Bpag1 localization to actin filaments and to the nucleus is regulated by its N-terminus

J Cell Sci. 2003 Nov 15;116(Pt 22):4543-55. doi: 10.1242/jcs.00764.

Abstract

Plakins are a family of giant cytoskeleton binding proteins. One member of this group is bullous pemphigoid antigen 1 (Bpag1)/dystonin, which has neuronal and muscle isoforms that consist of actin-binding and microtubule-binding domains at either end separated by a plakin domain and several spectrin repeats. The better-characterized epithelial isoform has only the plakin domain in common with the neuronal and muscle isoforms. Here, we have analyzed the localization of muscle/neuronal (Bpag1a/b) isoforms and the epithelial (Bpag1e) isoform within C2C12 myoblast cells. Although an antibody specific to Bpag1a/b isoform 2 detected protein co-aligning actin stress fibers, this same antibody and two Bpag1e antibodies predominantly detected protein in the nuclei. A Bpag1a/b isoform 2 N-terminal fusion protein containing the plakin domain also localized to actin stress fibers and to nuclei. Within the plakin domain, we characterized a functional nuclear localization signal, which was responsible for localization of the fusion protein to the nucleus. Bpag1a/b isoform 1 N-terminal fusion proteins differed in their interaction with the actin cytoskeleton and with their ability to localize to the nucleus, suggesting that Bpag1 isoforms with different N-termini have differing roles. These results show the importance of N-terminal domains in dictating the localization and function of Bpag1 isoforms. We provide the first indication that Bpag1 is not strictly a cytoplasmic/membrane protein but that it can also localize to the nucleus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / metabolism*
  • Amino Acid Sequence
  • Animals
  • Autoantigens / metabolism*
  • COS Cells
  • Carrier Proteins / metabolism
  • Cell Nucleus / metabolism*
  • Cells, Cultured
  • Chlorocebus aethiops
  • Collagen / metabolism*
  • Collagen Type XVII
  • Cytoskeletal Proteins / metabolism
  • Cytoskeleton / metabolism*
  • Dystonin
  • Fluorescent Antibody Technique
  • Molecular Sequence Data
  • Myoblasts / metabolism*
  • Nerve Tissue Proteins / metabolism
  • Non-Fibrillar Collagens*
  • Nuclear Localization Signals / metabolism
  • Protein Binding
  • Protein Isoforms / metabolism
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Stress Fibers / metabolism

Substances

  • Autoantigens
  • Carrier Proteins
  • Cytoskeletal Proteins
  • Dst protein, mouse
  • Dystonin
  • Nerve Tissue Proteins
  • Non-Fibrillar Collagens
  • Nuclear Localization Signals
  • Protein Isoforms
  • Recombinant Fusion Proteins
  • Collagen