Calreticulin.

Calreticulin is an ancient and highly conserved protein. It is intensively studied and has been assigned multiple functions, the scope and variety of which are exceptionally wide for a single protein. Subsequent to the description of its calcium binding properties, calreticulin has been characterized as a molecular chaperone, an extracellular lectin, an intracellular mediator of integrin function, an inhibitor of steroid hormone-regulated gene expression and a C1q-binding protein. That one protein can perform so many functions is at once intriguing and controversial and further investigation is clearly required in order to fully understand the functions of calreticulin and elucidate its roles in disease. Based on current knowledge, calreticulin is being examined as a possible target for therapeutic intervention in steroid hormone-dependent conditions, such as osteoporosis, as well as for the development of novel anti-thrombotic agents.