UPR activation is not sufficient for cell homeostasis and CRTAP-2, CRTAP-3, P3H1-2 and CyPB recessive OI fibroblasts also showed upregulated autophagy (Fig. 4), which is often activated to regulate the lysosome-dependent turnover of cell materials to reduce the ER overload (Galluzzi et al., 2017; Green and Levine, 2014). Here, PPIB is linked to osteogenesis imperfecta.