Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
J Biol Chem. 2010 Apr 23;285(17):12551-8. doi: 10.1074/jbc.M109.032771. Epub 2010 Feb 22.
The Ser/Thr/Tyr kinase activity of human biliverdin reductase (hBVR) and the expression of Goodpasture antigen-binding protein (GPBP), a nonconventional Ser/Thr kinase for the type IV collagen of basement membrane, are regulated by tumor necrosis factor (TNF-alpha). The pro-inflammatory cytokine stimulates kinase activity of hBVR and activates NF-kappaB, a transcriptional regulator of GPBP mRNA. Increased GPBP activity is associated with several autoimmune conditions, including Goodpasture syndrome. Here we show that in HEK293A cells hBVR binds to GPBP and down-regulates its TNF-alpha-stimulated kinase activity; this was not due to a decrease in GPBP expression. Findings with small interfering RNA to hBVR and to the p65 regulatory subunit of NF-kappaB show the hBVR role in the initial stimulation of GPBP expression by TNF-alpha-activated NF-kappaB; hBVR was not a factor in mediating GPBP mRNA stability. The interacting domain was mapped to the (281)CX(10)C motif in the C-terminal 24 residues of hBVR. A 7-residue peptide, KKRILHC(281), corresponding to the core of the consensus D(delta)-Box motif in the interacting domain, was as effective as the intact 296-residue hBVR polypeptide in inhibiting GPBP kinase activity. GPBP neither regulated hBVR expression nor TNF-alpha dependent NF-kappaB expression. Collectively, our data reveal that hBVR is a regulator of the TNF-alpha-GPBP-collagen type IV signaling cascade and uncover a novel biological interaction that may be of relevance in autoimmune pathogenesis.
人胆红素还原酶（hBVR）的丝氨酸/苏氨酸/酪氨酸激酶活性和 Goodpasture 抗原结合蛋白（GPBP）的表达受肿瘤坏死因子（TNF-α）调节，GPBP 是基膜 IV 型胶原的非传统丝氨酸/苏氨酸激酶。促炎细胞因子刺激 hBVR 的激酶活性并激活 NF-κB，NF-κB 是 GPBP mRNA 的转录调节剂。GPBP 活性增加与几种自身免疫病有关，包括 Goodpasture 综合征。在这里，我们表明在 HEK293A 细胞中 hBVR 与 GPBP 结合并下调其 TNF-α 刺激的激酶活性；这不是由于 GPBP 表达减少所致。用 hBVR 和 NF-κB 的 p65 调节亚基的小干扰 RNA 的发现表明 hBVR 在 TNF-α 激活的 NF-κB 对 GPBP 表达的初始刺激中起作用；hBVR 不是介导 GPBP mRNA 稳定性的因素。相互作用的结构域被映射到 hBVR 羧基末端 24 个残基中的（281）CX（10）C 基序。与相互作用结构域中核心 D（delta）-Box 基序相对应的 7 个残基肽 KKRILHC（281）与完整的 296 个残基 hBVR 多肽一样有效抑制 GPBP 激酶活性。GPBP 既不调节 hBVR 表达也不调节 TNF-α 依赖性 NF-κB 表达。总的来说，我们的数据表明 hBVR 是 TNF-α-GPBP-胶原 IV 信号级联的调节剂，并揭示了一种新的生物学相互作用，这可能与自身免疫发病机制有关。
