A novel AP-2 adaptor interaction motif initially identified in the long-splice isoform of synaptojanin 1, SJ170
A novel AP-2 adaptor interaction motif initially identified in the long-splice isoform of synaptojanin 1, SJ170
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DOI：
10.1074/jbc.m305644200
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发表时间：
2004-01-16
影响因子：
4.8
通讯作者：
Traub, LM
中科院分区：
文献类型：
--
作者：
Jha, A;Agostinelli, NR;Traub, LM
磷酸肌醇在细胞表面的网格蛋白-包被组装中起着重要作用。几种内吞成分和辅助因子含有独立折叠的磷酸肌醇结合模块，其部分地促进了芽部位的膜放置。随着网格蛋白外壳组装过程向深深内陷的芽进展，局部合成的磷酸肌醇被去磷酸化，主要是通过磷酸肌醇多磷酸酶synaptojanin 1的作用。不能分解代谢多磷酸肌醇阻碍了分裂过程和内吞活性。synaptojanin 1的长剪接异构体，称为SJ 170，含有羧基末端延伸，其具有用于接合内吞机器的几个组件的相互作用基序。在这里，我们证明，除了DPF和FXS 170序列，SJ 170羧基末端含有一个新的AP-2结合序列，WXXF基序。WXXF序列接合从异源四聚体AP-2衔接子核心突出的独立折叠的α-亚基附属物。内吞蛋白激酶AAK 1和GAK除了两个DPF重复序列外还含有功能性WXX（FW）基序，而石蛋白2含有三个串联WXXF重复序列。每个离散的SJ 170衔接子相互作用基序与附属物的结合相对较弱，但在SJ 170延伸内串联排列时，可以协同以良好的表观亲和力结合二价AP-2。这些相互作用可能有助于某些内吞组分适当靶向组装在细胞表面的网格蛋白芽位点。
Phosphoinositides play a fundamental role in clathrin-coat assembly at the cell surface. Several endocytic components and accessory factors contain independently folded phosphoinositide-binding modules that facilitate, in part, membrane placement at the bud site. As the clathrin-coat assembly process progresses toward deeply invaginated buds, focally synthesized phosphoinositides are dephosphorylated, principally through the action of the phosphoinositide polyphosphatase synaptojanin 1. Failure to catabolize polyphosphoinositides retards the fission process and endocytic activity. The long-splice isoform of synaptojanin 1, termed SJ170, contains a carboxyl-terminal extension that harbors interaction motifs for engaging several components of the endocytic machinery. Here, we demonstrate that in addition to DPF and FXDXF sequences, the SJ170 carboxyl terminus contains a novel AP-2 binding sequence, the WXXF motif. The WXXF sequence engages the independently folded alpha-subunit appendage that projects off the heterotetrameric AP-2 adaptor core. The endocytic protein kinases AAK1 and GAK also contain functional WXX(FW) motifs in addition to two DPF repeats, whereas stonin 2 harbors three tandem WXXF repeats. Each of the discrete SJ170 adaptor-interaction motifs bind to appendages relatively weakly but, as tandemly arrayed within the SJ170 extension, can cooperate to bind bivalent AP-2 with good apparent affinity. These interactions likely contribute to the appropriate targeting of certain endocytic components to clathrin bud sites assembling at the cell surface.