Identification of trichoplein, a novel keratin filament-binding protein

Abstract

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.

Trichoplein controls microtubule anchoring at the centrosome by binding to Odf2 and ninein

“…1B,C). These staining patterns confirm the previous observation that trichoplein localizes to keratin IFs and desmosomes in the epithelia (Nishizawa et al, 2005).…”

“…Nishizawa and colleagues (Nishizawa et al, 2005) previously reported that trichoplein keratin filament-binding protein (trichoplein or TCHP) serves as a keratin IF scaffold protein.…”

Biological Functions of Cytokeratin 18 in Cancer

“…In addition to plectin and H3 histones, trichoplein and Albatross were also identified as CK8/18-binding proteins (32,33). Trichoplein shows a low degree of sequence similarity to trichohyalin, plectin, and myosin heavy chain, and colocalizes with CK8/18 filaments in HeLa cells (32).…”

“…Trichoplein shows a low degree of sequence similarity to trichohyalin, plectin, and myosin heavy chain, and colocalizes with CK8/18 filaments in HeLa cells (32). Trichoplein may be involved in the organization of the apical network of keratin filaments and desmosomes in simple epithelial cells (32). Albatross (also known as Fas-binding factor-1) also has a trichohyalin and plectin homology (TPHD) domain, which binds to CK18 directly in a yeast two-hybrid system.…”

Dynamics and unexpected localization of the plakin binding protein, kazrin, in mouse eggs and early embryos

“…healing, and overall tissue integrity (McLean et al, 1996;Boudreau and Bissell, 1998;Gallicano, 2001;Gallicano et al, 2001;Leung et al, 2002;Grossmann et al, 2004;Setzer et al, 2004;Weber et al, 2004;Nishizawa et al, 2005). One of the oldest known, and yet still growing, family of cytoskeletal crosslinking proteins is the plakin family (Leung et al, 2002).…”