Tyrosine-protein kinase 2 pseudokinase domain (JH2) (TYK2 JH2)

Tyrosine-protein kinase 2 (TYK2) is a non-receptor tyrosine kinase and a member of the Janus kinase (JAK) family that plays a pivotal role in the signaling pathways of Type I interferons, IL-12, and IL-23 (UniProt P29597). The JH2 domain, also known as the pseudokinase domain, is a distinct structural region of TYK2 that lacks catalytic activity but functions as a critical regulatory switch for the adjacent JH1 catalytic domain (PubMed: 30933475). Under physiological conditions, the JH2 domain maintains the JH1 domain in an autoinhibited state, preventing spontaneous signaling in the absence of cytokine stimulation. Therapeutic targeting of the JH2 domain involves the use of allosteric inhibitors that bind to its unique regulatory site, thereby stabilizing the autoinhibitory interaction with the JH1 domain (PubMed: 31116584). This allosteric mechanism provides exceptional selectivity for TYK2 over other JAK family members, such as JAK1, JAK2, and JAK3, which is difficult to achieve with traditional ATP-competitive inhibitors targeting the JH1 domain. Clinically, this selectivity translates to a reduced risk of off-target effects like anemia, neutropenia, and lipid elevations typically associated with pan-JAK inhibition. The TYK2 JH2 domain is a validated target for the treatment of immune-mediated inflammatory diseases, including plaque psoriasis, psoriatic arthritis, and systemic lupus erythematosus (PubMed: 35533154). Deucravacitinib is the first-in-class drug approved to target this domain, demonstrating significant efficacy in managing moderate-to-severe psoriasis. Ongoing research continues to explore the potential of TYK2 JH2 inhibition in other conditions such as Crohn's disease and ulcerative colitis.

Other names

TYK2 JH2Janus homology 2 domain of TYK2Tyrosine kinase 2 pseudokinase domainTYK2-JH2Pseudokinase domain of TYK2

Allosteric inhibition of the TYK2 enzyme by binding to the JH2 pseudokinase domain, which stabilizes the autoinhibitory interaction between the JH2 and JH1 domains.