AOP-1 interacts with cardiac-specific protein kinase TNNI3K and down-regulates its kinase activity.

In the present study, a yeast two-hybrid screening system was used to identify the interaction partners of cardiac troponin I-interacting kinase (TNNI3K) that might serve as regulators or targets, and thus in turn to gain some insights on the roles of TNNI3K. After screening the adult heart cDNA library with a bait construct encoding the ANK motif of TNNI3K, antioxidant protein 1 (AOP-1) was isolated. The interaction between TNNI3K and AOP-1 was confirmed by the in vitro binding assay and coexpression experiments in vivo. The colocalization of TNNI3K and AOP-1 was clarified by confocal immunofluorescence. Moreover, coexpression of AOP-1 inhibited TNNI3K kinase activity in the in vitro kinase assay.