GSN and chronic obstructive pulmonary disease: GSN is an actin-modifying cytoskeletal protein that has been shown to be increased in plasma from healthy smokers compared with healthy nonsmokers (18) and in the urine of individuals with α-1 antitrypsin deficiency–related COPD (19), and dysregulation has been implicated in other pulmonary diseases, including interstitial lung disease and acute lung injury (20–22).