Radixin: cytoskeletal adopter and signaling protein.

Radixin functions as a membrane-cytoskeletal crosslinkers in actin-rich cell surface structures and is thereby thought to be essential for cortical cytoskeleton organization, cell motility, adhesion and proliferation. This modular polypeptide consists of a long, central helix, termed the alpha-domain, which connects an N-terminal 4.1/ezrin/radixin/moesin (FERM) domain required for membrane binding and a C-terminal region that contains a major actin-binding motif. Conformational regulation of radixin protein function occurs by association of the FERM and C-terminal domains, whereby the membrane- and actin-binding activities are mutually suppressed and the protein is thought to take an inactive 'closed' form. Further analyses of radixin and its family members have also revealed associations with human disease. With the rudimentary state of our present knowledge and the pivotal roles these proteins play, studies on this protein family are sure to continue to attract considerable interest.