Expression of the β subunit of spectrin in nonerythroid cells
Antibodies raised against electrophoretically purified chicken erythrocyte β subunit of spectrin, called "β-spectrin," have been used to demonstrate the presence of an immunoreactive form of this polypeptide in nonerythroid tissues. Immunoautoradiography shows that, in chicken erythrocytes, this antiserum reacts with β-spectrin (M_r 220,000) and another polypeptide (M_r 230,000) that, by two-dimensional tryptic peptide analysis, shows extensive homology with β-spectrin but not with the alpha subunit of spectrin, called "α-spectrin." Immunoautoradiography and immunoprecipitation of various chicken tissues with this antiserum shows that either one variant or both variants of β-spectrin are expressed. Indirect immunofluorescence reveals that the antiserum reacts with a plasma membrane-associated component of erythroid and some nonerythroid cells. Particularly strong fluorescence is observed in skeletal and cardiac muscle cells where β-spectrin appears to form a grid-like network along the inner surface of the sarcolemma. The noncoordinated distribution of α- and β-spectrin variants indicates that their expression may be tailored to the functional requirements of the plasma membrane in different cells.
Additional Information© 1983 National Academy of Sciences. Communicated by Norman H. Horowitz, October 7, 1982. We are grateful to Dr. B. L. Granger, J. J. Ngai, and R. Gomer for advice during various parts of this study and to Dr. B. L. Granger for his cogent comments on the manuscript. This work was supported by grants from the National Institutes of Health, the National Science Foundation, and the Muscular Dystrophy Association of America and by a Biomedical Research Support Grant to the Division of Biology, California Institute of Technology, W.J.N. also was supported by an international fellowship from the Cancer Research Campaign awarded by the International Union Against Cancer. E.L. is a recipient of a Research Career Development Award from the National Institutes of Health. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.
Published - PNAS-1983-Nelson-363-7.pdf