Expression of the phosphorylated myristoylated alanine-rich C kinase substrate (MARCKS) in COPD bronchial glands

Myristoylated alanine-rich C kinase substrate (MARCKS) is a central regulatory molecule involved in mucin granule release by normal human bronchial epithelial cells in vitro. Upon stimulation, activated PKC phosphorylates MARCKS (p-MARCKs), causing translocation of p-MARCKS from the plasma membrane to the cytoplasm, where it is then dephosphorylated, thus interacting with mucin granule membranes and mediating their subsequent exocytosis. The aim of our study was to investigate by immunohistochemistry (IHC) the expression of protein p-MARCKS in the bronchial rings, obtained during lung resection surgery, of smokers (current and ex) with or without COPD compared with non-smoker subjects. We examined formalin-fixed paraffin-embedded bronchial rings by IHC for identification of total p-MARCKS+ cells. The number of p-MARCKS+ve cells was determined among the mucous cells in the bronchial submucosal glands. Samples from 10 age-matched non-smokers subjects, 29 smokers with normal lung function and 29 smokers with COPD were obtained. We were unable to detect any significant differences in p-MARCKS in the bronchial mucous glands between the 3 groups of subjects. This data suggests that the p-MARCKS pathway is not critical for mucin secretion in the bronchial glands of COPD patients.