Ankyrin microfilaments

This spectrin network further binds to actin microfilaments and to numerous other ligands. These associations are probably dynamic. For example, phosphorylation of ankyrin can alter its affinity for spectrin. The functions of the multiple protein-interaction domains of both spectrin and ankyrin have been as yet only partially defined (see Ch. 8). 

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. 

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). 

Both microfilaments and microtubules undergo carefully regulated disassembly to and reassembly from their component molecules chiefly actin and tubulin respectively. They influence cell shape. Microfilament roles include cell locomotion, cell adhesion, cell division and endocytosis. The structural status of microfilaments may be modulated by over 30 different proteins some of which, e.g. ankyrin, spectrin... 

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See also in sourсe #XX -- [ , ]

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