Autophagy protein microtubule-associated protein 1 light chain-3B (LC3B) activates extrinsic apoptosis during cigarette smoke-induced emphysema.
Chronic obstructive pulmonary disease (COPD) is a debilitating disease caused by chronic exposure to cigarette smoke (CS), which involves airway obstruction and alveolar loss (i.e., emphysema). The mechanisms of COPD pathogenesis remain unclear. Our previous studies demonstrated elevated autophagy in human COPD lung, and as a cellular and tissue response to CS exposure in an experimental model of emphysema in vivo. We identified the autophagic protein microtubule-associated protein 1 light chain-3B (LC3B) as a positive regulator of CS-induced lung epithelial cell death. We now extend these initial observations to explore the mechanism by which LC3B mediates CS-induced apoptosis and emphysema development in vivo. Here, we observed that LC3B(-/-) mice had significantly decreased levels of apoptosis in the lungs after CS exposure, and displayed resistance to CS-induced airspace enlargement, relative to WT littermate mice. We found that LC3B associated with the extrinsic apoptotic factor Fas in lipid rafts in an interaction mediated by caveolin-1 (Cav-1). The siRNA-dependent knockdown of Cav-1 sensitized epithelial cells to CS-induced apoptosis, as evidenced by enhanced death-inducing signaling complex formation and caspase activation. Furthermore, Cav-1(-/-) mice exhibited higher levels of autophagy and apoptosis in the lung in response to chronic CS exposure in vivo. In conclusion, we demonstrate a pivotal role for the autophagic protein LC3B in CS-induced apoptosis and emphysema, suggestive of novel therapeutic targets for COPD treatment. This study also introduces a mechanism by which LC3B, through interactions with Cav-1 and Fas, can regulate apoptosis.
Chen
Zhi-Hua
ZH
Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Lam
Hilaire C
HC
Jin
Yang
Y
Kim
Hong-Pyo
HP
Cao
Jiaofei
J
Lee
Seon-Jin
SJ
Ifedigbo
Emeka
E
Parameswaran
Harikrishnan
H
Ryter
Stefan W
SW
Choi
Augustine M K
AM
D000818:Animals; D017209:Apoptosis; D001343:Autophagy / Q000235:genetics; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000378:metabolism*; D021962:Membrane Microdomains / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D029424:Pulmonary Disease, Chronic Obstructive / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism*; D011656:Pulmonary Emphysema / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism*; D020545:Respiratory Mucosa / Q000378:metabolism; D012907:Smoking / Q000009:adverse effects* / Q000235:genetics / Q000378:metabolism; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism
C495540:CAV1 protein, human; C495541:Cav1 protein, mouse; D051242:Caveolin 1; C491901:FAS protein, human; C491899:Fas protein, mouse; C477012:MAP1LC3A protein, human; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D019014:fas Receptor