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分泌载体膜蛋白2调节脑富集型钠氢交换体NHE5的细胞表面靶向定位。

Secretory Carrier Membrane Protein 2 Regulates Cell-surface Targeting of Brain-enriched Na+/H+ Exchanger NHE5.

作者信息

Diering Graham H, Church John, Numata Masayuki

机构信息

Departments of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.

Cellular and Physiological Sciences, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.

出版信息

J Biol Chem. 2009 May 15;284(20):13892-13903. doi: 10.1074/jbc.M807055200. Epub 2009 Mar 10.

Abstract

NHE5 is a brain-enriched Na(+)/H(+) exchanger that dynamically shuttles between the plasma membrane and recycling endosomes, serving as a mechanism that acutely controls the local pH environment. In the current study we show that secretory carrier membrane proteins (SCAMPs), a group of tetraspanning integral membrane proteins that reside in multiple secretory and endocytic organelles, bind to NHE5 and co-localize predominantly in the recycling endosomes. In vitro protein-protein interaction assays revealed that NHE5 directly binds to the N- and C-terminal cytosolic extensions of SCAMP2. Heterologous expression of SCAMP2 but not SCAMP5 increased cell-surface abundance as well as transporter activity of NHE5 across the plasma membrane. Expression of a deletion mutant lacking the SCAMP2-specific N-terminal cytosolic domain, and a mini-gene encoding the N-terminal extension, reduced the transporter activity. Although both Arf6 and Rab11 positively regulate NHE5 cell-surface targeting and NHE5 activity across the plasma membrane, SCAMP2-mediated surface targeting of NHE5 was reversed by dominant-negative Arf6 but not by dominant-negative Rab11. Together, these results suggest that SCAMP2 regulates NHE5 transit through recycling endosomes and promotes its surface targeting in an Arf6-dependent manner.

摘要

NHE5是一种在大脑中高度富集的Na(+)/H(+)交换蛋白,它在质膜和循环内体之间动态穿梭,作为一种可急性调控局部pH环境的机制。在本研究中,我们发现分泌载体膜蛋白(SCAMPs),即一组存在于多个分泌和内吞细胞器中的四次跨膜整合膜蛋白,可与NHE5结合,并主要共定位于循环内体。体外蛋白质-蛋白质相互作用分析表明,NHE5直接与SCAMP2的N端和C端胞质延伸区结合。SCAMP2而非SCAMP5的异源表达增加了NHE5跨质膜的细胞表面丰度以及转运体活性。缺乏SCAMP2特异性N端胞质结构域的缺失突变体和编码N端延伸区的微型基因的表达降低了转运体活性。虽然Arf6和Rab11均正向调控NHE5的细胞表面靶向以及NHE5跨质膜的活性,但SCAMP2介导的NHE5表面靶向被显性负性Arf6逆转,而未被显性负性Rab11逆转。总之,这些结果表明SCAMP2通过循环内体调控NHE5的转运,并以Arf6依赖的方式促进其表面靶向。

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