RAP1GAP inhibits cytoskeletal remodeling and motility in thyroid cancer cells.
RAP1GAP inhibits cytoskeletal remodeling and motility in thyroid cancer cells.
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DOI：
10.1530/erc-12-0086
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发表时间：
2012-08
影响因子：
3.9
通讯作者：
Meinkoth JL
中科院分区：
文献类型：
--
作者：
Dong X;Tang W;Stopenski S;Brose MS;Korch C;Meinkoth JL
RAP1GAP蛋白表达减少在人类肿瘤中的功能意义尚不清楚。为了鉴定甲状腺中RAP1GAP下调的靶点，分析了人甲状腺细胞和原发性甲状腺肿瘤中的RAP 1和RAP 2蛋白表达。RAP1GAP和RAP2在正常甲状腺滤泡细胞中共表达。有趣的是，尽管在也表达RAP 2的乳头状甲状腺癌中检测到RAP 1，但在正常甲状腺细胞中并未检测到RAP 1。在乳头状甲状腺肿瘤的细胞膜上检测到两种RAP蛋白，这表明当RAP1GAP下调时它们被激活。为了探索RAP 1GAP耗竭的功能意义，RAP 1GAP以足以阻断乳头状和未分化甲状腺癌细胞系中内源性RAP 2活性的最低水平瞬时表达。RAP1GAP损伤了细胞在胶原上的扩散和迁移能力。虽然RAP1GAP对生长中的细胞中的蛋白酪氨酸磷酸化没有影响，但RAP1GAP在急性接种在胶原上的细胞中SRC磷酸化的位点处损害粘着斑激酶和桩蛋白的磷酸化。SRC活性在悬浮细胞中增加，其中它被RAP1GAP抑制。抑制SRC激酶活性会损害细胞的铺展和运动性。这些发现确定SRC作为RAP1GAP耗竭的靶点，并表明甲状腺肿瘤中RAP1GAP的下调增强了SRC依赖的信号，这些信号调节细胞的结构和运动。
The functional significance of decreased RAP1GAP protein expression in human tumors is unclear. To identify targets of RAP1GAP downregulation in the thyroid gland, RAP1 and RAP2 protein expression in human thyroid cells and in primary thyroid tumors were analyzed. RAP1GAP and RAP2 were co-expressed in normal thyroid follicular cells. Intriguingly, RAP1 was not detected in normal thyroid cells, although it was detected in papillary thyroid carcinomas, which also expressed RAP2. Both RAP proteins were detected at the membrane in papillary thyroid tumors, suggesting that they are activated when RAP1GAP is downregulated. To explore the functional significance of RAP1GAP depletion, RAP1GAP was transiently expressed at the lowest level that is sufficient to block endogenous RAP2 activity in papillary and anaplastic thyroid carcinoma cell lines. RAP1GAP impaired the ability of cells to spread and migrate on collagen. Although RAP1GAP had no effect on protein tyrosine phosphorylation in growing cells, RAP1GAP impaired phosphorylation of focal adhesion kinase and paxillin at sites phosphorylated by SRC in cells acutely plated on collagen. SRC activity was increased in suspended cells, where it was inhibited by RAP1GAP. Inhibition of SRC kinase activity impaired cell spreading and motility. These findings identify SRC as a target of RAP1GAP depletion and suggest that the downregulation of RAP1GAP in thyroid tumors enhances SRC-dependent signals that regulate cellular architecture and motility.