Adiponectin Receptors Form Homomers and Heteromers Exhibiting Distinct Ligand Binding and Intracellular Signaling Properties
Adiponectin Receptors Form Homomers and Heteromers Exhibiting Distinct Ligand Binding and Intracellular Signaling Properties
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DOI：
10.1074/jbc.m112.404624
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发表时间：
2013-02-01
影响因子：
4.8
通讯作者：
Malagon, Maria M.
中科院分区：
文献类型：
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作者：
Almabouada, Farid;Diaz-Ruiz, Alberto;Malagon, Maria M.
脂联素与两种广泛表达的受体（AdipoR1和AdipoR2）结合，这两种受体含有7个跨膜结构域，但与G蛋白偶联受体不同，它们存在一个细胞外C末端和一个细胞溶质N末端。最近，发现AdipoR1在高级复合物中缔合。然而，目前还不清楚AdipoR2是否也可以与AdipoR1形成同聚体或异聚体，或者这种相互作用是否可能在功能上相关。在此，我们已经分析了寡聚化模式的AdipoRs的FRET和免疫沉淀和评估的内在化的AdipoRs的各种脂联素亚型和不同的AdipoR组合AMP激活的蛋白激酶磷酸化和过氧化物酶体增殖物激活受体α激活的影响结合脂联素。用AdipoR1和AdipoR2转染HEK293AD细胞显示，两种受体共定位于质膜和内质网。与不同的AdipoR对共转染在非刺激细胞中产生高FRET效率，这表明AdipoR1和AdipoR2在静息条件下形成同源和异源复合物。实时FRET成像表明，同源和异源聚体的AdipoR复合物解离响应脂联素，但异源聚体分离速度比同源聚体。最后，腺苷酸激活的蛋白激酶的磷酸化反应脂联素被延迟在细胞中，其中异聚体的形成是有利的。总之，我们的研究结果表明，AdipoR1和AdipoR2形成同源和异源聚体，呈现独特的相互作用行为和信号传导特性。这提出了脂联素的多效性、组织依赖性功能取决于AdipoR1和AdipoR2的表达水平，因此取决于同源和异源复合物的稳态比例的可能性。
Adiponectin binds to two widely expressed receptors (AdipoR1 and AdipoR2) that contain seven transmembrane domains but, unlike G-protein coupled receptors, present an extracellular C terminus and a cytosolic N terminus. Recently, AdipoR1 was found to associate in high order complexes. However, it is still unknown whether AdipoR2 may also form homomers or heteromers with AdipoR1 or if such interactions may be functionally relevant. Herein, we have analyzed the oligomerization pattern of AdipoRs by FRET and immunoprecipitation and evaluated both the internalization of AdipoRs in response to various adiponectin isoforms and the effect of adiponectin binding to different AdipoR combinations on AMP-activated protein kinase phosphorylation and peroxisome proliferator-activated receptor alpha activation. Transfection of HEK293AD cells with AdipoR1 and AdipoR2 showed that both receptors colocalize at both the plasma membrane and the endoplasmic reticulum. Co-transfection with the different AdipoR pairs yielded high FRET efficiencies in non-stimulated cells, which indicates that AdipoR1 and AdipoR2 form homo- and heteromeric complexes under resting conditions. Live FRET imaging suggested that both homo-and heteromeric AdipoR complexes dissociate in response to adiponectin, but heteromers separate faster than homomers. Finally, phosphorylation of AMP-activated protein kinase in response to adiponectin was delayed in cells wherein heteromer formation was favored. In sum, our findings indicate that AdipoR1 and AdipoR2 form homo-and heteromers that present unique interaction behaviors and signaling properties. This raises the possibility that the pleiotropic, tissue-dependent functions of adiponectin depend on the expression levels of AdipoR1 and AdipoR2 and, therefore, on the steady-state proportion of homo-and heteromeric complexes.