The Ras-like GTPase Gem is involved in cell shape remodelling and interacts with the novel kinesin-like protein KIF9

Gem belongs to the Rad/Gem/Kir (RGK) subfamily of Ras-related GTPases, whic h also comprises Rem, Rem2 and Ges. The RGK family members Ges and Rem have been shown to produce endothelial cell sprouting and reorganization of the actin cytoskeleton upon overexpression. Here we show that high intracellul ar Gem levels promote profound changes in cell morphology and we investigat e how this phenotype arises dynamically. We also show that this effect requ ires intact microtubules and microfilaments, and that Gem is associated wit h both cytoskeletal components. In order to investigate the mechanisms of G em recruitment to the cytoskeleton, we performed a yeast two-hybrid screen and identified a novel kinesin-like protein, termed KIF9, as a new Gem inte racting partner. We further show that Gem and KIF9 interact by co-immunopre cipitation. Furthermore, Gem and KIF9 display identical patterns of gene ex pression in different tissues and developmental stages. The Gem-KIF9 intera ction reported here is the first molecular link between RGK family members and the microtubule cytoskeleton.