FN1 and pulmonary arterial hypertension: As mentioned earlier, our results confirmed that TG2 was a ubiquitous multifunctional protein that catalyzed the PTM, which was consistent with the increased activity of TG2 that promoted fibronectin (sFn) serotonylation in the sera of humans with pulmonary arterial hypertension (PAH) and in the sera and lungs of experimental rodent models of PH (Penumatsa et al., 2014a).