Cell Biology

Moesin as Rho Inhibitor

Science's STKE  07 Jan 2003:
Vol. 2003, Issue 164, pp. tw18-TW18
DOI: 10.1126/stke.2003.164.tw18

Proteins of the ERM (for ezrin, radixin, and moesin) family are thought to function in linking proteins in the plasma membrane to the actin cytoskeleton. Speck et al. examined the function of ERM proteins in Drosophila, which have only one family member, moesin. Cells in the epithelium of imaginal discs that lacked moesin had defects in actin assembly and apical-basal polarity and showed inappropriate migration and invasive properties. Reducing expression of the small guanosine triphosphatase (GTPase) Rho by one half suppressed the effects of loss of moesin, and overexpression of Rho in epithelial cells produced a phenotype similar to that caused by lack of moesin. Thus, moesin's effects on epithelial cells appear to result from inhibition of Rho signaling. ERM proteins have been proposed to serve a structural role in linkage of the cytoskeletion to the plasma membrane, but the rescue of cells lacking moesin by modulation of Rho signaling indicates that inhibition of Rho activity may be a more critical function of moesin. ERM proteins are also themselves regulated by Rho: ERM proteins exist in inactive and active conformations and Rho promotes formation of the active form. The authors propose that the negative feedback loop produced by Rho's activation of ERM may be an important mechanism that prevents the excessive migratory and invasive properties characteristic of metastatic cancer cells.

O. Speck, S. C. Hughes, N. K. Noren, R. M. Kulikauskas, R. G. Fehon, Moesin functions antagonistically to the Rho pathway to maintain epithelial integrity. Nature 421, 83-87 (2003). [Online Journal]