Department of Biochemistry, Gachon University School of Medicine, Incheon 406-799, Korea.
Cell Signal. 2013 Apr;25(4):883-97. doi: 10.1016/j.cellsig.2012.12.016. Epub 2012 Dec 28.
AMP-activated protein kinase (AMPK) has been implicated in anti-proliferative actions in a range of cell systems. Recently, it was observed that Compound C, an inhibitor of AMPK, also reduced the cell viability in human diploid fibroblasts (HDFs). Compound C-induced growth arrest was associated with a decrease in the cell cycle regulatory proteins, such as proliferating cell nuclear antigen, phosphorylated pRB, cyclin-dependent protein kinases (Cdk 2 and 4), cyclins (D and E), and the Cdk inhibitors (p21, p16, and p27). Therefore, the present study examined the molecular mechanism of the antiproliferative effects of Compound C. Although Compound C inhibited serum-induced phosphorylation of Akt and its substrate, glycogen synthase kinase-3β, it did not affect the Akt activity in vitro. Compound C significantly inhibited the receptor tyrosine phosphorylation and the activity of downstream signaling molecules, such as p85 phosphoinositide 3-kinase, phospholipase C-γ1, and extracellular signal-regulated kinase 1/2, induced by platelet-derived growth factor (PDGF) but not by epidermal growth factor- and insulin-like growth factor. In vitro growth factor receptor tyrosine kinase activity profiling revealed the IC50 for PDGF receptor-β (PDGFRβ) to be 5.07μM, whereas the IC50 for the epidermal growth factor receptor and insulin-like growth factor receptor was ≥100μM. The inhibitory effect of Compound C on PDGFRβ and Akt was also observed in AMPKα1/α2-knockout mouse embryonic fibroblasts, indicating that its inhibitory effect is independent of the AMPK activity. The inhibitory effect of Compound C on cell proliferation and PDGFRβ tyrosine phosphorylation was also demonstrated in various PDGFR-expressing cells, including MRC-5, BEAS-2B, rat aortic vascular smooth muscle cells, and A172 glioblastoma cells. These results indicate that Compound C can be used as a potential antiproliferative agent for PDGF- or PDGFR-associated diseases, such as cancer, atherosclerosis, and fibrosis.
AMP 激活的蛋白激酶（AMPK）已被牵涉到多种细胞系统的抗增殖作用中。最近，人们观察到 AMPK 的抑制剂 Compound C 也能降低人二倍体成纤维细胞（HDFs）的细胞活力。Compound C 诱导的生长停滞与细胞周期调节蛋白的减少有关，如增殖细胞核抗原、磷酸化的 pRB、细胞周期蛋白依赖性激酶（Cdk2 和 4）、细胞周期蛋白（D 和 E）和 Cdk 抑制剂（p21、p16 和 p27）。因此，本研究检查了 Compound C 的抗增殖作用的分子机制。虽然 Compound C 抑制了血清诱导的 Akt 及其底物糖原合酶激酶-3β的磷酸化，但它并不影响体外的 Akt 活性。Compound C 显著抑制了血小板衍生生长因子（PDGF）诱导的受体酪氨酸磷酸化和下游信号分子的活性，如 p85 磷酸肌醇 3-激酶、磷脂酶 C-γ1 和细胞外信号调节激酶 1/2，但不影响表皮生长因子和胰岛素样生长因子诱导的这些信号分子的活性。体外生长因子受体酪氨酸激酶活性分析显示，PDGF 受体-β（PDGFRβ）的 IC50 为 5.07μM，而表皮生长因子受体和胰岛素样生长因子受体的 IC50 均≥100μM。在 AMPKα1/α2 基因敲除的小鼠胚胎成纤维细胞中也观察到了 Compound C 对 PDGFRβ 和 Akt 的抑制作用，表明其抑制作用不依赖于 AMPK 活性。在各种表达 PDGFR 的细胞中，包括 MRC-5、BEAS-2B、大鼠主动脉血管平滑肌细胞和 A172 胶质母细胞瘤细胞，也证明了 Compound C 对细胞增殖和 PDGFRβ 酪氨酸磷酸化的抑制作用。这些结果表明，Compound C 可作为 PDGF 或 PDGFR 相关疾病（如癌症、动脉粥样硬化和纤维化）的潜在抗增殖剂。
