Erythrocyte ankyrin: immunoreactive analogues are associated with mitotic structures in cultured cells and with microtubules in brain

Abstract

Human erythrocyte ankyrin, the membrane attachment protein for spectrin, has been detected by radioimmunoassay in a variety of cells and tissues. This report identifies polypeptides crossreacting with ankyrin in brain and HeLa cells and demonstrates that one function of these ankyrin analogues involves association with microtubules. Ankyrin immunoreactivity was localized by indirect immunofluorescence in a colchicine- and detergent-sensitive cytoplasmic meshwork in interphase cells. There also was specific nuclear staining, localized in a bright spots, which was displaced entirely by ankyrin or by high molecular weight microtubule-associated proteins (MAPs) from brain. In dividing cells, the punctate nuclear staining and the meshwork disappeared. Fluorescence was localized at the spindle pole during metaphase and was redistributed to the cleavage furrow in later stages of mitosis. An immunoreactive Mr 370,000 polypeptide comigrating with MAP1 was identified in brain extracts and copolymerized with microtubules through repeated cycles of polymerization and depolymerization. Finally, erythrocyte ankyrin associated with microtubules prepared from pure tubulin, and this binding was displaced by brain MAPs.