P4HB and amyotrophic lateral sclerosis: Both BiP and PDI have been observed in ALS spinal cord tissue (Ilieva et al., 2007; Sasaki, 2010; Montibeller et al., 2020), as have UPRER transcription factors XBP1 (Hetz et al., 2009) and CHOP (Ito et al., 2009).