Department of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands.
Mol Immunol. 2010 Feb;47(5):1023-30. doi: 10.1016/j.molimm.2009.11.016. Epub 2009 Dec 16.
IFN-gamma plays an essential role in the IL-12/IL-23/IFN-gamma pathway that is required for the defense against intracellular pathogens. In the IFN-gammaR1 several amino acid substitutions have been reported that abrogate IFN-gamma signaling. These substitutions can lead to a null phenotype and enhanced susceptibility to infection by poorly pathogenic mycobacteria, a disorder known as Mendelian Susceptibility to Mycobacterial Disease (MSMD). More common amino acid variations in the IFN-gammaR1 may also influence IFN-gammaR function, albeit more subtle. To determine the effect of various amino acid substitutions on IFN-gammaR1 expression and function we cloned two newly identified amino acid substitutions (S149L, I352M), four common variations (V14M, V61I, H335P, L467P), seven reported missense mutations (V61Q, V63G, Y66C, C77Y, C77F, C85Y, I87T) and the 818delTTAA mutation in a retroviral expression vector. IFN-gammaR1 expression was determined as well as responsiveness to IFN-gamma stimulation. The two newly discovered variants, and the four common polymorphisms could be detected on the cell surface, however, the V14M, H335P and I352M variants were significantly lower expressed at the cell membrane, compared to the wild type receptor. Despite the variance in cell surface expression, these IFN-gammaR1 variants did not affect function. In contrast to literature, in our model the expression of the V63G variant was severely reduced and its function was severely impaired but not completely abrogated. In addition, we confirmed the severely reduced function of the I87T mutant receptor, the completely abrogated expression and function of the V61E, V61Q, C77F, C77Y and the C85Y mutations, as well as the overexpression pattern of the 818delTTAA mutant receptor. The Y66C mutation was expressed at the cell surface, it was however, not functional. We conclude that the V14M, V61I, S149L, H335P, I352M and L467P are functional polymorphisms. The other variants are deleterious mutations with V61E, V61Q, Y66C, C77F, C77Y and C85Y leading to complete IFN-gammaR1 deficiency, while V63G and I87T lead to partial IFN-gammaR1 deficiency.
IFN-γ 在 IL-12/IL-23/IFN-γ 通路中发挥着至关重要的作用，该通路对于抵抗细胞内病原体的防御至关重要。在 IFN-γR1 中，已经报道了几个氨基酸取代，这些取代会导致 IFN-γ 信号失活。这些取代可以导致无效表型，并增强对低致病性分枝杆菌的易感性，这种疾病被称为孟德尔易感性分枝杆菌病（MSMD）。IFN-γR1 中的更常见的氨基酸变异也可能影响 IFN-γR 的功能，尽管更为微妙。为了确定各种氨基酸取代对 IFN-γR1 表达和功能的影响，我们在逆转录病毒表达载体中克隆了两个新发现的氨基酸取代（S149L、I352M）、四个常见的变异（V14M、V61I、H335P、L467P）、七个报道的错义突变（V61Q、V63G、Y66C、C77Y、C77F、C85Y、I87T）和 818delTTAA 突变。我们测定了 IFN-γR1 的表达以及对 IFN-γ 刺激的反应性。两种新发现的变体以及四种常见的多态性都可以在细胞表面检测到，然而，与野生型受体相比，V14M、H335P 和 I352M 变体在细胞膜上的表达显著降低。尽管细胞表面表达存在差异，但这些 IFN-γR1 变体并未影响功能。与文献相反，在我们的模型中，V63G 变体的表达严重减少，其功能严重受损，但并未完全失活。此外，我们还证实了 I87T 突变受体的严重功能缺陷、V61E、V61Q、C77F、C77Y 和 C85Y 突变的完全失活表达和功能，以及 818delTTAA 突变受体的过表达模式。Y66C 突变在细胞表面表达，但没有功能。我们得出结论，V14M、V61I、S149L、H335P、I352M 和 L467P 是功能性多态性。其他变体是有害突变，V61E、V61Q、Y66C、C77F、C77Y 和 C85Y 导致完全的 IFN-γR1 缺陷，而 V63G 和 I87T 导致部分 IFN-γR1 缺陷。
