TNF receptor-associated factor 2 (TRAF2) is involved in different cellular processes including signal transduction and transcription regulation. We here provide evidence of a direct interaction between the TRAF domain of TRAF2 and the monosialotetrahexosylganglioside (GM1). Previously, we showed that the TRAF domain occurs mainly in a trimeric form in solution, but it can also exist as a stable monomer when in the nanomolar concentration range. Here, we report that the quaternary structure of the TRAF domain is also affected by pH changes, since a weakly acidic pH (5.5) favors the dissociation of the trimeric TRAF domain into stable monomers, as previously observed at neutral pH (7.6) with the diluted protein. The TRAF domain-GM1 binding was similar at pH 5.5 and 7.6, suggesting that GM1 interacts with both the trimeric and monomeric forms of the protein. However, only the monomeric protein appeared to cause membrane deformation and inward vesiculation in GM1-containing giant unilamellar vesicles (GUVs). The formation of complexes between GM1 and TRAF2, or its TRAF domain, was also observed in cultured human leukemic HAP1 cells expressing either the truncated TRAF domain or the endogenous full length TRAF2. The GM1-protein complexes were observed after treatment with tunicamycin and were more concentrated in cells undergoing apoptosis, a condition which is known to cause cytoplasm acidification. These findings open the avenue for future studies aimed at deciphering the physiopathological relevance of the TRAF domain-GM1 interaction.

TNF 受体相关因子 2 (TRAF2) 参与不同的细胞过程，包括信号转导和转录调节。我们在此提供了 TRAF2 的 TRAF 结构域与单唾液酸四己糖神经节苷脂 (GM1) 之间直接相互作用的证据。此前，我们表明TRAF结构域在溶液中主要以三聚体形式存在，但在纳摩尔浓度范围内也可以作为稳定的单体存在。在这里，我们报告 TRAF 结构域的四级结构也受到 pH 变化的影响，因为弱酸性 pH (5.5) 有利于三聚体 TRAF 结构域解离成稳定的单体，正如之前在中性 pH (7.6) 下观察到的那样稀释的蛋白质。TRAF 结构域-GM1 结合在 pH 5.5 和 7.6 下相似，表明 GM1 与蛋白质的三聚体和单体形式相互作用。然而，在含有 GM1 的巨型单层囊泡 (GUV) 中，似乎只有单体蛋白引起膜变形和向内囊泡形成。在表达截短的 TRAF 结构域或内源性全长 TRAF2 的培养的人白血病 HAP1 细胞中也观察到 GM1 和 TRAF2 或其 TRAF 结构域之间形成复合物。用衣霉素处理后观察到 GM1-蛋白复合物，并且更集中在正在凋亡的细胞中，已知这种情况会导致细胞质酸化。这些发现为未来的研究开辟了道路，旨在破译 TRAF 结构域与 GM1 相互作用的病理生理学相关性。