Troponin I type 1 (skeletal, slow) (TNNI1)

Troponin I type 1 (skeletal, slow) is a muscle-specific regulatory protein encoded by the TNNI1 gene and predominately expressed in slow-twitch skeletal muscle fibers. It is one of three subunits of the troponin complex, where it serves as the inhibitory component that prevents actin-myosin interactions, thus regulating contraction and relaxation through its calcium-dependent conformational change[1][2]. TNNI1 is essential for normal muscle function, fine-tuning the calcium sensitivity of force development. Pathogenic variants cause a spectrum of myopathies, with loss-of-function mutations leading to muscle weakness, and gain-of-function mutations associated with hypercontractile symptoms[3]. TNNI1 can serve as a specific biomarker for slow-twitch muscle injury and has attracted experimental therapeutic research, but it is not classified as a conventional drug target like a receptor or enzyme[1][2][3].

Other names

Troponin I, slow skeletal muscleTNN1ssTnITroponin I, slow-twitch isoformSSTNItroponin I slow skeletal muscle isoformtroponin I type 1 (skeletal, slow)

Activators: Increase contractility by sensitizing the troponin complex to calcium (for loss-of-function TNNI1 variants); Inhibitors: Reduce excessive contractility by inhibiting myosin activity (for gain-of-function TNNI1 variants)