Nitration of protein kinase G-Iα modulates cyclic nucleotide crosstalk via phosphodiesterase 3A: Implications for acute lung injury

Abstract

Phosphodiesterase 3A (PDE3A) selectively cleaves the phosphodiester bond of cyclic AMP, and is inhibited by cGMP, making it an important regulator of cAMP/cGMP signaling crosstalk in the pulmonary vasculature. In addition, the nitric oxide (NO)-cGMP axis is known to play an important role in maintaining endothelial barrier function. However, the potential role of protein kinase G-Iα (PKG-Iα) in this protective process is unresolved and was the focus of our study. We describe here a novel mechanism regulating PDE3A activity which involves a protein kinase G-Iα (PKG-Iα)-dependent inhibitory phosphorylation of PDE3A at Serine (S)654. We also show that this phosphorylation is critical for maintaining intracellular cAMP levels in the pulmonary endothelium and endothelial barrier integrity. In an animal model of acute lung injury (ALI) induced by challenging mice with lipopolysaccharide (LPS), an increase in PDE3 activity and a decrease in cAMP levels in lung tissue was associated with reduced PKG activity upon PKG-Iα nitration at tyrosine (Y)247. The peroxynitrite scavenger manganese (III) tetrakis(1-methyl-4pyridyl)porphyrin (MnTMPyP) prevented this increase in PDE3 activity in LPS-exposed lungs. In addition, site-directed mutagenesis of PDE3A to replace S654 with alanine yielded a mutant protein that was insensitive to PKG-dependent regulation. Taken together, our data demonstrate a novel functional link Journal P between nitrosative stress induced by LPS during ALI and the downregulation of barrier-protective intracellular cAMP levels. Our data also provide new evidence that PKG-Iα is critical for endothelial barrier maintenance, and that preservation of its catalytic activity may be efficacious in ALI therapy. © 2021 THE AUTHORS. Published by Elsevier Inc on behalf of American Society for Biochemistry and Molecular Biology.