A new 82-kD barbed end-capping protein (radixin) localized in the cell-to-cell adherens junction: purification and characterization.

Abstract

An 82-kD protein has been purified from the undercoat of the adherens junction isolated from the rat liver. The purification scheme includes low salt extraction followed by DEAE-cellulose ion exchange, DNase I- actin affinity, and carboxyl methyl-cellulose ion exchange chromatographies. The purified 82-kD protein was essentially free of contaminants as judged by SDS-PAGE combined with silver staining. The substoichiometric 82-kD protein largely inhibited the actin filament assembly; when the molar ratio of the 82-kD protein to G-actin was 1:1,000, the viscosity was reduced to 28% of the control value. Direct electron microscopic studies revealed that the 82-kD protein selectively inhibited monomer addition at the barbed ends of actin filaments. By use of the antibody raised against the 82-kD protein, this protein was shown by immunofluorescence microscopy to be localized at the cell-to-cell adherens junction in various types of cells. In contrast, the 82-kD protein was not concentrated at the cell-to- substrate adherens junctions (focal contacts). These findings have led us to conclude that the 82-kD protein is a barbed end-capping protein which is associated with the undercoat of the cell-to-cell adherens junction. Hence, we have tentatively designated the 82-kD protein as radixin (from the Latin word radix meaning root).

Polarized distribution of actin isoforms in gastric parietal cells.

“…Talin links the fibronectin receptor to the actin cytoskeleton via vinculin and a-actinin (Rees et al, 1990). Radixin, one ERM family member originally isolated from the adherens junction of hepatocyte, has shown actin-binding activity via capping the barbed end of actin filament in vitro (Tsukita et al, 1989). Those authors subsequently showed that radixin is highly concentrated at the cleavage furrow in a variety of culture cells during cytokinesis, which implies that radixin might modulate the actin filament-plasma membrane interaction at the furrow (Sato et al, 1991).…”

Altered Expression of the ERM Proteins in Lung Adenocarcinoma

“…Radixin is a member of the ERM (ezrin/radixin/ moesin) family of proteins (Mangeat et al, 1999;Sato et al, 1992), which was first isolated as a constituent of adherence junctions in rat liver (Tsukita and Hieda, 1989). Ezrin was first purified as a component of intestinal microvilli that is tyrosine-phosphorylated by epidermal growth factor receptor (EGFR; Bretscher, 1989), and moesin was originally identified as a heparin-binding protein (Lankes and Furthmayr, 1991).…”

“…Identification of genes that are involved in tumorigenesis and in the progression of lung cancer will be required to formulate more effective therapies. One approach to the identification of such genes is to use differential display analysis (Bauer et al, 1993;Liang et al, , 1993Sager et al, 1993;Yoshikawa et al, 1998).Radixin is a member of the ERM (ezrin/radixin/ moesin) family of proteins (Mangeat et al, 1999;Sato et al, 1992), which was first isolated as a constituent of adherence junctions in rat liver (Tsukita and Hieda, 1989). Ezrin was first purified as a component of intestinal microvilli that is tyrosine-phosphorylated by epidermal growth factor receptor (EGFR; Bretscher, 1989), and moesin was originally identified as a heparin-binding protein (Lankes and Furthmayr, 1991).…”

Ezrin, Radixin and Moesin: Minor Molecule with Major Impact: A Review

“…The localization of radixin is slightly distinct from ezrin and moesin since it was originally identified as a component of adherent junctions. It is also localized at focal contacts, in the cleavage furrow and the contractile ring of cultured cells [13,14] . However, these localizations are controversial [18] .…”

“…Ezrin is highly concentrated in intestine, stomach, lung and kidney although moesin is prominent in lung and spleen, and radixin in liver and intestine [13,14] . Ezrin is expressed in epithelial and mesothelial cells while moesin is expressed in endothelial cells [12] .…”