S100A1 and acne: Since the formation of TJs is a Ca2+-dependent process, the role of calcium-binding and highly elevated in acne lesions S100A proteins, such as psoriasin (S100A7), S100A8/A9 (calprotectin), S100A12 (calgranulin C), and koebnerisin (S100A15, S100A7A), appear to be fundamental.