Regulating rhotraction of axonal branches

Abstract

During the past decade, we learned that small GTPases of the Rho family regulate the assembly of actin fibers. Standard texts on Rho GTPases state that Cdc42 is required for filopodia formation, Rac for lamellapodia formation and Rho for formation of stress fibers. Rho GTPase signaling pathways play important roles in regulating multiple processes in the morphological development of neurons, including axon growth, guidance and the elaboration of dendrites. The activities of Rho GTPases are regulated positively by GDP–GTP exchange factors (GEFs) and negatively by GTPase-activating proteins (GAPs). In turn, Rho GEFs and RhoGAPs can be regulated upstream by cell-surface receptors. Billuart et al. [ 1 Billuart P. et al. Regulating axon branch stability: the role of p190 RhoGAP in repressing a retraction signaling pathway. Cell. 2001; 107: 195-207 Abstract Full Text Full Text PDF PubMed Scopus (179) Google Scholar ] have now performed an interesting state-of-the-art study in Drosophila that opens up a way to understand how Rho GTPases can act specifically in a cellular context.