Protein phosphatase 4 (protein phosphatase X) is a 35kD serine/threonine phosphatase with predicted binding sites for iron and manganese. It is found in both the cytoplasm and the nucleus. The phophoprotein alpha 4 has been identified as a potential regulatory subunit. PPP4C has been shown to localize to centrosomes/spindle pole bodies and is believed to be involved in microtubule organization. It may also play a role in relaying the TNF-alpha signal to the JNK pathway. Additionally, it has been shown to associate with C-Rel, NF-Kappa B p50, and RelA. Hence, it may be involved in the activation of these key mediators of immune response and apoptosis.Synonyms: PP-X, PP4C, PPP4, PPX, Protein phosphatase X, Serine/threonine-protein phosphatase 4 catalytic subunit