The reference OMIM entry for this protein is 179410

Radixin; rdx

CLONING

Radixin is a cytoskeletal protein that may be important in linking actin to the plasma membrane. Cloning of the murine and porcine radixin cDNAs demonstrated a protein highly homologous to ezrin (123900) and moesin (309845). Wilgenbus et al. (1993) cloned and sequenced the human radixin cDNA and found the predicted amino acid sequence for the human protein to be nearly identical to those predicted for radixin in the two other species. By immunocytochemical analysis of isolated inner ear hair cells, Pataky et al. (2004) demonstrated that radixin is expressed at the base of hair bundles in chicken, frog, mouse, and zebrafish. Electron microscopic analysis found labeling in the stereociliary taper and the lower stereociliary shaft, with progressively less labeling toward the top of the hair bundle. Pataky et al. (2004) concluded that radixin may participate in anchoring the 'pointed' ends of actin filaments to the membrane in stereocilia. Khan et al. (2007) identified 6 alternatively spliced RDX isoforms in human retina and inner eye. The major full-length protein contains 627 amino acids forming 3 known functional domains: an N-terminal FERM domain that localizes the protein to the plasma membrane, a central helical alpha-domain, and a C-terminal actin-binding domain. By immunohistochemical analysis of mouse inner ear, Khan et al. (2007) confirmed the localization of radixin along the length of cochlear hair cell stereocilia and in hair cells of the crista ampullaris at postnatal day 30.

GENE FUNCTION

Using antigen-activated T cells, Faure et al. (2004) showed that the ezrin-radixin-moesin (ERM) proteins are rapidly inactivated through a VAV1 (164875)-RAC1 (602048) pathway. The resulting disanchoring of the cortical actin cytoskeleton from the plasma membrane decreased cellular rigidity, leading to more efficient T cell-APC (antigen-presenting cell) conjugate formation. The authors concluded that this pathway favors immunologic synapse formation and the development of an effective immune response.

MAPPING

Wilgenbus et al. (1993) used PCR of Chinese hamster/human somatic cell hybrid DNAs, as well as standard Southern analysis of somatic cell hybrids, to assign the RDX gene to 11q. By fluorescence in situ hybridization, they further localized the gene to 11q23. - Pseudogenes Wilgenbus et al. (1993) assigned a truncated version of the RDX gene representing a pseudogene (RDXP2) was assigned to Xp21.3. Another pseudogene that seemed to lack introns (RDXP1) was mapped to 11p by Southern and PCR analyses.

MOLECULAR GENETICS

Khan et al. (2007) identified 3 respective pathogenic mutations in the RDX gene (179410.0001-179410.0003) in affected members of 3 Pakistani families with autosomal recessive deafness-24 (DFNB24; 611022). The mutations were predicted to disrupt or delete the actin-binding domain of the protein. None of the affected individuals had vestibular dysfunction or hyperbilirubinemia.

ANIMAL MODEL

The ERM family of proteins crosslink actin filaments and integral membrane proteins. Radixin is the dominant ERM protein in the liver of wildtype mice and is concentrated at bile canalicular membranes (BCM). Kikuchi et al. (2002) showed that Rdx -/- mice are normal at birth, but their serum concentrations of conjugated bilirubin begin to increase gradually around 4 weeks of age, and they show mild liver injury after 8 weeks. This phenotype is similar to human conjugated hyperbili ... More on the omim web site

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Feb. 2, 2018: Protein entry updated
Automatic update: Uniprot description updated

Dec. 19, 2017: Protein entry updated
Automatic update: Uniprot description updated

March 16, 2016: Protein entry updated
Automatic update: OMIM entry 179410 was added.