scholarly journals The Central Role of the F-Actin Surface in Myosin Force Generation

Biology ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1221
Author(s):  
Matthew H. Doran ◽  
William Lehman
Keyword(s):  
Critical Role ◽  
Structural Features ◽  
Force Generation ◽  
Actin Binding ◽  
Myosin Isoforms ◽  
Thin Filaments ◽  
Cellular Processes ◽  
Muscle Myosin ◽  
Kinetics Of

Actin is one of the most abundant and versatile proteins in eukaryotic cells. As discussed in many contributions to this Special Issue, its transition from a monomeric G-actin to a filamentous F-actin form plays a critical role in a variety of cellular processes, including control of cell shape and cell motility. Once polymerized from G-actin, F-actin forms the central core of muscle-thin filaments and acts as molecular tracks for myosin-based motor activity. The ATP-dependent cross-bridge cycle of myosin attachment and detachment drives the sliding of myosin thick filaments past thin filaments in muscle and the translocation of cargo in somatic cells. The variation in actin function is dependent on the variation in muscle and non-muscle myosin isoform behavior as well as interactions with a plethora of additional actin-binding proteins. Extensive work has been devoted to defining the kinetics of actin-based force generation powered by the ATPase activity of myosin. In addition, over the past decade, cryo-electron microscopy has revealed the atomic-evel details of the binding of myosin isoforms on the F-actin surface. Most accounts of the structural interactions between myosin and actin are described from the perspective of the myosin molecule. Here, we discuss myosin-binding to actin as viewed from the actin surface. We then describe conserved structural features of actin required for the binding of all or most myosin isoforms while also noting specific interactions unique to myosin isoforms.

scholarly journals The WASP Homologue Las17 Activates the Novel Actin-regulatory Activity of Ysc84 to Promote Endocytosis in Yeast

2009 ◽  
Vol 20 (6) ◽  
pp. 1618-1628 ◽  
Author(s):  
Alastair S. Robertson ◽  
Ellen G. Allwood ◽  
Adam P.C. Smith ◽  
Fiona C. Gardiner ◽  
Rosaria Costa ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Actin Polymerization ◽  
Actin Binding ◽  
The Novel ◽  
Cellular Processes ◽  
New Class ◽  
Actin Binding Domain ◽  
Kinetics Of ◽  
Actin Binding Site

Actin plays an essential role in many eukaryotic cellular processes, including motility, generation of polarity, and membrane trafficking. Actin function in these roles is regulated by association with proteins that affect its polymerization state, dynamics, and organization. Numerous proteins have been shown to localize with cortical patches of yeast actin during endocytosis, but the role of many of these proteins remains poorly understood. Here, we reveal that the yeast protein Ysc84 represents a new class of actin-binding proteins, conserved from yeast to humans. It contains a novel N-terminal actin-binding domain termed Ysc84 actin binding (YAB), which can bind and bundle actin filaments. Intriguingly, full-length Ysc84 alone does not bind to actin, but binding can be activated by a specific motif within the polyproline region of the yeast WASP homologue Las17. We also identify a new monomeric actin-binding site on Las17. Together, the polyproline region of Las17 and Ysc84 can promote actin polymerization. Using live cell imaging, kinetics of assembly and disassembly of proteins at the endocytic site were analyzed and reveal that loss of Ysc84 and its homologue Lsb3 decrease inward movement of vesicles consistent with a role in actin polymerization during endocytosis.

scholarly journals Direct real-time detection of the structural and biochemical events in the myosin power stroke

2015 ◽  
Vol 112 (46) ◽  
pp. 14272-14277 ◽  
Author(s):  
Joseph M. Muretta ◽  
John A. Rohde ◽  
Daniel O. Johnsrud ◽  
Sinziana Cornea ◽  
David D. Thomas
Keyword(s):  
Force Generation ◽  
Actin Binding ◽  
Power Stroke ◽  
Transient Time ◽  
Time Resolved ◽  
Phosphate Release ◽  
Biochemical Kinetics ◽  
Temporal Coupling ◽  
Muscle Myosin ◽  
Kinetics Of

A principal goal of molecular biophysics is to show how protein structural transitions explain physiology. We have developed a strategic tool, transient time-resolved FRET [(TR)2FRET], for this purpose and use it here to measure directly, with millisecond resolution, the structural and biochemical kinetics of muscle myosin and to determine directly how myosin’s power stroke is coupled to the thermodynamic drive for force generation, actin-activated phosphate release, and the weak-to-strong actin-binding transition. We find that actin initiates the power stroke before phosphate dissociation and not after, as many models propose. This result supports a model for muscle contraction in which power output and efficiency are tuned by the distribution of myosin structural states. This technology should have wide application to other systems in which questions about the temporal coupling of allosteric structural and biochemical transitions remain unanswered.

scholarly journals Dynamics of Tpm1.8 domains on actin filaments with single molecule resolution

2020 ◽  
Author(s):  
Ilina Bareja ◽  
Hugo Wioland ◽  
Miro Janco ◽  
Philip R. Nicovich ◽  
Antoine Jégou ◽  
...  
Keyword(s):  
Actin Filament ◽  
Single Molecule ◽  
Actin Filaments ◽  
High Probability ◽  
Actin Binding ◽  
Single Molecule Level ◽  
Filament Dynamics ◽  
Kinetics Of ◽  
Insight Into

ABSTRACTTropomyosins regulate dynamics and functions of the actin cytoskeleton by forming long chains along the two strands of actin filaments that act as gatekeepers for the binding of other actin-binding proteins. The fundamental molecular interactions underlying the binding of tropomyosin to actin are still poorly understood. Using microfluidics and fluorescence microscopy, we observed the binding of fluorescently labelled tropomyosin isoform Tpm1.8 to unlabelled actin filaments in real time. This approach in conjunction with mathematical modeling enabled us to quantify the nucleation, assembly and disassembly kinetics of Tpm1.8 on single filaments and at the single molecule level. Our analysis suggests that Tpm1.8 decorates the two strands of the actin filament independently. Nucleation of a growing tropomyosin domain proceeds with high probability as soon as the first Tpm1.8 molecule is stabilised by the addition of a second molecule, ultimately leading to full decoration of the actin filament. In addition, Tpm1.8 domains are asymmetrical, with enhanced dynamics at the edge oriented towards the barbed end of the actin filament. The complete description of Tpm1.8 kinetics on actin filaments presented here provides molecular insight into actin-tropomyosin filament formation and the role of tropomyosins in regulating actin filament dynamics.

scholarly journals Immunoepigenetics Combination Therapies: An Overview of the Role of HDACs in Cancer Immunotherapy

2019 ◽  
Vol 20 (9) ◽  
pp. 2241 ◽  
Author(s):  
Debarati Banik ◽  
Sara Moufarrij ◽  
Alejandro Villagra
Keyword(s):  
Histone Deacetylase Inhibitors ◽  
Critical Role ◽  
Preclinical Studies ◽  
Clinical Use ◽  
Combination Therapies ◽  
Drug Candidates ◽  
Cellular Processes ◽  
Fda Approval

Long-standing efforts to identify the multifaceted roles of histone deacetylase inhibitors (HDACis) have positioned these agents as promising drug candidates in combatting cancer, autoimmune, neurodegenerative, and infectious diseases. The same has also encouraged the evaluation of multiple HDACi candidates in preclinical studies in cancer and other diseases as well as the FDA-approval towards clinical use for specific agents. In this review, we have discussed how the efficacy of immunotherapy can be leveraged by combining it with HDACis. We have also included a brief overview of the classification of HDACis as well as their various roles in physiological and pathophysiological scenarios to target key cellular processes promoting the initiation, establishment, and progression of cancer. Given the critical role of the tumor microenvironment (TME) towards the outcome of anticancer therapies, we have also discussed the effect of HDACis on different components of the TME. We then have gradually progressed into examples of specific pan-HDACis, class I HDACi, and selective HDACis that either have been incorporated into clinical trials or show promising preclinical effects for future consideration. Finally, we have included examples of ongoing trials for each of the above categories of HDACis as standalone agents or in combination with immunotherapeutic approaches.

scholarly journals The Canonical Wnt Pathway as a Key Regulator in Liver Development, Differentiation and Homeostatic Renewal

Genes ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1163
Author(s):  
Sebastian L. Wild ◽  
Aya Elghajiji ◽  
Carmen Grimaldos Rodriguez ◽  
Stephen D. Weston ◽  
Zoë D. Burke ◽  
...  
Keyword(s):  
Critical Role ◽  
Hypoxia Inducible Factor ◽  
Signalling Pathway ◽  
Fate Specification ◽  
Cellular Processes ◽  
Recent Developments ◽  
Body Patterning ◽  
Important Regulator ◽  
Canonical Wnt

The canonical Wnt (Wnt/β-catenin) signalling pathway is highly conserved and plays a critical role in regulating cellular processes both during development and in adult tissue homeostasis. The Wnt/β-catenin signalling pathway is vital for correct body patterning and is involved in fate specification of the gut tube, the primitive precursor of liver. In adults, the Wnt/β-catenin pathway is increasingly recognised as an important regulator of metabolic zonation, homeostatic renewal and regeneration in response to injury throughout the liver. Herein, we review recent developments relating to the key role of the pathway in the patterning and fate specification of the liver, in the directed differentiation of pluripotent stem cells into hepatocytes and in governing proliferation and zonation in the adult liver. We pay particular attention to recent contributions to the controversy surrounding homeostatic renewal and proliferation in response to injury. Furthermore, we discuss how crosstalk between the Wnt/β-catenin and Hedgehog (Hh) and hypoxia inducible factor (HIF) pathways works to maintain liver homeostasis. Advancing our understanding of this pathway will benefit our ability to model disease, screen drugs and generate tissue and organ replacements for regenerative medicine.

ProatherogenIc Inflamatory mRNAs Have structural Features for Being Regulated by MicroRNAs

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 5316-5316
Author(s):  
Xiao-Feng Yang ◽  
Anthony Virtue ◽  
Jietang Mai ◽  
Ying Yin ◽  
Xiaohua Jiang ◽  
...  
Keyword(s):  
Conflicts Of Interest ◽  
Critical Role ◽  
Structural Features ◽  
Database Mining ◽  
Mirna Regulation ◽  
Inflammatory Gene Expression ◽  
Inflammatory Genes ◽  
Mining Technique ◽  
Atherosclerotic Lesions

Abstract Abstract 5316 The current literature focusing on miRNAs has failed to adequately address two important questions - how miRNAs modulate atherogenic inflammatory genes from a panoramic viewpoint and whether the augmented expression of the atherogenic inflammatory genes is the result of miRNAs suppression. To resolve these knowledge gaps, we have employed a novel database mining technique in conjunction with statistical analysis criteria established from experimentally verified miRNAs. Utilizing this strategy we were able to conclude that the expression of 33 inflammatory genes is upregulated in atherosclerotic lesions and that these genes contain structural features in the 3'UTR of their mRNA for potential miRNAs regulation. Additionally, the binding features governing the interactions between the miRNAs and the inflammatory genes were statistically identical to the features of experimentally verified miRNAs. It was also determined that 21 (64%) of the 33 inflammatory genes were targeted by highly expressed miRNAs while the remaining 12 genes (36%) were targeted by normally expressed miRNAs. In addition, 10 of the 21 highly expressed miRNA-targeted inflammatory genes (48%) were targeted by a single miRNA, suggesting miRNA regulation specificity. Furthermore, 12 (48%) out of the 25 miRNAs found to meet our criteria targeted individual inflammatory genes while the other 13 miRNAs targeted multiple inflammatory genes. These results indicate a critical role of miRNAs in regulating proatherogenic inflammatory gene expression. Disclosures: No relevant conflicts of interest to declare.

scholarly journals The nebulin repeat protein Lasp regulates I-band architecture and filament spacing in myofibrils

2014 ◽  
Vol 206 (4) ◽  
pp. 559-572 ◽  
Author(s):  
Isabelle Fernandes ◽  
Frieder Schöck
Keyword(s):  
Thin Filament ◽  
Muscle Protein ◽  
Nemaline Myopathy ◽  
Single Amino Acid ◽  
Actin Binding ◽  
Filament Length ◽  
Thin Filaments ◽  
Single Amino Acid Change ◽  
Filament Spacing

Mutations in nebulin, a giant muscle protein with 185 actin-binding nebulin repeats, are the major cause of nemaline myopathy in humans. Nebulin sets actin thin filament length in sarcomeres, potentially by stabilizing thin filaments in the I-band, where nebulin and thin filaments coalign. However, the precise role of nebulin in setting thin filament length and its other functions in regulating power output are unknown. Here, we show that Lasp, the only member of the nebulin family in Drosophila melanogaster, acts at two distinct sites in the sarcomere and controls thin filament length with just two nebulin repeats. We found that Lasp localizes to the Z-disc edges to control I-band architecture and also localizes at the A-band, where it interacts with both actin and myosin to set proper filament spacing. Furthermore, introducing a single amino acid change into the two nebulin repeats of Lasp demonstrated different roles for each domain and established Lasp as a suitable system for studying nebulin repeat function.

scholarly journals Critical Role of Non-Muscle Myosin Light Chain Kinase in Thrombin-Induced Endothelial Cell Inflammation and Lung PMN Infiltration

PLoS ONE ◽  
2013 ◽  
Vol 8 (3) ◽  
pp. e59965 ◽  
Author(s):  
Fabeha Fazal ◽  
Kaiser M. Bijli ◽  
Matthew Murrill ◽  
Antony Leonard ◽  
Mohammad Minhajuddin ◽  
...  
Keyword(s):  
Endothelial Cell ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Critical Role ◽  
Muscle Myosin

scholarly journals Positive-strand RNA viruses stimulate host phosphatidylcholine synthesis at viral replication sites

2016 ◽  
Vol 113 (8) ◽  
pp. E1064-E1073 ◽  
Author(s):  
Jiantao Zhang ◽  
Zhenlu Zhang ◽  
Vineela Chukkapalli ◽  
Jules A. Nchoutmboube ◽  
Jianhui Li ◽  
...  
Keyword(s):  
Viral Replication ◽  
Rna Viruses ◽  
Critical Role ◽  
Brome Mosaic Virus ◽  
Alternate Host ◽  
Positive Strand ◽  
Cellular Processes ◽  
Replication Sites ◽  
Positive Strand Rna

All positive-strand RNA viruses reorganize host intracellular membranes to assemble their viral replication complexes (VRCs); however, how these viruses modulate host lipid metabolism to accommodate such membrane proliferation and rearrangements is not well defined. We show that a significantly increased phosphatidylcholine (PC) content is associated with brome mosaic virus (BMV) replication in both natural host barley and alternate host yeast based on a lipidomic analysis. Enhanced PC levels are primarily associated with the perinuclear ER membrane, where BMV replication takes place. More specifically, BMV replication protein 1a interacts with and recruits Cho2p (choline requiring 2), a host enzyme involved in PC synthesis, to the site of viral replication. These results suggest that PC synthesized at the site of VRC assembly, not the transport of existing PC, is responsible for the enhanced accumulation. Blocking PC synthesis by deleting theCHO2gene resulted in VRCs with wider diameters than those in wild-type cells; however, BMV replication was significantly inhibited, highlighting the critical role of PC in VRC formation and viral replication. We further show that enhanced PC levels also accumulate at the replication sites of hepatitis C virus and poliovirus, revealing a conserved feature among a group of positive-strand RNA viruses. Our work also highlights a potential broad-spectrum antiviral strategy that would disrupt PC synthesis at the sites of viral replication but would not alter cellular processes.

scholarly journals The role of profilin-1 in cardiovascular diseases

2021 ◽  
Vol 134 (9) ◽  
Author(s):  
Abigail Allen ◽  
David Gau ◽  
Partha Roy
Keyword(s):  
Cardiovascular Diseases ◽  
Actin Cytoskeleton ◽  
Cell Cycle Progression ◽  
Neurological Diseases ◽  
Essential Feature ◽  
Actin Binding ◽  
Cycle Progression ◽  
Cellular Processes ◽  
Damage Response

ABSTRACT Dynamic remodeling of the actin cytoskeleton is an essential feature for virtually all actin-dependent cellular processes, including cell migration, cell cycle progression, chromatin remodeling and gene expression, and even the DNA damage response. An altered actin cytoskeleton is a structural hallmark associated with numerous pathologies ranging from cardiovascular diseases to immune disorders, neurological diseases and cancer. The actin cytoskeleton in cells is regulated through the orchestrated actions of a myriad of actin-binding proteins. In this Review, we provide a brief overview of the structure and functions of the actin-monomer-binding protein profilin-1 (Pfn1) and then discuss how dysregulated expression of Pfn1 contributes to diseases associated with the cardiovascular system.

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