PDGF-MEDIATED ACTIVATION OF PHOSPHATIDYLINOSITOL 3-KINASE IN HUMAN MESANGIAL CELLS
PDGF-MEDIATED ACTIVATION OF PHOSPHATIDYLINOSITOL 3-KINASE IN HUMAN MESANGIAL CELLS
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DOI：
10.1038/ki.1994.242
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发表时间：
1994-07-01
影响因子：
19.6
通讯作者：
ABBOUD, HE
中科院分区：
文献类型：
--
作者：
CHOUDHURY, GG;BISWAS, P;ABBOUD, HE
血小板衍生生长因子(PDGF)刺激肾小球系膜细胞有丝分裂并发挥其他生物学活性。PDGF诱导这些细胞有丝分裂的确切机制尚不清楚。信号转导酶磷脂酰肌醇-3-激酶(PI-3-K)的激活与细胞有丝分裂有关。PI3K的激活是通过刺激酪氨酸激酶和G蛋白偶联的受体来实现的。这种酶反应的产物D3磷酸化肌苷的合成依赖于蛋白激酶C的激活和G蛋白。我们研究了PDGF对人肾小球系膜细胞PI-3K的激活作用。用PI3K 85kD亚基特异性抗体检测肾小球系膜细胞PI3K蛋白为110kD和85kD异二聚体。PDGF以剂量依赖的方式刺激PI3K活性，在12 ng/ml时最大激活，PI3K活性呈双相动力学变化，在2min内快速达到峰值，10min后出现第二个峰值。抗磷酸酪氨酸和PI3K免疫沉淀研究表明，85kD的PI3K亚基与PDGFR有关。PDGFRβ抗体直接免疫沉淀显示PI3K活性与PDGF受体相关。在抑制PDGF刺激的PKC活性的浓度下，异喹啉磺酰哌嗪化合物H7对PDGF刺激的抗磷蛋白酪氨酸免疫沉淀物中的PI 3激酶活性无影响。这些数据表明，PI3激酶的激活对PKC不敏感。用部分抑制PDGF诱导的人肾小球系膜细胞DNA合成的百日咳毒素处理系膜细胞，不能抑制PDGF诱导的PI 3激酶的激活。这些结果表明，PDGF激活系膜细胞PI-3K，百日咳毒素敏感的G蛋白不参与PI-3K的激活。这些数据进一步分离了人系膜细胞PI-3K的激活与有丝分裂的关系。
Platelet-derived growth factor (PDGF) stimulates mitogenesis and exerts other biologic activities in glomerular mesangial cells. The precise mechanism of PDGF-induced mitogenesis in these cells is not clear. The activation of a signal transducing enzyme, phosphatidylinositol 3 kinase (PI 3 kinase) is associated with mitogenesis. Activation of PI 3 kinase results from stimulation of tyrosine kinase and G-protein-coupled classes of receptors. The synthesis of D3 phosphorylated inositides, the products of this enzymatic reaction, in non-nucleated cells such as blood platelets is dependent upon protein kinase C activation and G-proteins. We studied the activation of PI 3 kinase in response to PDGF in human glomerular mesangial cells. Using a PI 3 kinase 85 kD subunit specific antibody, we detected mesangial cell PI 3 kinase protein as 110 and 85 kD heterodimer. PDGF stimulated PI 3 kinase activity in antiphosphotyrosine immunoprecipitates in a dose-dependent manner showing maximum activation at 12 ng/ml. The antiphosphotyrosine associated PI 3 kinase activity showed biphasic kinetics with a fast peak within two minutes followed by a second peak at 10 minutes. Antiphosphotyrosine and PI 3 kinase immunoprecipitation studies indicated the association of the 85 kD PI 3 kinase subunit with PDGFR. Direct immunoprecipitation with PDGFR beta antibody showed the association of PI 3 kinase activity with the PDGF-receptor. The isoquinoline sulfonyl piperazine compound H7 at concentrations that inhibit PDGF-stimulated PKC activity had no effect on PDGF-stimulated PI 3 kinase activity in antiphospotyrosine immunoprecipates. These data indicate that PI3 kinase activation is insensitive to PKC. Treatment of mesangial cells with pertussis toxin at concentrations that partially inhibited PDGF-induced DNA synthesis in human mesangial cells did not inhibit PDGF-induced PI 3 kinase activation. These data indicate that PDGF activates PI 3 kinase in mesangial cells and that pertussis toxin-sensitive G-proteins are not involved in PI 3 kinase activation. The data further dissociate activation of PI 3 kinase from mitogenesis in human mesangial cells.