We have recently found that the erythroid ankyrin gene, Ank1, expresses isoforms in mouse skeletal muscle, several of which share COOH-terminal sequence with previously known Ank1 isoforms but have a novel, highly hydrophobic 72–amino acid segment at their NH2 termini. Here, through the use of domainspecific peptide antibodies, we report the presence of the small ankyrins in rat and rabbit skeletal muscle and demonstrate their selective association with the sarcoplasmic reticulum. In frozen sections of rat skeletal muscle, antibodies to the spectrin-binding domain (anti-p65) react only with a 210-kD Ank1 and label the sarcolemma and nuclei, while antibodies to the COOH terminus of the small ankyrin (anti-p6) react with peptides of 20 to 26 kD on immunoblots and decorate the myoplasm in a reticular pattern. Mice homozygous for the normoblastosis mutation (gene symbol nb) are deficient in the 210-kD ankyrin but contain normal levels of the small ankyrins in the myoplasm. In nb/nb skeletal muscle, anti-p65 label is absent from the sarcolemma, whereas anti-p6 label shows the same distribution as in control skeletal muscle. In normal skeletal muscle of the rat, anti-p6 decorates Z lines, as defined by antidesmin distribution, and is also present at M lines where it surrounds the thick myosin filaments. Immunoblots of the proteins isolated with rabbit sarcoplasmic reticulum indicate that the small ankyrins are highly enriched in this fraction. When expressed in transfected HEK 293 cells, the small ankyrins are distributed in a reticular pattern resembling the ER if the NH2-terminal hydrophobic domain is present, but they are uniformly distributed in the cytosol if this domain is absent. These results suggest that the small ankyrins are integral membrane proteins of the sarcoplasmic reticulum. We propose that, unlike the 210-kD form of Ank1, previously localized to the sarcolemma and believed to be a part of the supporting cytoskeleton, the small Ank1 isoforms may stabilize the sarcoplasmic reticulum by linking it to the contractile apparatus.
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10 February 1997
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February 10 1997
Small, Membrane-bound, Alternatively Spliced Forms of Ankyrin 1 Associated with the Sarcoplasmic Reticulum of Mammalian Skeletal Muscle
Daixing Zhou,
Daixing Zhou
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
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Connie S. Birkenmeier,
Connie S. Birkenmeier
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
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McRae W. Williams,
McRae W. Williams
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
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John J. Sharp,
John J. Sharp
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
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Jane E. Barker,
Jane E. Barker
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
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Robert J. Bloch
Robert J. Bloch
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
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Daixing Zhou
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
Connie S. Birkenmeier
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
McRae W. Williams
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
John J. Sharp
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
Jane E. Barker
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
Robert J. Bloch
*Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201; and ‡The Jackson Laboratory, Bar Harbor, Maine 04609
Address all correspondence to Robert J. Bloch, Department of Physiology, University of Maryland School of Medicine, 660 W. Redwood St., Baltimore, MD 21201. Tel.: (410) 706-3020. Fax: (410) 706-2894. E-mail: [email protected]
Received:
July 02 1996
Revision Received:
November 04 1996
Online ISSN: 1540-8140
Print ISSN: 0021-9525
1997
J Cell Biol (1997) 136 (3): 621–631.
Article history
Received:
July 02 1996
Revision Received:
November 04 1996
Citation
Daixing Zhou, Connie S. Birkenmeier, McRae W. Williams, John J. Sharp, Jane E. Barker, Robert J. Bloch; Small, Membrane-bound, Alternatively Spliced Forms of Ankyrin 1 Associated with the Sarcoplasmic Reticulum of Mammalian Skeletal Muscle. J Cell Biol 10 February 1997; 136 (3): 621–631. doi: https://doi.org/10.1083/jcb.136.3.621
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