Translational Regulation in the Cellular Response to Biosynthetic Load on the Endoplasmic Reticulum

Proteins destined for secretion, membrane insertion,and retention within the lumen of the exocytic compartment are synthesized on ribosomes bound to the endoplasmic reticulum (ER). The nascent peptide is translocated across the ER membrane and encounters theluminal environment, where it undergoes specific posttranslational modifications and folding reactions. Theflux of such client proteins through the ER varies considerably between different cell types and is influenced substantially by physiological conditions. For example, theload on the ER of a pancreatic acinar cell that secreteslarge quantities of digestive enzymes will be muchgreater than that placed on a maturing erythroblast whoseribosomes are active mainly in the synthesis of cytoplasmic proteins such as globins...