ABSTRACT

Calcyclin (CaCY, S100A6) is a member of the S100 family of small Ca²⁺-binding proteins exhibiting both tissue and cellular specific distribution in mammalian cells. One unique feature that sets CaCY apart from other S100 proteins is that the expression level of CaCY inside the cell fluctuates. The mode of fluctuation depends upon the physiological state of the cell (e.g whether it is undergoing proliferation, differentiation, secretion or pathological transformation). Particularly, high amounts of CaCY are found in many tumor cells. The biochemical properties of CaCY have been characterized, however, its function remains unclear. This review intends to summarize previous studies on CaCY with respect to its suggested functional roles. The in situ localization of CaCY is also discussed. When CaCY is tagged with green fluorescent protein, the fusion protein is closely associated with intracellular elements surrounding the nucleus. Such a distribution may be indicative of a role for CaCY in certain cellular processes.