A Tight-Knit Group: Protein glycosylation, endoplasmic reticulum stress and the unfolded protein response

Although the dependence upon glycosylation for protein folding and function is understood to be a key part of protein maturation within the endoplasmic reticulum (ER), details concerning the interconnected nature of pathways associated with protein glycosylation, ER stress and the unfolded protein response are only now beginning to come to light. Changes in glycosylation may induce ER stress or may be induced by ER stress. It has been established that glycosylation and ER stress are essential in a variety of cellular processes and diseases. N-linked glycosylation within the ER is necessary for monitoring the state of protein folding and the state of glycosylation in the ER is a determinant for further processing of proteins in Golgi or destruction of improperly folded proteins in the ER associated degradation (ERAD) process. This chapter explores the interdependence of ER stress and glycosylation during protein quality control and cellular response to physiological stress.