Catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides (PubMed:24429998). Exerts a strong chemotactic effect on leukocytes partly through activation of one of its membrane receptors BSG/CD147, initiating a signaling cascade that culminates in MAPK/ERK activation (By similarity). Activates endothelial cells (ECs) in a pro-inflammatory manner by stimulating activation of NF-kappa-B and ERK, JNK and p38 MAP-kinases and by inducing expression of adhesion molecules including SELE and VCAM1 (By similarity). Induces apoptosis in ECs by promoting the FOXO1-dependent expression of CCL2 and BCL2L11 which are involved in EC chemotaxis and apoptosis (By similarity). In response to oxidative stress, initiates proapoptotic and antiapoptotic signaling in ECs via activation of NF-kappa-B and AKT1 and up-regulation of antiapoptotic protein BCL2 (By similarity). Negatively regulates MAP3K5/ASK1 kinase activity, autophosphorylation and oxidative stress-induced apoptosis mediated by MAP3K5/ASK1 (By similarity). Necessary for the assembly of TARDBP in heterogeneous nuclear ribonucleoprotein (hnRNP) complexes and regulates TARDBP binding to RNA UG repeats and TARDBP-dependent expression of HDAC6, ATG7 and VCP which are involved in clearance of protein aggregates (PubMed:25678563). Plays an important role in platelet activation and aggregation (PubMed:24429998). Regulates calcium mobilization and integrin ITGA2B:ITGB3 bidirectional signaling via increased ROS production as well as by facilitating the interaction between integrin and the cell cytoskeleton (PubMed:24429998). Binds heparan sulfate glycosaminoglycans (By similarity). [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Binds cyclosporin A (CsA). CsA mediates some of its effects via an inhibitory action on PPIase. Interacts with protein phosphatase PPP3CA/calcineurin A (By similarity). Interacts with PRPF19 isoform 2 (via N-terminus) (PubMed:16352598). Interacts with isoform 2 of BSG/CD147 (By similarity). Interacts with FOXO1; the interaction promotes FOXO1 dephosphorylation, nuclear accumulation and transcriptional activity (By similarity). Interacts with integrin ITGA2B:ITGB3; the interaction is ROS and PPIase activity-dependent and is increased in the presence of thrombin (PubMed:24429998). Interacts with MAP3K5 (By similarity). Interacts with TARDBP (PubMed:25678563). The interaction with TARDBP is dependent on the RNA-binding activity of TARDBP and the PPIase activity of PPIA/CYPA and the acetylation of PPIA/CYPA at Lys-125 favors the interaction (By similarity). Interacts with HNRNPA1, HNRNPA2B1, HNRNPC, RBMX, HNRNPK and HNRNPM (By similarity). Secretion occurs in response to oxidative stress in vascular smooth muscle through a vesicular secretory pathway that involves actin remodeling and myosin II activation, and mediates ERK1/2 activation. Expressed in the kidney thick ascending limb (at protein level) (PubMed:25967121). Expressed in neurons and motor neurons (at protein level) (PubMed:25678563). Expressed in platelets (PubMed:24429998). Acetylation at Lys-125 markedly inhibits catalysis of cis to trans isomerization (By similarity). PPIA acetylation also antagonizes the immunosuppressive effects of cyclosporine by inhibiting the sequential steps of cyclosporine binding and calcineurin inhibition (By similarity). Acetylation at Lys-125 favors the interaction with TARDBP (By similarity). Mice exhibit prolonged tail bleeding time compared to wild-type mice despite equivalent platelet numbers (PubMed:24429998). Platelets exhibit significantly reduced thrombin-induced platelet aggregation and activation, ROS production, calcium mobilization and activation of integrin ITGA2B:ITGB3 (PubMed:24429998). Fibrinogen-platelet binding, platelet spreading and cytoskeleton reorganization are also impaired (PubMed:24429998). Belongs to the cyclophilin-type PPIase family. PPIase A subfamily.