Exchange is necessary for migration

Mira Krendel, Frank Zenke, and Gary Bokoch (Scripps Research Institute, La Jolla, CA) have identified a bridge between microtubule assembly and actin polymerization that links these processes during cell migration.

During migration, microtubule polymerization at the leading edge leads to increased Rac GTPase activity and the formation of lamellipodia via actin polymerization. Conversely, microtubule depolymerization in the cell body activates Rho and leads to myosin contractility. Now, it seems that a guanine nucleotide exchange factor (GEF) is “the missing link between microtubule activation and RhoGTPase regulation of the actin cytoskeleton,” according to Bokoch.

Bokoch found that GEF-H1 activates Rho GTPase, but only when the exchange factor is not associated with microtubules. Disassembly of microtubules in the cell body of a migrating cell frees GEF-H1, which activates Rho to promote myosin contractility and actin stress fiber formation....