Department of Surgery, Michigan State University, East Lansing, Michigan 48912, USA.
Am J Physiol Gastrointest Liver Physiol. 2012 Oct 15;303(8):G951-60. doi: 10.1152/ajpgi.00158.2012. Epub 2012 Aug 23.
Mixed-lineage kinase 3 (MLK3) activates multiple MAPK pathways and can initiate apoptosis, proliferation, migration, or differentiation in different cell types. However, whether MLK3 signaling regulates intestinal epithelial cell sheet migration in vivo is not known. We sought to investigate whether MLK3 signaling is important in intestinal mucosal healing and epithelial cell motility in vivo and in vitro. In vivo, we compared the healing of jejunal mucosal ulcers induced in MLK3 knockout (KO) mice with healing in wild-type (WT) mice. Ulcer healing was 20.8% less at day 3 (P < 0.05) and 18.9% less at day 5 (P < 0.05) in MLK3 KO than WT mice. Within the intestinal mucosa of MLK3 KO mice, ERK and JNK signaling were reduced, phosphatase and tensin homolog deleted on chromosome 10 (PTEN) level was increased, and p38 signaling was unchanged. Parallel in vitro studies using an MLK inhibitor assessed the role of MLK signaling in human Caco-2 intestinal epithelial migration across collagen substrates. The MLK inhibitor reduced closure of circular wounds in Caco-2 monolayers. MLK inhibition reduced ERK and JNK, but not p38, signaling in Caco-2 cells. Although PTEN is increased after MLK inhibition, it does not influence MLK-mediated cell migration. These findings indicate that disruption of MLK3 signaling impairs ulcer healing by suppressing ERK and JNK signaling in vitro and in mouse intestinal mucosa in vivo. These results reveal a novel role for MLK3 signaling in the regulation of intestinal epithelial migration in vivo and suggest that MLK3 may be an important target for the regulation of intestinal mucosal healing.
混合谱系激酶 3（MLK3）激活多种 MAPK 途径，并能在不同细胞类型中启动细胞凋亡、增殖、迁移或分化。然而，MLK3 信号是否调节体内肠道上皮细胞片层迁移尚不清楚。我们试图研究 MLK3 信号在体内和体外的肠道黏膜愈合和上皮细胞迁移中的重要性。在体内，我们比较了 MLK3 敲除（KO）小鼠和野生型（WT）小鼠诱导的空肠黏膜溃疡的愈合情况。与 WT 小鼠相比，MLK3 KO 小鼠的溃疡愈合在第 3 天减少了 20.8%（P < 0.05），第 5 天减少了 18.9%（P < 0.05）。在 MLK3 KO 小鼠的肠黏膜中，ERK 和 JNK 信号被削弱，磷酸酶和张力蛋白同源物缺失于染色体 10（PTEN）水平增加，p38 信号不变。平行的体外研究使用 MLK 抑制剂评估了 MLK 信号在人 Caco-2 肠道上皮细胞穿过胶原底物迁移中的作用。MLK 抑制剂减少了 Caco-2 单层闭合圆形伤口。MLK 抑制减少了 ERK 和 JNK，但不减少 p38 信号，在 Caco-2 细胞中。尽管 MLK 抑制后 PTEN 增加，但它不影响 MLK 介导的细胞迁移。这些发现表明，MLK3 信号的破坏通过抑制体外和体内小鼠肠黏膜中的 ERK 和 JNK 信号来损害溃疡愈合。这些结果揭示了 MLK3 信号在体内调节肠道上皮细胞迁移的新作用，并表明 MLK3 可能是调节肠道黏膜愈合的重要靶点。
