Differential phosphorylation patterns of macrophage cytoskeletal proteins in COPD following phagocytosis

Bacterial clearance by COPD alveolar macrophages is reduced and is mimicked by monocyte-derived macrophages (MDM), providing a useful cell model. Phagocytosis requires appropriate functioning of the cytoskeleton and many cytoskeletal proteins are regulated by phosphorylation. Therefore, we hypothesised that regulation of these proteins differs in COPD and relates to reduced phagocytosis. To test this, the phosphorylation profiles of 584 proteins were examined prior to and post exposure to Haemophilus influenzae (Fig.1) in MDM from non-smokers (n=3) and COPD patients (n=3). Phosphorylation profiles were measured by antibody array. Phagocytosis of H. influenzae changed protein phosphorylation compared to non-stimulated control in cells from both controls and COPD patients (proteins >1.5-fold: 88 COPD, 56 non-smoker; proteins <0.7-fold: 45 COPD, 50 non-smoker). There were key differences in responses between control and COPD cells: Tau (Thr205) phosphorylation in stimulated COPD MDM increased by 2.7-fold, compared to 1.25-fold change in non-smokers and merlin (Ser10) phosphorylation by 2-fold change, compared to no change in non-smokers. These data suggest that phagocytosis results in differential phosphorylation profiles in COPD patients, which may be resulting in altered regulation of cytoskeleton associated proteins. This difference may be responsible for reduced uptake of pathogens and bacteria colonisation.