Cytochalasins are

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

metabolites that have the ability to bind to

actin 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 ...

filaments and block

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer, monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are ...

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 Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...

, and even cause cells to undergo

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...

. 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 Cytochalasin D is a member of the class of mycotoxins known as cytochalasins. Cytochalasin D is an alkaloid produced by Helminthosporium and other molds. Cytochalasin D is a cell-permeable and potent inhibitor of actin polymerization. It disrupts ...

inhibits protein synthesis and cytochalasin E prevents angiogenesis.

Binding to actin filaments

Cytochalasins are known to bind to the barbed, fast growing plus ends of

microfilaments 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 pr ...

, which then blocks both the assembly and disassembly of individual actin monomers from the bound end. Once bound, cytochalasins essentially cap the end of the new actin filament. One cytochalasin will bind to one actin filament. Studies done with

(CD) have found that CD-actin dimers contain ATP-bound actin upon formation. These CD-actin dimers are reduced to CD-actin monomers as a result of ATP hydrolysis. The resulting CD-actin monomer can bind ATP-actin monomer to reform the CD-actin dimer. CD is very effective; only low concentrations (0.2 μM) are needed to prevent membrane ruffling and disrupt treadmilling. The effects of many different cytochalasins on actin filaments were analyzed and higher concentrations (2-20 μM) of CD were found to be needed to remove stress fibers. In contrast, latrunculin inhibits actin filament polymerization by binding to actin monomers.

Uses and applications of cytochalasins

Actin microfilaments have been widely studied using cytochalasins. Due to their chemical nature, cytochalasins can help researchers understand the importance of actin in various biological processes. The use of cytochalasins has allowed researchers to better understand actin polymerization, cell motility, ruffling, cell division, contraction, and cell stiffness. The use of cytochalasins has been so important to understanding cytoskeletal movement and many other biological processes, researchers have created two synthetic cytochalasins. Cytochalasin has found practical application in thromboelastometry (TEM) whole blood assays for the assessment of fibrinogen and fibrin polymerization disorders in the FIBTEM assay on ROTEM. This test is based on the principle that

very effectively inhibits platelet function by inhibition of the contractile elements. The platelet inhibition is more effective than when platelets are blocked by

GPIIb/IIIa In medicine, glycoprotein IIb/IIIa (GPIIb/IIIa, also known as integrin αIIbβ3) is an integrin complex found on platelets. It is a receptor for fibrinogen and von Willebrand factor and aids platelet activation. The complex is formed via calcium ...

antagonists An antagonist is a character in a story who is presented as the chief foe of the protagonist. Etymology The English word antagonist comes from the Greek ἀνταγωνιστής – ''antagonistēs'', "opponent, competitor, villain, enemy, riv ...

. In vitro and clinical data indicate that the clot strength in FIBTEM increases in a fibrinogen concentration-dependent manner independent of platelet count. Therefore, fibrinogen deficiency or fibrin polymerization disorders can be rapidly detected.

Chemical structures

File:Cytochalasin A.png, Cytochalasin A File:Cytochalasin B.png, Cytochalasin B File:Cytochalasin C.png, Cytochalasin C File:Cytochalasin D.png,

Cytochalasin D Cytochalasin D is a member of the class of mycotoxins known as cytochalasins. Cytochalasin D is an alkaloid produced by Helminthosporium and other molds. Cytochalasin D is a cell-permeable and potent inhibitor of actin polymerization. It disrupts ...

File:Cytochalasin E.png, Cytochalasin E File:Cytochalasin F.png, Cytochalasin F File:Cytochalasin H.png, Cytochalasin H File:Cytochalasin J.png, Cytochalasin J

References

{{Toxins Mycotoxins Actin inhibitors

Binding to actin filaments

Uses and applications of cytochalasins

Chemical structures

See also

References