Microfilaments cortical

Two of the cytoskeletal components, the actin filaments and the microtubules have been studied with molecular rotors. The main component of the actin filaments is the actin protein, a 44 kD molecule found in two forms within the cell the monomeric globulin form (G-actin) and the filament form (F-actin). Actin binds with ATP to form the microfilaments that are responsible for cell shape and motility. The rate of polymerization from the monomeric form plays a vital role in cell movement and signaling. Actin filaments form the cortical mesh that is the basis of the cytoskeleton. The cytoskeleton has an active relationship with the plasma membrane. Functional proteins found in both structures... 

The cytoskeleton is found near the axonal membrane and consists of microfilaments linked internally to microtubules and the plasma membrane by a network of filamentous protein that includes the brain-specific protein fodrin. This protein forms attachment sites for integral membrane proteins either by means of the neuronal cell adhesion molecule (N-CAM) or indirectly by means of a specific protein called ankyrin in the case of the sodium channels. This may provide a means whereby the sodium channels are concentrated in the region of the nodes of Ranvier. Thus the cortical cytoskeleton plays a vital role in neuronal function by acting as an attachment site for various receptors and ion channels, but also for s)maptic vesicles at nerve terminals, thereby providing a mechanism for concentrating the vesicles prior to the release of the neurotransmitter. 

In addition, several annexins have been shown to interact directly or indirectly with actin microfilaments and microtubules, thus annexins have the potential to form a structural link between the membrane and the underlying cortical cytoskeleton (reviewed in Gerke et al. 2005 Hayes et al., 2004). As well as lateral inter-annexin interactions (either homotypic or heterotypic with other types of annexin)... 

Cortical spectrin-actin networks are attached to the cell membrane by bivalent membrane-microfilament binding proteins such as ankyrin and band 4.1 (see Figure 5-31). 

With respect to the mechanical properties of the plasma membrane the microfilament system is considered the most important since a network of these filaments imderhes the plasma membrane and stabilizes it. This membrane supporting network of actin filaments is often called the cortical actin. In order to test whether the mechanical properties of the membrane (de-... 

Actin polymers form the thin filaments (also called microfilaments) in the cell that are organized into compact ordered bundles or loose network arrays by cross-linking proteins. Short actin filaments bind to the cross-linking protein spectrin to form the cortical actin skeleton network (see Fig. 10.6). In muscle cells, long actin fdaments combine with thick filaments, composed of the protein myosin, to produce muscle contraction. The assembly of G-actin subunits into polymers, bundling of fibers, and attachments of actin to spectrin and to the plasma membrane proteins and organelles, are mediated by a number of actin-binding proteins and G-proteins from the Rho family. 

As indicated above, the macrofibrils in human hair contain subfilamentous structures called intermediate filaments (IF) or microfibrils (microfilaments), arranged in spiral formation in the cortical cells. The radius of each spiral, the macrofibril, is approximately 4,000 angstroms [99], and the width or diameter of an intermediate filament is close to 75 angstroms (see Figure 1-17). 

Mayboroda O, Schliiter K, Jockusch BM (1997) Differential colocalization of profilin with microfilaments in RK2 cells. Cell Motil. Cell Motil Cytoskeleton 37 166-177 McCollum D, Feoktistova A, Morphew M, Balasubramanian M, Gould KL (1996) The Schizosaccharomyces pombe actin-related protein, Arp3, is a component of the cortical actin cytoskeleton and interacts with profilin. EMBO J 15 6438-6446... 

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