Caldesmon also known as CDM, CALD1 is a calmodulin- and actin-binding protein that plays an essential role in the regulation of smooth muscle and nonmuscle contraction. Caldesmon is essential for maintaining the structural integrity of the cytoskeleton and facilitating muscle function. Caldesmon exists in two main forms: muscular Caldesmon, predominantly found in smooth muscle, and non-muscular Caldesmon, which is expressed in various non-muscle tissues. The gene encoding Caldesmon undergoes alternative splicing, resulting in five isoforms, each with distinct regulatory roles. Muscular Caldesmon, also known as high molecular weight Caldesmon or H-Caldesmon, is primarily located on thin filaments in smooth muscle, while the non-muscular isoforms (2-5), referred to as low molecular weight Caldesmon or L-Caldesmon, are widely distributed in non-muscle cells.