Laboratory of Cell and Developmental Signaling, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702 USA.
National Cancer Institute RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, MD 21702 USA.
Mol Cell. 2022 Nov 17;82(22):4262-4276.e5. doi: 10.1016/j.molcel.2022.10.016. Epub 2022 Nov 7.
BRAF is frequently mutated in human cancer and the RASopathy syndromes, with RASopathy mutations often observed in the cysteine-rich domain (CRD). Although the CRD participates in phosphatidylserine (PS) binding, the RAS-RAF interaction, and RAF autoinhibition, the impact of these activities on RAF function in normal and disease states is not well characterized. Here, we analyze a panel of CRD mutations and show that they increase BRAF activity by relieving autoinhibition and/or enhancing PS binding, with relief of autoinhibition being the major factor determining mutation severity. Further, we show that CRD-mediated autoinhibition prevents the constitutive plasma membrane localization of BRAF that causes increased RAS-dependent and RAS-independent function. Comparison of the BRAF- and CRAF-CRDs also indicates that the BRAF-CRD is a stronger mediator of autoinhibition and PS binding, and given the increased catalytic activity of BRAF, our studies reveal a more critical role for CRD-mediated autoinhibition in BRAF regulation.
BRAF 在人类癌症和 RAS 病综合征中经常发生突变，而 RAS 病突变经常发生在富含半胱氨酸的结构域（CRD）中。尽管 CRD 参与磷脂酰丝氨酸（PS）结合、RAS-RAF 相互作用和 RAF 自身抑制，但这些活性对 RAF 在正常和疾病状态下的功能的影响尚未很好地描述。在这里，我们分析了一组 CRD 突变体，并表明它们通过解除自身抑制和/或增强 PS 结合来增加 BRAF 的活性，解除自身抑制是决定突变严重程度的主要因素。此外，我们还表明，CRD 介导的自身抑制可防止 BRAF 的组成型质膜定位，从而导致增加的 RAS 依赖性和 RAS 非依赖性功能。对 BRAF 和 CRAF-CRD 的比较也表明，BRAF-CRD 是自身抑制和 PS 结合的更强调节剂，并且鉴于 BRAF 的催化活性增加，我们的研究揭示了 CRD 介导的自身抑制在 BRAF 调节中的更关键作用。
