Yoshii S, Tanaka M, Otsuki Y, Fujiyama T, Kataoka H, Arai H, Hanai H, Sugimura H
First Department of Pathology, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan.
Mol Cell Biol. 2001 Oct;21(20):6796-807. doi: 10.1128/MCB.21.20.6796-6807.2001.
Benzo[a]pyrene [B(a)P], a potent procarcinogen found in combustion products such as diesel exhaust and cigarette smoke, has been recently shown to activate the c-Jun NH(2)-terminal kinase 1 (JNK1) and induce caspase-3-mediated apoptosis in Hepa1c1c7 cells. However, the molecules of the signaling pathway that control the mitogen-activated protein kinase cascades induced by B(a)P and the interaction between those and apoptosis by B(a)P have not been well defined. We report here that B(a)P promoted Cdc42/Rac1, p21-activated kinase 1 (PAK1), and JNK1 activities in 293T and HeLa cells. Moreover, alpha-PAK-interacting exchange factor (alpha PIX) mRNA and its protein expression were upregulated by B(a)P. While overexpression of an active mutant of alpha PIX (DeltaCH) facilitated B(a)P-induced activation of Cdc42/Rac1, PAK1, and JNK1, overexpression of mutated alphaPIX (L383R, L384S), which lacks guanine nucleotide exchange factor activity, SH3 domain-deleted alphaPIX (Delta SH3), which lacks the ability to bind PAK, kinase-negative PAK1 (K299R), and kinase-negative SEK1 (K220A, K224L) inhibited B(a)P-triggered JNK1 activation. Interestingly, overexpression of alphaPIX (Delta CH) and a catalytically active mutant PAK1 (T423E) accelerated B(a)P-induced apoptosis in HeLa cells, whereas alphaPIX (Delta SH3), PAK1 (K299R), and SEK 1 (K220A, K224L) inhibited B(a)P-initiated apoptosis. Finally, a preferential caspase inhibitor, Z-Asp-CH2-DCB, strongly blocked the alphaPIX (Delta CH)-enhanced apoptosis in cells treated with B(a)P but did not block PAK1/JNK1 activation. Taken together, these results indicate that alphaPIX plays a crucial role in B(a)P-induced apoptosis through activation of the JNK1 pathway kinases.
苯并[a]芘[B(a)P]是一种在柴油废气和香烟烟雾等燃烧产物中发现的强效前致癌物，最近研究表明它可激活c-Jun氨基末端激酶1（JNK1）并在Hepa1c1c7细胞中诱导caspase-3介导的细胞凋亡。然而，控制由B(a)P诱导的丝裂原活化蛋白激酶级联反应的信号通路分子，以及这些分子与B(a)P诱导的细胞凋亡之间的相互作用尚未明确。我们在此报告，B(a)P可促进293T和HeLa细胞中Cdc42/Rac1、p21活化激酶1（PAK1）和JNK1的活性。此外，B(a)P可上调α-PAK相互作用交换因子（αPIX）的mRNA及其蛋白表达。虽然αPIX的活性突变体（DeltaCH）的过表达促进了B(a)P诱导的Cdc42/Rac1、PAK1和JNK1的活化，但缺乏鸟嘌呤核苷酸交换因子活性的突变αPIX（L383R、L384S）、缺乏结合PAK能力的SH3结构域缺失的αPIX（Delta SH3）、激酶阴性的PAK1（K299R）和激酶阴性的SEK1（K220A、K224L）抑制了B(a)P触发的JNK1活化。有趣的是，αPIX（Delta CH）和催化活性突变体PAK1（T423E）的过表达加速了B(a)P诱导的HeLa细胞凋亡，而αPIX（Delta SH3）、PAK1（K299R）和SEK 1（K220A、K224L）抑制了B(a)P引发的细胞凋亡。最后，一种特异性caspase抑制剂Z-Asp-CH2-DCB强烈阻断了αPIX（Delta CH）增强的B(a)P处理细胞中的细胞凋亡，但未阻断PAK1/JNK1活化。综上所述，这些结果表明αPIX通过激活JNK1途径激酶在B(a)P诱导的细胞凋亡中起关键作用。
