Center for Investigation in Pediatrics, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil.
Center for Investigation in Pediatrics, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil ; Department of Pediatrics, Faculty of Medical Sciences, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil.
Immun Inflamm Dis. 2015 Sep;3(3):171-81. doi: 10.1002/iid3.57. Epub 2015 Jun 4.
Mutations in the Bruton agammaglobulinemia tyrosine kinase (BTK) gene are responsible for X-linked agammaglobulinemia (XLA). Unfolded or misfolded proteins can trigger stress pathways in the endoplasmic reticulum (ER), known as unfolded protein response (UPR). The aim was to clarify the involvement of UPR in XLA pathophysiology. By reverse transcription-quantitative PCR, we evaluated the expression of BTK and 12 UPR-related genes in eight patients. Moreover, we assessed the BTK protein expression and pattern in the patients' monocytes by flow cytometry and fluorescence immunocytochemistry. We found a reduced BTK expression in patients with stop codon mutations (P < 0.02). However, missense mutations did not affect BTK expression. Flow cytometry showed a reduction of BTK in patients which was corroborated by an absent or nonfunctional protein synthesis revealed by immunocytochemistry. In contrast with the other UPR-related genes, X-box binding protein 1 (XBP1) was markedly upregulated in the patients (P < 0.01), suggesting Toll-like receptor (TLR) activation since BTK directly interacts with TLRs as a negative regulator and XBP1 can be activated in direct response to TLR ligation. Different BTK mutations can be identified by the BTK expression. Inasmuch as UPR-related genes were downregulated or unaltered in patients, we speculate the involvement of the TLRs-XBP1 axis in the XLA pathophysiology. Such data could be the basis for further studies of this novel pathomechanism concerning XLA.
BTK 基因突变导致 X 连锁无丙种球蛋白血症（XLA）。未折叠或错误折叠的蛋白质可以触发内质网（ER）中的应激途径，称为未折叠蛋白反应（UPR）。目的是阐明 UPR 在 XLA 病理生理学中的作用。通过逆转录定量 PCR，我们评估了 8 名患者中 BTK 和 12 个 UPR 相关基因的表达。此外，我们通过流式细胞术和荧光免疫细胞化学评估了患者单核细胞中的 BTK 蛋白表达和模式。我们发现，具有终止密码子突变的患者 BTK 表达减少（P < 0.02）。然而，错义突变不影响 BTK 表达。流式细胞术显示患者 BTK 减少，免疫细胞化学证实存在或无功能性蛋白合成。与其他 UPR 相关基因相比，X 盒结合蛋白 1（XBP1）在患者中明显上调（P < 0.01），提示 Toll 样受体（TLR）激活，因为 BTK 直接作为负调节剂与 TLR 相互作用，并且 XBP1 可以直接响应 TLR 连接而被激活。不同的 BTK 突变可以通过 BTK 表达来识别。由于患者的 UPR 相关基因下调或未改变，我们推测 TLRs-XBP1 轴参与了 XLA 的病理生理学。这些数据可能是进一步研究 XLA 这一新型发病机制的基础。
