The unfolded protein response (UPR) is a set of pathways activated by the accumulation of
improperly folded proteins. It can be triggered by a broad range of stressful conditions which
disrupt successful maturation of proteins in the endoplasmic reticulum (ER) by interfering
with proper folding, assembly, and posttranslational modification. Recent studies have
demonstrated the induction of ER stress and activation of elements of the UPR in human
lung cells exposed to diesel exhaust particles, airborne particulate matter, and tobacco …