RANBP9: Proteins and Enzymes

Just as heat shock proteins function as chaperones for exposed hydrophobic patches, importins act as chaperones for exposed basic domains, and it is suggested that this represents a major and general cellular function of importins (1). RanBP9, a novel interacting protein, was localized within the centrosome throughout the cell cycle. Overexpression of RanBP9 produced multiple spots which were colocalized with gamma-tubulin and acted as ectopic microtubule nucleation sites, resulting in a reorganization of microtubule network (2). It has been shown that RanBP9 can induce GTP-Ras association and Erk phosphorylation and elevate serum response element-luciferase (SRE-LUC) expression, indicating that RanBP9 can activate the Ras-Erk-SRE pathway. Also RanBP9 stimulates Ras activation by recruiting Sos (3).