A fungal protease allergen directly enhances airway smooth muscle cell contraction

Thursday, November 07, 2013 — Poster Session II
12:00 p.m. – 2:00 p.m.	FAES Academic Center (Upper-Level Terrace)	NIAID	PHARM-2

Authors

N. Balenga
M. Zhao
J.A. Jude
R.A. Panettieri
Jr.
K.M. Druey

Abstract

Allergic asthma is a chronic disease where exposure of the airway epithelium to otherwise innocuous molecules (allergens) induces production of cytokines/chemokines, which in turn recruit leukocytes, leading to airway remodeling/hyper-responsiveness. Most allergens have protease activity. We hypothesized that the proteolytic activity of a typical allergen (the fungus Aspergillus fumigatus [Af]) permits diffusion into the subepithelial layer, where it exerts direct functional effects on Airway Smooth Muscle (ASM) cells. We found that while exposure of cultured human/mouse ASM cells to Af extract led to reduced adhesion in a serine protease-dependent manner due to loss of focal adhesions, it increased cytosolic Ca2+ responses to bradykinin. Moreover, mouse precision-cut lung slices (PCLS) pre-treated with Af exhibited increased contraction in a time/dose-dependent manner. Pre-treatment of cultured ASM cells with collagen abrogated the effects of Af on adhesion, and exposure of PCLS to Af reduced their collagen content, implicating the digestion of extracellular matrix (ECM) by Af. Using proteomic/biochemical approaches, we identified a single serine protease, Alkaline Protease 1 (Alp1, Asp f13 major allergen), as the ECM-degrading protease in Af. Current studies are aimed at further dissecting the mechanisms whereby Alp1 enhances ASM contractility and localizing Alp1 in lungs of allergen-challenged mice and human asthmatics.