Identification of trichoplein, a novel keratin filament-binding protein

J Cell Sci. 2005 Mar 1;118(Pt 5):1081-90. doi: 10.1242/jcs.01667.


Keratins 8 and 18 (K8/18) are major components of the intermediate filaments (IFs) of simple epithelia. We report here the identification of a novel protein termed trichoplein. This protein shows a low degree of sequence similarity to trichohyalin, plectin and myosin heavy chain, and is a K8/18-binding protein. Among interactions between trichoplein and various IF proteins that we tested using two-hybrid methods, trichoplein interacted significantly with K16 and K18, and to some extent with K5, K6a, K8 and K14. In in vitro co-sedimentation assays, trichoplein directly binds to K8/18, but not with vimentin, desmin, actin filaments or microtubules. An antibody raised against trichoplein specifically recognized a polypeptide with a relative molecular mass of 61 kDa in cell lysates. Trichoplein was immunoprecipitated using this antibody in a complex with K8/18 and immunostaining revealed that trichoplein colocalized with K8/18 filaments in HeLa cells. In polarized Caco-2 cells, trichoplein colocalized not only with K8/18 filaments in the apical region but also with desmoplakin, a constituent of desmosomes. In the absorptive cells of the small intestine, trichoplein colocalized with K8/18 filaments at the apical cortical region, and was also concentrated at desmosomes. Taken together, these results suggest that trichoplein is a keratin-binding protein that may be involved in the organization of the apical network of keratin filaments and desmosomes in simple epithelial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Caco-2 Cells
  • Carrier Proteins / chemistry
  • Carrier Proteins / physiology*
  • Cell Line, Tumor
  • Cloning, Molecular
  • Cytoskeletal Proteins / metabolism
  • DNA, Complementary / metabolism
  • Desmoplakins
  • Desmosomes / metabolism
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Humans
  • Immunoprecipitation
  • Intermediate Filament Proteins / chemistry
  • Intermediate Filaments / metabolism*
  • Keratin-18
  • Keratin-8
  • Keratins / chemistry*
  • Keratins / metabolism*
  • Mice
  • Microscopy, Electron
  • Microscopy, Fluorescence
  • Microtubules / chemistry
  • Molecular Sequence Data
  • Myosin Heavy Chains / chemistry
  • Peptides / chemistry
  • Plectin
  • Polymerase Chain Reaction
  • Protein Binding
  • Protein Precursors / chemistry
  • Protein Structure, Tertiary
  • Recombinant Proteins / metabolism
  • Transfection
  • Tubulin / chemistry
  • Two-Hybrid System Techniques


  • Carrier Proteins
  • Cytoskeletal Proteins
  • DNA, Complementary
  • DSP protein, human
  • Desmoplakins
  • Dsp protein, mouse
  • Intermediate Filament Proteins
  • KRT18 protein, human
  • KRT8 protein, human
  • Keratin-18
  • Keratin-8
  • PLEC protein, human
  • Peptides
  • Plec protein, mouse
  • Plectin
  • Protein Precursors
  • Recombinant Proteins
  • TCHP protein, human
  • Tubulin
  • trichohyalin
  • Green Fluorescent Proteins
  • Keratins
  • Myosin Heavy Chains