Nuclear epidermal growth factor receptor modulates skin laxity and fibrosis.

Summary: Abstract Body: Systemic sclerosis (SSc) is an autoimmune disease that causes high morbidity and mortality due to fibrosis of the skin and internal organs but lacks safe and effective therapies. Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is highly associated with fibrosis of multiple organs including the skin. In response to activation, EGFR is internalized and traffics to multiple cellular compartments, including the nucleus. The function of EGFR in the nucleus during fibrosis remains unexplored. We validate nuclear trafficking of EGFR occurs in fibroblasts in response to the high affinity EGFR ligand TGFA by cellular fractionation, immunofluorescence and electron microscopy. To assess the function of nuclear EGFR in vitro and in vivo, we generated mice lacking the EGFR nuclear localization sequence (EgfrΔNLS). Biophysical characterization of these mice showed a phenotype consistent with altered EGFR signaling, including wavy hair and whiskers. Assessment of EgfrΔNLS skin demonstrated increased skin laxity (p < 0.05) and reduced scarring due to full thickness skin wounds (p < 0.01) compared to wild type controls, suggesting nuclear EGFR can regulate pathways that drive wound repair associated fibrosis. To understand the mechanism, we isolated neonatal dermal fibroblasts from EgfrΔNLS mice and wild type controls. EgfrΔNLS fibroblasts showed decreased expression of interferon stimulated genes and EGR1 regulated genes in response to TGFA (p < 0.01). TGFA induced EGR1 expression in fibroblasts could also be abrogated by inhibition of importin b-dependent nuclear transport, supporting this as a profibrotic process. In all, our investigation of the role of nuclear EGFR in fibrosis has elucidated a new regulatory function of fibrotic transcriptional profile by this growth factor receptor in the nucleus. Anahi V. Odell^{1, 3}, Nathan M. Newton², Richard Flavell^{3, 4}, Ian D. Odell^{1, 3} 1. Dermatology, Yale University School of Medicine, New Haven, CT, United States. 2. Program of Translational Biomedicine, Yale University School of Medicine, New Haven, CT, United States. 3. Immunobiology, Yale University School of Medicine, New Haven, CT, United States. 4. Howard Hughes Medical Institute, Chevy Chase, MD, United States. Translational Studies: Cell and Molecular Biology