Approaches to study the role of S100 proteins in calcium-dependent cellular responses

Calcium is necessary for the optimal growth and cellular functions of most living organisms. For example, Ca is involved in the processes of muscle contraction, stimulus-secretion coupling, bone formation, blood clotting, cell proliferation and motility, and fertilization. Many regulatory actions of Ca are mediated through Ca-binding proteins. Calcium-modulated proteins are a subclass of Ca-binding proteins that are thought to be the major signal transducers of Ca acting as a cellular second messenger. Most Ca-modulated proteins are not enzymes but are effector proteins capable of transducing a Ca signal into a biological response by their ability to bind Ca reversibly and modulate the activity of other proteins in a Ca-dependent manner. This review focuses on a set of Ca-modulated proteins, the S100 proteins, and their possible roles in mediating Ca-dependent cellular events.