Sekiguchi Fumiko, Saito Shino, Takaoka Kaori, Hayashi Hitomi, Nagataki Mami, Nagasawa Keita, Nishikawa Hiroyuki, Matsui Hirofumi, Kawabata Atsufumi
Division of Physiology and Pathophysiology, School of Pharmacy, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan.
Biochem Pharmacol. 2007 Jan 1;73(1):103-14. doi: 10.1016/j.bcp.2006.09.016. Epub 2006 Sep 22.
Proteinase-activated receptor-1 (PAR1), a thrombin receptor, plays a protective role in gastric mucosa via prostanoid formation. Thus, we studied effects of PAR1 stimulation on prostaglandin E(2) (PGE(2)) formation in rat normal gastric mucosal epithelial RGM1 cells and analyzed the underlying signal transduction mechanisms. The PAR1-activating peptide (PAR1-AP) and thrombin increased PGE(2) release from RGM1 cells for 18h, an effect being suppressed by inhibitors of COX-1, COX-2, MEK, p38 MAP kinase (p38 MAPK), protein kinase C (PKC), Src and EGF receptor-tyrosine kinase (EGFR-TK), but not JNK and matrix metalloproteinase (MMP)/a disintegrin and metalloproteinases (ADAMs). PAR1-AP caused persistent (6h or more) and transient (5min) phosphorylation of ERK and p38 MAPK, respectively, followed by delayed reinforcement at 18h. PAR1-AP up-regulated COX-2 in a manner dependent on MEK and EGFR-TK, but not p38 MAPK. The PAR1-mediated persistent ERK phosphorylation was reduced by inhibitors of Src and EGFR-TK. PAR1-AP actually phosphorylated EGF receptors and up-regulated mRNA for heparin-binding-EGF (HB-EGF), the latter effect being blocked by inhibitors of Src, EGFR-TK and MEK. Heparin, an inhibitor for HB-EGF, suppressed PAR1-mediated PGE(2) formation and persistent ERK phosphorylation. These results suggest that PAR1 up-regulates COX-2 via persistent activation of MEK/ERK that is dependent on EGFR-TK activation following induction of HB-EGF, leading to PGE(2) formation. In addition, our data also indicate involvement of COX-1, PKC and p38 MAPK in PAR1-triggered PGE(2) formation. PAR1, thus stimulates complex multiple signaling pathways responsible for PGE(2) formation in RGM1 cells.
蛋白酶激活受体-1（PAR1）是一种凝血酶受体，通过前列腺素的形成在胃黏膜中发挥保护作用。因此，我们研究了PAR1刺激对大鼠正常胃黏膜上皮RGM1细胞中前列腺素E2（PGE2）形成的影响，并分析了潜在的信号转导机制。PAR1激活肽（PAR1-AP）和凝血酶可使RGM1细胞中的PGE2释放增加18小时，COX-1、COX-2、MEK、p38丝裂原活化蛋白激酶（p38 MAPK）、蛋白激酶C（PKC）、Src和表皮生长因子受体酪氨酸激酶（EGFR-TK）的抑制剂可抑制这种作用，但JNK和基质金属蛋白酶（MMP）/解聚素和金属蛋白酶（ADAMs）的抑制剂则无此作用。PAR1-AP分别导致ERK和p38 MAPK持续（6小时或更长时间）和短暂（5分钟）的磷酸化，随后在18小时出现延迟增强。PAR1-AP以依赖MEK和EGFR-TK而非p38 MAPK的方式上调COX-2。Src和EGFR-TK的抑制剂可降低PAR1介导的ERK持续磷酸化。PAR1-AP实际上使表皮生长因子受体磷酸化，并上调肝素结合表皮生长因子（HB-EGF）的mRNA，后者的作用被Src、EGFR-TK和MEK的抑制剂所阻断。肝素是HB-EGF的抑制剂，可抑制PAR1介导的PGE2形成和ERK持续磷酸化。这些结果表明，PAR1通过持续激活MEK/ERK上调COX-2，而MEK/ERK的持续激活依赖于HB-EGF诱导后的EGFR-TK激活，从而导致PGE2的形成。此外，我们的数据还表明COX-1、PKC和p38 MAPK参与了PAR1触发的PGE2形成。因此，PAR1刺激RGM1细胞中负责PGE2形成的复杂多重信号通路。
