Novel Roles for the E3 Ubiquitin Ligase Atrophin-interacting Protein 4 and Signal Transduction Adaptor Molecule 1 in G Protein-coupled Receptor Signaling
Novel Roles for the E3 Ubiquitin Ligase Atrophin-interacting Protein 4 and Signal Transduction Adaptor Molecule 1 in G Protein-coupled Receptor Signaling
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DOI：
10.1074/jbc.m111.336792
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发表时间：
2012-03-16
影响因子：
4.8
通讯作者：
Marchese, Adriano
中科院分区：
文献类型：
--
作者：
Malik, Rohit;Soh, Unice J. K.;Marchese, Adriano
CXCL12/CXCR4信号轴在人类健康和疾病中发挥重要作用；然而，介导CXCR4信号传导的分子机制仍然知之甚少。E3泛素连接酶AIP4对CXCR4进行泛素修饰是溶酶体分选和降解所必需的，这是由运输所需的内体分选复合体（ESCRT）机制介导的。CXCR4的分选受内体局部抑制蛋白2和斯塔姆-1 （ESCRT-0成分）之间的相互作用调节。在这里，我们报道了AIP4和stam1在CXCR4信号传导调控中的新作用，这与它们在CXCR4转运中的功能不同。siRNA缺失AIP4和stam1可显著抑制CXCR4诱导的ERK-1/2激活，而过表达这些蛋白可增强CXCR4信号传导。我们进一步证明AIP4和sam -1之间存在物理相互作用，AIP4中脯氨酸丰富的区域和sam -1中的SH3结构域对相互作用至关重要。与野生型AIP4相比，AIP4催化失活突变体和与斯塔姆-1结合不良的突变体的过表达不能增强cxcr4诱导的ERK-1/2信号传导，这表明AIP4与斯塔姆-1的相互作用以及AIP4的连接酶活性对于ERK-1/2激活至关重要。值得注意的是，AIP4和STAM-1的一个离散亚群与CXCR4一起存在于空泡微域，并介导ERK-1/2信号传导。我们认为aip4介导的小泡中斯塔姆-1泛素化协调了ERK-1/2信号的激活。因此，我们的研究揭示了泛素在调节CXCR4信号传导中的新功能，该功能可能广泛适用于其他G蛋白偶联受体。
The CXCL12/CXCR4 signaling axis plays an important role in human health and disease; however, the molecular mechanisms mediating CXCR4 signaling remain poorly understood. Ubiquitin modification of CXCR4 by the E3 ubiquitin ligase AIP4 is required for lysosomal sorting and degradation, which is mediated by the endosomal sorting complex required for transport (ESCRT) machinery. CXCR4 sorting is regulated by an interaction between endosomal localized arrestin-2 and STAM-1, an ESCRT-0 component. Here, we report a novel role for AIP4 and STAM-1 in regulation of CXCR4 signaling that is distinct from their function in CXCR4 trafficking. Depletion of AIP4 and STAM-1 by siRNA caused significant inhibition of CXCR4-induced ERK-1/2 activation, whereas overexpression of these proteins enhanced CXCR4 signaling. We further show that AIP4 and STAM-1 physically interact and that the proline-rich region in AIP4 and the SH3 domain in STAM-1 are essential for the interaction. Overexpression of an AIP4 catalytically inactive mutant and a mutant that shows poor binding to STAM-1 fails to enhance CXCR4-induced ERK-1/2 signaling, as compared with wild-type AIP4, suggesting that the interaction between AIP4 and STAM-1 and the ligase activity of AIP4 are essential for ERK-1/2 activation. Remarkably, a discrete subpopulation of AIP4 and STAM-1 resides in caveolar microdomains with CXCR4 and appears to mediate ERK-1/2 signaling. We propose that AIP4-mediated ubiquitination of STAM-1 in caveolae coordinates activation of ERK-1/2 signaling. Thus, our study reveals a novel function for ubiquitin in the regulation of CXCR4 signaling, which may be broadly applicable to other G protein-coupled receptors.