Calnexin - a stable component of the ribosome-translocon complex

© 2012 EPFL

Palmitoylated calnexin is a key component of the ribosome-translocon complex.

A third of the human genome encodes N-glycosylated proteins. These are cotranslationally translocated into the lumen/membrane of the endoplasmic reticulum (ER) where they fold and assemble before they are transported to their final destination. Here, the group of Gisou van der Goot ( Van der Goot Lab VDG ) shows that calnexin, a major ER chaperone involved in glycoprotein folding is palmitoylated and that this modification is mediated by the ER palmitoyltransferase DHHC6. This modification leads to the preferential localization of calnexin to the perinuclear rough ER, at the expense of ER tubules. Moreover, palmitoylation mediates the association of calnexin with the ribosome-translocon complex (RTC) leading to the formation of a supercomplex that recruits the actin cytoskeleton, leading to further stabilization of the assembly. These findings show that calnexin is a stable component of the RTC in a manner that is exquisitely dependent on its palmitoylation status. This association is essential for the chaperone to capture its client proteins as they emerge from the translocon, acquire their N-linked glycans and initiate folding.

Asvin K.K. Lakkaraju et al., EMBO Journal doi:10.1038/emboj.2012.15 (2012)