scholarly journals Ubiquitylation by Trim32 causes coupled loss of desmin, Z-bands, and thin filaments in muscle atrophy

2012 ◽  
Vol 198 (4) ◽  
pp. 575-589 ◽  
Author(s):  
Shenhav Cohen ◽  
Bo Zhai ◽  
Steven P. Gygi ◽  
Alfred L. Goldberg
Keyword(s):  
Muscle Atrophy ◽  
Ubiquitin Ligase ◽  
Thin Filament ◽  
Thick Filament ◽  
Myofibrillar Proteins ◽  
Rapid Loss ◽  
Thin Filaments ◽  
Thin Filament Proteins ◽  
Rapid Destruction ◽  
Fiber Atrophy

During muscle atrophy, myofibrillar proteins are degraded in an ordered process in which MuRF1 catalyzes ubiquitylation of thick filament components (Cohen et al. 2009. J. Cell Biol. http://dx.doi.org/10.1083/jcb.200901052). Here, we show that another ubiquitin ligase, Trim32, ubiquitylates thin filament (actin, tropomyosin, troponins) and Z-band (α-actinin) components and promotes their degradation. Down-regulation of Trim32 during fasting reduced fiber atrophy and the rapid loss of thin filaments. Desmin filaments were proposed to maintain the integrity of thin filaments. Accordingly, we find that the rapid destruction of thin filament proteins upon fasting was accompanied by increased phosphorylation of desmin filaments, which promoted desmin ubiquitylation by Trim32 and degradation. Reducing Trim32 levels prevented the loss of both desmin and thin filament proteins. Furthermore, overexpression of an inhibitor of desmin polymerization induced disassembly of desmin filaments and destruction of thin filament components. Thus, during fasting, desmin phosphorylation increases and enhances Trim32-mediated degradation of the desmin cytoskeleton, which appears to facilitate the breakdown of Z-bands and thin filaments.

scholarly journals Spaceflight results in increase of thick filament but not thin filament proteins in the paramyosin mutant of Caenorhabditis elegans

2008 ◽  
Vol 41 (5) ◽  
pp. 816-823 ◽  
Author(s):  
R. Adachi ◽  
T. Takaya ◽  
K. Kuriyama ◽  
A. Higashibata ◽  
N. Ishioka ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Thin Filament ◽  
Thick Filament ◽  
Thin Filament Proteins

scholarly journals During muscle atrophy, thick, but not thin, filament components are degraded by MuRF1-dependent ubiquitylation

2009 ◽  
Vol 185 (6) ◽  
pp. 1083-1095 ◽  
Author(s):  
Shenhav Cohen ◽  
Jeffrey J. Brault ◽  
Steven P. Gygi ◽  
David J. Glass ◽  
David M. Valenzuela ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Protein C ◽  
Thin Filament ◽  
Muscle Wasting ◽  
Ring Finger ◽  
Thick Filament ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Associated Proteins ◽  
Myosin Binding

Loss of myofibrillar proteins is a hallmark of atrophying muscle. Expression of muscle RING-finger 1 (MuRF1), a ubiquitin ligase, is markedly induced during atrophy, and MuRF1 deletion attenuates muscle wasting. We generated mice expressing a Ring-deletion mutant MuRF1, which binds but cannot ubiquitylate substrates. Mass spectrometry of the bound proteins in denervated muscle identified many myofibrillar components. Upon denervation or fasting, atrophying muscles show a loss of myosin-binding protein C (MyBP-C) and myosin light chains 1 and 2 (MyLC1 and MyLC2) from the myofibril, before any measurable decrease in myosin heavy chain (MyHC). Their selective loss requires MuRF1. MyHC is protected from ubiquitylation in myofibrils by associated proteins, but eventually undergoes MuRF1-dependent degradation. In contrast, MuRF1 ubiquitylates MyBP-C, MyLC1, and MyLC2, even in myofibrils. Because these proteins stabilize the thick filament, their selective ubiquitylation may facilitate thick filament disassembly. However, the thin filament components decreased by a mechanism not requiring MuRF1.

scholarly journals Novel insights into sarcomere regulatory systems control of cardiac thin filament activation

2021 ◽  
Vol 153 (7) ◽  
Author(s):  
Christopher Solís ◽  
R. John Solaro
Keyword(s):  
Thin Filament ◽  
Thick Filament ◽  
Detailed Knowledge ◽  
Thin Filaments ◽  
Myosin Binding Protein ◽  
Regulatory Systems ◽  
Associated Proteins ◽  
Filament Activation ◽  
Three State Model ◽  
Pointed End

Our review focuses on sarcomere regulatory mechanisms with a discussion of cardiac-specific modifications to the three-state model of thin filament activation from a blocked to closed to open state. We discuss modulation of these thin filament transitions by Ca2+, by crossbridge interactions, and by thick filament–associated proteins, cardiac myosin–binding protein C (cMyBP-C), cardiac regulatory light chain (cRLC), and titin. Emerging evidence supports the idea that the cooperative activation of the thin filaments despite a single Ca2+ triggering regulatory site on troponin C (cTnC) cannot be considered in isolation of other functional domains of the sarcomere. We discuss long- and short-range interactions among these domains with the regulatory units of thin filaments, including proteins at the barbed end at the Z-disc and the pointed end near the M-band. Important to these discussions is the ever-increasing understanding of the role of cMyBP-C, cRLC, and titin filaments. Detailed knowledge of these control processes is critical to the understanding of mechanisms sustaining physiological cardiac state with varying hemodynamic load, to better defining genetic and acquired cardiac disorders, and to developing targets for therapies at the level of the sarcomeres.

scholarly journals Thin filament diversity and physiological properties of fast and slow fiber types in astronaut leg muscles

2002 ◽  
Vol 92 (2) ◽  
pp. 817-825 ◽  
Author(s):  
Danny A. Riley ◽  
James L. W. Bain ◽  
Joyce L. Thompson ◽  
Robert H. Fitts ◽  
Jeffrey J. Widrick ◽  
...  
Keyword(s):  
Thin Filament ◽  
Thick Filament ◽  
Type I ◽  
Fiber Types ◽  
Shortening Velocity ◽  
Thin Filaments ◽  
Leg Muscles ◽  
Slow Type ◽  
Filament Spacing ◽  
Type I Fibers

Slow type I fibers in soleus and fast white (IIa/IIx, IIx), fast red (IIa), and slow red (I) fibers in gastrocnemius were examined electron microscopically and physiologically from pre- and postflight biopsies of four astronauts from the 17-day, Life and Microgravity Sciences Spacelab Shuttle Transport System-78 mission. At 2.5-μm sarcomere length, thick filament density is ∼1,012 filaments/μm2 in all fiber types and unchanged by spaceflight. In preflight aldehyde-fixed biopsies, gastrocnemius fibers possess higher percentages (∼23%) of short thin filaments than soleus (9%). In type I fibers, spaceflight increases short, thin filament content from 9 to 24% in soleus and from 26 to 31% in gastrocnemius. Thick and thin filament spacing is wider at short sarcomere lengths. The Z-band lattice is also expanded, except for soleus type I fibers with presumably stiffer Z bands. Thin filament packing density correlates directly with specific tension for gastrocnemius fibers but not soleus. Thin filament density is inversely related to shortening velocity in all fibers. Thin filament structural variation contributes to the functional diversity of normal and spaceflight-unloaded muscles.

scholarly journals Stress-dependent activation of myosin in the heart requires thin filament activation and thick filament mechanosensing

2021 ◽  
Vol 118 (16) ◽  
pp. e2023706118
Author(s):  
So-Jin Park-Holohan ◽  
Elisabetta Brunello ◽  
Thomas Kampourakis ◽  
Martin Rees ◽  
Malcolm Irving ◽  
...  
Keyword(s):  
Thin Filament ◽  
Thick Filament ◽  
Structural Basis ◽  
Thin Filaments ◽  
Regulatory Pathways ◽  
Calcium Dependent ◽  
Force Increase ◽  
Filament Activation ◽  
Myosin Motors ◽  
Stress Dependent

Myosin-based regulation in the heart muscle modulates the number of myosin motors available for interaction with calcium-regulated thin filaments, but the signaling pathways mediating the stronger contraction triggered by stretch between heartbeats or by phosphorylation of the myosin regulatory light chain (RLC) remain unclear. Here, we used RLC probes in demembranated cardiac trabeculae to investigate the molecular structural basis of these regulatory pathways. We show that in relaxed trabeculae at near-physiological temperature and filament lattice spacing, the RLC-lobe orientations are consistent with a subset of myosin motors being folded onto the filament surface in the interacting-heads motif seen in isolated filaments. The folded conformation of myosin is disrupted by cooling relaxed trabeculae, similar to the effect induced by maximal calcium activation. Stretch or increased RLC phosphorylation in the physiological range have almost no effect on RLC conformation at a calcium concentration corresponding to that between beats. These results indicate that in near-physiological conditions, the folded myosin motors are not directly switched on by RLC phosphorylation or by the titin-based passive tension at longer sarcomere lengths in the absence of thin filament activation. However, at the higher calcium concentrations that activate the thin filaments, stretch produces a delayed activation of folded myosin motors and force increase that is potentiated by RLC phosphorylation. We conclude that the increased contractility of the heart induced by RLC phosphorylation and stretch can be explained by a calcium-dependent interfilament signaling pathway involving both thin filament sensitization and thick filament mechanosensing.

scholarly journals Nature and origin of gap filaments in striated muscle

1991 ◽  
Vol 100 (4) ◽  
pp. 809-814 ◽  
Author(s):  
K. Trombitas ◽  
P.H. Baatsen ◽  
M.S. Kellermayer ◽  
G.H. Pollack
Keyword(s):  
Thin Filament ◽  
Sarcomere Length ◽  
Striated Muscle ◽  
Thick Filament ◽  
Abrupt Increase ◽  
Semitendinosus Muscle ◽  
Thin Filaments ◽  
Filament System ◽  
Anchor Points ◽  
High Degree

Immunoelectron microscopy was used to study the nature and origin of ‘gap’ filaments in frog semitendinosus muscle. Gap filaments are fine longitudinal filaments observable only in sarcomeres stretched beyond thick/thin filament overlap: they occupy the gap between the tips of thick and thin filaments. To test whether the gap filaments are part of the titin-filament system, we employed monoclonal antibodies to titin (T-11, Sigma) and observed the location of the epitope at a series of sarcomere lengths. At resting sarcomere length, the epitope was positioned in the I-band approximately 50 nm beyond the apparent ends of the thick filament. The location did not change perceptibly with increasing sarcomere length up to 3.6 microns. Above 3.6 microns, the span between the epitope and the end of the A-band abruptly increased, and above 4 microns, the antibodies could be seen to decorate the gap filaments. Between 5 and 6 microns, the epitope remained approximately in the middle of the gap. Even with this high degree of stretch, the label remained more or less aligned across the myofibril. The abrupt increase of span beyond 3.6 microns implies that the A-band domain of titin is pulled free of its anchor points along the thick filament, and moves toward the gap. Although this domain is functionally inextensible at physiological sarcomere length, the epitope movement in extremely stretched muscle shows that it is intrinsically elastic. Thus, the evidence confirms that gap filaments are clearly part of the titin-filament system. They are derived not only from the I-band domain of titin, but also from its A-band domain.

scholarly journals Overexpression of troponin T in Drosophila muscles causes a decrease in the levels of thin-filament proteins

2005 ◽  
Vol 386 (1) ◽  
pp. 145-152 ◽  
Author(s):  
Raquel MARCO-FERRERES ◽  
Juan J. ARREDONDO ◽  
Benito FRAILE ◽  
Margarita CERVERA
Keyword(s):  
Thin Filament ◽  
Troponin I ◽  
Troponin T ◽  
Thin Filaments ◽  
Muscle Formation ◽  
Thin Filament Proteins ◽  
Flight Muscles ◽  
Transgenic Drosophila ◽  
Regulated Thin Filament

Formation of the contractile apparatus in muscle cells requires co-ordinated activation of several genes and the proper assembly of their products. To investigate the role of TnT (troponin T) in the mechanisms that control and co-ordinate thin-filament formation, we generated transgenic Drosophila lines that overexpress TnT in their indirect flight muscles. All flies that overexpress TnT were unable to fly, and the loss of thin filaments themselves was coupled with ultrastructural perturbations of the sarcomere. In contrast, thick filaments remained largely unaffected. Biochemical analysis of these lines revealed that the increase in TnT levels could be detected only during the early stages of adult muscle formation and was followed by a profound decrease in the amount of this protein as well as that of other thin-filament proteins such as tropomyosin, troponin I and actin. The decrease in thin-filament proteins is not only due to degradation but also due to a decrease in their synthesis, since accumulation of their mRNA transcripts was also severely diminished. This decrease in expression levels of the distinct thin-filament components led us to postulate that any change in the amount of TnT transcripts might trigger the down-regulation of other co-regulated thin-filament components. Taken together, these results suggest the existence of a mechanism that tightly co-ordinates the expression of thin-filament genes and controls the correct stoichiometry of these proteins. We propose that the high levels of unassembled protein might act as a sensor in this process.

scholarly journals Decreased thin filament density and length in human atrophic soleus muscle fibers after spaceflight

2000 ◽  
Vol 88 (2) ◽  
pp. 567-572 ◽  
Author(s):  
Danny A. Riley ◽  
James L. W. Bain ◽  
Joyce L. Thompson ◽  
Robert H. Fitts ◽  
Jeffrey J. Widrick ◽  
...  
Keyword(s):  
Soleus Muscle ◽  
Thin Filament ◽  
Sarcomere Length ◽  
Muscle Fibers ◽  
Thick Filament ◽  
Thin Filaments ◽  
Contraction Velocity ◽  
Cross Bridge ◽  
Filament Spacing

Soleus muscle fibers were examined electron microscopically from pre- and postflight biopsies of four astronauts orbited for 17 days during the Life and Microgravity Sciences Spacelab Mission (June 1996). Myofilament density and spacing were normalized to a 2.4-μm sarcomere length. Thick filament density (∼1,062 filaments/μm2) and spacing (∼32.5 nm) were unchanged by spaceflight. Preflight thin filament density (2,976/μm2) decreased significantly ( P < 0.01) to 2,215/μm2 in the overlap A band region as a result of a 17% filament loss and a 9% increase in short filaments. Normal fibers had 13% short thin filaments. The 26% decrease in thin filaments is consistent with preliminary findings of a 14% increase in the myosin-to-actin ratio. Lower thin filament density was calculated to increase thick-to-thin filament spacing in vivo from 17 to 23 nm. Decreased density is postulated to promote earlier cross-bridge detachment and faster contraction velocity. Atrophic fibers may be more susceptible to sarcomere reloading damage, because force per thin filament is estimated to increase by 23%.

scholarly journals Myofibril breakdown during atrophy is a delayed response requiring the transcription factor PAX4 and desmin depolymerization

2017 ◽  
Vol 114 (8) ◽  
pp. E1375-E1384 ◽  
Author(s):  
Alexandra Volodin ◽  
Idit Kosti ◽  
Alfred Lewis Goldberg ◽  
Shenhav Cohen
Keyword(s):  
Transcription Factor ◽  
Muscle Atrophy ◽  
Ubiquitin Proteasome System ◽  
Delayed Response ◽  
Myofibrillar Proteins ◽  
Down Regulation ◽  
Two Phase ◽  
Gene Encoding ◽  
Thin Filaments ◽  
Ubiquitin Proteasome

A hallmark of muscle atrophy is the excessive degradation of myofibrillar proteins primarily by the ubiquitin proteasome system. In mice, during the rapid muscle atrophy induced by fasting, the desmin cytoskeleton and the attached Z-band–bound thin filaments are degraded after ubiquitination by the ubiquitin ligase tripartite motif-containing protein 32 (Trim32). To study the order of events leading to myofibril destruction, we investigated the slower atrophy induced by denervation (disuse). We show that myofibril breakdown is a two-phase process involving the initial disassembly of desmin filaments by Trim32, which leads to the later myofibril breakdown by enzymes, whose expression is increased by the paired box 4 (PAX4) transcription factor. After denervation of mouse tibialis anterior muscles, phosphorylation and Trim32-dependent ubiquitination of desmin filaments increased rapidly and stimulated their gradual depolymerization (unlike their rapid degradation during fasting). Trim32 down-regulation attenuated the loss of desmin and myofibrillar proteins and reduced atrophy. Although myofibrils and desmin filaments were intact at 7 d after denervation, inducing the dissociation of desmin filaments caused an accumulation of ubiquitinated proteins and rapid destruction of myofibrils. The myofibril breakdown normally observed at 14 d after denervation required not only dissociation of desmin filaments, but also gene induction by PAX4. Down-regulation of PAX4 or its target gene encoding the p97/VCP ATPase reduced myofibril disassembly and degradation on denervation or fasting. Thus, during atrophy, the initial loss of desmin is critical for the subsequent myofibril destruction, and over time, myofibrillar proteins become more susceptible to PAX4-induced enzymes that promote proteolysis.

scholarly journals THE MYOFILAMENT ARRANGEMENT IN THE FEMORAL MUSCLE OF THE COCKROACH, LEUCOPHAEA MADERAE FABRICIUS

1966 ◽  
Vol 28 (3) ◽  
pp. 545-562 ◽  
Author(s):  
Martin Hagopian
Keyword(s):  
Electron Microscopy ◽  
Tensile Strength ◽  
Epoxy Resin ◽  
Thin Filament ◽  
Light And Electron Microscopy ◽  
Thick Filament ◽  
Flexor Muscle ◽  
Thin Filaments ◽  
Leucophaea Maderae ◽  
Femoral Muscle

The structure of the femoral muscle of the cockroach, Leucophaea maderae, was investigated by light and electron microscopy. The several hundred fibers of either the extensor or flexor muscle are 20 to 40 µ in diameter in transverse sections and are subdivided into closely packed myofibrils. In glutaraldehyde-fixed and epoxy resin-embedded material of stretched fibers, the A band is about 4.5 µ long, the thin filaments are about 2.3 µ in length, the H zone and I band vary with the amount of stretch, and the M band is absent. The transverse sections of the filaments reveal in the area of a single overlap of thick and thin filaments an array of 10 to 12 thin filaments encircling each thick filament; whereas, in the area of double overlap in which the thin filaments interdigitate from opposite ends of the A band, the thin filaments show a twofold increase in number. The thick filament is approximately 205 to 185 A in diameter along most of its length, but at about 0.2 µ from the end it tapers to a point. Furthermore, some well oriented, very thin transverse sections show these filaments to have electron-transparent cores. The diameter of the thin filament is about 70 A. Transverse sections exhibit the sarcolemma invaginating clearly at regular intervals into the lateral regions of the A band. Three distinct types of mitochondria are associated with the muscle: an oval, an elongate, and a type with three processes. It is evident, in this muscle, that the sliding filament hypothesis is valid, and that perhaps the function of the extra thin filaments is to increase the tensile strength of the fiber and to create additional reactive sites between the thick and thin filaments. These sites are probably required for the functioning of the long sarcomeres.

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