Effect of NFE2L1 Overexpression and Knock Down on the Response of XBP1 Splice Variants to Endoplasmic Reticulum Stress

The unfolded protein response (UPR) is responsible for the degradation and refolding of misfolded proteins. Nuclear factor erythroid-2 like-1 (NFE2L1) basic leucine zipper (bZIP) transcription factor which respond primarily to oxidative stress and proteasome inhibition. In its role in maintaining proteostasis, NFE2L1 upregulates production of proteasomal subunits. Over the years, functional similarities and parallel response pathways have been observed between the UPR and NFE2L1. NFE2L1 may be involved in maintaining proteostasis via involvement in the UPR, directly. The activation of XBP1, a UPR effector, was analyzed under NFE2L1 knock down and overexpression. At the protein level, NFE2L1 knock down decreases the amount of activated XBP1 produced when treated with thapsigargin. NFE2L1 overexpression increased activated XBP1 synthesis under untreated conditions. NFE2L1 knock down resulted in significantly disrupted splicing of XBP1 RNA into its active form. These results suggest that NFE2L1 expression has an impact on UPR signaling.