Intracellular transport of class II MHC molecules directed by invariant chain

Three structural motifs in the invariant chain (li) control the intracellular transport of class II major histocompatibility complex molecules. An endo-plasmic reticulum retention signal in the full-length li suggests a role for li in the α-β heterodimer assembly. Another signal motif directs a truncated li, alone or associated with individual class II chains, to a degradation compartment by a pathway circumventing the Golgi. When this truncated li binds α-β dimers, a third signal dominates, directing the complex by way of the Golgi to vesicles in the cell periphery, which may represent a subcompartment of recycling endosomes.