Instituto de Ciências Biológicas, Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
Instituto de Ciências Biológicas, Departamento de Genética, Ecologia e Evolução, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
Front Immunol. 2024 Feb 8;15:1341464. doi: 10.3389/fimmu.2024.1341464. eCollection 2024.
Guanylate-binding proteins (GBPs) are produced in response to pro-inflammatory signals, mainly interferons. The most studied cluster of GBPs in mice is on chromosome 3. It comprises the genes for GBP1-to-3, GBP5 and GBP7. In humans, all GBPs are present in a single cluster on chromosome 1. Brucella abortus is a Gram-negative bacterium known to cause brucellosis, a debilitating disease that affects both humans and animals. Our group demonstrated previously that GBPs present on murine chromosome 3 (GBPchr3) is important to disrupt Brucella-containing vacuole and GBP5 itself is important to Brucella intracellular LPS recognition. In this work, we investigated further the role of GBPs during B. abortus infection.
We observed that all GBPs from murine chromosome 3 are significantly upregulated in response to B. abortus infection in mouse bone marrow-derived macrophages. Of note, GBP5 presents the highest expression level in all time points evaluated. However, only GBPchr3-/- cells presented increased bacterial burden compared to wild-type macrophages. Brucella DNA is an important Pathogen-Associated Molecular Pattern that could be available for inflammasome activation after BCV disruption mediated by GBPs. In this regard, we observed reduced IL-1β production in the absence of GBP2 or GBP5, as well as in GBPchr3-/- murine macrophages. Similar result was showed by THP-1 macrophages with downregulation of GBP2 and GBP5 mediated by siRNA. Furthermore, significant reduction on caspase-1 p20 levels, LDH release and Gasdermin-D conversion into its mature form (p30 N-terminal subunit) was observed only in GBPchr3-/- macrophages. In an perspective, we found that GBPchr3-/- mice had increased B. abortus burden and higher number of granulomas per area of liver tissue, indicating increased disease severity.
DISCUSSION/CONCLUSION: Altogether, these results demonstrate that although GBP5 presents a high expression pattern and is involved in inflammasome activation by bacterial DNA in macrophages, the cooperation of multiple GBPs from murine chromosome 3 is necessary for full control of Brucella abortus infection.
鸟苷酸结合蛋白（GBP）是对促炎信号（主要是干扰素）作出反应而产生的。在小鼠中，研究最多的一组 GBP 位于 3 号染色体上。它包含 GBP1-3、GBP5 和 GBP7 的基因。在人类中，所有的 GBP 都位于 1 号染色体的单个簇中。布鲁氏菌是一种革兰氏阴性细菌，已知会引起布鲁氏菌病，这是一种影响人类和动物的衰弱性疾病。我们的研究小组之前曾证明，存在于小鼠 3 号染色体上的 GBP（GBPchr3）对于破坏布鲁氏菌包含的空泡很重要，而 GBP5 本身对于布鲁氏菌细胞内 LPS 的识别很重要。在这项工作中，我们进一步研究了 GBP 在布鲁氏菌感染过程中的作用。
我们观察到，在小鼠骨髓来源的巨噬细胞中，所有来自 3 号染色体的 GBP 都因布鲁氏菌感染而显著上调。值得注意的是，在所有评估的时间点，GBP5 的表达水平最高。然而，只有 GBPchr3-/-细胞的细菌负荷比野生型巨噬细胞增加。布鲁氏菌 DNA 是一种重要的病原体相关分子模式（PAMP），在由 GBP 介导的 BCV 破坏后，它可能被用于激活炎症小体。在这方面，我们观察到在缺乏 GBP2 或 GBP5 的情况下，IL-1β 的产生减少，以及在 GBPchr3-/- 小鼠巨噬细胞中也是如此。通过 siRNA 下调 GBP2 和 GBP5 的 THP-1 巨噬细胞也显示出类似的结果。此外，只有在 GBPchr3-/- 巨噬细胞中，我们观察到 caspase-1 p20 水平、LDH 释放和 Gasdermin-D 转化为其成熟形式（p30 N 端亚基）的显著减少。从 角度来看，我们发现 GBPchr3-/- 小鼠的布鲁氏菌负荷增加，肝脏组织每单位面积的肉芽肿数量增加，表明疾病严重程度增加。
讨论/结论：总之，这些结果表明，尽管 GBP5 表现出高表达模式，并参与巨噬细胞中细菌 DNA 诱导的炎症小体激活，但来自 3 号染色体的多种 GBP 的合作对于完全控制布鲁氏菌感染是必要的。
