Fast skeletal troponin C (sTnC)

Fast skeletal troponin C is a calcium-binding regulatory protein found exclusively in fast-twitch (type II) skeletal muscle fibers, encoded by the TNNC2 gene[1][2][3][4][5][6]. It is one of three subunits of the troponin complex (along with troponin I and troponin T) that regulates striated muscle contraction in response to changes in intracellular calcium concentration. Upon Ca^2+^ binding, fast skeletal troponin C (sTnC) undergoes a conformational change that interacts with the troponin I subunit, leading to tropomyosin movement on actin filaments and ultimately permitting actin-myosin cross-bridge cycling and muscle contraction[1][2][5]. Fast skeletal troponin C is homologous but distinct from cardiac and slow skeletal muscle isoforms, with unique structural characteristics and tissue-restricted expression. Mutations in the TNNC2 gene have been implicated in certain congenital myopathies, though sTnC itself is not a common therapeutic target. Some investigational or off-label calcium sensitizers interact with the broader troponin complex but do not selectively target the skeletal isoform[1][3][6].

Other names

Skeletal muscle troponin CTroponin C, fast skeletal muscleTNNC2 (gene symbol)Troponin C type 2

Calcium sensitization by stabilizing Ca^2+^-bound conformation (for calcium sensitizers targeting troponin complex); Modulation of actin-myosin interaction through troponin complex