trans-Golgi retention of a plasma membrane protein: mutations in the cytoplasmic domain of the asialoglycoprotein receptor subunit H1 result in trans-Golgi retention

In the endoplasmic reticulum (ER), in addition, there are mechanisms to prevent improperly folded or oligomerized proteins from exiting and to degrade them. The ER thus performs a quality control function for secretory and membrane proteins (Hurtley and Helenius, 1989) . Many natural and artificial mutations in such proteins have been observed to result in ER retention and degradation, apparently because they affect protein folding or oligomerization. Alterations in the signals for targeted exit from the TGN generally cause missorting rather than TGN localization of the mutant. Only very few mutations have been documented that cause a specific accumulation of the mutant protein in post-ER compartments of the secretory pathway. Such mutations may reflect properties of retention or transport mechanisms in the Golgi. Here we describe mutants of the asialoglycoprotein (ASGP) 1 receptor subunit H1 that specifically accumulate in the trans-Golgi.