Role of IgE in modulating the expression and function of smMLCK in human airway smooth muscle cells
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Aberrant phenotypes of airway smooth muscle cells are central to the pathophysiology of asthma. The hypercontractile nature of these cells and hypertrophy are the key reasons for the excessive narrowing of the airways observed in allergic asthma. Although previous studies have indicated a role of enhanced content of smMLCK in modulating the contractile reactivity, as well as an indication of hypertrophy of HASM cells in asthmatic conditions, the effect of IgE on the expression of smMLCK in HASM cells is not fully understood. In this study, we demonstrate that IgE augments the expression of smMLCK at the mRNA and protein level. Inhibition of IgE binding with anti-FcεRI blocking antibody, Syk silencing, pharmacological inhibitors to MAPK (ERK1/2, p38, and JNK) and PI3K significantly diminished the IgE-mediated smMLCK expression in HASM cells. Finally, we found that IgE, similar to metacholine induces the contraction of HASM cells grown on collagen gel matrix. Our data suggest that IgE stimulates the phosphorylation of ERK, P38, STAT3 and induces the dephosphorylation of smMLCK to phosphorylate myosin regulatory light chain in HASM cells. Taken together, our data suggest a modulatory role of IgE in regulating the contractile machinery and hypertrophic phenotype of HASM cells.