Caldesmon, HMW (h-Caldesmon) [h-CALD]

Caldesmon was identified as a Ca2+/Calmodulin-binding protein with molecular weight of 120-150kDa high molecular weight Caldesmon (H-Caldesmon) and 70-80kDa low molecular weight (L-Caldesmon). H-Caldesmon (isoform 1) which is an actin, myosin, tropomyosin, and calmodulin-binding protein, is expressed in differentiated contractile smooth muscle cells (SMC) while L-Caldesmon (isoforms 2, 3, 4 and 5) is most abundant in non-muscle tissue and cells. Neither of the two variants has been detected in skeletal muscle or heart. As such, H‐Caldesmon is a specific marker for SMC and could aid in the differential diagnosis of tumors with a SMC component (e.g. leiomyosarcoma) from other tumors with smooth muscle‐like differentiation e.g. myofibroblastic tumors. L-Caldesmon may play an important function in motile processes such as secretion and organelle movement. This antibody recognizes only the 150kDa variant H-Caldesmon, labels smooth muscle and tumors of smooth muscle.