The GoLoco motif:: a Gαi/o binding motif and potential guanine nucleotide exchange factor
The GoLoco motif:: a Gαi/o binding motif and potential guanine nucleotide exchange factor
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DOI：
10.1016/s0968-0004(99)01441-3
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发表时间：
1999-09-01
影响因子：
13.8
通讯作者：
De Vries, L
中科院分区：
文献类型：
--
作者：
Siderovski, DP;Diverse-Pierluissi, MA;De Vries, L
对 G 蛋白偶联信号转导脱敏的研究发现了异三聚体 G 蛋白亚基的 GTP 酶激活蛋白 (GAP) 家族，即“G 蛋白信号传导调节器”或 RGS 蛋白1、2。RGS12 是目前已知的最大的哺乳动物 RGS 蛋白2，具有类似于接头蛋白和支架蛋白的多结构域结构（图 1a）。它由 N 端 PDZ (PSD-95/Dlg/ZO-1) 结构域组成，该结构域结合 RGS12 本身和 G 蛋白偶联的白细胞介素 8 受体 B 或 CXCR2（参考文献 3）的 C 端；磷酸酪氨酸结合 (PTB) 结构域（DP Siderovski、L. De Vries 和 MA Diversé-Pierluissi，未发表）和中央 RGS 结构域，是 Gi/o 类异源三聚体 G 蛋白亚基的 GAP3。在这里，我们发现 RGS12 的 C 末端包含一个新的 19 个氨基酸基序，该基序也存在于结合 Gi/o 类亚基的其他蛋白质中（图 1b）。由于该基序最初是通过比较哺乳动物 RGS 蛋白与果蝇 RGS12 同源物 Loco 发现的，因此我们将其命名为 Gi/o-Loco 或“GoLoco”基序。 loco 是在增强子陷阱筛选基因中发现的，这些基因在神经胶质细胞中的表达取决于 Pointed 的活性，Pointed 是翼状螺旋-转角-螺旋转录因子 ets 家族的成员4。在同一份报告中，Granderath 及其同事使用果蝇 Gi 作为“诱饵”进行了酵母双杂交筛选，并鉴定了四个重叠的基因座 cDNA 作为相互作用克隆：其中三个缺乏假定的 G 相互作用结构域（即 RGS 结构域），但全部包含 C 端区域的最后 43 个氨基酸，与 RGS12 具有 39% 的同一性。使用大鼠 RGS12 的相应 51 个氨基酸区域（SP 的氨基酸 1171-1221：RGSC_RAT）和 E 值阈值 1（需要在第一次迭代中识别 Loco；E 4 10-1）进行迭代 PSI-BLAST 搜索5，识别出其他已知 G 相互作用蛋白中的相似区域：RGS14（E 4 10-6；迭代 0）、人类嵌合蛋白 LGN（E 3 10–1；迭代 0）和浦肯野细胞蛋白-2（Pcp2；E 8 10–1；迭代 1）。 RGS12 和 RGS14 是密切相关的 RGS 蛋白，我们之前报道了 RGS12 和 RGS14 之间共享的 17 个氨基酸序列，其功能未知（参考文献 6）。这个 17 个氨基酸区域包括 GoLoco 基序的最后三个氨基酸残基，可能反映另一个功能域
Studies of the desensitization of G-protein-coupled signal transduction have led to the discovery of a family of GTPase-activating proteins (GAPs) for heterotrimeric G-protein subunits–the ‘regulator of G-protein signaling’or RGS proteins1, 2. RGS12 is the largest mammalian RGS protein that is currently known2 and has a multi-domain structure reminiscent of both adaptor and scaffold proteins (Fig. 1a). It consists of an N-terminal PDZ (PSD-95/Dlg/ZO-1) domain, which binds the C-termini of both RGS12 itself and the G-proteincoupled interleukin-8 receptor B or CXCR2 (Ref. 3), a phosphotyrosinebinding (PTB) domain (DP Siderovski, L. De Vries, and MA Diversé-Pierluissi, unpublished), and a central RGS domain, which is a GAP for Gi/o-class heterotrimeric G protein subunits3. Here, we show that the C-terminus of RGS12 contains a new 19-amino-acid motif, also present in other proteins that bind Gi/o-class subunits (Fig. 1b). As this motif was initially discovered by comparison of mammalian RGS proteins with Loco, the Drosophila RGS12 homologue, we have named it the Gi/o-Loco or ‘GoLoco’motif. loco was identified in an enhancer-trap screen for genes whose expression in glial cells depends on the activity of Pointed, a member of the ets family of winged helix–turn–helix transcription factors4. In the same report, Granderath and colleagues performed a yeast twohybrid screen employing Drosophila Gi as ‘bait’and identified four overlapping loco cDNAs as interacting clones: three lacking the presumptive G-interacting domain (ie the RGS domain), but all containing the final 43 amino acids of a C-terminal region with 39% identity to RGS12. An iterative PSI-BLAST search5, using the corresponding 51-amino-acid region of rat RGS12 (aa 1171–1221 of SP: RGSC_RAT) and an E-value threshold of 1 (required to identify Loco in the first iteration; E 4 10–1), identified similar regions within other known G-interacting proteins: RGS14 (E 4 10–6; iteration 0), the human mosaic protein LGN (E 3 10–1; iteration 0) and Purkinje-cell protein-2 (Pcp2; E 8 10–1; iteration 1). RGS12 and RGS14 are closely related RGS proteins and we previously reported a 17-amino-acid sequence of unknown function shared between RGS12 and RGS14 (Ref. 6). This 17-amino-acid region includes the final three amino-acid residues of the GoLoco motif and might reflect another functional domain