. Beyond providing direct evidence that vinculin is activated at focal adhesions, this study shows that the specific functional conformation correlates with regional cellular dynamics.

Abstract 187: αB-crystallin Interacts And Prevents Stress-activated Proteolysis Of Focal Adhesion Kinase In Cardiomyocytes

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Aline M dos Santos ◽  
Michelle B Pereira ◽  
Danieli C Gonçalves ◽  
Alisson C Cardoso ◽  
Silvio R Consonni ◽  
...  
Keyword(s):  
Focal Adhesion Kinase ◽  
Mechanical Stress ◽  
Focal Adhesion ◽  
Resonance Energy Transfer ◽  
Pressure Overload ◽  
Resonance Energy ◽  
Calpain Inhibitor ◽  
Biochemical Assays ◽  
Αb Crystallin ◽  
Response To Stress

Focal adhesion kinase (FAK) contributes to cellular homeostasis under stress conditions. Here, we show that αB-crystallin confers protection to FAK against calpain-mediated proteolysis under mechanical stress in cardiomyocytes. Biochemical assays, chemical cross-linking coupled to mass spectrometry experiments, mutational analyses and Förster resonance energy transfer (FRET) were combined to investigate the basis of FAK and αB-crystallin interaction. A hydrophobic patch mapped between helices 1 and 4 of the FAK FAT domain was found to bind to the β4-β8 groove of αB-crystallin. Such an interaction requires FAK tyrosine 925 and is enhanced following its phosphorylation by Src, which occurs upon FAK stimulation by mechanical stress. αB-crystallin silencing results in calpain-dependent FAK depletion and in increased apoptosis of cardiomyocytes. The overexpression of a myc-FAK construct or treatment with a calpain inhibitor (E64) restored the survival of cardiomyocytes depleted of αB-crystallin. The association between FAK and αB-crystallin was also demonstrated to occur in response to pressure overload in rat left ventricle. The myocardial depletion of αB-crystallin by siRNA results in enhanced apoptosis of cardiomyocytes and myocardial fibrosis in overloaded hearts. These alterations were markedly attenuated in the overloaded left ventricles of transgenic mice with cardiac specific FAK expression. These findings define a novel mechanism by which αB-crystallin controls FAK function, with impact on cardiomyocyte survival and cardiac remodelling in response to stress.

Engineering Tools for Studying Coordination Between Biochemical and Biomechanical Activities in Cell Migration

2011 ◽  
Author(s):  
Sungsoo Na
Keyword(s):  
Cell Migration ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Resonance Energy Transfer ◽  
Focal Adhesions ◽  
Resonance Energy ◽  
Leading Edge ◽  
Dynamic Feedback ◽  
Chemical Signaling ◽  
Directed Cell Migration

Cell migration is achieved by the dynamic feedback interactions between traction forces generated by the cell and exerted onto the underlying extracellular matrix (ECM), and intracellular mechano-chemical signaling pathways, e.g., Rho GTPase (RhoA, Rac1, and Cdc42) activities [1,2,3]. These components are differentially distributed within a cell, and thus the coordination between tractions and mechanotransduction (i.e, RhoA and Rac1 activities) must be implemented at a precise spatial and temporal order to achieve optimized, directed cell migration [4,5]. Recent studies have shown that focal adhesions at the leading edge exert strong tractions [6], and these traction sites are co-localized with focal adhesion sites [7]. Further, by using the fluorescence resonance energy transfer (FRET) technology coupled with genetically encoded biosensors, researchers reported that Rho GTPases, such as RhoA [8], Rac1 [9], and Cdc42 [10] are maximally activated at the leading edge, suggesting the leading edge of the cell as its common functional site for Rho GTPase activities. All these works, however, were done separately, and the relationship between tractions and mechanotransduction during cell migration has not been demonstrated directly because of the difficulty in simultaneously recording tractions and mechanotransduction in migrating cells, precluding direct comparison between these results. Furthermore, these studies have been conducted by monitoring cells on glass coverslips, the stiffness of which is ∼ 65 giga pascal (GPa), at least three to six order higher than the physiological range of ECM stiffness. Although it is increasingly accepted that ECM stiffness influences cell migration, it is not known exactly how physiologically relevant ECM stiffness (order of kPa range) affects the dynamics of RhoA and Rac1 activities. For a complete understanding of the mechanism of mechano-chemical signaling in the context of cell migration, the dynamics and interplay between biomechanical (e.g., tractions) and biochemical (e.g., Rho GTPase) activities should be visualized within the physiologically relevant range of ECM stiffness.

scholarly journals Exploring Protein–Protein Interaction in the Study of Hormone-Dependent Cancers

2018 ◽  
Vol 19 (10) ◽  
pp. 3173 ◽  
Author(s):  
Yasuhiro Miki ◽  
Erina Iwabuchi ◽  
Katsuhiko Ono ◽  
Hironobu Sasano ◽  
Kiyoshi Ito
Keyword(s):  
Protein Interactions ◽  
Technology Development ◽  
Cultured Cells ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Super Resolution ◽  
Proximity Ligation Assay ◽  
Confocal Laser ◽  
Resolution Limit ◽  
Antibody Technology

Estrogen receptors promote target gene transcription when they form a dimer, in which two identical (homodimer) or different (heterodimer) proteins are bound to each other. In hormone-dependent cancers, hormone receptor dimerization plays pivotal roles, not only in the pathogenesis or development of the tumors, but also in the development of therapeutic resistance. Protein–protein interactions (PPIs), including dimerization and complex formation, have been also well-known to be required for proteins to exert their functions. The methods which could detect PPIs are genetic engineering (i.e., resonance energy transfer) and/or antibody technology (i.e., co-immunoprecipitation) using cultured cells. In addition, visualization of the target proteins in tissues can be performed using antigen–antibody reactions, as in immunohistochemistry. Furthermore, development of microscopic techniques (i.e., electron microscopy and confocal laser microscopy) has made it possible to visualize intracellular and/or intranuclear organelles. We have recently reported the visualization of estrogen receptor dimers in breast cancer tissues by using the in situ proximity ligation assay (PLA). PLA was developed along the lines of antibody technology development, and this assay has made it possible to visualize PPIs in archival tissue specimens. Localization of PPI in organelles has also become possible using super-resolution microscopes exceeding the resolution limit of conventional microscopes. Therefore, in this review, we summarize the methodologies used for studying PPIs in both cells and tissues, and review the recently reported studies on PPIs of hormones.

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