Evidence, hypotheses and significance of MAP kinase TNNI3K interacting with its partners

TNNI3K is a cardiac-specific and cardiac troponin I（cT n I）-interacting MAP kinase, known to play important roles in promoting cardiac differentiation, maintenance of beating rhythm and contractual force. The molecular structure of TNNI3 K contains three kinds of domain: a seven or ten NH2-terminal ankyrin repeat domain followed by a protein kinase domain and a COOH-terminal serine-rich domain. There are many binding sites in the structure of TNNI3 K for binding to ATP, magnesium, nucleotide, protein kinase C, antioxidant protein 1（AOP-1） and cT n I, indicating TNNI3 K has many interacting partners. This review summarizes the evidence, hypothesis and significance of TNNI3 K interacting with TNNI3 and its other putative interaction partners. From the literature, the interaction partners of TNNI3 K are divided into 2 types following their phenotypic pattern of functions, positive interaction（to increase the cardiac performance） or negative interaction（to suppress the cardiac performance）. Following their binding sites, it also can be divided into other 2 types: binding to C-terminal domain（e.g., cT n I） or binding to both ankyrin repeat domain and C-terminal domains（AOP-1）.To date, a well understood partner of TNNI3 K is cT nI, from the molecular structure, physiological function, mechanisms and its significance in some physiological and pathophysiological conditions. There are many reasons to believe that, with more understanding on the TNNI3 K interacting with its partners, we can understand more roles of TNNI3 K in some cardiac diseases.