IP3RCYT is an IP 3 R inhibitory peptide, which can inhibit the binding of cytochrome C to IP 3 R with an IC 50 about 100 nM. IP3RCYT regulates calcium signaling within cells. P3RCYT inhibits apoptosis in HeLa and Jurkat cells treated with Staurosporine or Membrane-bound Fas ligand (FasL).