Regulation of calpain by ERK-dependent phosphorylation in pulmonary vascular remodeling

Pulmonary vascular remodeling is an important feature in the progression of pulmonary arterial hypertension (PAH). Common mediators in PAH including platelet-derived growth factor (PDGF), inflammatory cytokines (e.g., interleukin-6, IL-6), reactive oxygen species (ROS, e.g., H2O2), vasoactive substances such as serotonin (5-HT), and endothelin-1 (ET-1) contribute to pulmonary vascular remodeling. Calpain mediates collagen synthesis, cell proliferation, and migration of pulmonary artery smooth muscle cells (PASMCs) and plays an important role in hypoxia- and monocrotaline (MCT)-induced pulmonary vascular remodeling and PAH. We will test our hypothesis that calpain is activated via ERK-mediated phosphorylation in pulmonary vascular remodeling. First, we will determine whether PAH mediators induce calpain activation and phosphorylation via ERK signaling pathway. We will study whether inhibition of ERK prevents PAH mediator-induced calpain phosphorylation and activation. The ERK-phosphorylated sites will be identified by using MALDI-TOF-TOF mass spectrometry and site-directed mutagenesis. Second, we will determine whether inhibition of ERK activity prevents or attenuates pulmonary vascular remodeling in animal models. The proposed research is to answer the question whether PAH mediators (PDGF, 5-HT, H2O2, ET-1, and IL-6) activate calpain through ERK-dependent phosphorylation in PASMCs in pulmonary vascular remodeling. This proposal for the first time identifies the ERK-phosphorylated residues of calpain and demonstrates that calpain signaling may be a critical common signal pathway for these PAH mediators. Successful completion of this proposal will provide a strong rationale for manipulating calpain and ERK in the treatment of pulmonary hypertension. (AHA Program: Postdoctoral Fellowship)