Fodrin: axonally transported polypeptides associated with the internal periphery of many cells.

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Abstract
Fodrin (formerly designated 26 and 27) comprises 2 polypeptides (250,000 and 240,000 MW) that are axonally transported at a maximum time-averaged velocity of 40 mm/d-slower than the most rapidly moving axonally transported proteins, but faster than at least 3 additional groups of proteins. The intracellular distribution of fodrin is reported. Fodrin was purified from guinea pig brain, and a specific antifodrin antibody was produced in rabbit and used to localize fodrin in tissue sections and cultured cells by indirect immunofluorescence. Fodrin antigens were highly concentrated in the cortical cytoplasm of neurons and nonneuronal tissues (e.g., skeletal muscle, uterus, intestinal epithelium). Their disposition resembles a lining of the cell. In cultured fibroblasts, immunofluorescently labeled fodrin antigens were arranged in parallel arrays of bands in the plane of the plasma membrane, possibly reflecting an exclusion of labeled fodrin from some areas occupied by stress fibers. The distribution of fodrin antigens in mouse 3T3 cells transformed with simian virus 40 was more diffuse, indicating that the disposition of fodrin is responsive to altered physiological states of the cell. When mixtures of fodrin and F-actin were centrifuged, fodrin cosedimented with the actin, indicating that these proteins interact in vitro. Fodrin is a specific component of the cortical cytoplasm of many cells. It may be indirectly attached to the plasma membrane via cortical actin filaments. Fodrin may be mobile within the cortical cytoplasm; in axons a cortical lining may be in constant motion relative to the internal cytoplasm. Fodrin could serve to link other proteins and organelles to a submembrane force-generating system.