IRE1α mediated dysregulation of the pulmonary epithelium in lung fibrosis - Project Summary / Abstract Idiopathic pulmonary fibrosis (IPF) is a disease of progressive interstitial fibrosis, which leads to severe debilitation and eventually respiratory failure and death. Protein folding stress in the endoplasmic reticulum (ER stress) triggers the unfolded protein response (UPR), which has been implicated in IPF. The most deeply conserved mediator of the UPR is IRE1α, a bifunctional kinase/endoribonuclease that mediates XBP1 mRNA splicing, degradation of ER-localized mRNAs (RIDD), and degradation of the microRNA miR-17. Under severe ER stress, IRE1α hyperactivity promotes cell death, a condition termed the terminal UPR. A parsimonious view holds that the terminal UPR causes ongoing alveolar epithelial cell death which leads ultimately to fibrosis. The laboratory of Dr. Feroz Papa (co-mentor) developed and characterized Kinase Inhibiting RNase Attenuator (KIRA) compounds that inhibit all the major functions of IRE1α. We previously showed that mice treated with KIRA compounds were protected from bleomycin-induced fibrosis. In new preliminary data, a mono- selective KIRA compound decreased miR-17 degradation, TGFβ signaling and the senescence-associated secretory phenotype (SASP) in the lung epithelium after bleomycin. In fibrotic mouse lungs and human IPF lungs, these IRE1α-regulated pathological gene signatures were preferentially found in dysfunctional progenitor cells. These results challenge the current paradigm that the UPR contributes to fibrosis exclusively through cell death. Instead, the central hypothesis of this proposal is that hyperactivation of IRE1α in injured epithelial progenitor cells triggers a network of mutually reinforcing fibrotic pathways, including gene repression by miR- 17, senescence, and TGFβ signaling. Specific Aim 1 will test the hypothesis that IRE1α is necessary and sufficient for epithelial progenitor cell dysfunction by interrogating the effects of chemical or genetic inhibition of IRE1α in the bleomycin model and two genetic models of fibrosis based on senescence (Sin3a knockout) and ER stress (SftpcC121G). Specific Aim 2 will test the hypothesis that IRE1α regulates progenitor cell dysfunction through miR-17 using conditional deletion and conditional overexpression mice. The training plan is focused on the skills and concepts of lung regeneration and developmental biology, in vitro models of lung biology, epithelial cell dysfunction, and responsible laboratory management. Training will include didactic courses, focused symposia, and international conferences. The primary mentor and co-mentor are Dr. Dean Sheppard and Dr. Feroz Papa, both accomplished physician-scientists with long track records of mentorship. Dr. Auyeung has laboratory and office space at the UCSF Mission Bay campus, a fertile environment for collaboration with ready access to the facilities and equipment necessary for this research. In summary this Career Development Award application merges an exceptional candidate, an innovative and tractable research plan, rigorous training, and the support of world-class physician-scientists into a powerful springboard for the launch of a productive and independent career with high impact on lung disease.
