Novel regulatory role of post-translational structural modification in modulating Src kinase activity in pulmonary arterial hypertension

Under conditions that lead to pulmonary arterial hypertension (PAH), the pro-proliferative oncoprotein Src kinase activity is elevated, contributing to pulmonary arterial smooth muscle cell remodeling, increasing vascular resistance, and leading to PAH. In addition, reactive oxygen species (ROS), including Hydrogen peroxide (H2O2), are elevated in the pulmonary vasculature under pro-PAH conditions. Therefore, we hypothesized that Src kinase is subject to redox modulation by elevated hydrogen peroxide (H2O2) under pro-PAH conditions. We intended to explore whether increased H2O2 can cause the oxidation of Src kinase thiol groups resulting in an inter-molecular disulfide bond forming Src kinase homodimer, increasing its catalytic activity. The results of this study detected evidence that Src kinase undergoes redox-induced homodimer formation as illustrated by western blot analysis under non-reducing conditions of rat MCT-induced PAH lung lysates. Furthermore, the redox-mediated Src kinase homodimer formation was associated with the increased catalytic activity of Src kinase, as seen in its intra-molecular auto-phosphorylation of its tyrosine 416 residue. This process was accompanied by activating one of Src kinase downstream substrates, STAT3, via the phosphorylation of its tyrosine 705 residue. Moreover, these mechanistic changes were associated with a PAH disease state confirmed with elevated right ventricle systolic pressure and right ventricle hypertrophy through right ventricle catheterization and the Fulton index, respectively. From the results above, we can conclude that in rat MCT-PAH lung lysates, Src kinase undergoes a redox-induced modulation that results in a structural modification associated with increased Src kinase activity, as observed in its autophosphorylation and the phosphorylation of its downstream substrate STAT3. In conclusion, under conditions that lead to PAH, Src kinase undergoes a post-translational structural modification. This modification occurs in redox-induced oxidation of Src kinase thiol groups. This process results in an inter-molecular disulfide bond formation yielding a homodimer associated with elevated Src kinase catalytic activity, further adding a mechanistic layer to Src kinase regulation in PAH. Kuwait University Research Sector This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.