Interferon protein phosphatase activity

Cyclosporine can bind to the cytosolic protein cy-tophilin C. This drug-protein complex inhibits cal-cineurin phosphatase activity, which leads to a decreased synthesis and release of several cytokines, including interleukins IL-2, IL-3, IL-4, interferon-a, and tumor necrosis factor. 

Abbreviations used tumor necrosis factor-a (TNF-a), interferon-y (INF-y), interleukin-ip (IL-1P), sphingosine kinase (SK), protein kinase C (PKC), sphingomyelinase (SMase), extra-cellular-regulated mitogen-activated protein kinase (ERK), stress-activated protein kinase (SAPK), ceramide activated protein kinase (CAPK), ceramide activated protein phosphatase (CAPP), mitogen activated kinase (MEK), phosphatidylinositol-3-kinase (PI3K), phospholipase C (PLC), phospholipase D (PLD), SIPR (SIP receptor). 

He B, Gross M, Roizman B (1997) The gamma(l)34.5 protein of herpes simplex virus 1 complexes with protein phosphatase 1 alpha to dephosphorylate the alpha subunit of the eukaryotic translation initiation factor 2 and preclude the shutoff of protein synthesis by double-stranded RNA-activated protein kinase. Proc Natl Acad Sci USA 94 843-848 Hollander MC, Zhan Q, Bae I, Fornace AJ, Jr (1997) Mammalian GADD34, an apoptosis- and DNA damage-inducible gene. J Biol Chem 272 13731-13737 Isaacs A, Lindenmann J (1957) Virus interference. I. The interferon. Proceedings of the Royal Society of London 147 258-267... 

Figure 3 Separation of various translation regulatory activities on DEAE cellulose. Cell sap from interferon-treated cultures was fractionated and assayed on mengo RNA translation (as in Table 2) in S10 from control (c) and interferon-treated cells (int) with O.O4 M g/ml dsENA. Activity without fraction = 1. Oligo-isoadenylate synthetase E (IO), factor F (18). Protein phosphatase (P) and protein kinase activator A, are discussed in the text.

We also examined whether factor A could be alone responsible for the increased PK-i activity after interferon treatment. Factor A stimulated slightly eIF-2 and histone phosphorylation in control cell extracts but not nearly as much as in interferon-treated cell extracts. Factor A was found in control cell preparations. Some component of the protein kinase PK-i itself seems, therefore, to change after interferon treatment. Finally, protein phosphatase P is found both in control cell sap and, in lower amounts, in... 

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