Tyrosine phosphatase which dephosphorylates or contributes to the dephosphorylation of CTNND1, FLT3, PDGFRB, MET, KDR, LYN, SRC, MAPK1, MAPK3, EGFR, TJP1, OCLN, PIK3R1 and PIK3R2 (PubMed:10821867, PubMed:12062403, PubMed:12370829, PubMed:12475979, PubMed:18348712, PubMed:19494114, PubMed:19922411, PubMed:21262971). Plays a role in cell adhesion, migration, proliferation and differentiation (PubMed:12370829, PubMed:14709717, PubMed:16682945, PubMed:19836242). Has a role in megakaryocytes and platelet formation (PubMed:30591527). Involved in vascular development (By similarity). Regulator of macrophage adhesion and spreading (By similarity). Positively affects cell-matrix adhesion (By similarity). Positive regulator of platelet activation and thrombosis. Negative regulator of cell proliferation (PubMed:16682945). Negative regulator of PDGF-stimulated cell migration; through dephosphorylation of PDGFR (PubMed:21091576). Positive regulator of endothelial cell survival, as well as of VEGF- induced SRC and AKT activation; through KDR dephosphorylation (PubMed:18936167). Negative regulator of EGFR signaling pathway; through EGFR dephosphorylation (PubMed:19836242). Enhances the barrier function of epithelial junctions during reassembly (PubMed:19332538). Negatively regulates T-cell receptor (TCR) signaling (PubMed:11259588, PubMed:9531590, PubMed:9780142). Upon T-cell TCR activation, it is up- regulated and excluded from the immunological synapses, while upon T- cell-antigen presenting cells (APC) disengagement, it is no longer excluded and can dephosphorylate PLCG1 and LAT to down-regulate prolongation of signaling (PubMed:11259588, PubMed:12913111). {ECO:0000250|UniProtKB:Q64455, ECO:0000269|PubMed:10821867, ECO:0000269|PubMed:11259588, ECO:0000269|PubMed:12062403, ECO:0000269|PubMed:12370829, ECO:0000269|PubMed:12475979, ECO:0000269|PubMed:12913111, ECO:0000269|PubMed:14709717, ECO:0000269|PubMed:16682945, ECO:0000269|PubMed:18348712, ECO:0000269|PubMed:18936167, ECO:0000269|PubMed:19332538, ECO:0000269|PubMed:19494114, ECO:0000269|PubMed:19836242, ECO:0000269|PubMed:19922411, ECO:0000269|PubMed:21091576, ECO:0000269|PubMed:21262971, ECO:0000269|PubMed:30591527, ECO:0000269|PubMed:9531590, ECO:0000269|PubMed:9780142}. [Isoform 2]: Activates angiogenesis and cell migration (PubMed:28052032). Downregulates the expression of the endothelial adhesion molecules ICAM1 and VCAM1 (PubMed:28052032). . This is the function of Ensembl gene identifier ENSG00000149177 (PTPRJ, protein tyrosine phosphatase receptor type J).