Mattera Rafael, Arighi Cecilia N, Lodge Robert, Zerial Marino, Bonifacino Juan S
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
EMBO J. 2003 Jan 2;22(1):78-88. doi: 10.1093/emboj/cdg015.
Cargo transfer from trans-Golgi network (TGN)-derived transport carriers to endosomes involves a still undefined set of tethering/fusion events. Here we analyze a molecular interaction that may play a role in this process. We demonstrate that the GGAs, a family of Arf-dependent clathrin adaptors involved in selection of TGN cargo, interact with the Rabaptin-5-Rabex-5 complex, a Rab4/Rab5 effector regulating endosome fusion. These interactions are bipartite: GGA-GAE domains recognize an FGPLV sequence (residues 439-443) in a predicted random coil of Rabaptin-5 (a sequence also recognized by the gamma1- and gamma2-adaptin ears), while GGA-GAT domains bind to the C-terminal coiled-coils of Rabaptin-5. The GGA-Rabaptin-5 interaction decreases binding of clathrin to the GGA-hinge domain, and expression of green fluorescent protein (GFP)-Rabaptin-5 shifts the localization of endogenous GGA1 and associated cargo to enlarged early endosomes. These observations thus identify a binding sequence for GAE/gamma-adaptin ear domains and reveal a functional link between proteins regulating TGN cargo export and endosomal tethering/fusion events.
从反式高尔基体网络（TGN）衍生的运输载体向内涵体的货物转运涉及一系列尚未明确的拴系/融合事件。在此，我们分析了一种可能在此过程中发挥作用的分子相互作用。我们证明，GGA（参与TGN货物选择的一类Arf依赖性网格蛋白衔接蛋白）与Rabaptin-5-Rabex-5复合物相互作用，Rabaptin-5-Rabex-5复合物是一种调节内涵体融合的Rab4/Rab5效应器。这些相互作用是双向的：GGA-GAE结构域识别Rabaptin-5预测的无规卷曲中的FGPLV序列（第439 - 443位氨基酸残基）（该序列也被γ1-和γ2-衔接蛋白耳识别），而GGA-GAT结构域与Rabaptin-5的C末端卷曲螺旋结合。GGA与Rabaptin-5的相互作用降低了网格蛋白与GGA铰链结构域的结合，并且绿色荧光蛋白（GFP）-Rabaptin-5的表达将内源性GGA1及相关货物的定位转移至扩大的早期内涵体。因此，这些观察结果确定了GAE/γ-衔接蛋白耳结构域的结合序列，并揭示了调节TGN货物输出的蛋白质与内涵体拴系/融合事件之间的功能联系。
