Kinectin-dependent assembly of translation elongation factor-1 complex on endoplasmic reticulum regulates protein synthesis

Kinectin is an integral membrane protein with many isoforms primarily found on the endoplasmic reticulum. It has been found to bind kinesin, Rho GTPase and translation elongation factor-1 delta. None of the existing models for the quaternary organization of the elongation factor-1 complex in higher eukaryotes involves kinectin. We have investigated here the assembly of the elongation factor-1 complex onto endoplasmic reticulum via kinectin using in vitro and in vivo assays. We established that the entire elongation factor-1 complex can be anchored to endoplasmic reticulum via kinectin and the interacting partners are: kinectin binds EF-1 delta which in turn binds EF-1 gamma but not EF-1 beta; EF-1 gamma binds EF-1 delta and EF-1 beta but not kinectin. In vivo splice-blocking of the kinectin exons 36 and 37 produced kinectin lacking the EF-1 delta binding domain, which disrupted the membrane localization of EF-1 delta, EF-1 gamma and EF-1 beta on endoplasmic reticulum, similar to the disruptions seen with the over-expression of kinectin fragments containing the EF-1 delta binding domain. The disruptions of the EF-1 delta/kinectin interaction inhibited expression of membrane proteins but enhances synthesis of cytosolic proteins in vivo. These findings suggest that anchoring the elongation factor-1 complex onto endoplasmic reticulum via EF-1 delta/kinectin interaction is important for regulating protein synthesis in eukaryotic cells.