AM, Shen H. Interaction of caveolin-1 with ATG12-ATG5 system suppresses autophagy in lung epithelial cells. Am J Physiol Lung Cell Mol Physiol 306: L1016 -L1025, 2014. First published April 11, 2014 doi:10.1152/ajplung.00268.2013.-Autophagy plays a pivotal role in cellular homeostasis and adaptation to adverse environments, although the regulation of this process remains incompletely understood. We have recently observed that caveolin-1 (Cav-1), a major constituent of lipid rafts on plasma membrane, can regulate autophagy in cigarette smoking-induced injury of lung epithelium, although the underlying molecular mechanisms remain incompletely understood. In the present study we found that Cav-1 interacted with and regulated the expression of ATG12-ATG5, an ubiquitin-like conjugation system crucial for autophagosome formation, in lung epithelial Beas-2B cells. Deletion of Cav-1 increased basal and starvation-induced levels of ATG12-ATG5 and autophagy. Biochemical analyses revealed that Cav-1 interacted with ATG5, ATG12, and their active complex ATG12-ATG5. Overexpression of ATG5 or ATG12 increased their interactions with Cav-1, the formation of ATG12-ATG5 conjugate, and the subsequent basal levels of autophagy but resulted in decreased interactions between Cav-1 and another molecule. Knockdown of ATG12 enhanced the ATG5-Cav-1 interaction. Mutation of the Cav-1 binding motif on ATG12 disrupted their interaction and further augmented autophagy. Cav-1 also regulated the expression of ATG16L, another autophagy protein associating with the ATG12-ATG5 conjugate during autophagosome formation. Altogether these studies clearly demonstrate that Cav-1 competitively interacts with the ATG12-ATG5 system to suppress the formation and function of the latter in lung epithelial cells, thereby providing new insights into the molecular mechanisms by which Cav-1 regulates autophagy and suggesting the important function of Cav-1 in certain lung diseases via regulation of autophagy homeostasis.caveolin-1; ATG12-ATG5; ATG16L; autophagy; lung diseases AUTOPHAGY IS A DYNAMIC PROCESS responsible for the turnover of cellular organelles and long-lived proteins. During this process, cytosolic proteins and organelles (e.g., mitochondria and endoplasmic reticulum) are engulfed into double-membranebound vesicles, autophagosomes. The outer membrane of the autophagosome subsequently fuses with lysosomes to form autolysosomes in which the engulfed components are degraded by lysosomal hydrolases, regenerating metabolic precursors that are recycled for macromolecular synthesis and ATP generation (20, 42). Autophagy is induced above basal levels in response to diverse stimuli including nutrient starvation, genotoxic agents, cytokines, and oxidative stress. This process provides an essential function in the maintenance of cellular homeostasis and adaptation to adverse environments (16,29,35).More than 30 autophagy-related genes and gene products critical in the regulation of autophagy, designated "ATG," have been identified heretofore in yeast and hi...

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Background and objective: Some types of T lymphocytes, especially cytotoxic T-cells (Tc1) and T-helper (Th17) cells, play a pivotal role in cigarette smokeinduced lung diseases. However, whether Tc17 cells are involved remains largely unknown.We investigated Tc17 involvement using a cigarette smoke-exposure model. Methods: Groups of mice were exposed to cigarette smoke or filtered air. At weeks 2, 8, 12 and 24, mice were sacrificed to observe histological changes by HE stain and/or immunohistochemical staining.The frequency of T cell subsets in the lung and spleen were detected by flow cytometry. In addition, the expression levels of T cellrelated factors were measured by real-time polymerase chain reaction or enzyme-linked immunosorbent assay. Results: Cigarette smoke caused substantial inflammatory cell infiltration and led to emphysema. Cigarette smoke exposure promoted the expression of interferon-gamma (IFN)-γ and interleukin (IL)-17A at the messenger ribonucleic acid and protein levels. In addition to Tc1 and Th17 cells, pulmonary and splenic Tc17 cells increased, which was accompanied by the upregulation of cytokines IL-6, transforming growth factor beta (TGF)-β) and transcriptional factors Stat3 and RAR-related orphan receptor gamma. Compared with untreated mice, γH2AX-positive cells were more frequently observed in mice exposed to cigarette smoke. Conclusions: Long-term cigarette smoke exposure induced Tc17 cell expansion both locally and distally, which was associated with emphysema and deoxyribonucleic acid damage. As an important source of IL-17A, this T cell subset may be a potential target for chronic obstructive pulmonary disease therapy.

Histone deacetylase (HDAC)2 is expressed in airway epithelium and plays a pivotal role in inflammatory cells. However, the role of HDAC2 in allergic airway inflammation remains poorly understood. In the present study, we determined the role of HDAC2 in airway inflammation using in vivo models of house dust mite (HDM)-induced allergic inflammation and in vitro cultures of human bronchial epithelial (HBE) cells exposed to HDM, IL-17A, or both. We observed that HDM-challenged Hdac2+/− mice exhibited substantially enhanced infiltration of inflammatory cells. Higher levels of T helper 2 cytokines and IL-17A expression were found in lung tissues of HDM-challenged Hdac2+/− mice. Interestingly, IL-17A deletion or anti-IL-17A treatment reversed the enhanced airway inflammation induced by HDAC2 impairment. In vitro, HDM and IL-17A synergistically decreased HDAC2 expression in HBE cells. HDAC2 gene silencing further enhanced HDM- and/or IL-17A-induced inflammatory cytokines in HBE cells. HDAC2 overexpresion or blocking IL-17A gene expression restored the enhanced inflammatory cytokines. Collectively, these results support a protective role of HDAC2 in HDM-induced airway inflammation by suppressing IL-17A production and might suggest that activation of HDAC2 and/or inhibition of IL-17A production could prevent the development of allergic airway inflammation.