Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria
Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria.
Proc Natl Acad Sci U S A. 2021 Jan 5;118(1). doi: 10.1073/pnas.2010054118. Epub 2020 Dec 18.
The differentiation of cells depends on a precise control of their internal organization, which is the result of a complex dynamic interplay between the cytoskeleton, molecular motors, signaling molecules, and membranes. For example, in the developing neuron, the protein ADAP1 (ADP-ribosylation factor GTPase-activating protein [ArfGAP] with dual pleckstrin homology [PH] domains 1) has been suggested to control dendrite branching by regulating the small GTPase ARF6. Together with the motor protein KIF13B, ADAP1 is also thought to mediate delivery of the second messenger phosphatidylinositol (3,4,5)-trisphosphate (PIP) to the axon tip, thus contributing to PIP polarity. However, what defines the function of ADAP1 and how its different roles are coordinated are still not clear. Here, we studied ADAP1's functions using in vitro reconstitutions. We found that KIF13B transports ADAP1 along microtubules, but that PIP as well as PI(3,4)P act as stop signals for this transport instead of being transported. We also demonstrate that these phosphoinositides activate ADAP1's enzymatic activity to catalyze GTP hydrolysis by ARF6. Together, our results support a model for the cellular function of ADAP1, where KIF13B transports ADAP1 until it encounters high PIP/PI(3,4)P concentrations in the plasma membrane. Here, ADAP1 disassociates from the motor to inactivate ARF6, promoting dendrite branching.
细胞的分化取决于其内部组织的精确控制，这是细胞骨架、分子马达、信号分子和膜之间复杂动态相互作用的结果。例如，在发育中的神经元中，蛋白 ADAP1（ADP-核糖基化因子 GTP 酶激活蛋白[ArfGAP]，具有双pleckstrin 同源[PH]结构域 1）被认为通过调节小 GTPase ARF6 来控制树突分支。ADAP1 与马达蛋白 KIF13B 一起，也被认为介导第二信使磷脂酰肌醇（3,4,5）-三磷酸（PIP）向轴突尖端的传递，从而有助于 PIP 极性。然而，ADAP1 的功能是什么，以及如何协调其不同的作用仍然不清楚。在这里，我们使用体外重组研究了 ADAP1 的功能。我们发现 KIF13B 沿微管运输 ADAP1，但 PIP 以及 PI(3,4)P 作为这种运输的停止信号，而不是被运输。我们还证明这些磷酸肌醇激活 ADAP1 的酶活性，以催化 ARF6 的 GTP 水解。总之，我们的结果支持了 ADAP1 的细胞功能模型，其中 KIF13B 运输 ADAP1，直到它在质膜中遇到高 PIP/PI(3,4)P 浓度。在这里，ADAP1 与马达分离以失活 ARF6，促进树突分支。
