scholarly journals Microtubule Organization in Striated Muscle Cells

Cells ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1395 ◽  
Author(s):  
Robert Becker ◽  
Marina Leone ◽  
Felix Engel
Keyword(s):  
Nuclear Envelope ◽  
Mammalian Cells ◽  
Cell Cycle Progression ◽  
Striated Muscle ◽  
Muscle Cells ◽  
Cell Types ◽  
Microtubule Organizing Center ◽  
Microtubule Organization ◽  
Cardiac Muscle Cells ◽  
Microtubule Networks

Distinctly organized microtubule networks contribute to the function of differentiated cell types such as neurons, epithelial cells, skeletal myotubes, and cardiomyocytes. In striated (i.e., skeletal and cardiac) muscle cells, the nuclear envelope acts as the dominant microtubule-organizing center (MTOC) and the function of the centrosome—the canonical MTOC of mammalian cells—is attenuated, a common feature of differentiated cell types. We summarize the mechanisms known to underlie MTOC formation at the nuclear envelope, discuss the significance of the nuclear envelope MTOC for muscle function and cell cycle progression, and outline potential mechanisms of centrosome attenuation.

Identification of intermediate filaments in mature mammalian skeletal muscle by TEM

1990 ◽  
Vol 48 (3) ◽  
pp. 454-455
Author(s):  
Masako Yagyu ◽  
Richard M. Robson ◽  
Marvin H. Stromer
Keyword(s):  
Skeletal Muscle ◽  
Intermediate Filaments ◽  
Mammalian Cells ◽  
Striated Muscle ◽  
Muscle Cells ◽  
Mammalian Skeletal Muscle ◽  
Semitendinosus Muscle ◽  
Cardiac Muscle Cells ◽  
Adult Skeletal Muscle ◽  
Transmission Electron

It is generally assumed that desmin in mature striated muscle cells is in the form of intermediate filaments (IFs) and that its primary locus is at or near the myofibrillar Z-lines. Although IFs have been identified by transmission electron microscopy (TEM) in embryonic and adult smooth and cardiac muscle cells and in differentiating or diseased skeletal muscle cells, IFs have rarely been unambiguously visualized in adult skeletal muscle (especially mammalian) cells by TEM. This is due in part to the small amount of IF protein in normal mature skeletal muscle, and in part to the heavily-packed, myofibril-dominated, intracellular cytoskeleton of these cells. In order to help ascertain the possible mechanism(s) of attachment of IFs to myofibrils, our objectives in this study were to identify, by TEM, IFs in adult mammalian skeletal muscle and to study the structural relationship of IFs and the muscle Z-lines.Samples of porcine semitendinosus muscle were removed from mature animals immediately after death, isometrically restrained and fixed in Karnovsky's fixative for 3 hours at 25°C, and processed by conventional methods followed by embedment in Epon-Araldite resin.

scholarly journals The Golgi Protein GM130 Regulates Centrosome Morphology and Function

2008 ◽  
Vol 19 (2) ◽  
pp. 745-753 ◽  
Author(s):  
Andrew Kodani ◽  
Christine Sütterlin
Keyword(s):  
Mammalian Cells ◽  
Cell Cycle Progression ◽  
Human Cell Lines ◽  
Microtubule Organizing Center ◽  
Microtubule Organization ◽  
Cycle Progression ◽  
Multipolar Spindles ◽  
Organizing Center ◽  
Golgi Protein ◽  
And Function

The Golgi apparatus (GA) of mammalian cells is positioned in the vicinity of the centrosome, the major microtubule organizing center of the cell. The significance of this physical proximity for organelle function and cell cycle progression is only beginning to being understood. We have identified a novel function for the GA protein, GM130, in the regulation of centrosome morphology, position and function during interphase. RNA interference–mediated depletion of GM130 from five human cell lines revealed abnormal interphase centrosomes that were mispositioned and defective with respect to microtubule organization and cell migration. When GM130-depleted cells entered mitosis, they formed multipolar spindles, arrested in metaphase, and died. We also detected aberrant centrosomes during interphase and multipolar spindles during mitosis in ldlG cells, which do not contain detectable GM130. Although GA proteins have been described to regulate mitotic centrosomes and spindle formation, this is the first report of a role for a GA protein in the regulation of centrosomes during interphase.

scholarly journals Myogenin controls via AKAP6 non-centrosomal microtubule organizing center formation at the nuclear envelope

2020 ◽  
Author(s):  
Robert Becker ◽  
Silvia Vergarajauregui ◽  
Florian Billing ◽  
Maria Sharkova ◽  
Eleonora Lippolis ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Nuclear Envelope ◽  
Muscle Cells ◽  
Cell Types ◽  
Microtubule Organizing Center ◽  
Anchor Protein ◽  
Organizing Center ◽  
Multiple Cell ◽  
Promoter Studies ◽  
Centrosomal Proteins

AbstractNon-centrosomal microtubule organizing centers (ncMTOC) are pivotal for the function of multiple cell types, but the processes initiating their formation are unknown. Here, we find that the transcription factor myogenin is required in myoblasts for recruiting centrosomal proteins. Moreover, myogenin is sufficient in fibroblasts for ncMTOC formation and centrosome attenuation. Bioinformatics combined with loss- and gain-of-function experiments identified induction of AKAP6 expression as one central mechanism for myogenin-mediated ncMTOC formation. Promoter studies indicate that myogenin preferentially induces the transcription of muscle- and ncMTOC-specific isoforms of Akap6 and Syne1, which encodes nesprin-1α, the ncMTOC anchor protein in muscle cells. Overexpression of AKAP6β and nesprin-1α was sufficient to recruit endogenous centrosomal proteins to the nuclear envelope of myoblasts in the absence of myogenin. Taken together, our results illuminate how mammals transcriptionally control the switch from a centrosomal MTOC to an ncMTOC and identify AKAP6 as a novel ncMTOC component in muscle cells.

scholarly journals Myogenin controls via AKAP6 non-centrosomal microtubule organizing center formation at the nuclear envelope

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Robert Becker ◽  
Silvia Vergarajauregui ◽  
Florian Billing ◽  
Maria Sharkova ◽  
Eleonora Lippolis ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Nuclear Envelope ◽  
Muscle Cells ◽  
Cell Types ◽  
Microtubule Organizing Center ◽  
Gain Of Function ◽  
Anchor Protein ◽  
Organizing Center ◽  
Multiple Cell ◽  
Promoter Studies

Non-centrosomal microtubule organizing centers (MTOC) are pivotal for the function of multiple cell types, but the processes initiating their formation are unknown. Here, we find that the transcription factor myogenin is required in murine myoblasts for the localization of MTOC proteins to the nuclear envelope. Moreover, myogenin is sufficient in fibroblasts for nuclear envelope MTOC (NE-MTOC) formation and centrosome attenuation. Bioinformatics combined with loss- and gain-of-function experiments identified induction of AKAP6 expression as one central mechanism for myogenin-mediated NE-MTOC formation. Promoter studies indicate that myogenin preferentially induces the transcription of muscle- and NE-MTOC-specific isoforms of Akap6 and Syne1, which encodes nesprin-1α, the NE-MTOC anchor protein in muscle cells. Overexpression of AKAP6β and nesprin-1α was sufficient to recruit endogenous MTOC proteins to the nuclear envelope of myoblasts in the absence of myogenin. Taken together, our results illuminate how mammals transcriptionally control the switch from a centrosomal MTOC to an NE-MTOC and identify AKAP6 as a novel NE-MTOC component in muscle cells.

Insulin stimulation of protein synthesis in cultured skeletal and cardiac muscle cells

1982 ◽  
Vol 243 (1) ◽  
pp. C81-C86 ◽  
Author(s):  
J. Airhart ◽  
J. A. Arnold ◽  
W. S. Stirewalt ◽  
R. B. Low
Keyword(s):  
Protein Synthesis ◽  
Specific Activity ◽  
Muscle Cells ◽  
Cell Types ◽  
Cardiac Cells ◽  
Cardiac Muscle Cells ◽  
Significant Stimulation ◽  
Chick Heart ◽  
Embryonic Chick Heart ◽  
Stimulation Of

The effects of acute exposure to insulin on protein synthesis were examined in primary, differentiated cultures of embryonic chick heart and skeletal muscle cells. Synthetic rates were calculated using the specific activity of tRNA-bound leucine as precursor, a specific activity that was significantly less than that of extracellular leucine but greater than that of free, intracellular leucine at 0.2 mM external leucine. Insulin did not alter these relationships. Doses of insulin in the physiological range produced significant stimulation of protein synthesis in both cell types. Maximal responses, involving approximately 30% increases in both absolute and fractional rates, were observed at higher insulin concentrations. Significant stimulation by insulin was seen in cardiac cells after only 1 h of insulin treatment, and the effects of the hormone were observed both in the presence and absence of serum in the culture medium.

scholarly journals 3D FIB-SEM reconstruction of microtubule–organelle interaction in whole primary mouse β cells

2020 ◽  
Vol 220 (2) ◽  
Author(s):  
Andreas Müller ◽  
Deborah Schmidt ◽  
C. Shan Xu ◽  
Song Pang ◽  
Joyson Verner D’Costa ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Cell Function ◽  
Secretory Granules ◽  
Detailed Knowledge ◽  
Β Cells ◽  
Microtubule Organization ◽  
Supportive Role ◽  
Primary Mouse ◽  
Microtubule Networks ◽  
Insulin Secretory Granule

Microtubules play a major role in intracellular trafficking of vesicles in endocrine cells. Detailed knowledge of microtubule organization and their relation to other cell constituents is crucial for understanding cell function. However, their role in insulin transport and secretion is under debate. Here, we use FIB-SEM to image islet β cells in their entirety with unprecedented resolution. We reconstruct mitochondria, Golgi apparati, centrioles, insulin secretory granules, and microtubules of seven β cells, and generate a comprehensive spatial map of microtubule–organelle interactions. We find that microtubules form nonradial networks that are predominantly not connected to either centrioles or endomembranes. Microtubule number and length, but not microtubule polymer density, vary with glucose stimulation. Furthermore, insulin secretory granules are enriched near the plasma membrane, where they associate with microtubules. In summary, we provide the first 3D reconstructions of complete microtubule networks in primary mammalian cells together with evidence regarding their importance for insulin secretory granule positioning and thus their supportive role in insulin secretion.

scholarly journals Intracellular Localization in Zebrafish Muscle and Conserved Sequence Features Suggest Roles for Gelatinase A Moonlighting in Sarcomere Maintenance

Biomedicines ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 93 ◽  
Author(s):  
Amina M. Fallata ◽  
Rachael A. Wyatt ◽  
Julie M. Levesque ◽  
Antoine Dufour ◽  
Christopher M. Overall ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Catalytic Domain ◽  
Striated Muscle ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Intracellular Localization ◽  
Muscle Cells ◽  
Matrix Remodeling ◽  
Gelatinase A ◽  
Conserved Sequence

Gelatinase A (Mmp2 in zebrafish) is a well-characterized effector of extracellular matrix remodeling, extracellular signaling, and along with other matrix metalloproteinases (MMPs) and extracellular proteases, it plays important roles in the establishment and maintenance of tissue architecture. Gelatinase A is also found moonlighting inside mammalian striated muscle cells, where it has been implicated in the pathology of ischemia-reperfusion injury. Gelatinase A has no known physiological function in muscle cells, and its localization within mammalian cells appears to be due to inefficient recognition of its N-terminal secretory signal. Here we show that Mmp2 is abundant within the skeletal muscle cells of zebrafish, where it localizes to the M-line of sarcomeres and degrades muscle myosin. The N-terminal secretory signal of zebrafish Mmp2 is also challenging to identify, and this is a conserved characteristic of gelatinase A orthologues, suggesting a selective pressure acting to prevent the efficient secretion of this protease. Furthermore, there are several strongly conserved phosphorylation sites within the catalytic domain of gelatinase A orthologues, some of which are phosphorylated in vivo, and which are known to regulate the activity of this protease. We conclude that gelatinase A likely participates in uncharacterized physiological functions within the striated muscle, possibly in the maintenance of sarcomere proteostasis, that are likely regulated by kinases and phosphatases present in the sarcomere.

scholarly journals Kinetics and intermediates of marginal band reformation: evidence for peripheral determinants of microtubule organization.

1984 ◽  
Vol 99 (1) ◽  
pp. 70s-75s ◽  
Author(s):  
M Miller ◽  
F Solomon
Keyword(s):  
Cell Types ◽  
Microtubule Assembly ◽  
Cell Periphery ◽  
Microtubule Organizing Center ◽  
Microtubule Organization ◽  
Mature Erythrocyte ◽  
The Reformation ◽  
Marginal Band ◽  
Organizing Center

The microtubules of the mature erythrocyte of the chicken are confined to a band at the periphery. Whole-mount electron microscopy after extraction reveals that the number of microtubules in each cell is almost the same. All the microtubules can be depolymerized by incubation in the cold, and the marginal band can be quantitatively and qualitatively reformed by return to 39 degrees C. These properties allow the reformation of the marginal band to be treated as an in vivo microtubule assembly reaction. The kinetics of this reaction and the intermediates detected during reformation suggest a mechanism of microtubule organization that is distinct from that observed in other cell types. Apparently only one or two growing microtubule ends are available for assembly--assembly is only detected at the cell periphery, even at early times--and there is no evidence of the participation of a microtubule-organizing center.

scholarly journals Myogenic conversion of mammalian fibroblasts induced by differentiating muscle cells

1995 ◽  
Vol 108 (8) ◽  
pp. 2733-2739 ◽  
Author(s):  
G. Salvatori ◽  
L. Lattanzi ◽  
M. Coletta ◽  
S. Aguanno ◽  
E. Vivarelli ◽  
...  
Keyword(s):  
Muscle Fibre ◽  
Striated Muscle ◽  
Muscle Cells ◽  
Cell Types ◽  
Sole Source ◽  
Cell Interaction ◽  
C2c12 Cells ◽  
Membrane Function ◽  
Beta Galactosidase

Somite-derived skeletal myoblasts are supposed to be the sole source of muscle fibre nuclei during pre- and postnatal development, but evidence is accumulating for unorthodox contributions to muscle fibre nuclei from other cell types. For example, in tissue culture, fibroblasts can fuse with dysgenic myoblasts and restore correct membrane function. We report here the results of a series of experiments investigating this phenomenon and its possible mechanism. 10T1/2 cells, infected with a replication defective retrovirus encoding the bacterial enzyme beta-galactosidase, fused to form beta-galactosidase positive, differentiated myotubes when cocultured with differentiating uninfected C2C12 or primary myogenic cells, but this did not occur when they were cocultured with other cells such as 3T3 fibroblasts or PC12 pheochromocytoma cells. Myogenic conversion ranged from 1 to 10% of the 10T1/2 cell population and required close cell interaction between the different cells types: it was not induced by conditioned medium or extracellular matrix deposited by C2C12 cells. Myogenic conversion was also observed in vivo, after injection of similarly infected 10T1/2 cells into regenerating muscle. Conversion was seen also after coculture of uninfected 10T1/2 cells with primary chick myoblasts, thus demonstrating that it was not dependent upon viral infection and that there is no species or class barrier in this phenomenon. Primary fibroblasts, isolated from different organs of transgenic mice carrying a Lac Z marker under the control of a muscle-specific promoter, restricting beta-galactosidase expression to striated muscle cells, also underwent myogenic conversion, when cocultured with C2C12 myoblasts.(ABSTRACT TRUNCATED AT 250 WORDS)

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