A cellular response to environmental insults that cause disruptions in PROTEIN FOLDING and/or accumulation of defectively folded protein in the ENDOPLASMIC RETICULUM. It consists of a group of regulatory cascades that are triggered as a response to altered levels of calcium and/or the redox state of the endoplasmic reticulum. Persistent activation of the unfolded protein response leads to the induction of APOPTOSIS.

Synonyms: Response, Unfolded Protein, Responses, Unfolded Protein, Unfolded Protein Responses, Unfolded Protein Response, Protein Response, Unfolded, Protein Responses, Unfolded