Organ specificity of insulin resistance induced by Protein-tyrosine phosphatase

蛋白酪氨酸磷酸酶诱导的胰岛素抵抗的器官特异性

• 批准号: 14571088
• 负责人: MAEGAWA Hiroshi
• 金额: $ 2.18万
• 依托单位: Shiga University of Medical Science
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14571088/
• 关键词: Protein-tyrosine phosphatase; PTP1B; insulin resistance; Protein phosphatase; PP2A; SREBP-1

We investigated the effect of PTP1B overexpression for insulin signaling in 3T3L1 adipocytes. 0verexpression of wild-type PTP1B in L1 adipocytes led to the profound decrease in the insulin-stimulated phosphorylation of mitogen-activated protein (MAP) kinase as well as in L6 myocytes. Even though the identical decrease in IRS-1 phosphorylation as in L6 myocytes, wild-type PTP1B overexpression in L1 adipocytes led to a small inhibition in the insulin-stimulated Akt phosphorylation as accompanied with a small, but significant attenuation in the insulin-stimulated glucose uptake, when compared with phosphatase-negative mutant. Regarding the relatively small effect on Akt phosphorylation, we found the identical findings in rat 1 fibroblasts overexpressing human insulin receptor, suggesting that the higher expression levels of insulin receptor and IRS-1 might be responsible. With regard to the large effect on MAP kinase phosphorylation, we found that PTP1B overexpression led to the impairmen … More ts of both phosphorylation of IRS-1 and Shc, resulting in a decrease in their association with Grb2. Furthermore, platelet derived growth factor stimulated Shc phosphorylation was also attenuated, without any change in its receptors, suggesting that PTP1B directly attacked Shc. These data demonstrate that PTP1B negatively regulates insulin signaling, and MAP kinase cascade is much sensitive as compared with Akt pathway in some cell lines, especially in L1 adipocytes.Insulin-resistant rats fed a diet high in fructose showed an increased protein-tyrosine phosphatase 1B (PTP1B) content with strong expression of sterol regulatory element binding protein (SREBP)-1 mRNA in the liver. To clarify the association of PTP1B with SREBP-1 gene expression, we overexpressed PTP1B in rat hepatocytes, which led to increased mRNA content and promoter activity of SREBP-1a and -1c, including increased nuclear Sp1 binding. Since PTP1B overexpression increased phosphatase 2A (PP2A) activity, we inhibited PP2A activity by expression of its selective inhibitor, SV40 small t antigen, and found that this normalized the PTP1B-enhanced SREBP-1a and -1c mRNA expressions through activation of Sp1 site. Furthermore, a transient liver-specific overexpression of PTP1B protein led to increased serum triglyceride levels with enhanced SREBP-1a and -1c gene expressions in mouse liver. Finally, administration of a new PTP1B inhibitor (JTP-55773) to db/db mice led to amelioration of both postprandial hypertriglyceridemia and fatty liver with decreased SREBP-1 mRNA expression. These results indicate that PTP1B may regulate gene expression of SREBP-1 via enhancing PP2A activity, thus mediating hepatic lipogenesis and postprandial hypertriglyceridemia. Therefore, PTP1B is a newly identified therapeutic target for the amelioration of postprandial hypertriglyceridemia, as well as for the reduction of resistance to insulin. Less

我们研究了PTP1B过表达对3T3L1脂肪细胞中胰岛素信号传导的影响。野生型PTP1B在L1脂肪细胞中的过表达导致胰岛素刺激的丝裂原活化蛋白（MAP）激酶磷酸化以及在L6肌细胞中的显著降低。与磷酸酶阴性突变体相比，野生型PTP1B在L1脂肪细胞中的过表达导致胰岛素刺激的Akt磷酸化受到轻微抑制，同时胰岛素刺激的葡萄糖摄取受到轻微但显著的抑制。对于Akt磷酸化的影响相对较小，我们在过表达人胰岛素受体的大鼠1号成纤维细胞中发现了相同的结果，提示胰岛素受体和IRS-1的高表达水平可能是原因。关于对MAP激酶磷酸化的较大影响，我们发现PTP1B过表达导致IRS-1和Shc的磷酸化均受损，导致其与Grb2的相关性降低。此外，血小板衍生生长因子刺激的Shc磷酸化也被减弱，其受体未发生任何变化，表明PTP1B直接攻击Shc。这些数据表明，PTP1B负调控胰岛素信号通路，并且MAP激酶级联在某些细胞系中比Akt通路更为敏感，特别是在L1脂肪细胞中。饲喂高果糖饮食的胰岛素抵抗大鼠肝脏中蛋白-酪氨酸磷酸酶1B （PTP1B）含量增加，甾醇调节元件结合蛋白(SREBP)-1 mRNA表达强烈。为了明确PTP1B与SREBP-1基因表达的关系，我们在大鼠肝细胞中过表达PTP1B，导致SREBP-1a和-1c mRNA含量和启动子活性增加，包括核Sp1结合增加。由于PTP1B过表达增加了磷酸酶2A （PP2A）的活性，我们通过表达其选择性抑制剂SV40小t抗原来抑制PP2A的活性，并发现这通过激活Sp1位点使PTP1B增强的SREBP-1a和-1c mRNA表达正常化。此外，PTP1B蛋白的肝脏特异性短暂过表达导致小鼠肝脏中SREBP-1a和-1c基因表达增强，血清甘油三酯水平升高。最后，给db/db小鼠一种新的PTP1B抑制剂（JTP-55773）可以改善餐后高甘油三酯血症和脂肪肝，并降低SREBP-1 mRNA的表达。这些结果表明，PTP1B可能通过增强PP2A活性调控SREBP-1基因表达，从而介导肝脏脂肪生成和餐后高甘油三酯血症。因此，PTP1B是一个新发现的改善餐后高甘油三酯血症以及降低胰岛素抵抗的治疗靶点。少

项目成果

Shimizu S, Ugi S, Maegawa H, et al.: "Protein-Tyrosine Phosphatase 1B as New Activator for Hepatic Lipogenesis via Sterol Regulatory Element-Binding Protein-1 Gene Expression."J Biol Chem. 278. 43095-43101 (2002)

Shimizu S、Ugi S、Maekawa H 等人：“蛋白质酪氨酸磷酸酶 1B 通过甾醇调节元件结合蛋白 1 基因表达作为肝脂肪生成的新激活剂。”J Biol Chem。

Egawa K, Maegawa H, et al.: "Membrane localization of 3-phosphoinositide-dependent protein kinase-1 stimulates activities of Akt and atypical PKC, but does not stimulate glucose transport and glycogen synthesis in 3T3-L1 adipocytes."J Biol Chem. 277. 3886

Ekawa K、Maekawa H 等人：“3-磷酸肌醇依赖性蛋白激酶 1 的膜定位会刺激 Akt 和非典型 PKC 的活性，但不会刺激 3T3-L1 脂肪细胞中的葡萄糖转运和糖原合成。”J Biol Chem

Shimizu S, Maegawa H, et al.: "Mechanism for differential effect of PTP1B on Akt versus MAP kinase in 3T3L1 adipocytes."Endocrinology. 143. 4563-4569 (2002)

Shimizu S、Maekawa H 等人：“PTP1B 对 3T3L1 脂肪细胞中 Akt 与 MAP 激酶的差异作用机制。”内分泌学。

Shimizu S, Ugi S, Maegawa H, et al.: "Protein-Tyrosine Phosphatase 1B as New Activator for Hepatic Lipogenesis via Sterol Regulatory Element-Binding Protein-1 Gene Expression."J Biol Chem. 278. 43095-43101 (2003)

Shimizu S、Ugi S、Maekawa H 等人：“蛋白质酪氨酸磷酸酶 1B 通过甾醇调节元件结合蛋白 1 基因表达作为肝脂肪生成的新激活剂。”J Biol Chem。

Egawa K, Maegawa H, et al.: "Membrane localization of 3-phosphoinositide-dependent protein kinase-1 stimulates activities of Akt and atypical PKC, but does not stimulate glucose transport and glycogen synthesis in 3T3-L1 adipocytes"J Biol Chem. 277. 38863

Ekawa K、Maekawa H 等人：“3-磷酸肌醇依赖性蛋白激酶 1 的膜定位会刺激 Akt 和非典型 PKC 的活性，但不会刺激 3T3-L1 脂肪细胞中的葡萄糖转运和糖原合成”J Biol Chem。