Jikuhara Atsushi, Yoshii Masanori, Iwagaki Hiromi, Mori Shuji, Nishibori Masahiro, Tanaka Noriaki
Department of Gastroenterological Surgery and Transplant, Okayama University Graduate School of Medicine and Dentistry, 2-5-1 Shikata-cho, Okayama 700-8558, Japan.
Life Sci. 2003 Oct 17;73(22):2817-29. doi: 10.1016/s0024-3205(03)00702-1.
Protease-activated receptor-2 (PAR-2) has been demonstrated to be highly expressed in the gastrointestinal tract. In the present study, we investigated the effects of PAR-2 stimulation on the cell signaling and proliferation of DLD-1, a human colon carcinoma cell line, in comparison with the PAR-1 stimulation. PAR-2 stimulation by agonist peptide SLIGKV concentration-dependently induced the increase in [Ca2+]i and the proliferation of DLD-1 whereas the inverse peptide LSIGKV did not. Trypin (10(-9) M), an agonist protease for PAR-2, also enhanced the proliferation of DLD-1. The proliferative response of DLD-1 to PAR-2 stimulation was associated with the transient phosphorylation of MEK and MAP kinase, but not p38 MAP kinase and JNK. Inhibition of MEK by PD98059 (50 microM) completely inhibited the proliferation-stimulating effects as well as the phosphorylation of MAP kinase induced by PAR-2 agonist peptide (100 microM) and trypsin (10(-9) M). The prolonged treatment with PAR-2 agonist peptide for more than one hour was required for the enhanced proliferative response, suggesting the existence of unknown long-lasting cooperative signaling with MAP kinase cascade. PAR-1 stimulation by the agonist peptide SFLLRN (100 microM) or thrombin (10(-8) M) produced Ca2+ signaling, however, the stimulation neither produced the cell proliferative response nor the activation of MEK-MAP kinase cascade. These results indicated that Ca2+ signaling induced by PARs activation was not enough for inducing the cell proliferation in DLD-1 cells and that stimulation of PAR-2 can induce the activation of MEK-MAP kinase cascade, leading to the growth promoting response.
蛋白酶激活受体-2（PAR-2）已被证明在胃肠道中高度表达。在本研究中，我们研究了PAR-2刺激对人结肠癌细胞系DLD-1的细胞信号传导和增殖的影响，并与PAR-1刺激进行了比较。激动剂肽SLIGKV对PAR-2的刺激浓度依赖性地诱导了DLD-1细胞内钙离子浓度（[Ca2+]i）的升高和细胞增殖，而反向肽LSIGKV则没有此作用。胰蛋白酶（10^(-9) M），一种PAR-2的激动剂蛋白酶，也增强了DLD-1的增殖。DLD-1对PAR-2刺激的增殖反应与MEK和丝裂原活化蛋白激酶（MAP激酶）的瞬时磷酸化有关，但与p38 MAP激酶和JNK无关。PD98059（50 microM）对MEK的抑制完全抑制了PAR-2激动剂肽（100 microM）和胰蛋白酶（10^(-9) M）诱导的增殖刺激作用以及MAP激酶的磷酸化。PAR-2激动剂肽延长处理超过一小时才会出现增强的增殖反应，这表明存在与MAP激酶级联的未知持久协同信号。激动剂肽SFLLRN（100 microM）或凝血酶（10^(-8) M）对PAR-1的刺激产生了钙离子信号，然而，该刺激既未产生细胞增殖反应，也未激活MEK-MAP激酶级联。这些结果表明，PARs激活诱导的钙离子信号不足以诱导DLD-1细胞的增殖，并且PAR-2的刺激可以诱导MEK-MAP激酶级联的激活，从而导致生长促进反应。
