The role of the ERM protein family in maintaining cellular polarity, adhesion and regulation of cell motility

Abstract

Ezrin, radixin and moesin, forming the ERM protein family, act as molecular crosslinkers between actin filaments and proteins anchored in the cell membrane. By participating in a complex intracellular network of signal transduction pathways, ERM proteins play a key role in the regulation of adhesion and polarity of normal cells through interactions with membrane molecules, e.g. E-cadherin. Dynamic cytoskeletal transformations, in which the ERM and Rho GTPases are involved, lead to the formation of membrane-cytoplasmic structures, such as filopodia and lamellipodia, which are responsible for cellular motility. The interactions of ERM proteins with active Akt kinase cause the acquisition of antiapoptotic cellular features by downregulation of the proapoptotic protein Bad. ERM protein activity is regulated by phosphorylation/dephosphorylation reactions and linking phosphatidylinositols. The model of activation based on the molecular conformation changes by breaking the intramolecular bonds and exposing actin binding sites is essential for the proper functioning of the ERM proteins. Additionally, the connection types between the ERM and membrane proteins (direct or indirect by EBP50 and E3KARP) play an important role in transduction of signals from the extracellular matrix. Due to the wide range of ezrin, radixin and moesin cytophysiological features, detailed exploration of the ERM biochemistry will provide a series of answers to questions about ambiguous functions in many intracellular signal transduction pathways.