How myosin organization of the actin cytoskeleton contributes to the cancer phenotype

The human genome contains 39 genes that encode myosin heavy chains, classified on the basis of their sequence similarity into 12 classes. Most cells express at least 12 different genes, from at least 8 different classes, which are typically composed of several class 1 genes, at least one class 2 gene and classes 5, 6, 9, 10, 18 and 19. Although the different myosin isoforms all have specific and non-overlapping roles in the cell, in combination they all contribute to the organization of the actin cytoskeleton, and the shape and phenotype of the cell. Over (or under) expression of these different myosin isoforms can have strong effects on actin organization, cell shape and contribute to the cancer phenotype as discussed in this review.

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Chronic denervation of rat hemidiaphragm: maintenance of fiber heterogeneity with associated increasing uniformity of myosin isoforms.

The Journal of Cell Biology ◽

10.1083/jcb.100.1.161 ◽

1985 ◽

Vol 100 (1) ◽

pp. 161-174 ◽

Cited By ~ 54

Author(s):

U Carraro ◽

D Morale ◽

I Mussini ◽

S Lucke ◽

M Cantini ◽

...

Keyword(s):

Light And Electron Microscopy ◽

Myosin Isoforms ◽

Myosin Heavy Chains ◽

Denervated Muscle ◽

Slow Myosin ◽

Heavy Chains ◽

Fast Myosin ◽

Long Time ◽

Chronic Denervation

During several months of denervation, rat mixed muscles lose slow myosin, though with variability among animals. Immunocytochemical studies showed that all the denervated fibers of the hemidiaphragm reacted with anti-fast myosin, while many reacted with anti-slow myosin as well. This has left open the question as to whether multiple forms of myosin co-exist within individual fibers or a unique, possibly embryonic, myosin is present, which shares epitopes with fast and slow myosins. Furthermore, one can ask if the reappearance of embryonic myosin in chronically denervated muscle is related both to its re-expression in the pre-existing fibers and to cell regeneration. To answer these questions we studied the myosin heavy chains from individual fibers of the denervated hemidiaphragm by SDS PAGE and morphologically searched for regenerative events in the long term denervated muscle. 3 mo after denervation the severely atrophic fibers of the hemidiaphragm showed either fast or a mixture of fast and slow myosin heavy chains. Structural analysis of proteins sequentially extracted from muscle cryostat sections showed that slow myosin was still present 16 mo after denervation, in spite of the loss of the selective distribution of fast and slow features. Therefore muscle fibers can express adult fast myosin not only when denervated during their differentiation but also after the slow program has been expressed for a long time. Light and electron microscopy showed that the long-term denervated muscle maintained a steady-state atrophy for the rat's life span. Some of the morphological features indicate that aneural regeneration events continuously occur and significantly contribute to the increasing uniformity of the myosin gene expression in long-term denervated diaphragm.

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Neonatal and adult myosin heavy chains form homodimers during avian skeletal muscle development.

The Journal of Cell Biology ◽

10.1083/jcb.113.2.303 ◽

1991 ◽

Vol 113 (2) ◽

pp. 303-310 ◽

Cited By ~ 16

Author(s):

S Lowey ◽

G S Waller ◽

E Bandman

Keyword(s):

Skeletal Muscle ◽

Muscle Development ◽

Coiled Coil ◽

Myosin Isoforms ◽

Myosin Heavy Chains ◽

Electron Microscopic ◽

Hybrid Species ◽

Heavy Chains ◽

Stage Of Development ◽

Microscopic Techniques

Myosin isoforms contribute to the heterogeneity and adaptability of skeletal muscle fibers. Besides the well-characterized slow and fast muscle myosins, there are those isoforms that appear transiently during the course of muscle development. At a stage of development when two different myosins are coexpressed, the possibility arises for the existence of heterodimers, molecules containing two different heavy chains, or homodimers, molecules with two identical heavy chains. The question of whether neonatal and adult myosin isoforms can associate to form a stable heterodimer was addressed by using stage-specific monoclonal antibodies in conjunction with immunological and electron microscopic techniques. We find that independent of the ratio of adult to neonatal myosin, depending on the age of the animal, the myosin heavy chains form predominantly homodimeric molecules. The small amount of hybrid species present suggests that either the rod portion of the two heavy chain isoforms differs too much in sequence to form a stable alpha-helical coiled coil, or that the biosynthesis of the heavy chains precludes the formation of heterodimeric molecules.

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Effect of ROCK Pathway Manipulation on Actin Cytoskeleton Architecture: The Third Dimension

10.21203/rs.3.rs-646017/v1 ◽

2021 ◽

Author(s):

Carolin Grandy ◽

Fabian Port ◽

Jonas Pfeil ◽

Kay-Eberhard Gottschalk

Keyword(s):

Actin Cytoskeleton ◽

Driving Force ◽

Cell Shape ◽

Dynamic Properties ◽

Three Dimensional ◽

Structural Behaviour ◽

Actin Organization ◽

Biochemical Processes ◽

The Third ◽

Third Dimension

Abstract The actin cytoskeleton with its dynamic properties serves as the driving force for the movement and division of cells and gives the cell shape and structure. Disorders in the actin cytoskeleton occur in many diseases. Deeper understanding of the regulation is essential in order to better understand these biochemical processes. In our study, we use metal-induced energy transfer (MIET) as a tool to quantitatively examine the rarely considered third dimension of the actin cytoskeleton with nanometer accuracy. In particular, we investigate the influence of different drugs acting on the ROCK pathway on the three-dimensional actin organization. We find that cells treated with inhibitors have a lower actin height to the substrate while treatment with a stimulator for the ROCK pathway increases the actin height to the substrate. This reveals the precise tuning of adhesion and cytoskeleton tension, which leads to a rich three-dimensional structural behaviour of the actin cytoskeleton. This finetuning is differentially affected by either inhibition or stimulation.

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Treatment with beta bungarotoxin blocks muscle spindle formation in fetal rats

Development ◽

10.1242/dev.110.2.483 ◽

1990 ◽

Vol 110 (2) ◽

pp. 483-489

Author(s):

J. Kucera ◽

J.M. Waldro

Keyword(s):

Peripheral Nerves ◽

Muscle Fibers ◽

Muscle Spindles ◽

Myosin Isoforms ◽

Myosin Heavy Chains ◽

Heavy Chains ◽

Intrafusal Fibers ◽

Intramuscular Nerves ◽

Fetal Rats ◽

Intramuscular Nerve

Sensory and motor fibers of peripheral nerves were irreversibly destroyed in fetal rats by administering beta bungarotoxin (BTX) on embryonic day 16 or 17, after assembly of primary myotubes, but before the formation of muscle spindles. Soleus muscles of toxin-treated fetuses and their untreated littermates were removed just prior to birth and were examined by light microscopy of serial transverse sections for the presence of spindles and immunocytochemical expression of several isoforms of myosin heavy chains (MHC). Untreated muscles exhibited numerous spindles that were innervated by branches of intramuscular nerves and contained muscle fibers expressing a slow-tonic MHC isoform characteristic of the intrafusal but not extrafusal fibers. Toxin-treated muscles were devoid of intramuscular nerve bundles and perineurial structures. Encapsulations of muscle fibers resembling spindles were absent and no myotubes expressed the slow-tonic MHC isoform associated with intrafusal fibers in beta BTX-treated muscles. Thus, the assembly of muscle spindles, formation of the spindle capsule, and transformation of undifferentiated myotubes into the intrafusal fibers that contain spindle-specific myosin isoforms all depend on the presence of innervation in prenatal rat muscles.

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Smooth muscle myosin heavy chains combine to form three native myosin isoforms

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1993.264.5.h1653 ◽

1993 ◽

Vol 264 (5) ◽

pp. H1653-H1662 ◽

Cited By ~ 1

Author(s):

A. E. Tsao ◽

T. J. Eddinger

Keyword(s):

Smooth Muscle ◽

Sodium Dodecyl ◽

Coiled Coil ◽

Smooth Muscle Myosin ◽

Polyacrylamide Gel ◽

Myosin Isoforms ◽

Myosin Heavy Chains ◽

Polyacrylamide Gels ◽

Heavy Chains ◽

Muscle Myosin

Two smooth muscle myosin heavy chains (MHC; SM1 and SM2) of approximately 204 and 200 kDa exist in smooth muscle cells and can be visualized on reducing sodium dodecyl sulfate (SDS)-polyacrylamide gels. Chymotryptic digestion of the native myosin molecule results in two fragments: heavy meromyosin (HMM) and light meromyosin (LMM). LMM is the alpha-helical coiled-coil carboxy terminal half of the molecule containing the difference peptide between SM1 and SM2. Electrophoresis of the LMM fragments on a reducing SDS-polyacrylamide gel resolves two subunits from the two MHC [LM1 from SM1 (approximately 100 kDa) and LM2 from SM2 (approximately 95 kDa), where LM1 and LM2 are LMM from SM1 and SM2, respectively]. CuCl2 oxidation of the LMM fragment forms intramolecular disulfide bonds between adjacent cysteines on the two LMM fragments. When the native LMM is oxidized with CuCl2 and run on a nonreducing SDS-polyacrylamide gel, three bands are observed, which migrate at approximately 195, 190, and 185 kDa (bands 1, 2, and 3). Excision of these bands and electrophoresis on a reducing SDS-polyacrylamide gel show their subunit composition. Band 1 is composed solely of LM1. Band 2 is composed of an equal ratio of LM1 and LM2, and band 3 is composed solely of LM2. Using a variety of biochemical procedures, along with nonreducing SDS-polyacrylamide gels, we interpret these results to indicate that there are three smooth muscle myosin isoforms that result from the various combinations of the two smooth muscle MHC (SM1 homodimer, SM1-SM2 heterodimer, and SM2 homodimer).

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