Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA.
Nat Commun. 2024 Aug 21;15(1):7176. doi: 10.1038/s41467-024-51445-z.
RHOA mutations are found at diverse residues in various cancer types, implying mutation- and cell-specific mechanisms of tumorigenesis. Here, we focus on the underlying mechanisms of two gain-of-function RHOA mutations, A161P and A161V, identified in adult T-cell leukemia/lymphoma. We find that RHOA and RHOA are both fast-cycling mutants with increased guanine nucleotide dissociation/association rates compared with RHOA and show reduced GTP-hydrolysis activity. Crystal structures reveal an altered nucleotide association in RHOA and an open nucleotide pocket in RHOA. Both mutations perturb the dynamic properties of RHOA switch regions and shift the conformational landscape important for RHOA activity, as shown by P NMR and molecular dynamics simulations. Interestingly, RHOA and RHOA can interact with effectors in the GDP-bound state. H-N HSQC NMR spectra support the existence of an active population in RHOA-GDP. The distinct interaction mechanisms resulting from the mutations likely favor an RHOA-like "ON" conformation, endowing GDP-bound state effector binding activity.
RHOA 突变发生在各种癌症类型的不同残基上，这表明肿瘤发生存在突变和细胞特异性机制。在这里，我们专注于两种功能获得性 RHOA 突变（A161P 和 A161V）的潜在机制，这两种突变已在成人 T 细胞白血病/淋巴瘤中被发现。我们发现，与 RHOA 相比，RHOA 和 RHOA 都是快速循环突变体，具有更高的鸟嘌呤核苷酸解离/缔合速率，并表现出降低的 GTP 水解活性。晶体结构揭示了 RHOA 中改变的核苷酸结合以及 RHOA 中开放的核苷酸口袋。这两种突变都破坏了 RHOA 开关区域的动态特性，并改变了对 RHOA 活性很重要的构象景观，这一点通过 P NMR 和分子动力学模拟得到了证实。有趣的是，RHOA 和 RHOA 可以在 GDP 结合状态下与效应物相互作用。H-N HSQC NMR 光谱支持 RHOA-GDP 中存在活性群体。突变导致的独特相互作用机制可能有利于类似于 RHOA 的“ON”构象，赋予 GDP 结合状态下的效应物结合活性。
