Signal transduction mechanism of a peptide mimetic of interferon-gamma.
Signal transduction mechanism of a peptide mimetic of interferon-gamma.
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DOI：
10.1021/bi036213t
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发表时间：
2004-04
期刊：
影响因子：
2.9
通讯作者：
P. Subramaniam;Lawrence O. Flowers;S. Mohammed I. Haider;Howard M. Johnson
中科院分区：
文献类型：
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作者：
P. Subramaniam;Lawrence O. Flowers;S. Mohammed I. Haider;Howard M. Johnson
干扰素-γ（IFN γ）的C-末端含有转录因子STAT 1 α的激活和核转位以及IFN γ激活基因的诱导所需的核定位序列（NLS）。在此和其他研究的基础上，我们开发了具有抗病毒活性和上调MHC II类分子的IFN γ功能的IFN γ肽模拟物。该模拟物还与IFN γ共享诱导STAT 1 α和IFN γ受体（IFNGR）-1亚基的活化和核转位的能力。模拟物IFN γ（95-132）是由鼠IFN γ的C-末端残基95-132组成的肽，并且含有所需的α-螺旋结构域和IFN γ的NLS。在这项研究中，我们确定了模拟物的细胞内作用的信号转导水平的机制。我们表明，模拟物介导IFNGR-1的核转运，通过其与IFNGR-1的胞浆区253-287通过螺旋区和IFN γ（95-132）的NLS的相互作用。模拟物的NLS的丙氨酸取代表明NLS是核转位所需的，并且模拟物的核转运性质与其结合IFNGR-1的能力相关。这些数据还表明，IFN γ（95-132）的NLS可以同时与IFNGR-1和核输入机制相互作用。我们发现，在体外核转运试验中，酪氨酸磷酸化的STAT 1 α在核输入因子存在下不能进行核转位，但在IFN γ（95-132）和JAK 2磷酸化的IFN-γ-1存在下转运到细胞核，STAT 1 α与IFN-γ（95-132）/IFN-γ-1/STAT 1 α结合。因此，具有IFN γ功能的模拟物作为伴侣蛋白直接参与STAT 1 α的核转运，并与先前描述的IFN γ共享这种作用机制。类似于IFN γ的模拟物能够上调肿瘤抑制因子p21 WAF 1/CIP 1，这是STAT 1 α的直接靶点，并且这种能力需要模拟物的NLS。然而，与IFN γ不同，模拟物不能下调c-myc，因此不会抑制细胞的周期。这表明IFN γ具有与STAT 1 α的核转位不直接相关的额外功能。
The C-terminus of interferon-gamma (IFNgamma) contains a nuclear localization sequence (NLS) required for the activation and nuclear translocation of the transcription factor STAT1alpha and induction of IFNgamma-activated genes. On the basis of this and other studies, we developed a peptide mimetic of IFNgamma that possesses the IFNgamma functions of antiviral activity and upregulation of MHC class II molecules. The mimetic also shares with IFNgamma the ability to induce the activation and nuclear translocation of STAT1alpha and the IFNgamma receptor (IFNGR)-1 subunit. The mimetic, IFNgamma(95-132), is a peptide that consists of the C-terminal residues 95-132 of murine IFNgamma and contains a required alpha-helical domain and the NLS of IFNgamma. In this study, we determined the mechanism of the intracellular action of the mimetic at the level of signal transduction. We show that the mimetic mediates the nuclear transport of IFNGR-1 through its interaction with IFNGR-1 cytoplasmic region 253-287 via both the helical region and the NLS of IFNgamma(95-132). Alanine substitutions of the NLS of the mimetic showed that the NLS was required for nuclear translocation and that the nuclear transport properties of the mimetic correlated with its ability to bind IFNGR-1. These data also show that the NLS of IFNgamma(95-132) can interact simultaneously with IFNGR-1 and the nuclear import machinery. We found that in in vitro nuclear transport assays tyrosine-phosphorylated STAT1alpha failed to undergo nuclear translocation in the presence of nuclear import factors, but was transported to nucleus in the presence of IFNgamma(95-132) and JAK2-phosphorylated IFNGR-1, to which STAT1alpha binds, as a complex of IFNgamma(95-132)/IFNGR-1/STAT1alpha. Thus, the mimetic, which possesses IFNgamma function, is directly involved as a chaperone in the nuclear transport of STAT1alpha and shares this mechanism of action with that previously described for IFNgamma. The mimetic, like IFNgamma, is able to upregulate the tumor suppressor p21WAF1/CIP1, a direct target of STAT1alpha, and this ability requires the NLS of the mimetic. However, unlike IFNgamma, the mimetic is unable to downregulate c-myc and hence does not inhibit the cycling of cells. This suggests that IFNgamma has additional functions that are not tied directly to the nuclear translocation of STAT1alpha.