Distinct beta-subunits are present in hybrid insulin-like-growth-factor-1 receptors in the central nervous system.
Distinct beta-subunits are present in hybrid insulin-like-growth-factor-1 receptors in the central nervous system.
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中枢神经系统中的混合型胰岛素样生长因子-1 受体中存在不同的 β 亚基。
DOI：
10.1042/bj2940685
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Livingston,JN
中科院分区：
文献类型：
--
作者：
Moss,AM;Livingston,JN
以前的工作表明，在各种组织中存在不同的胰岛素样生长因子-1（IGF-1）受体亚型。在本研究中，我们提供了支持的概念，即异质性IGF-1受体存在于大脑中，部分的异质性是来自IGF-1受体杂交形成的不同的β-亚基。从成年大鼠前脑突触体中提取IGF-1受体，并通过麦胚凝集素（WGA）层析进行部分纯化。该制剂中的激素结合研究表明存在IGF-1和胰岛素受体。使用对大鼠胰岛素受体具有特异性的抗体a-RIR从WGA提取物中除去胰岛素受体。免疫耗竭材料的研究表明，在与低浓度IGF-1孵育期间，92和99 kDa的两种蛋白质在酪氨酸上磷酸化。这两种蛋白质都与固定在琼脂糖上的IGF-1具有高亲和力和特异性结合，并且当琼脂糖珠与[γ-32 P]ATP和MnCl 2孵育时，每种蛋白质都经历磷酸化。两种蛋白质的胰蛋白酶处理后的二维磷酸肽图显示出显着的差异，它们的结构以及胰岛素受体的β-亚基的磷酸肽图的差异。这两种蛋白质与IGF-1受体的关系进一步通过针对人IGF-1受体β-亚基中的特定序列产生的抗体（α-HF）和针对与IGF-1受体交叉反应的肝胰岛素受体（L1）产生的多克隆抗体来探测。两种抗体免疫沉淀两种磷酸化蛋白质。然而，受体还原形成受体二聚体或单体表明，α-HF仅沉淀99 kDa蛋白，而L1主要沉淀92 kDa蛋白。总之，脑IGF-1受体显然具有两个结构不同的β亚基，一个为92 kDa，另一个为99 kDa。有趣的是，至少一部分IGF-1受体群体在同一受体中具有两种亚型。
Previous work suggests the existence of different isoforms of the insulin-like-growth-factor-1 (IGF-1) receptor in various tissues. In the present study we provide support for the concept that heterogeneous IGF-1 receptors exist in the brain and that part of the heterogeneity is derived from IGF-1 receptor hybrids formed from different beta-subunits. IGF-1 receptors were extracted from adult-rat forebrain synaptosomes and partially purified by wheat-germ agglutinin (WGA) chromatography. Hormone-binding studies in this preparation demonstrate the presence of receptors for IGF-1 and insulin. An antibody, a-RIR, specific for the rat insulin receptor was used to remove insulin receptors from the WGA extract. Studies with the immunodepleted material demonstrated two proteins of 92 and 99 kDa that are phosphorylated on tyrosine during incubation with low concentrations of IGF-1. Both proteins bound with high affinity and specificity to IGF-1 immobilized on agarose, and each underwent phosphorylation when the agarose beads were incubated with [gamma-32P]ATP and MnCl2. Two-dimensional phosphopeptide maps after exhaustive trypsin treatment of the two proteins showed significant differences in their structure as well as differences from the phosphopeptide map for the beta-subunit of the insulin receptor. The relationship of the two proteins to the IGF-1 receptor was further probed by an antibody (a-HF) raised against a specific sequence in the beta-subunit of the human IGF-1 receptor, and a polyclonal antibody raised against the liver insulin receptor (L1) which cross-reacts with the IGF-1 receptor. Both antibodies immunoprecipitated the two phosphorylated proteins. However, reduction of the receptors to form receptor dimers or monomers showed that a-HF precipitated only the 99 kDa protein, whereas L1 precipitated primarily the 92 kDa protein. In conclusion, the brain IGF-1 receptor apparently has two structurally different beta-subunits, one of 92 kDa and a second of 99 kDa. Interestingly, at least a portion of the IGF-1 receptor population has both isoforms in the same receptor.