Fig. 1

JAK structure. There are seven homologous domains in the JAK family, ranging from JH1 to JH7. The Janus homology 1 (JH1) domain functions primarily as a kinase domain. The pseudokinase domain, denoted as Janus homology 2 (JH2), exhibits kinase-like features but lacks typical kinase activity. The SH2 domain is formed by a combination of JH3 and JH4 domains, facilitating protein-protein interactions. Consisting of JH5, JH6, and a segment of the JH4 domains, the protein 4.1, ezrin, radixin, moesin (FERM) domain is involved in membrane attachment, protein interactions, and the modulation of JAK activity [6,7,8]