View Abstract

A1308 - MAPK13 Induction Co-Locates with MUC5AC to Mucin Granules
Author Block: B. Gerovac1, J. Yantis2, S. L. Brody2, S. P. Keeler2, M. J. Holtzman2; 1Washington Univ Sch of Med, St. Louis, MO, United States, 2Washington Univ Sch of Med, Saint Louis, MO, United States.
Rationale:
Excess mucus production and consequent airway obstruction is a major factor in the morbidity and mortality of acute and chronic respiratory diseases, including asthma and COPD. However, the precise basis for increased mucus formation and effective means to specifically and safely down-regulate mucus to physiological levels remain uncertain. In that context, we discovered that IL-13-induced mucus production in primary-culture human airway epithelial cells was associated with selective MAPK13 activation and was blocked with MAPK13 inhibition using siRNA specific for MAPK13 mRNA or small-molecules designed to target the MAPK13 ATP-binding site. In addition, we found increased levels of activated MAPK13 in lung tissue from patients with excess mucus due to COPD. Therefore, we further studied MAPK13 to define activation and localization in relation to mucus production in primary-culture human airway epithelial cells.
Methods:
Primary-culture human tracheobronchial epithelial cells (hTECs) were generated under air-liquid interface (ALI) conditions and were treated with or without IL-13 for 0-21 d. The levels of phospho-MAPK13 were monitored using phospho-MAPK antibody array, and the cellular level and location of MAPK13 and mucin MUC5AC were monitored using confocal laser scanning microscopy.
Results:
Levels of phospho-MAPK13 were increased by 0.5 h and were maximal at 2 d of IL-13 treatment compared to vehicle-treated controls. MAPK13 immunostaining was detectable at near background levels at 0-21 d without IL-13 treatment but was markedly increased to intense cytoplasmic staining in a subset of cells at 7-21 d with IL-13 treatment. These MAPK13-positive cells were also selectively and intensely stained positive for MUC5AC. Further, the pattern of MAPK13 and MUC5AC immunostaining in the cytoplasm was identical, consistent with co-localization of these proteins to mucin granules.
Conclusions:
These data show that MAPK13 activation (based on phospho-MAPK array) develops quickly (within 0.5 h) in response to IL-13 in human airway epithelial cells. This activation is followed by prolonged induction (lasting at least 21 d) of MAPK13 expression that co-locates precisely with MUC5AC in mucous cells and therefore likely to mucin granules within those cells. Together with our previous work showing that MAPK13 and CLCA1 blockade can inhibit excess mucus production and MUC5AC and CLCA1 induction also co-locates after IL-13 treatment, the results suggest that MAPK13, CLCA1, and MUC5AC might associate at the level of mucin granules to regulate mucus formation during inflammatory airway disease.