scholarly journals Lysine acetylation of cytoskeletal proteins: Emergence of an actin code

2020 ◽  
Vol 219 (12) ◽  
Author(s):  
Mu A ◽  
Casey J. Latario ◽  
Laura E. Pickrell ◽  
Henry N. Higgs
Keyword(s):  
Chromatin Remodeling ◽  
Actin Polymerization ◽  
Regulatory Mechanism ◽  
Mitochondrial Fission ◽  
Cytoskeletal Proteins ◽  
Multiple Roles ◽  
Lysine Acetylation ◽  
Post Translational Modifications ◽  
Cytoplasmic Actin ◽  
Downstream Effects

Reversible lysine acetylation of nuclear proteins such as histones is a long-established important regulatory mechanism for chromatin remodeling and transcription. In the cytoplasm, acetylation of a number of cytoskeletal proteins, including tubulin, cortactin, and the formin mDia2, regulates both cytoskeletal assembly and stability. More recently, acetylation of actin itself was revealed to regulate cytoplasmic actin polymerization through the formin INF2, with downstream effects on ER-to-mitochondrial calcium transfer, mitochondrial fission, and vesicle transport. This finding raises the possibility that actin acetylation, along with other post-translational modifications to actin, might constitute an “actin code,” similar to the “histone code” or “tubulin code,” controlling functional shifts to these central cellular proteins. Given the multiple roles of actin in nuclear functions, its modifications might also have important roles in gene expression.

scholarly journals Rubisco lysine acetylation occurs at very low stoichiometry in mature Arabidopsis leaves: implications for regulation of enzyme function

2020 ◽  
Vol 477 (19) ◽  
pp. 3885-3896 ◽  
Author(s):  
Brendan M. O'Leary ◽  
Andrew P. Scafaro ◽  
Ricarda Fenske ◽  
Owen Duncan ◽  
Elke Ströher ◽  
...  
Keyword(s):  
Regulatory Mechanism ◽  
Biological Significance ◽  
Maximal Activity ◽  
Enzyme Function ◽  
Lysine Acetylation ◽  
Night Time ◽  
Bisphosphate Carboxylase ◽  
Post Translational Modifications ◽  
Catalytic Function

Multiple studies have shown ribulose-1,5-bisphosphate carboxylase/oxygenase (E.C. 4.1.1.39; Rubisco) to be subject to Lys-acetylation at various residues; however, opposing reports exist about the biological significance of these post-translational modifications. One aspect of the Lys-acetylation that has not been addressed in plants generally, or with Rubisco specifically, is the stoichiometry at which these Lys-acetylation events occur. As a method to ascertain which Lys-acetylation sites on Arabidopsis Rubisco might be of regulatory importance to its catalytic function in the Calvin–Benson cycle, we purified Rubisco from leaves in both the day and night-time and performed independent mass spectrometry based methods to determine the stoichiometry of Rubisco Lys-acetylation events. The results indicate that Rubisco is acetylated at most Lys residues, but each acetylation event occurs at very low stoichiometry. Furthermore, in vitro treatments that increased the extent of Lys-acetylation on purified Rubisco had no effect on Rubisco maximal activity. Therefore, we are unable to confirm that Lys-acetylation at low stoichiometries can be a regulatory mechanism controlling Rubisco maximal activity. The results highlight the need for further use of stoichiometry measurements when determining the biological significance of reversible PTMs like acetylation.

scholarly journals Lysine post-translational modifications and the cytoskeleton

2012 ◽  
Vol 52 ◽  
pp. 135-145 ◽  
Author(s):  
Wendy D. Zencheck ◽  
Hui Xiao ◽  
Louis M. Weiss
Keyword(s):  
Protein Interactions ◽  
Intracellular Transport ◽  
Cytoskeletal Proteins ◽  
Lysine Acetylation ◽  
Protein Protein Interactions ◽  
Cellular Division ◽  
Post Translational Modifications ◽  
Cell Form ◽  
Cytoskeletal Regulation ◽  
Lysine Residues

PTMs (post-translational modifications) of lysine residues have proven to be major regulators of gene expression, protein–protein interactions, and protein processing and degradation. This is of particular importance in regulating the cytoskeleton, an enormously complex system of proteins responsible for cell motility, intracellular trafficking, and maintenance of cell form and structure. The cytoskeleton is present in all cells, including eukaryotes and prokaryotes, and comprises structures such as flagella, cilia and lamellipodia which play critical roles in intracellular transport and cellular division. Cytoskeletal regulation relies on numerous multi-component assemblies. In this chapter, we focus on the regulation of the cytoskeleton by means of PTMs of lysine residues on the cytoskeletal subunits and their accessory proteins. We specifically address the three main classes of cytoskeletal proteins in eukaryotes that polymerize into filaments, including microfilaments (actin filaments), intermediate filaments and microtubules. We discuss the identification and biological importance of lysine acetylation, a regulator of all three filament types. We also review additional lysine modifications, such as ubiquitination and SUMOylation, and their role in protein regulation and processing.

scholarly journals Two distinct actin filament populations have effects on mitochondria, with differences in stimuli and assembly factors

2019 ◽  
Author(s):  
Tak Shun Fung ◽  
Wei-Ke Ji ◽  
Henry N. Higgs ◽  
Rajarshi Chakrabarti
Keyword(s):  
Mitochondrial Membrane ◽  
Actin Polymerization ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Actin Assembly ◽  
Mitochondrial Depolarization ◽  
Inner Mitochondrial Membrane ◽  
Cytoplasmic Actin ◽  
Summary Statement ◽  
Shape Changes

AbstractRecent studies show that mitochondria and actin filaments work together in two contexts: 1) increased cytoplasmic calcium induces cytoplasmic actin polymerization that stimulates mitochondrial fission, and 2) mitochondrial depolarization causes actin assembly around mitochondria, with roles in mitophagy. It is unclear whether these two processes utilize similar actin assembly mechanisms. Here, we show that these are distinct actin assembly mechanisms in the acute phase after treatment (<10 min). Calcium-induced actin assembly is INF2-dependent and Arp2/3 complex-independent, whereas depolarization-induced actin assembly is Arp2/3 complex-dependent and INF2-independent. The two types of actin polymerization are morphologically distinct, with calcium-induced filaments throughout the cytosol and depolarization-induced filaments as “clouds” around depolarized mitochondria. We have previously shown that calcium-induced actin stimulates increases in both mitochondrial calcium and recruitment of the dynamin GTPase Drp1. In contrast, depolarization-induced actin is temporally-associated with extensive mitochondrial dynamics that do not result in mitochondrial fission, but in circularization of the inner mitochondrial membrane (IMM). These dynamics are dependent upon the protease Oma1 and independent of Drp1. Actin cloud inhibition causes increased IMM circularization, suggesting that actin clouds limit these dynamics.Summary statementMitochondrial depolarization induces Arp2/3 complex-dependent actin clouds that restrain mitochondrial shape changes induced by Oma1 on the inner mitochondrial membrane. A distinct actin network stimulates mitochondrial fission in response to calcium.

The challenge of detecting modifications on proteins

2020 ◽  
Vol 64 (1) ◽  
pp. 135-153 ◽  
Author(s):  
Lauren Elizabeth Smith ◽  
Adelina Rogowska-Wrzesinska
Keyword(s):  
Mass Spectrometry ◽  
Protein Function ◽  
Chemical Properties ◽  
Lysine Acetylation ◽  
Mass Determination ◽  
Post Translational Modifications ◽  
Site Specific ◽  
The Common

Abstract Post-translational modifications (PTMs) are integral to the regulation of protein function, characterising their role in this process is vital to understanding how cells work in both healthy and diseased states. Mass spectrometry (MS) facilitates the mass determination and sequencing of peptides, and thereby also the detection of site-specific PTMs. However, numerous challenges in this field continue to persist. The diverse chemical properties, low abundance, labile nature and instability of many PTMs, in combination with the more practical issues of compatibility with MS and bioinformatics challenges, contribute to the arduous nature of their analysis. In this review, we present an overview of the established MS-based approaches for analysing PTMs and the common complications associated with their investigation, including examples of specific challenges focusing on phosphorylation, lysine acetylation and redox modifications.

Abstract 17084: Nuclear Smooth Muscle α-actin Participates in Chromatin Remodeling at Smooth Muscle Contractile Gene Promoters

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Callie Kwartler ◽  
Shuangtao Ma ◽  
Caroline Kernell ◽  
Xue-yan Duan ◽  
Charis Wang ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Cardiac Muscle ◽  
Chromatin Remodeling ◽  
Muscle Cells ◽  
Cytoskeletal Proteins ◽  
Nuclear Localization Sequence ◽  
Serum Starvation ◽  
Cell Fractionation ◽  
Gene Promoters ◽  
Chromatin Remodeling Complexes

Actin genes encode for cytoskeletal proteins that polymerize to function in cellular motility, adhesion, and contraction. In mammalian cells, ubiquitously expressed β-actin also moves into the nucleus and associates with chromatin remodeling complexes, however a nuclear function of muscle-specific α-actins has not been previously assessed. We hypothesized that smooth muscle α-actin (SMA) plays a role in chromatin remodeling during the differentiation of smooth muscle cells (SMCs) to enable cell fate specification of SMCs. In explanted SMCs from human and mouse ascending aortas, cell fractionation and 2D gel electrophoresis identify both SMA and β-actin in the nuclear lysates. Nuclear SMA but not β-actin accumulates with SMC differentiation driven by serum starvation and transforming growth factor-β1 treatment. SMA accumulates into the nucleus early in the differentiation of SMCs from neural crest progenitor cells, prior to cytosolic accumulation. Immunoprecipitation studies show that SMA binds specifically to the INO80 and the SWI/SNF chromatin remodeling complexes, and this binding increases with SMC differentiation. Chromatin immunoprecipitation reveals that SMA is bound to the promoters of SMC-specific genes, including Acta2 , Cnn1, and Myh11 and that SMA is enriched over β-actin at these promoters with SMC differentiation. Finally, overexpression of SMA tagged with a nuclear localization sequence (NLS) in multiple cell types increases expression of SMC markers, whereas NLS-tagged β-actin localizes to the nucleus to the same extent but does not increase SMC marker expression in any cell type. Finally, we assessed whether skeletal muscle α-actin (SKA) and cardiac muscle α-actin (CMA) may play a similar role in skeletal and cardiac muscle cells. Both SKA and CMA translocate into the nucleus. CMA accumulates into the nucleus early in the differentiation of cardiomyocytes from pluripotent stem cells. Immunoprecipitation reveals that SKA binds to the SWI/SNF complex in differentiated C2C12 myotube cell cultures. These data support that nuclear SMA enriches with and participates in SMC differentiation, and suggest a potential nuclear role for other muscle specific α-actins in developing muscle cells.

Association of cyclin-bound p34cdc2 with subcellular structures in xenopus eggs

1992 ◽  
Vol 102 (2) ◽  
pp. 285-297 ◽  
Author(s):  
D. Leiss ◽  
M.A. Felix ◽  
E. Karsenti
Keyword(s):  
Cell Cycle ◽  
Ribosomal Proteins ◽  
Cell Cycle Progression ◽  
Gradient Centrifugation ◽  
Preliminary Evidence ◽  
Embryonic Cell ◽  
Cytoskeletal Proteins ◽  
Cyclin B ◽  
Post Translational Modifications ◽  
Egg Extracts

Cell cycle progression is controlled by changes in kinase activity of homologs of the fission yeast protein p34cdc2. The p34cdc2 kinase is activated by its association with a cyclin subunit, followed by post-translational modifications. Here, we show that in Xenopus eggs stimulated to enter the early embryonic cell cycle by an electric shock, part of the p34cdc2 becomes associated with subcellular fractions as the eggs progress towards mitosis. This occurs as a result of cyclin accumulation because most of the B-type cyclins and some of the A-type cyclins are found in the particulate fraction. Moreover, as soon as cyclins are degraded, p34cdc2 is released in the soluble fraction. The p34cdc2-cyclin complex can be solubilised by 80 mM beta-glycerophosphate (in the standard MPF extraction buffer) or by high salt concentrations. The post-translational modifications leading to cdc2 kinase activation by cyclin occur in the insoluble form. Following fractionation of egg extracts by sucrose gradient centrifugation, the p34cdc2-cyclin B complex is found in several fractions, but especially in two discrete peaks. We present evidence that in the slow-sedimenting peak the p34cdc2-cyclin B complex is associated with the 60 S subunit of monoribosomes. It could be targeted in this fashion to substrates such as ribosomal proteins and maybe to cytoskeletal proteins, since ribosomes bind to microtubules and are present in the spindle. The p34cdc2-cyclin B complex is also found in a faster-migrating fraction containing various membranous structures, including Golgi stacks. Therefore, as observed by immunofluorescence in other systems, it seems that cyclin subunits target p34cdc2 to specific cellular sites and this is certainly important for its function. In addition, we present preliminary evidence suggesting that some component present in the ribosome-containing fraction is required for activation of the p34cdc2-cyclin B complex.

scholarly journals Chlamydial Lytic Exit from Host Cells Is Plasmid Regulated

mBio ◽  
2015 ◽  
Vol 6 (6) ◽  
Author(s):  
Chunfu Yang ◽  
Tregei Starr ◽  
Lihua Song ◽  
John H. Carlson ◽  
Gail L. Sturdevant ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Actin Polymerization ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Cytoskeletal Proteins ◽  
Host Cells ◽  
Genetic Mechanism ◽  
Developmental Cycle ◽  
Obligate Intracellular ◽  
Type Iii

ABSTRACTChlamydia trachomatisis an obligate intracellular bacterium that is a globally important human pathogen. The chlamydial plasmid is an attenuating virulence factor, but the molecular basis for attenuation is not understood. Chlamydiae replicate within a membrane-bound vacuole termed an inclusion, where they undergo a biphasic developmental growth cycle and differentiate from noninfectious into infectious organisms. Late in the developmental cycle, the fragile chlamydia-laden inclusion retains its integrity by surrounding itself with scaffolds of host cytoskeletal proteins. The ability of chlamydiae to developmentally free themselves from this cytoskeleton network is a fundamental virulence trait of the pathogen. Here, we show that plasmidless chlamydiae are incapable of disrupting their cytoskeletal entrapment and remain intracellular as stable mature inclusions that support high numbers of infectious organisms. By using deletion mutants of the eight plasmid-carried genes (Δpgp1to Δpgp8), we show that Pgp4, a transcriptional regulator of multiple chromosomal genes, is required for exit. Exit of chlamydiae is dependent on protein synthesis and is inhibited by the compound C1, an inhibitor of the type III secretion system (T3S). Exit of plasmid-free and Δpgp4organisms, which failed to lyse infected cells, was rescued by latrunculin B, an inhibitor of actin polymerization. Our findings describe a genetic mechanism of chlamydial exit from host cells that is dependent on an unknownpgp4-regulated chromosomal T3S effector gene.IMPORTANCEChlamydia's obligate intracellular life style requires both entry into and exit from host cells. Virulence factors that function in exiting are unknown. The chlamydial inclusion is stabilized late in the infection cycle by F-actin. A prerequisite of chlamydial exit is its ability to disassemble actin from the inclusion. We show that chlamydial plasmid-free organisms, and also a plasmid gene protein 4 (pgp4) null mutant, do not disassociate actin from the inclusion and fail to exit cells. We further provide evidence that Pgp4-regulated exit is dependent on the chlamydial type III secretion system. This study is the first to define a genetic mechanism that functions in chlamydial lytic exit from host cells. The findings also have practical implications for understanding why plasmid-free chlamydiae are highly attenuated and have the ability to elicit robust protective immune responses.

scholarly journals The Role of HO-1 and Its Crosstalk with Oxidative Stress in Cancer Cell Survival

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2401
Author(s):  
Shih-Kai Chiang ◽  
Shuen-Ei Chen ◽  
Ling-Chu Chang
Keyword(s):  
Oxidative Stress ◽  
Redox Regulation ◽  
Oxidative Status ◽  
Multiple Roles ◽  
Mitochondrial Enzymes ◽  
Heme Oxygenases ◽  
Downstream Effects ◽  
Cancer Cell Survival ◽  
And Oxidative Stress

Heme oxygenases (HOs) act on heme degradation to produce carbon monoxide (CO), free iron, ferritin, and biliverdin. Upregulation of cellular HO-1 levels is signature of oxidative stress for its downstream effects particularly under pro-oxidative status. Subcellular traffics of HO-1 to different organelles constitute a network of interactions compromising a variety of effectors such as pro-oxidants, ROS, mitochondrial enzymes, and nucleic transcription factors. Some of the compartmentalized HO-1 have been demonstrated as functioning in the progression of cancer. Emerging data show the multiple roles of HO-1 in tumorigenesis from pathogenesis to the progression to malignancy, metastasis, and even resistance to therapy. However, the role of HO-1 in tumorigenesis has not been systematically addressed. This review describes the crosstalk between HO-1 and oxidative stress, and following redox regulation in the tumorigenesis. HO-1-regulated signaling pathways are also summarized. This review aims to integrate basic information and current progress of HO-1 in cancer research in order to enhance the understandings and facilitate following studies.

scholarly journals Mechanosensing through direct binding of tensed F-actin by LIM domains

2020 ◽  
Author(s):  
Xiaoyu Sun ◽  
Donovan Y. Z. Phua ◽  
Lucas Axiotakis ◽  
Mark A. Smith ◽  
Elizabeth Blankman ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Point Mutations ◽  
Cytoskeletal Proteins ◽  
Actin Binding ◽  
General Mechanism ◽  
Protein Protein Interaction ◽  
Cytoplasmic Actin ◽  
Lim Domains ◽  
Lim Proteins

SummaryMechanical signals transmitted through the cytoplasmic actin cytoskeleton must be relayed to the nucleus to control gene expression. LIM domains are protein-protein interaction modules found in cytoskeletal proteins and transcriptional regulators; however, it is unclear if there is a direct link between these two functions. Here we identify three LIM protein families (zyxin, paxillin, and FHL) whose members preferentially localize to the actin cytoskeleton in mechanically-stimulated cells through their tandem LIM domains. A minimal actin-myosin reconstitution system reveals that representatives of all three families directly bind F-actin only in the presence of mechanical force. Point mutations at a site conserved in each LIM domain of these proteins selectively disrupt tensed F-actin binding in vitro and cytoskeletal localization in cells, demonstrating a common, avidity-based mechanism. Finally, we find that binding to tensed F-actin in the cytoplasm excludes the cancer-associated transcriptional co-activator FHL2 from the nucleus in stiff microenvironments. This establishes direct force-activated F-actin binding by FHL2 as a mechanosensing mechanism. Our studies suggest that force-dependent sequestration of LIM proteins on the actin cytoskeleton could be a general mechanism for controlling nuclear localization to effect mechanical signaling.

scholarly journals Nucleus, Mitochondrion, or Reticulum? STAT3 à La Carte

2018 ◽  
Vol 19 (9) ◽  
pp. 2820 ◽  
Author(s):  
Lidia Avalle ◽  
Valeria Poli
Keyword(s):  
Energy Production ◽  
Energy Homeostasis ◽  
Multiple Roles ◽  
Pharmaceutical Companies ◽  
Signal Transducer ◽  
Post Translational Modifications ◽  
Pathological Conditions ◽  
Different Types ◽  
Tumor Transformation ◽  
Context Specific

The transcription factor signal transducer and activator of transcription (STAT)3 mediates the functions of cytokines, growth factors, and oncogenes under both physiological and pathological conditions. Uncontrolled/constitutive STAT3 activity is often detected in tumors of different types, where its role is mostly that of an oncogene, contributing in multiple ways to tumor transformation, growth, and progression. For this reason, many laboratories and pharmaceutical companies are making efforts to develop specific inhibitors. However, STAT3 has also been shown to act as a tumor suppressor in a number of cases, suggesting that its activity is strongly context-specific. Here, we discuss the bases that can explain the multiple roles of this factor in both physiological and pathological contexts. In particular, we focus on the following four features: (i) the distinct properties of the STAT3α and β isoforms; (ii) the multiple post-translational modifications (phosphorylation on tyrosine or serine, acetylation and methylation on different residues, and oxidation and glutathionylation) that can affect its activities downstream of multiple different signals; (iii) the non-canonical functions in the mitochondria, contributing to the maintenance of energy homeostasis under stress conditions; and (iv) the recently discovered functions in the endoplasmic reticulum, where STAT3 contributes to the regulation of calcium homeostasis, energy production, and apoptosis.

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