Wu H, Reuver S M, Kuhlendahl S, Chung W J, Garner C C
Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294-0021, USA.
J Cell Sci. 1998 Aug;111 ( Pt 16):2365-76. doi: 10.1242/jcs.111.16.2365.
The synapse-associated protein SAP97 is a member of a novel family of cortical cytoskeletal proteins involved in the localization of ion channels at such membrane specializations as synaptic junctions. These multidomain proteins have binding sites for protein 4.1, GKAPs/SAPAPs, voltage- and ligand-gated ion channels and cell-adhesion molecules containing C-terminal T/SXV motifs. In this study, we evaluated the contribution of individual domains in SAP97 to its selective recruitment and attachment to the cortical cytoskeleton in epithelial cells. We find that the PDZ, SH3 and GK domains, as well as the I3 insert in SAP97, are not essential for subcellular targeting, though both PDZ1-2 domains and the I3 insert affect the efficiency of localization. Instead, we show that the first 65 amino acid residues in SAP97, which are absent from SAP90/PSD-95 and SAP102, direct the selective subcellular localization and can mediate at least one point of attachment of SAP97 to the cytoskeleton assembled at sites of cell-cell contact. Our data demonstrate that it is the sequences unique to SAP97 that direct its subcellular targeting to the epithelial lateral membrane.
突触相关蛋白SAP97是一类新型皮质细胞骨架蛋白家族的成员，该家族蛋白参与离子通道在诸如突触连接等膜特化结构处的定位。这些多结构域蛋白具有与蛋白4.1、GKAPs/SAPAPs、电压门控和配体门控离子通道以及含有C末端T/SXV基序的细胞粘附分子的结合位点。在本研究中，我们评估了SAP97中各个结构域对其在上皮细胞中选择性募集并附着于皮质细胞骨架的作用。我们发现，SAP97中的PDZ、SH3和GK结构域以及I3插入序列对于亚细胞靶向并非必不可少，尽管PDZ1 - 2结构域和I3插入序列都会影响定位效率。相反，我们表明，SAP97中最初的65个氨基酸残基（SAP90/PSD - 95和SAP102中不存在这些残基）指导选择性亚细胞定位，并可介导SAP97与在细胞 - 细胞接触位点组装的细胞骨架的至少一个附着点。我们的数据表明，正是SAP97特有的序列将其亚细胞靶向定位于上皮细胞侧膜。
