Cytochalasin B

Last updated
Cytochalasin B
Cytochalasin B.svg
Names
IUPAC name
(1S,4E,6R,10R,12E,14S,15S,17S,18S,19S)-19-benzyl-6,15-dihydroxy-10,17-dimethyl-16-methylidene-2-oxa-20-azatricyclo[12.7.0.01,18]henicosa-4,12-diene-3,21-dione
Other names
Phomin
Identifiers
3D model (JSmol)
3DMet
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.035.440 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 239-000-2
KEGG
PubChem CID
RTECS number
  • RO0205000
UNII
  • InChI=1S/C29H37NO5/c1-18-9-7-13-22(31)15-16-25(32)35-29-23(14-8-10-18)27(33)20(3)19(2)26(29)24(30-28(29)34)17-21-11-5-4-6-12-21/h4-6,8,11-12,14-16,18-19,22-24,26-27,31,33H,3,7,9-10,13,17H2,1-2H3,(H,30,34)/b14-8+,16-15+/t18-,19-,22-,23+,24+,26+,27-,29-/m1/s1 X mark.svgN
    Key: GBOGMAARMMDZGR-TYHYBEHESA-N X mark.svgN
  • InChI=1/C29H37NO5/c1-18-9-7-13-22(31)15-16-25(32)35-29-23(14-8-10-18)27(33)20(3)19(2)26(29)24(30-28(29)34)17-21-11-5-4-6-12-21/h4-6,8,11-12,14-16,18-19,22-24,26-27,31,33H,3,7,9-10,13,17H2,1-2H3,(H,30,34)/b14-8+,16-15+/t18-,19-,22-,23+,24+,26+,27-,29-/m1/s1
    Key: GBOGMAARMMDZGR-TYHYBEHEBX
  • C[C@@H]1CCC[C@H](/C=C/C(=O)O[C@]23[C@@H](/C=C/C1)[C@@H](C(=C)[C@H]([C@H]2[C@@H](NC3=O)Cc4ccccc4)C)O)O
Properties
C29H37NO5
Molar mass 479.6 g/mol
Appearancewhite to off-white powder
Density 1.21 g/cm3 (predicted)
Melting point 215 to 223 °C (419 to 433 °F; 488 to 496 K)
Boiling point 740.56 °C (1,365.01 °F; 1,013.71 K) at 760 mmHg (predicted)
insoluble
Solubility in DMSO and MeOHsoluble
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
acute toxicity, health hazards
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg
Danger
H300, H310, H330, H361
P201, P202, P260, P262, P264, P270, P271, P280, P281, P284, P301+P310, P302+P350, P304+P340, P308+P313, P310, P320, P321, P322, P330, P361, P363, P403+P233, P405, P501
Safety data sheet (SDS) Cytochalasin B MSDS from Fermentek
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Cytochalasin B, the name of which comes from the Greek cytos (cell) and chalasis (relaxation), [1] is a cell-permeable mycotoxin. It was found that substoichiometric concentrations of cytochalasin B (CB) strongly inhibit network formation by actin filaments. Due to this, it is often used in cytological research. It inhibits cytoplasmic division by blocking the formation of contractile microfilaments. It inhibits cell movement and induces nuclear extrusion. Cytochalasin B shortens actin filaments by blocking monomer addition at the fast-growing end of polymers. [2] Cytochalasin B inhibits glucose transport [3] and platelet aggregation. It blocks adenosine-induced apoptotic body formation without affecting activation of endogenous ADP-ribosylation in leukemia HL-60 cells. [4] It is also used in cloning through nuclear transfer. Here enucleated recipient cells are treated with cytochalasin B. Cytochalasin B makes the cytoplasm of the oocytes more fluid and makes it possible to aspirate the nuclear genome of the oocyte within a small vesicle of plasma membrane into a micro-needle. Thereby, the oocyte genome is removed from the oocyte, while preventing rupture of the plasma membrane.

Contents

This alkaloid is isolated from a fungus, Helminthosporium dematioideum .

History

1960s

Cytochalasin B was first described in 1967, when it had been isolated from moulds by Dr W.B. Turner. [5] Smith et al. found that CB causes multinucleation in cells and significantly affects cell motility. The multinucleated cells probably arise from failure of mitotic control, leading to variations in size and shape of interphase nuclei. [6]

1970s

In the 1970s, research on the mitosis of polynucleated cells was done. It appeared that these cells were created through progressive nuclear addition instead of nuclear division. [7] The process by which this occurs is called pseudomitosis, which is the synchronous mitosis resulting in the division of just one nucleus. [7] The separate nuclei are bound by a nuclear bridge and in binucleated cells the centrioles are doubled. Furthermore, it was found that CB causes the disorganization of the 50Å microfilaments of mouse epithelial cells which causes the cells to lose their shape. [8] It also affects the appearance of young glands in cells and new gland formation [9] in other cells. Another group found that CB inhibits the ability of HeLa cells to undergo cytokinesis by decomposition of the contractile ring. [10] Research from 1971 showed that CB interferes with the release of iodine derived from thyroglobulin and blocks colloid endocytosis. [11] Moreover, it was found that CB has an inhibitory effect on the uptake of sucrose-3H by chang-strain human liver cells and in CB-treated cells alterations in the appearance and location of microfilaments were observed. [12] Furthermore, it was found that CB reversibly inhibits melanin granule movement in melanocytes. [13] One year later, research on the influence of cytochalasin B on chloroplasts was done. It was found that the light-oriented movement of chloroplasts is reversibly inhibited by cytochalasin B. [14] In 1973 researches found that cytochalasin B is a powerful non-competitive inhibitor of glucose transport. One of the major electrophoretic identifiable erythrocyte membrane proteins may be the cytochalasin B binding site of erythrocytes. [15]

From 1980

In the following years, the knowledge concerning cytochalasin B was broadened. As the more general knowledge had been elucidated, more detailed analysis of e.g. the mechanism of action took place.

Production

Cytochalasins can be isolated from the fungi in which they naturally occur. Originally, they were isolated from Helminthosporium dematioideum. Other producers include Phoma spp., Hormiscium spp. and Curvularia lunata . [16] Additionally, it can be synthesized in the laboratory. There are several approaches to do so. Firstly, it is possible to form the six-membered ring of the isoindolone core and the larger macrocyclic ring simultaneously in a late-stage intramolecular Diels-Alder cyclization. Secondly, it is possible to first form the isoindolone core in an intermolecular Diels-Alder reaction and in a second step append the macrocycle in a stepwise fashion. [17]

Properties

Cytochalasin B contains several highly polar keto- and hydroxyl groups and one peripheric lipophilic benzyl unit.

Mechanism

It is suggested that the predominant mechanism of cytochalasin B is the inhibition of actin filament polymerization through binding to the fast-growing (barbed) end of F-actin filaments. [18] [19] An alternative could involve capping proteins. By doing so, CB not only inhibits actin polymerization but also consecutive processes such as filament network build-up. This inhibition can affect all three major steps of actin polymerization

  1. Nucleation: A core of minimal 3 actin monomers is formed.
  2. Elongation: The core is used for elongation by addition of actin monomers.
  3. Steady state/Annealing: A balance between polymerisation and depolymerisation is reached (steady-state). The F-actin filament stops growing and two barbed ends fuse to create one filament.

Nucleation is essential for filament build-up. [20] The oligomerization is the rate-determining step, considering actin filament formation as a whole. The so-called lag phase of actin polymerization originates from this step. It takes quite a while until polymerization starts, but once it has, the process is autocatalytic until the physiological maximum of the polymerization rate is reached.

Elongation is favored at the barbed end of the growing filament. [21] Here, the influence of cytochalasin B strongly depends on the overall conditions for elongation. If ideal physiological conditions are present, the inhibitory influence of cytochalasin B is minuscule. If the conditions are less optimal, elongation can be inhibited by up to 90 percent. [17]

Annealing is the last step in polymerization. Cells treated with cytochalasin B and control group cells could not be distinguished. This indicated, that CB has no significant effect at this stage.

CB contains a beta-unsaturated ester which can undergo a Michael-type conjugation with nucleophiles. [22] If this is the case, DNA-adduction might be a plausible reaction afterwards. A more suitable reaction seems to be the one with thiol-groups of several biomolecules. [23] The thiol-groups would then no longer be available for disulfide bonds for further actin polymerization [24] and thus a crucial step in actin polymerization is inhibited as the barbed ends of the filaments are blocked. An analogue principle is used by the well-studied capping proteins which are responsible for a natural limiting factor of actin polymerization. The first step in actin polymerization, after polymerization is initiated, is the deprotonation of the thiol group of G-actin. This renders the sulfur atom charged and makes it available for actin polymerization. If cytochalasin B is present in the cell, the deprotonation of thiol is competed. The reactive beta-unsaturated ester group of cytochalasin B reacts with the thiol group of actin via a nucleophilic attack of the charged sulfur onto the beta-carbon atom. This forces the π-bond to get dislocated on the left site of the beta-carbon. Consequently, mesomerism occurs, dislocating the negative charge between the alpha-carbon and the oxygen atom. This step is followed by a protonation step to counteract the negative charge. The hydronium ion needed to do so was produced during the activation of the sulfur atom in an earlier step.

Metabolism

There are ten possible sites for the in vitro degradation of cytochalasin B. There is not yet any evidence that the same sites are used for degradation in vivo , but evidence has confirmed the in vitro sites. [25] Degradation is initialized by a periodate cleavage of the compound, [26] taking place at carbon 14 and 21. As a result, carbonic acid (A), formaldehyde (B), 5-methylhexane-1,1,6-triol (C) and a large remaining molecule (D) are released. Molecules C and D are then oxidized via Kuhn Roth reaction, leading to the formation of 7-hydroxyheptanal (F), acetic acid (G) and benzoic acid (I). Again, a larger molecule remains (J). F, G and I can undergo Schmidt reaction, if not degraded via acidic degradation by alcohol dehydrogenase (ADH) to methylamine and carbon dioxide (H). 7-hydroxyheptane is oxidized to 3-methylheptanedioic acid (K). Further metabolism leads to the formation of several smaller organic molecules such as amines (M), carbon dioxide (N) and acetic acid (O). The latter is again metabolized by ADH to methylamine and carbon dioxide (Q). Molecule J is cleaved into a number of small compounds such as acetic acid (L), methylamine and carbon dioxide (P), and a series of small methylated compounds. [26]

Efficacy and adverse effects

Interactions

When adding cytochalasin B and the beta-andrenergic agonist (-)-isoproterenol, prostaglandin E1 or cholera toxin to wild type S49 lymphoma cells, cAMP accumulates. [27] Cytochalasin B is unable to transform 3T3-like tumor cells, but it did increase the frequency of cell transformation by the polyoma virus 8-40 fold. [28] Furthermore, CB can intensify pinocytosis, which is induced by concanavalin A in amoeba proteus. [29] Cytochalasin B can also interact with the auxin indole-3-acetic acid which occurs in wheat coleoptile segments and maize roots. This interaction leads to the inhibition of vesicle transport and secretion of cell wall components and thereby blocks elongation and growth. [30]

Efficacy

In vitro studies showed that a concentration of 30 μM of cytochalasin B significantly reduces the relative viscosity of a 20 μM normal actin filament solution as well as it has decreased in a 20 μMm glutathionyl-actin filament solution. [31] In vivo the effective concentration is even lower. It seemed that a 2 μM concentration is sufficient in living cells to accomplish a measurable influence on the actin polymerization. The nucleation phase took 2-4 times as long as in the control groups. On elongation, the effects were minimal; on annealing negligible. [18] This might be due to an actual difference in molecular interactions of cytochalasin B during those three steps or simply due to the fact that the lag phase is the rate-determining step in the overall polymerization.

Applications

Actin polymerization studies

As cytochalasin B inhibits actin filament polymerization, many cellular processes depending on actin filament functions are affected. Cytokinesis is inhibited, however, mitosis is unaffected. Due to the effects on several cellular functions but lack of general toxicity, cytochalasin B is applied in actin polymerization studies, cell imaging methods, cell cycle studies and can possibly be used as anticancer drug. [1] [32]

Inhibits cell division

Cytochalasin B is used for testing of the genotoxicity of substances. In order to do so, cytokinesis-block micronucleus assay (CBMN assay) with human lymphocytes is applied. [33] This works in vitro. During anaphase of mitosis of meiosis, micronuclei can be detected. [34] These are small nuclei containing one chromosome or part of a chromosome which did not get to one of the cell poles during cell division. [35] The CBMN test is based on the fact that only dividing cells can express micronuclei, which means that only in those cells, chromosome damage can be detected. [33] Because genotoxicity causes abnormalities in cell division, micronuclei can be detected in binucleated cells. Cytokinesis, which is the next stage, is inhibited by cytochalasin B. A key advantage of this method is that it allows simultaneous detection of multiple molecular events leading to chromosome damage and chromosomal instability. [35] The CBMN assay has successfully been applied to normal human lymphocytes, mouse spleen lymphocytes, mouse fibroblasts and Chinese hamster fibroblasts. [36]

Inhibits cell movement

Cytochalasin B can decrease the number of motile cells when it is added to Yoshida Sarcoma Cells. It can also decrease the motility of the cells and dose-dependently inhibits their growth. [37] Since cytochalasin B unevenly penetrates cells it promotes focal contractions of the broken cortical actin filament network by myosin. This causes superprecipitation which requires active contractions and thus an active energy metabolism. The disorganized cortical contractions disrupt the assembly of pseudopodia which are involved in cell movement. [38]

Induces nuclear extrusion

Nuclear extrusion induced by cytochalasin B begins with the movement of the nucleus to the plasma membrane, followed by bulge formation in the membrane. The nucleus then moves to the outside of the membrane, but stays connected to the cell by a thread-like cytoplasmic bridge. If the cells are kept in cytochalasin B containing medium for several hours, the process becomes irreversible. Extrusion could be assisted by the CB-induced weakening of the plasma membrane. [39]

Inhibits glucose transport

It has been shown that cytochalasin B binds covalently to mammalian glucose transporter proteins when irradiated with UV light. [40] It bound tighter to AraE and GalP than their usual substrates. [41] Cytochalasin B has been shown to inhibit GLUT1, 2, 3 and 4. [42] Binding to GLUT1 occurs at the inside as cytochalasin B acts as it acts as a competitive inhibitor of glucose exit. [43] Additional evidence comes from photolabeling studies in which the Trp388 and Trp412 in TM10 and TM11 of the purified protein are labeled upon exposure to labeled cytochalasin B. Since mutating Trp388 and Trp412 does not completely reduce inhibition of GLUT1, it is assumed that other sites are involved in CB binding as well. [44]

Therapeutic uses

For therapeutic purposes, research on cytochalasin B is done. In order to do so, the effects of cytochalasin B on tumor cells by BCG (Bacillus Calmette-Guerin)-activated macrophages were examined. It showed that cytochalasin B enhances tumor cell lysis and stasis due to activated macrophages at a concentration of 10−7 M. Cytochalasin B does not act on the macrophage itself, but does exert its effect predominantly on the tumor cell. A reason for this could be, that the actin filament formation, which could be important for the destruction of tumor cells by activated macrophages, is inhibited by cytochalasin B. [45]

Further effects

Cytochalasin B has an effect on thyroid hormone and growth hormone secretion. [1] Phosphatidylcholine and phosphatidylethanolamine biosynthesis is inhibited by cytochalasin B, as shown by George et al. [46] It does so by inhibiting the conversion of phosphoethanolamine to cytidinediphosphate-ethanolamine. It was proposed that the mechanism is associated with alterations of intracellular calcium ions. Cytochalasin B also has effects on bacteria. For example, the growth and differentiation of E. histolytica is inhibited.[56] Furthermore, cytochalasin B has been shown to have an inhibitory effect on tumor cell growth without causing prolonged and/or profound immunosuppressive effects. [47]

Natural context

In nature, cytochalasin B is involved in fungal virulence, food spoilage and the maintenance of the symbiosis between host and symbiont. [37]

Related Research Articles

<span class="mw-page-title-main">Cytoskeleton</span> Network of filamentous proteins that forms the internal framework of cells

The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is composed of similar proteins in the various organisms. It is composed of three main components: microfilaments, intermediate filaments, and microtubules, and these are all capable of rapid growth or disassembly depending on the cell's requirements.

<span class="mw-page-title-main">Cytokinesis</span> Part of the cell division process

Cytokinesis is the part of the cell division process and part of mitosis during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of nuclear division in mitosis and meiosis. During cytokinesis the spindle apparatus partitions and transports duplicated chromatids into the cytoplasm of the separating daughter cells. It thereby ensures that chromosome number and complement are maintained from one generation to the next and that, except in special cases, the daughter cells will be functional copies of the parent cell. After the completion of the telophase and cytokinesis, each daughter cell enters the interphase of the cell cycle.

<span class="mw-page-title-main">Microfilament</span> Filament in the cytoplasm of eukaryotic cells

Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other proteins in the cell. Microfilaments are usually about 7 nm in diameter and made up of two strands of actin. Microfilament functions include cytokinesis, amoeboid movement, cell motility, changes in cell shape, endocytosis and exocytosis, cell contractility, and mechanical stability. Microfilaments are flexible and relatively strong, resisting buckling by multi-piconewton compressive forces and filament fracture by nanonewton tensile forces. In inducing cell motility, one end of the actin filament elongates while the other end contracts, presumably by myosin II molecular motors. Additionally, they function as part of actomyosin-driven contractile molecular motors, wherein the thin filaments serve as tensile platforms for myosin's ATP-dependent pulling action in muscle contraction and pseudopod advancement. Microfilaments have a tough, flexible framework which helps the cell in movement.

<span class="mw-page-title-main">Cleavage furrow</span> Plasma membrane invagination at the cell division site

In cell biology, the cleavage furrow is the indentation of the cell's surface that begins the progression of cleavage, by which animal and some algal cells undergo cytokinesis, the final splitting of the membrane, in the process of cell division. The same proteins responsible for muscle contraction, actin and myosin, begin the process of forming the cleavage furrow, creating an actomyosin ring. Other cytoskeletal proteins and actin binding proteins are involved in the procedure.

<span class="mw-page-title-main">Actin</span> Family of proteins

Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over 100 μM; its mass is roughly 42 kDa, with a diameter of 4 to 7 nm.

<span class="mw-page-title-main">Filopodia</span> Actin projections on the leading edge of lamellipodia of migrating cells

Filopodia are slender cytoplasmic projections that extend beyond the leading edge of lamellipodia in migrating cells. Within the lamellipodium, actin ribs are known as microspikes, and when they extend beyond the lamellipodia, they're known as filopodia. They contain microfilaments cross-linked into bundles by actin-bundling proteins, such as fascin and fimbrin. Filopodia form focal adhesions with the substratum, linking them to the cell surface. Many types of migrating cells display filopodia, which are thought to be involved in both sensation of chemotropic cues, and resulting changes in directed locomotion.

<span class="mw-page-title-main">ADF/Cofilin family</span> Family of actin-binding proteins

ADF/cofilin is a family of actin-binding proteins associated with the rapid depolymerization of actin microfilaments that give actin its characteristic dynamic instability. This dynamic instability is central to actin's role in muscle contraction, cell motility and transcription regulation.

<span class="mw-page-title-main">Cell cortex</span> Layer on the inner face of a cell membrane

The cell cortex, also known as the actin cortex, cortical cytoskeleton or actomyosin cortex, is a specialized layer of cytoplasmic proteins on the inner face of the cell membrane. It functions as a modulator of membrane behavior and cell surface properties. In most eukaryotic cells lacking a cell wall, the cortex is an actin-rich network consisting of F-actin filaments, myosin motors, and actin-binding proteins. The actomyosin cortex is attached to the cell membrane via membrane-anchoring proteins called ERM proteins that plays a central role in cell shape control. The protein constituents of the cortex undergo rapid turnover, making the cortex both mechanically rigid and highly plastic, two properties essential to its function. In most cases, the cortex is in the range of 100 to 1000 nanometers thick.

Cytochalasins are fungal metabolites that have the ability to bind to actin filaments and block polymerization and the elongation of actin. As a result of the inhibition of actin polymerization, cytochalasins can change cellular morphology, inhibit cellular processes such as cell division, and even cause cells to undergo apoptosis. Cytochalasins have the ability to permeate cell membranes, prevent cellular translocation and cause cells to enucleate. Cytochalasins can also have an effect on other aspects of biological processes unrelated to actin polymerization. For example, cytochalasin A and cytochalasin B can also inhibit the transport of monosaccharides across the cell membrane, cytochalasin H has been found to regulate plant growth, cytochalasin D inhibits protein synthesis and cytochalasin E prevents angiogenesis.

The latrunculins are a family of natural products and toxins produced by certain sponges, including genus Latrunculia and Negombata, whence the name is derived. It binds actin monomers near the nucleotide binding cleft with 1:1 stoichiometry and prevents them from polymerizing. Administered in vivo, this effect results in disruption of the actin filaments of the cytoskeleton, and allows visualization of the corresponding changes made to the cellular processes. This property is similar to that of cytochalasin, but has a narrow effective concentration range. Latrunculin has been used to great effect in the discovery of cadherin distribution regulation and has potential medical applications. Latrunculin A, a type of the toxin, was found to be able to make reversible morphological changes to mammalian cells by disrupting the actin network.

<span class="mw-page-title-main">Cytochalasin E</span> Chemical compound

Cytochalasin E, a member of the cytochalasin group, is an inhibitor of actin polymerization in blood platelets. It inhibits angiogenesis and tumor growth. Unlike cytochalasin A and cytochalasin B, it does not inhibit glucose transport. Cytochalasin E, however, was noted to decrease glucose absorption in mice around the intestinal tissues by increasing the Km needed for glucose to reach the Vmax, which meant that a higher concentration of glucose was required in its presence to attain Vmax. Since Vmax remained the same according to another study, it is evident that CE is indeed a competitive inhibitor at the intestinal receptor sites for glucose.

<span class="mw-page-title-main">Protein filament</span> Long chain of protein monomers

In biology, a protein filament is a long chain of protein monomers, such as those found in hair, muscle, or in flagella. Protein filaments form together to make the cytoskeleton of the cell. They are often bundled together to provide support, strength, and rigidity to the cell. When the filaments are packed up together, they are able to form three different cellular parts. The three major classes of protein filaments that make up the cytoskeleton include: actin filaments, microtubules and intermediate filaments.

<span class="mw-page-title-main">Tropomodulin</span>

Tropomodulin (TMOD) is a protein which binds and caps the minus end of actin, regulating the length of actin filaments in muscle and non-muscle cells.

CapZ, also known as CAPZ, CAZ1 and CAPPA1, is a capping protein that caps the barbed end of actin filaments in muscle cells.

<span class="mw-page-title-main">Actin assembly-inducing protein</span>

The Actin assembly-inducing protein (ActA) is a protein encoded and used by Listeria monocytogenes to propel itself through a mammalian host cell. ActA is a bacterial surface protein comprising a membrane-spanning region. In a mammalian cell, the bacterial ActA interacts with the Arp2/3 complex and actin monomers to induce actin polymerization on the bacterial surface generating an actin comet tail. The gene encoding ActA is named actA or prtB.

Actin remodeling is the biochemical process that allows for the dynamic alterations of cellular organization. The remodeling of actin filaments occurs in a cyclic pattern on cell surfaces and exists as a fundamental aspect to cellular life. During the remodeling process, actin monomers polymerize in response to signaling cascades that stem from environmental cues. The cell's signaling pathways cause actin to affect intracellular organization of the cytoskeleton and often consequently, the cell membrane. Again triggered by environmental conditions, actin filaments break back down into monomers and the cycle is completed. Actin-binding proteins (ABPs) aid in the transformation of actin filaments throughout the actin remodeling process. These proteins account for the diverse structure and changes in shape of Eukaryotic cells. Despite its complexity, actin remodeling may result in complete cytoskeletal reorganization in under a minute.

<span class="mw-page-title-main">Rho-associated protein kinase</span>

Rho-associated protein kinase (ROCK) is a kinase belonging to the AGC family of serine-threonine specific protein kinases. It is involved mainly in regulating the shape and movement of cells by acting on the cytoskeleton.

<span class="mw-page-title-main">MDia1</span> Protein

mDia1 is a member of the protein family called the formins and is a Rho effector. It is the mouse version of the diaphanous homolog 1 of Drosophila. mDia1 localizes to cells' mitotic spindle and midbody, plays a role in stress fiber and filopodia formation, phagocytosis, activation of serum response factor, formation of adherens junctions, and it can act as a transcription factor. mDia1 accelerates actin nucleation and elongation by interacting with barbed ends of actin filaments. The gene encoding mDia1 is located on Chromosome 18 of Mus musculus and named Diap1.

<span class="mw-page-title-main">Arp2/3 complex</span> Macromolecular complex

Arp2/3 complex is a seven-subunit protein complex that plays a major role in the regulation of the actin cytoskeleton. It is a major component of the actin cytoskeleton and is found in most actin cytoskeleton-containing eukaryotic cells. Two of its subunits, the Actin-Related Proteins ARP2 and ARP3, closely resemble the structure of monomeric actin and serve as nucleation sites for new actin filaments. The complex binds to the sides of existing ("mother") filaments and initiates growth of a new ("daughter") filament at a distinctive 70-degree angle from the mother. Branched actin networks are created as a result of this nucleation of new filaments. The regulation of rearrangements of the actin cytoskeleton is important for processes like cell locomotion, phagocytosis, and intracellular motility of lipid vesicles.

<span class="mw-page-title-main">Cytoskeletal drugs</span> Substances or medications that interact with actin or tubulin

Cytoskeletal drugs are small molecules that interact with actin or tubulin. These drugs can act on the cytoskeletal components within a cell in three main ways. Some cytoskeletal drugs stabilize a component of the cytoskeleton, such as taxol, which stabilizes microtubules, or Phalloidin, which stabilizes actin filaments. Others, such as Cytochalasin D, bind to actin monomers and prevent them from polymerizing into filaments. Drugs such as demecolcine act by enhancing the depolymerisation of already formed microtubules. Some of these drugs have multiple effects on the cytoskeleton: for example, Latrunculin both prevents actin polymerization as well as enhancing its rate of depolymerization. Typically the microtubule targeting drugs can be found in the clinic where they are used therapeutically in the treatment of some forms of cancer. As a result of the lack of specificity for specific type of actin, the use of these drugs in animals results in unacceptable off-target effects. Despite this, the actin targeting compounds are still useful tools that can be used on a cellular level to help further our understanding of how this complex part of the cells' internal machinery operates. For example, Phalloidin that has been conjugated with a fluorescent probe can be used for visualizing the filamentous actin in fixed samples.

References

  1. 1 2 3 Scherlach, K; et al. (2010). "The chemistry and biology of cytochalasans". Natural Product Reports. 27 (6): 869–86. doi:10.1039/b903913a. PMID   20411198.
  2. ↑ Theodoropoulos, PA; Gravanis, A; Tsapara, A; Margioris, AN; Papadogiorgaki, E; Galanopoulos, V; Stournaras, C (1994). "Cytochalasin B may shorten actin filaments by a mechanism independent of barbed end capping". Biochemical Pharmacology. 47 (10): 1875–81. doi:10.1016/0006-2952(94)90318-2. PMID   8204105.
  3. ↑ Jung, C. Y.; Rampal, A. L. (1977). "Cytochalasin B binding sites and glucose transport carrier in human erythrocyte ghosts". The Journal of Biological Chemistry. 252 (15): 5456–5463. doi: 10.1016/S0021-9258(19)63372-7 . PMID   885863.
  4. ↑ Tanaka, Y.; Yoshihara, K.; Tsuyuki, M.; Kamiya, T. (1994). "Apoptosis Induced by Adenosine in Human Leukemia HL-60 Cells". Experimental Cell Research. 213 (1): 242–559. doi:10.1006/excr.1994.1196. PMID   8020596.
  5. ↑ Smith, GF; Ridler, MA; Faunch, JA (16 December 1967). "Action of Cytochalasin B on Cultured Human Lymphocytes". Nature. 216 (5120): 1134–1135. Bibcode:1967Natur.216.1134S. doi:10.1038/2161134a0. PMID   6075266. S2CID   4186253.
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  7. 1 2 Smith, G; O'Hara, P; Ridler, M (1970). "The Production of Multinucleated Lymphocytes by Cytochalasin B. An Electron Microscopic Study". Pediatric Research. 4 (5): 441. doi: 10.1203/00006450-197009000-00032 .
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  46. ↑ George, TP; et al. (1991). "Inhibition of Phosphatidylcholine and Phosphatidylethanoamine Biosynthesis by Cytochalasin B in Cultured Glioma Cells: Potential Regulation of Biosynthesis by Ca2+-Dependent Mechanisms". Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism. 1084 (2): 185–193. doi:10.1016/0005-2760(91)90219-8. PMID   1854804.
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