Fig. 1

Structure of Bruton’s tyrosine kinase (BTK) and associated cross-linking signaling pathways. a BTK comprises five structural domains. BTK activation occurs twice during phosphorylation upon the plasma membrane. The first phosphorylation occurs on the Tyr551 site within the kinase domain by the Syk or Src family kinase, which subsequently leads to autophosphorylation of Tyr223 in the SH3 domain, achieving full activation of BTK kinase activity. b BTK activation process and inhibited result of cross-linking pathways by BTK inhibitors. The left figure shows when extracellular antigen bond BCR, BTK can regulate adverse cellular biological processes by activating multiple important pathways, such as NF-kB, MAPK, NFAT, and mTOR pathway. The right figure shows when the BCR pathway is irreversibly inhibited by small-molecule BTK inhibitors, its downstream pathway such as NF-kB, MAPK, and NFAT will also be inhibited, resulting in anti-tumor activity in B cell lymphoma