Enables interleukin-12 receptor binding activity and protein tyrosine kinase activity. Involved in several processes, including hemopoiesis; positive regulation of macromolecule metabolic process; and regulation of signal transduction. Acts upstream of or within several processes, including cell surface receptor signaling pathway; cellular response to lipid; and regulation of apoptotic process. Located in caveola and nucleus. Is expressed in several structures, including alimentary system; central nervous system; genitourinary system; liver and biliary system; and musculoskeletal system. Used to study essential thrombocythemia; myelofibrosis; myeloproliferative neoplasm; and polycythemia vera. Human ortholog(s) of this gene implicated in several diseases, including gastrointestinal system cancer (multiple); hematologic cancer (multiple); hepatic vascular disease (multiple); inflammatory bowel disease (multiple); and lung non-small cell carcinoma (multiple). Orthologous to human JAK2 (Janus kinase 2). [provided by Alliance of Genome Resources, Apr 2022]