Structural insights into the unique activation mechanisms of receptor tyrosine kinases

受体酪氨酸激酶(RTK)在调节正常的细胞过程中起着关键作用，并与许多 人类疾病。每个RTK原基都包含一个结合激活配体的胞外区，单个 跨膜螺旋，以及包含细胞内必需的激酶域的胞内区域 发信号。对于许多RTK，它们的同源配体形成稳定的同源二聚体，二聚体配体与 RTK的胞外区驱动受体二聚化，从而使两个细胞内的激酶接近 接近，使它们能够自动磷酸化。磷酸化的激酶可以进一步招募效应器蛋白， 从而触发下行信令级联。这种“配体诱导二聚”是由来已久的 RTK的激活模型，具有广泛的结构和功能 学习。然而，有人建议RTK家族中的几个成员使用独特的激活 机械装置。例如，仅有麝香受体不能直接与其配体结合并被其激活 Agin，但需要肌肉细胞表面的辅助受体Lrp4来激活。此外， 受体的激活不仅需要其配体的结合，还需要 质膜磷脂酰丝氨酸脂(PtdSer)。此外，我们的初步结构结果 研究表明，与所有其他RTK不同的是，一个HGF分子可以同时与两个c-met受体结合 通过利用两个不同的接口；因此，单个HGF足以激活c-Met受体， 这代表了RTK激活机制中的另一种范式。这个项目的目标是研究 几种特殊RTK的结构和功能，包括穆斯克、和c-Met受体，其 激活机制目前仍知之甚少。求解不同唯一性的高分辨率结构 处于配体结合激活状态的RTK家族成员将解释区分它们的具体特征 其他RTK的受体，揭示了RTK激活的共同机制和多样性。 目的1重点分析麝香受体复合体的功能和结构。这项研究将 揭示了Musk、Lrp4和Agin之间的详细结合方式，并解释了为什么共同受体Lrp4是关键 用来激活马斯克。目标2将集中在受体的生化和结构分析上。 膜相关功能状态。这项研究的结果将使我们能够解释 PtdSer在激活中的重要性。目标3将集中在c-met的结构测定上。 处于HGF结合活性状态的受体以理解为什么单个HGF分子足以与c-MET结合 激活。

Receptor tyrosine kinases (RTKs) play key roles in regulating normal cellular processes and are linked to many human diseases. Each RTK protomer contains an extracellular region that binds activating ligands, a single transmembrane helix, and an intracellular region that contains the kinase domain necessary for intracellular signaling. For many RTKs, their cognate ligands form stable homodimers, and the binding of dimeric ligand to the extracellular region of RTK drives receptor dimerization, which then brings two intracellular kinases in close proximity, enabling their autophosphorylation. The phosphorylated kinases can further recruit effector proteins, and thereby triggering downstream signaling cascade. This “ligand-induced-dimerization” is the long-standing model for the activation of RTKs, and has been well characterized by extensive structural and functional studies. Nevertheless, it has been suggested that several members in RTK family use unique activation mechanisms. For instance, the MuSK receptor alone cannot directly bind to and be activated by its ligand Agrin, but requiring assistance of the co-receptor Lrp4 on the muscle cell surface for activation. In addition, the activation of TAM receptor requires not only the binding of its ligands, but also the involvement of phosphatidylserine lipid (PtdSer) from plasma membrane. Furthermore, our preliminary structure results showed that, different to all other RTKs, one HGF molecular can simultaneously engages two c-MET receptors by utilizing two distinct interfaces; therefore, a single HGF is sufficient for the activation of c-MET receptor, which represents another paradigm in activation mechanisms of RTK. The goal of this project is to study the structures and functions of several special RTKs, including MuSK, TAM and c-MET receptors, whose activation mechanism are still poorly understood. Solving the high-resolution structures of different unique members of RTK family in the ligand-bound active state will explain the specific features that differentiate these receptors from other RTKs, and reveal the common mechanism and diversification in the activation of RTK. Aim 1 will be focused on the functional and structural analyses of MuSK receptor complex. This study will reveal the detailed binding mode between MuSK, Lrp4 and Agrin, and explain why co-receptor Lrp4 is critical for the activation of MuSK. Aim 2 will be focused on biochemical and structural analyses of TAM receptor in the membrane associated functional state. The result from this study will allow us to explain the functional importance of PtdSer in TAM activation. Aim 3 will be focused on the structural determination of c-MET receptor in the HGF bound active state to understand why single HGF molecular is sufficient for c-MET activation.