Rathinaswamy Manoj K, Dalwadi Udit, Fleming Kaelin D, Adams Carson, Stariha Jordan T B, Pardon Els, Baek Minkyung, Vadas Oscar, DiMaio Frank, Steyaert Jan, Hansen Scott D, Yip Calvin K, Burke John E
Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada.
Life Sciences Institute, Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada.
Sci Adv. 2021 Aug 27;7(35). doi: 10.1126/sciadv.abj4282. Print 2021 Aug.
The class IB phosphoinositide 3-kinase (PI3K), PI3Kγ, is a master regulator of immune cell function and a promising drug target for both cancer and inflammatory diseases. Critical to PI3Kγ function is the association of the p110γ catalytic subunit to either a p101 or p84 regulatory subunit, which mediates activation by G protein-coupled receptors. Here, we report the cryo-electron microscopy structure of a heterodimeric PI3Kγ complex, p110γ-p101. This structure reveals a unique assembly of catalytic and regulatory subunits that is distinct from other class I PI3K complexes. p101 mediates activation through its Gβγ-binding domain, recruiting the heterodimer to the membrane and allowing for engagement of a secondary Gβγ-binding site in p110γ. Mutations at the p110γ-p101 and p110γ-adaptor binding domain interfaces enhanced Gβγ activation. A nanobody that specifically binds to the p101-Gβγ interface blocks activation, providing a novel tool to study and target p110γ-p101-specific signaling events in vivo.
I类B型磷酸肌醇3激酶（PI3K），即PI3Kγ，是免疫细胞功能的主要调节因子，也是癌症和炎症性疾病颇具前景的药物靶点。PI3Kγ发挥功能的关键在于p110γ催化亚基与p101或p84调节亚基的结合，这介导了G蛋白偶联受体的激活。在此，我们报道了异二聚体PI3Kγ复合物p110γ-p101的冷冻电镜结构。该结构揭示了催化亚基和调节亚基的独特组装方式，这与其他I类PI3K复合物不同。p101通过其Gβγ结合结构域介导激活，将异二聚体招募至细胞膜，并使得p110γ中的第二个Gβγ结合位点得以结合。p110γ-p101和p110γ-衔接子结合结构域界面处的突变增强了Gβγ激活。一种特异性结合p101-Gβγ界面的纳米抗体可阻断激活，为在体内研究和靶向p110γ-p101特异性信号事件提供了一种新工具。
