tyk2 belongs to the JAK family of nonreceptor protein tyrosine kinases recently found implicated in signaling through a large number of cytokine receptors. These proteins are characterized by a large amino-terminal region and two tandemly arranged kinase domains, a kinase-like and a tyrosine kinase domain. Genetic and biochemical evidence supports the requirement for tyk2 in interferon-alpha/beta binding and signaling. To study the rob of the distinct domains of tyk2, constructs lacking one or both kinase domains were stably transfected in recipient cells lacking the endogenous protein. Removal of either or both kinase domains resulted in loss of the in vitro kinase activity. The mutant form truncated of the tyrosine kinase domain was found to reconstitute binding of interferon-alpha 8 and partial signaling. While no contribution of this protein toward interferon-beta binding was evident, increased signaling could be measured. The mutant form lacking both kinase domains did not exhibit any detectable activity. Altogether, these results show that a sequential deletion of domains engenders a sequential loss of function and that the different domains of tyk2 have distinct functions, all essential for full interferon-alpha and -beta binding and signaling.
Distinct Domains of the Protein-Tyrosine Kinase Tyk2 Required for Binding of Interferon-Alpha/Beta and for Signal-Transduction
Velazquez, L.; Mogensen, K. E.; Barbieri, G.; Fellous, M.; Uze, G.; Pellegrini, S.
Journal of Biological Chemistry
1995-02-17 / vol 270 / pages 3327-3334
expression; receptor; pathway; catalytic domain; cells; jak