Community analysis of large-scale molecular dynamics simulations elucidated dynamics-driven allostery in tyrosine kinase 2.

TYK2 is a nonreceptor tyrosine kinase, member of the Janus kinases (JAK), with a central role in several diseases, including cancer. The JAKs' catalytic domains (KD) are highly conserved, yet the isolated TYK2-KD exhibits unique specificities. In a previous work, using molecular dynamics (MD) simulations of a catalytically impaired TYK2-KD variant (P1104A) we found that this amino acid change of its JAK-characteristic insert (αFG), acts at the dynamics level. Given that structural dynamics is key to the allosteric activation of protein kinases, in this study we applied a long-scale MD simulation and investigated an active TYK2-KD form in the presence of adenosine 5'-triphosphate and one magnesium ion that represents a dynamic and crucial step of the catalytic cycle, in other protein kinases. Community analysis of the MD trajectory shed light, for the first time, on the dynamic profile and dynamics-driven allosteric communications within the TYK2-KD during activation and revealed that αFG and amino acids P1104, P1105, and I1112 in particular, hold a pivotal role and act synergistically with a dynamically coupled communication network of amino acids serving intra-KD signaling for allosteric regulation of TYK2 activity. Corroborating our findings, most of the identified amino acids are associated with cancer-related missense/splice-site mutations of the Tyk2 gene. We propose that the conformational dynamics at this step of the catalytic cycle, coordinated by αFG, underlie TYK2-unique substrate recognition and account for its distinct specificity. In total, this work adds to knowledge towards an in-depth understanding of TYK2 activation and may be valuable towards a rational design of allosteric TYK2-specific inhibitors.

Insights on the alteration of functionality of a tyrosine kinase 2 variant: a molecular dynamics study.

Motivation: The tyrosine kinase 2 protein (Tyk2), encoded by the TYK2 gene, has a crucial role in signal transduction and the pathogenesis of many diseases. A single nucleotide polymorphism of the TYK2 gene, SNP rs34536443, is of major importance, since it has been shown to confer protection against various, mainly, autoimmune diseases. This polymorphism results in a Pro to Ala change at amino acid position 1104 of the encoded Tyk2 protein that affects its enzymatic activity. However, the details of the underlined mechanism are unknown. To address this issue, in this study, we used molecular dynamics simulations on the kinase domains of both wild type and variant Tyk2 protein. Results: Our MD results provided information, at atomic level, on the consequences of the Pro1104 to Ala substitution on the structure and dynamics of the kinase domain of Tyk2 and suggested reduced enzymatic activity of the resulting protein variant due to stabilization of inactive conformations, thus adding to knowledge towards the elucidation of the protection mechanism against autoimmune diseases associated with this point mutation.