Enables SH3 domain binding activity and kinase binding activity. Involved in several processes, including regulation of T cell activation; regulation of cytokine production; and regulation of signal transduction. Acts upstream of or within T cell differentiation; T cell receptor signaling pathway; and protein dephosphorylation. Located in cytoplasm; cytoplasmic side of plasma membrane; and nucleus. Is expressed in dorsal root ganglion; peripheral nervous system; and thymus primordium. Human ortholog(s) of this gene implicated in several diseases, including Addison's disease; Meniere's disease; autoimmune disease (multiple); chronic lymphocytic leukemia; and pulmonary tuberculosis. Orthologous to human PTPN22 (protein tyrosine phosphatase non-receptor type 22). [provided by Alliance of Genome Resources, Apr 2022]