Redistribution of Caldesmon and Tropomyosin Associated With Concanavalin a Receptor Capping on Splenic T-Lymphocytes

The present study was undertaken to investigate the involvement of actin-linked regulatory proteins (caldesmon and tropomyosin) in concanavalin A (Con A) receptor capping of mouse splenic T-lymphocytes. Caldesmons with a high molecular weight (130-150 kDa) as well as those with a relatively low molecular weight (70-77 kDa) are shown to be present in a wide range of tissues and cells. By a technique of immunoblotting, we demonstrated that T-lymphocytes contain exclusively the low molecular weight form of caldesmon in addition to tropomyosin with a nonmuscle type. Using immunofluorescence microscopy, caldesmon and tropomyosin are revealed to redistribute into subcaps during Con A-receptor capping of T-lymphocytes. Such redistributions of caldesmon and tropomyosin and the capping of Con A-receptor are inhibited by calmodulin antagonists. These observations suggest that the calmodulin-caldesmon-tropomyosin system is involved in the capping processes of Con A receptors mediated through the control of the actinmyosin interaction.