Pathways that Regulate Antigrowth Effects of Interferons

描述（由申请人提供）：1型干扰素是先天免疫和抗病毒反应的关键调节因子。为了发挥它们的作用，它们通常也抑制细胞生长。干扰素抑制细胞增殖的机制各不相同，在许多情况下尚不清楚。在一些细胞中，1型干扰素（ifn - α / β）诱导细胞凋亡；在其他细胞系中，ifn - α / β抑制细胞生长而不诱导细胞凋亡，在某些情况下，这些细胞因子实际上通过其他刺激阻止细胞凋亡。在体内和细胞培养中，ifn - α / β刺激未成熟B细胞凋亡。使用来自敲除小鼠的不表达Stat1、Stat1、Stat5a/ B或Tyk2的bll-7依赖性B细胞的初步结果表明，干扰素激活由Stat1和Stat2转录因子调控的早期反应基因对IFNa/a的凋亡作用不是必需的。然而，酪氨酸激酶Tyk2的表达是IFNalkpha/ β刺激的pro B细胞死亡以及这些细胞因子激活Stat3所必需的。这些体外结果在体内也可以看到，tyk2缺失的小鼠可以抵抗LCMV刺激的骨髓和脾脏B细胞的损失。我们假设ifn - α / β介导的细胞凋亡需要Tyk2的激酶活性，从而导致stat3的酪氨酸磷酸化和该转录因子对基因的调控，从而导致前B细胞的程序性细胞死亡。

DESCRIPTION (provided by applicant): Type 1 interferons are critical regulators of innate immunity and antiviral responses. To exert their actions they often also inhibit cell growth. The mechanisms by which interferons inhibit cell proliferation vary and in many circumstances are not well understood. In some cells type 1 interferons (IFNalpha/beta) induce apoptosis; in other cell lines IFNalpha/beta inhibit cell growth without induction of apoptosis, and in certain circumstances these cytokines actually prevent apoptosis by other stimuli. In vivo and in cell culture, IFNalpha/beta stimulates apoptosis of immature B cells. Preliminary results using bll-7-dependent B cells from knock out mice that do not express Stat1, Stat1, Stat5a/b, or Tyk2 indicate that interferon activation of early response genes regulated by the Stat1 and Stat2 transcription factors is not necessary for the apoptotic actions of IFNa/a. However, expression of the tyrosine kinase Tyk2 is required for IFNalkpha/beta stimulated death of pro B cells as well as activation of Stat3 by these cytokines. These in vitro results are also seen in vivo where Tyk2-null mice are resistant to LCMV stimulated loss of B cells from bone marrow and spleen. We hypothesize that IFNalpha/beta mediated apoptosis requires the kinase activity of Tyk2, resulting in tyrosine phosphorylation ofStat3 and regulation of genes by this transcription factor that lead to programmed cell death of pro B cells. The Specific Aims are: 1. Determine the domains in Tyk2 required for IFNBeta stimulated apoptosis of IL-7-dependent bone marrow-derived B cells. 2. Determine the role of phosphorylated Stat3 in IFNBeta stimulated PCD of B cells 3. Identify proteins in primary IL-7 dependent B cells that require the expression of Tyk2 to activate Stat3 and cause IFNBeta stimulated apoptosis.