S100A6

S100A6 protein belongs to the A group of the S100 protein family of Ca2+-binding proteins. Its expression is restricted to a limited number of cell types in adult normal tissues and in several tumor cell types. As an intracellular protein, S100A6 has been implicated in the regulation of several cellular functions such as proliferation, apoptosis, the cytoskeleton dynamics, and the cellular response to different stress factors. However, functional studies are scarce. Studies of S100A6’s interaction with and inhibition of its partner, CacyBP/SIP - an inhibitor of cell proliferation and tumorigenesis by virtue of its ability to promote degradation of beta-catenin – support a role for S100A6 as a positive regulator of cell proliferation in the epidermis and tumor cells and an antiapoptotic factor in certain leukemias. Also, upregulation of S100A6 in periinfarct cardiomyocytes results in reduction of p53-induced apoptosis via interference with p53 phosphorylation and inhibition ofinduction of fetal genes responsible for cardiomyocytes hypertrophy. On the other hand, interaction with the tumor suppressor, p53, implicates S100A6 in apoptosis, with high concentrations of S100A6, as is typical of certain tumor cells, protecting p53 from inactivation by p300 acetyltransferase and degradation by MDM2. S100A6 can be secreted/released by certain cell types which points to extracellular effects of the protein. RAGE and integrin b1 might transduce extracellular S100A6’s effects, but further analyses in physiological and pathological contexts are required. Lastly, dosage of serum S100A6 might aid in diagnosis in oncology.