Eroglu Cagla, Brugger Britta, Wieland Felix, Sinning Irmgard
Biochemie-Zentrum Heidelberg, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany.
Proc Natl Acad Sci U S A. 2003 Sep 2;100(18):10219-24. doi: 10.1073/pnas.1737042100. Epub 2003 Aug 15.
Metabotropic glutamate receptors (mGluRs) are responsible for the effects of glutamate in slow synaptic transmission, and are implicated in the regulation of many processes in the CNS. Recently, we have reported the expression and purification of a mGluR from Drosophila melanogaster (DmGluRA), a homologue of mammalian group II mGluRs. We have shown that ligand binding to reconstituted DmGluRA requires the presence of ergosterol in the liposomes [Eroglu, C., Cronet, P., Panneels, V., Beaufils, P. & Sinning, I. (2002) EMBO Rep. 3, 491-496]. Here we demonstrate that the receptor exists in different affinity states for glutamate, depending on the membrane composition. The receptor is in a high-affinity state when associated with sterol-rich lipid microdomains (rafts), and in a low-affinity state out of rafts. Enrichment of the membranes with cholesterol shifts the receptor into the high-affinity state, and induces its association with rafts. The receptor was crosslinked to photocholesterol. Our data suggest that sterol-rich lipid rafts act as positive allosteric regulators of DmGluRA.
代谢型谷氨酸受体（mGluRs）负责谷氨酸在慢突触传递中的作用，并参与中枢神经系统中许多过程的调节。最近，我们报道了从果蝇（DmGluRA）中表达和纯化的一种mGluR，它是哺乳动物II组mGluRs的同源物。我们已经表明，配体与重组的DmGluRA结合需要脂质体中存在麦角固醇[Eroglu，C.，Cronet，P.，Panneels，V.，Beaufils，P.和Sinning，I.（2002年）《欧洲分子生物学组织报告》3，491 - 496]。在这里，我们证明该受体对谷氨酸存在不同的亲和状态，这取决于膜的组成。当与富含固醇的脂质微区（脂筏）结合时，受体处于高亲和状态，而在脂筏之外则处于低亲和状态。用胆固醇富集膜会使受体转变为高亲和状态，并诱导其与脂筏结合。该受体与光胆固醇发生交联。我们的数据表明，富含固醇的脂质筏作为DmGluRA的正变构调节剂发挥作用。
