SIGMAR1 and major depressive disorder: Taking into account the significance of Sigma1R for the mechanisms of response to ER stress (UPR) [247] and the implication of UPR processes to the pathogenesis of depression [235], the decreased expression of mir-214 and enhanced production of the transcription factor XBP1 are of interest upon thapsigargin- or tunicamycin-elicited ER stress in tumor cell culture [270].