Changes in Actin Dynamics Regulated by Villin-1 and Gelsolin Are Determinants of Cell Fate and Are Key to Gastrointestinal Inflammatory Disease

Diverse cell stress signaling pathways result in phosphorylation of the eukaryotic translation initiation factor 2 subunit alpha (EIF2S1 or EIF2A) resulting in rapid and reversible regulation of global protein translation. Translation reprogramming mitigates stress by activating pathways that result in autophagy and cell death, to eliminate damaged cells. Actin is an early target of cellular stress that also regulates the dephosphorylation of phosphorylated EIF2A (pEIF2A) to restore homeostasis. It is not clear how actin affects EIF2A signaling. In this study, we characterized the molecular mechanisms by which two actin-binding proteins villin-1 and gelsolin, regulate cell stress response to influence innate immune signaling. A double knockout (DKO) mouse with genetic deletion of villin-1 and gelsolin was analyzed together with ileal tissue from Crohn’s disease (CD) patients. Additional mechanistic studies were done using epithelial cell lines including HT-29 as well as mouse embryonic fibroblasts (MEFs). In intestinal epithelial cells (IECs) exposed to cell stressors, EIF2A signaling reduced expression of villin-1 and gelsolin. However, villin-1 and gelsolin were required for dephosphorylation of EIF2A and recovery from cell stress. In mouse and human IECs, loss of villin-1 and gelsolin expression resulted in constitutive phosphorylation of EIF2A and overexpression of the immunity related GTPase IRGM (or IRGM1), which regulates autophagy. Overexpression of IRGM (or IRGM1) induced cell death by necroptosis, accompanied by the release of damage associated molecular patterns (DAMPs). In DKO mice, constitutive phosphorylation of EIF2A and over-expression of IRGM1 resulted in spontaneous ileitis that resembled human CD in symptoms and histology. Distal ileum tissues from patients with CD had lower levels of villin-1 and gelsolin, increased phosphorylation of EIF2A, and increased levels of IRGM, necroptosis, and increased release of nuclear DAMPs compared to controls. Our findings highlight changes in IEC actin dynamics can modulate cell stress response between cell survival and cell death and intersect with signaling pathways pivotal to inflammation and disease pathogenesis. Our study also advances a molecular mechanism for IRGM in regulating necroptosis, the release of DAMPs and the initiation of inflammation thus, providing its pathophysiological link to CD.