Mahadev K, Zilbering A, Zhu L, Goldstein B J
Dorrance H. Hamilton Research Laboratories, Division of Endocrinology and Metabolic Diseases, Department of Medicine, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
J Biol Chem. 2001 Jun 15;276(24):21938-42. doi: 10.1074/jbc.C100109200. Epub 2001 Apr 10.
The insulin signaling pathway is activated by tyrosine phosphorylation of the insulin receptor and key post-receptor substrate proteins and balanced by the action of specific protein-tyrosine phosphatases (PTPases). PTPase activity, in turn, is highly regulated in vivo by oxidation/reduction reactions involving the cysteine thiol moiety required for catalysis. Here we show that insulin stimulation generates a burst of intracellular H(2)O(2) in insulin-sensitive hepatoma and adipose cells that is associated with reversible oxidative inhibition of up to 62% of overall cellular PTPase activity, as measured by a novel method using strictly anaerobic conditions. The specific activity of immunoprecipitated PTP1B, a PTPase homolog implicated in the regulation of insulin signaling, was also strongly inhibited by up to 88% following insulin stimulation. Catalase pretreatment abolished the insulin-stimulated production of H(2)O(2) as well as the inhibition of cellular PTPases, including PTP1B, and was associated with reduced insulin-stimulated tyrosine phosphorylation of its receptor and high M(r) insulin receptor substrate (IRS) proteins. These data provide compelling new evidence for a redox signal that enhances the early insulin-stimulated cascade of tyrosine phosphorylation by oxidative inactivation of PTP1B and possibly other tyrosine phosphatases.
胰岛素信号通路通过胰岛素受体和关键的受体后底物蛋白的酪氨酸磷酸化而被激活，并由特定蛋白酪氨酸磷酸酶（PTPases）的作用来平衡。反过来，PTPase活性在体内通过涉及催化所需的半胱氨酸硫醇部分的氧化/还原反应受到高度调节。在这里我们表明，胰岛素刺激在胰岛素敏感的肝癌细胞和脂肪细胞中产生一阵细胞内H₂O₂，这与通过一种使用严格厌氧条件的新方法所测量的高达62%的总体细胞PTPase活性的可逆氧化抑制有关。胰岛素刺激后，免疫沉淀的PTP1B（一种与胰岛素信号调节有关的PTPase同源物）的比活性也强烈受到抑制，高达88%。过氧化氢酶预处理消除了胰岛素刺激产生的H₂O₂以及对细胞PTPases（包括PTP1B）的抑制，并与胰岛素刺激的其受体和高分子量胰岛素受体底物（IRS）蛋白的酪氨酸磷酸化减少有关。这些数据为一种氧化还原信号提供了令人信服的新证据，该信号通过PTP1B和可能的其他酪氨酸磷酸酶的氧化失活增强了早期胰岛素刺激的酪氨酸磷酸化级联反应。
