嗜酸乳杆菌胞外蛋白调控MAPK和PI3K-AKT信号途径关键蛋白活化水平

探讨并揭示嗜酸乳杆菌(Lactobacillus acidophilus)CICC6005分泌的相关蛋白质促进肠道健康及分子机制具有重要研究价值。本实验在确定了L.acidophilus CICC6005分泌的胞外蛋白抑制HT-29结肠癌细胞增殖的基础上,进一步探讨67 ku和37 ku的胞外蛋白通过何种途径发挥抑制结肠癌细胞增殖。研究以HT-29细胞作为靶细胞,用丝裂原激活的蛋白激酶(mitogen activated protein kinase,MAPK)和磷脂酰肌醇-3激酶-丝氨酸/苏氨酸蛋白激酶(phosphatidylinositol 3-kinase-protein kinase B,PI3K-AKT)信号通路为考察对象,以Western Blotting为手段,分析两个通路中关键的靶点蛋白p38、c-Jun氨基末端激酶(c-Jun N-terminal kinase,JNK)、胞外信号调节激酶(extracellular signal-regulated kinase,ERK)、磷酸化p38(phosphorylated p38,p-p38)、磷酸化c-Jun氨基末端激酶(phosphorylated c-Jun N-terminal kinase,p-JNK)、磷酸化的细胞外信号调节蛋白激酶(phosphorylated extracellular signal-regulated kinase,p-ERK)、磷酸化蛋白激酶B(phosphorylated AKT,p-AKT)、PI3K的表达水平,以探讨并阐述源于L.acidophilus CICC6005胞外蛋白调控结肠癌细胞增殖状况的分子机制。结果表明,不同质量浓度的67 ku和37 ku胞外蛋白分别作用HT-29细胞一定时间后,两种胞外蛋白均具有下调两个信号通路途径中p-ERK1/2、p-p38、p-AKT、PI3K蛋白的表达,且存在浓度依赖关系;但对p-JNK、ERK1/2、p38、JNK蛋白的表达没有影响。因此,源于L.acidophilus CICC6005分泌的37 ku和67 ku胞外蛋白表现出显著的抑制HT-29细胞增殖的功能,其机制可能与调控MAPK和PI3K-AKT两个信号通路中几个关键的靶点蛋白的活化水平相关。该研究结果提示,食用嗜酸乳杆菌其分泌的胞外蛋白质将达到维护肠道健康的目标。

Extracellular Proteins from Lactobacillus acidophilus Regulate the Activation of Critical Proteins Involved in the MAPK and PI3K-AKT Signaling Pathways

Purpose: To explore the role and molecular mechanism of proteins secreted by L. acidophilus CICC6005 in promoting intestinal health and to reveal that this topic is well worth further investigation. Methods: This experiment determined extracellular proteins secreted by L. acidophilus CICC6005 to inhibit the proliferation of HT-29 cells and further explored the pathway by which the extracellular proteins 67 and 37 ku inhibited tumor proliferation. In the present study, HT-29 cells were used as target cells to evaluate the expression levels of the critical target protein p38, c-Jun N-terminal kinase (JNK), c-Jun N-terminal kinase (ERK), phosphorylated p38 (p-p38), phosphorylated c-Jun N-terminal kinase (p-JNK), phosphorylated extracellular signal-regulated kinase (p-ERK), phosphorylated protein kinase B (p-AKT), phosphatidylinositol-3-kinase (PI3K) in the mitogen activated protein kinase (MAPK) and (phosphatidylinositol 3-kinase-protein kinase B) PI3K-AKT signaling pathways through Western blotting in order to explore the molecular mechanism by which that the extracellular proteins from L. acidophilus CICC6005 regulated the proliferation of colon cancer cells. Results: Exposure of HT-29 cells to different concentrations of 67 and 37 ku extracellular proteins from L. acidophilus CICC6005 could significantly inhibit the expression of p-ERK1/2, p-p38, p-AKT and PI3K in a dosedependent manner for both signaling pathways but not the expression of p-JNK, ERK1/2, p38 and JNK. Conclusion: The extracellular proteins 37 and 67 ku from L. acidophilus CICC6005 could inhibit the proliferation of HT-29 cells, and the mechanism might be related to the activation level of the critical proteins involved in the MAPK and PI3K-AKT pathways. Consumption of extracellular proteins from L. acidophilus could help to maintain intestinal health.