CRM1 (also known as XPO1 and exportin 1) mediates nuclear export of hundreds of proteins through the recognition of the leucine-rich nuclear export signal (LR-NES). Here we present the 2.9Å structure of CRM1 bound to snurportin 1 (SNUPN). Snurportin 1 binds CRM1 in a bipartite manner by means of an amino-terminal LR-NES and its nucleotide-binding domain. The LR-NES is a combined α-helical-extended structure that occupies a hydrophobic groove between two CRM1 outer helices. The LR-NES interface explains the consensus hydrophobic pattern, preference for intervening electronegative residues and inhibition by leptomycin B. The second nuclear export signal epitope is a basic surface on the snurportin 1 nucleotide-binding domain, which binds an acidic patch on CRM1 adjacent to the LR-NES site. Multipartite recognition of individually weak nuclear export signal epitopes may be common to CRM1 substrates, enhancing CRM1 binding beyond the generally low affinity LR-NES. Similar energetic construction is also used in multipartite nuclear localization signals to provide broad substrate specificity and rapid evolution in nuclear transport.

Proline–tyrosine nuclear localization signals (PY-NLSs) are recognized and transported into the nucleus by human Karyopherin (Kap) β2/Transportin and yeast Kap104p. Multipartite PY-NLSs are highly diverse in sequence and structure, share a common C-terminal R/H/KX2–5PY motif, and can be subdivided into hydrophobic and basic subclasses based on loose N-terminal sequence motifs. PY-NLS variability is consistent with weak consensus motifs, but such diversity potentially renders comprehensive genome-scale searches intractable. Here, we use yeast Kap104p as a model system to understand the energetic organization of this NLS. First, we show that Kap104p substrates contain PY-NLSs, demonstrating their generality across eukaryotes. Previously reported Kapβ2–NLS structures explain Kap104p specificity for the basic PY-NLS. More importantly, thermodynamic analyses revealed physical properties that govern PY-NLS binding affinity: (1) PY-NLSs contain three energetically significant linear epitopes, (2) each epitope accommodates substantial sequence diversity, within defined limits, (3) the epitopes are energetically quasi-independent, and (4) a given linear epitope can contribute differently to total binding energy in different PY-NLSs, amplifying signal diversity through combinatorial mixing of energetically weak and strong motifs. The modular organization of the PY-NLS coupled with its combinatorial energetics lays a path to decode this diverse and evolvable signal for future comprehensive genome-scale identification of nuclear import substrates.

The epithelial complement inhibitory proteins (CIPs) cluster of differentiation 46 and 55 (CD46 and CD55) regulate circulating immune complex-mediated complement activation in idiopathic pulmonary fibrosis (IPF). Our previous studies demonstrated that IL-17A mediates epithelial injury via transforming growth factor ␤1 (TGF-␤1) and down-regulates CIPs. In the current study, we examined the mechanistic role of TGF-␤1 in complement activationmediated airway epithelial injury in IPF pathogenesis. We observed lower epithelial CIP expression in IPF lungs compared to normal lungs, associated with elevated levels of complement component 3a and 5a (C3a and C5a), locally and systemically. In normal primary human small airway epithelial cells ( Idiopathic pulmonary fibrosis (IPF) is a disease of high mortality for which lung transplantation is considered the only definitive therapy. Its pathogenesis remains largely unknown (1), but emerging concepts point to repeated injury to bronchiole-like epithelial cells and hyperplastic type II alveolar epithelial cells lining areas of honeycomb fibrosis (1, 2). These injured epithelial cells produce key profibrotic factors, including transforming growth factor ␤ (TGF-␤), which is implicated in epithelial injury (3-5) and epithelial-tomesenchymal transition (EMT; refs. 6, 7).The complement system is an integral arm of innate and adaptive immunity. Early studies demonstrated evidence of circulating immune complexes (8) and complement activation (9) in patients with IPF. In experimental models of IPF, antifibrotic effects due to deletion of complete downstream complement factors (10), specifically complement component 5 (C5; ref. 11), were reported. C3a and C5a are implicated in autoimmune diseases (12), chronic lung transplant rejection (13), experimental allergic asthma (14), and Abbreviations: ATII, alveolar type II; C3a, complement component 3a; C3aR, complement component 3a receptor; C5a, complement component 5a; C5aR, complement component 5a receptor; CD46, cluster of differentiation 46; CD55, cluster of differentiation 55; CIP, complement inhibitory protein; E-CAD, E-cadherin; EMT, epithelial-mesenchymal transition; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IL-17A, interleukin-17A; IPF, idiopathic pulmonary fibrosis; p38MAPK, mitogen-activated protein kinase; PARP, poly(ADP-ribose) polymerase; PCR, polymerase chain reaction; RNAi, RNA interference; SABM, small airway basal medium; SAEC, small airway epithelial cell; siRNA, small interference RNA; SMAD7, mothers against decapentaplegic homolog 7; TGF-␤1, transforming growth factor ␤, isoform 1 4223 0892-6638/14/0028-4223 © FASEB wnloaded from www.fasebj.org by (158

erative bronchiolitis (OB), a fibrotic airway lesion, is the leading cause of death after lung transplantation. Type V collagen [col(V)] overexpression and IL-17-mediated anti-col(V) immunity are key contributors to OB pathogenesis. Here, we report a previously undefined role of IL-17 in inducing col(V) overexpression, leading to epithelial mesenchymal transition (EMT) and subsequent OB. We observed IL-17-mediated induction of col(V) ␣1 chains [␣1 (V)] in normal airway epithelial cells in vitro and detected ␣1 (V)-specific antibodies in bronchoalveolar lavage fluid of lung transplant patients. Overexpression of IL-17 and col(V) was detected in OB lesions in patient lung biopsies and in a murine OB model. IL-17 is shown to induce EMT, TGF-␤ mRNA expression, and SMAD3 activation, whereas downregulating SMAD7 expression in vitro. Pharmacological inhibition of TGF-␤RI tyrosine kinase, p38 MAPK, or focal adhesion kinase prevented col(V) overexpression and EMT. In murine orthotopic lung transplants, neutralizing IL-17 significantly decreased TGF-␤ mRNA and protein expression and prevented epithelial repair/ OB. Our findings highlight a feed-forward loop between IL-17 and TGF-␤, leading to induction of col(V) and associated epithelial repair, thus providing one possible link between autoimmunity and OB after lung transplantation. autoimmunity; p38 MAPK; focal adhesion kinase; small-airway epithelial cells; RLE-6TN; mouse transplant model; epithelial-mesenchymal transition OBLITERATIVE BRONCHIOLITIS (OB) is characterized by extensive peribronchiolar fibrosis with plugs of granulation tissues (fibroblasts and collagen) that occlude small airways. OB is the key reason that the 5-yr survival of lung transplant recipients is only 50%, the worst of all major solid organ transplants (42,48).Aberrant epithelial repair is a key event in the transplanted lung (1, 9) in which bronchioles lose resident epithelial cells and become occluded by granulation tissue. Abnormal epithelial repair eventually causes an epithelial-to-mesenchymal transition (EMT), a functional and phenotypic change of epithelial cells into spindle-shaped, migratory (43) and matrix-component-secreting mesenchymal cells (10, 41), and a process associated with lung fibrosis (15,27). However, the direct connection between EMT and the in vivo phenomena of fibrosis and fibro-obliterative disease remains controversial.We and others previously reported that OB is associated with dysregulation of two types of collagen: 1) marked increase in type V collagen [col(V)], a quantitatively minor lung collagen (8,14,40), and 2) a decrease in the major lung collagen type I [col(I)] (2, 53). We have shown that prospective monitoring of patients with human lung transplant revealed a critical role of col(V)-specific cellular immunity in OB pathogenesis (14,40). Although overexpression of col(V), an otherwise quantitatively minor collagen, is involved in OB pathology, mechanisms leading to col(V) overexpression are unknown. Thus a mechanistic understanding of the triggers of col(V)...

Background/Aims: Circular RNAs (circRNAs) are key regulators in the development and progression of human cancers, however its role in non-small cell lung cancer (NSCLC) tumorigenesis is not well understood. The aim of this study is to identify the expression level of circPVT1 in NSCLC and further investigated its functional relevance with NSCLC progression both in vitro and in vivo. Methods: Quantative real-time PCR was used for the measurement of circPVT1 in NSCLC specimens and cell lines. Fluorescence in situ hybridization analysis (FISH) assay was used for the identification of sublocation of circPVT1 in NSCLC cells. Bioinformatics analysis, luciferase reporter assay and RNA immunoprecipitation (RIP) were performed to verify the binding of c-Fos at circPVT1 promoter region, and the direct interaction between circPVT1 and miR-125b. Gain- or loss-function assays were performed to evaluate the effects of circPVT1 on cell proliferation and invasion. Western blot and immunohistochemistry assays were performed to detect the protein levels involved in E2F2 pathway. Results: We found that circPVT1 was upregulated in NSCLC specimens and cells. The transcription factor c-Fos binded to the promoter region of circPVT1, resulting in the overexpression of circPVT1 in NSCLC. Knockdown of circPVT1 suppressed NSCLC cell proliferation, migration and invasion, and increased apoptosis. In addition, circPVT1 mediated NSCLC progression via the regulation of E2F2 signaling pathway. More importantly, circPVT1 was predominantly abundant in the cytoplasm of NSCLC cells, and circPVT1 could serve as a competing endogenous RNA to regulate E2F2 expression and tumorigenesis in a miR-125b-dependent manner, which is further verified by using an in vivo xenograft model. Conclusion: circPVT1 promotes NSCLC cell growth and invasion, and may serve as a promising therapeutic target for NSCLC patients. Therefore, silence of circPVT1 could be a future direction to develop a novel treatment strategy.

RationaleIdiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease characterized by progressive scarring and matrix deposition. Recent reports highlight an autoimmune component in IPF pathogenesis. We have reported anti-col(V) immunity in IPF patients. The objective of our study was to determine the specificity of col(V) expression profile and anti-col(V) immunity relative to col(I) in clinical IPF and the efficacy of nebulized col(V) in pre-clinical IPF models.MethodsCol(V) and col(I) expression profile was analyzed in normal human and IPF tissues. C57-BL6 mice were intratracheally instilled with bleomycin (0.025 U) followed by col(V) nebulization at pre-/post-fibrotic stage and analyzed for systemic and local responses.ResultsCompared to normal lungs, IPF lungs had higher protein and transcript expression of the alpha 1 chain of col(V) and col(I). Systemic anti-col(V) antibody concentrations, but not of anti-col(I), were higher in IPF patients. Nebulized col(V), but not col(I), prevented bleomycin-induced fibrosis, collagen deposition, and myofibroblast differentiation. Col(V) treatment suppressed systemic levels of anti-col(V) antibodies, IL-6 and TNF-α; and local Il-17a transcripts. Compared to controls, nebulized col(V)-induced tolerance abrogated antigen-specific proliferation in mediastinal lymphocytes and production of IL-17A, IL-6, TNF-α and IFN-γ. In a clinically relevant established fibrosis model, nebulized col(V) decreased collagen deposition. mRNA array revealed downregulation of genes specific to fibrosis (Tgf-β, Il-1β, Pdgfb), matrix (Acta2, Col1a2, Col3a1, Lox, Itgb1/6, Itga2/3) and members of the TGF-β superfamily (Tgfbr1/2, Smad2/3, Ltbp1, Serpine1, Nfkb/Sp1/Cebpb).ConclusionsAnti-col(V) immunity is pathogenic in IPF, and col(V)-induced tolerance abrogates bleomycin-induced fibrogenesis and down regulates TGF- β-related signaling pathways.

Complement activation, an integral arm of innate immunity, may be the critical link to the pathogenesis of idiopathic pulmonary fibrosis (IPF). Whereas we have previously reported elevated anaphylatoxins—complement component 3a (C3a) and complement component 5a (C5a)—in IPF, which interact with TGF‐β and augment epithelial injury in vitro, their role in IPF pathogenesis remains unclear. The objective of the current study is to determine the mechanistic role of the binding of C3a/C5a to their respective receptors (C3aR and C5aR) in the progression of lung fibrosis. In normal primary human fetal lung fibroblasts, C3a and C5a induces mesenchymal activation, matrix synthesis, and the expression of their respective receptors. We investigated the role of C3aR and C5aR in lung fibrosis by using bleomycin‐injured mice with fibrotic lungs, elevated local C3a and C5a, and overexpression of their receptors via pharmacologic and RNA interference interventions. Histopathologic examination revealed an arrest in disease progression and attenuated lung collagen deposition (Masson's trichrome, hydroxyproline, collagen type I α 1 chain, and collagen type I α 2 chain). Pharmacologic or RNA interference‐specific interventions suppressed complement activation (C3a and C5a) and soluble terminal complement complex formation (C5b‐9) locally and active TGF‐β1 systemically. C3aR/C5aR antagonists suppressed local mRNA expressions of tgfb2, tgfbr1/2, ltbp1/2, serpine1, tsp1, bmp1/4, pdgfbb, igf1, but restored the proteoglycan, dcn. Clinically, compared with pathologically normal human subjects, patients with IPF presented local induction of C5aR, local and systemic induction of soluble C5b‐9, and amplified expression of C3aR/C5aR in lesions. The blockade of C3aR and C5aR arrested the progression of fibrosis by attenuating local complement activation and TGF‐β/bone morphologic protein signaling as well as restoring decorin, which suggests a promising therapeutic strategy for patients with IPF.—Gu, H., Fisher, A. J., Mickler, E. A., Duerson, F., III, Cummings, O. W., Peters‐Golden, M., Twigg, H. L., III, Woodruff, T. M., Wilkes, D. S., Vittal, R. Contribution of the anaphylatoxin receptors, C3aR and C5aR, to the pathogenesis of pulmonary fibrosis. FASEB J. 30, 2336–2350 (2016). http://www.fasebj.org

p62 is a scaffolding adaptor implicated in the clearance of protein aggregates by autophagy. Reactive oxygen species (ROS) can either stimulate or inhibit NFκB-mediated gene expression influencing cellular fate. We studied the effect of hydrogen peroxide (H2O2)-mediated oxidative stress and NFκB signaling on p62 expression in the retinal pigment epithelium (RPE) and investigated its role in regulation of autophagy and RPE survival against oxidative damage. Cultured human RPE cell line ARPE-19 and primary human adult and fetal RPE cells were exposed to H2O2-induced oxidative stress. The human apolipoprotein E4 targeted-replacement (APOE4) mouse model of AMD was used to study expression of p62 and other autophagy proteins in the retina. p62, NFκB p65 (total, phosphorylated, nuclear and cytoplasmic) and ATG10 expression was assessed by mRNA and protein analyses. Cellular ROS and mitochondrial superoxide were measured by CM-H2DCFDA and MitoSOX staining respectively. Mitochondrial viability was determined using MTT activity. qPCR-array system was used to investigate autophagic genes affected by p62. Nuclear and cytoplasmic levels of NFκB p65 were evaluated after cellular fractionation by Western blotting. We report that p62 is up-regulated in RPE cells under H2O2-induced oxidative stress and promotes autophagic activity. Depletion of endogenous p62 reduces autophagy by downregulation of ATG10 rendering RPE more susceptible to oxidative damage. NFκB p65 phosphorylation at Ser-536 was found to be critical for p62 upregulation in response to oxidative stress. Proteasome inhibition by H2O2 causes p62-NFκB signaling as antioxidant pre-treatment reversed p62 expression and p65 phosphorylation when RPE was challenged by H2O2 but not when by Lactacystin. p62 protein but not RNA levels are elevated in APOE4-HFC AMD mouse model, suggesting reduction of autophagic flux in disease conditions. Our findings suggest that p62 is necessary for RPE cytoprotection under oxidative stress and functions, in part, by modulating ATG10 expression. NFκB p65 activity may be a critical upstream initiator of p62 expression in RPE cells under oxidative stress.