Amino acids(AA),including methionine(Met)and leucine(Leu),stimulate milk synthesis in bovine mammary epithelial cells(BMEC)via activation of protein kinase mechanistic target of rapamycin(mTOR).In this study,we furthe...Amino acids(AA),including methionine(Met)and leucine(Leu),stimulate milk synthesis in bovine mammary epithelial cells(BMEC)via activation of protein kinase mechanistic target of rapamycin(mTOR).In this study,we further explored the potential role of myotonic dystrophy-related CDC42-binding kinase alpha(MRCKα),previously identified as a critical mediator of prolactin-stimulated milk synthesis in BMEC.Administering different doses(0,0.2,0.4,0.6,0.8 mM)of Met or Leu to a primary BMEC culture showed that 0.6 mM was the optimal dose for stimulatingβ-casein production with both AA.At this dose,Met and Leu independently evoked higher(P<0.05)protein levels ofβ-casein,MRCKαand sterol regulatory element-binding protein 1(SREBP1),and increased(P<0.05)phosphorylation of mTOR(Ser2448)and phosphatidylinositol 3-kinase(PI3K)(Tyr317)after 24 h.The stimulatory effects of both AA on relative protein level ofβ-casein,phosphorylation of mTOR,and phosphorylation of protein kinase B(PKB)(Thr308),were blocked by silencing MRCKαexpression(P<0.05).Whereas,that on the phosphorylation of PI3K remained intact(P=0.385).Inhibiting PI3K with LY294002 blocked Met-and Leu-induced protein expression of MRCKαandβ-casein and phosphorylation of mTOR(P<0.05).Overexpression of MRCKαincreased protein levels ofβ-casein and phosphorylation of mTOR,which was prevented by PKB inhibitor MK2206(P<0.05).Our results indicate that MRCKαis a key mediator of the Met-and Leu-induced signaling cascade,acting downstream of PI3K and upstream of PKB to regulateβ-casein synthesis in BMEC.展开更多
细胞分裂周期蛋白42(cell division control protein 42 homolog,Cdc42)是一种Rho蛋白家族的小GTPase,可与GTP或GDP结合并在其活性型或失活型之间的转换充当"分子开关",参与了细胞黏附、迁移与极化的过程。纤维化是引起器官...细胞分裂周期蛋白42(cell division control protein 42 homolog,Cdc42)是一种Rho蛋白家族的小GTPase,可与GTP或GDP结合并在其活性型或失活型之间的转换充当"分子开关",参与了细胞黏附、迁移与极化的过程。纤维化是引起器官功能丧失的重要原因之一,有许多不同的机制可以导致纤维化。以往的研究表明,Cdc42与癌症、心血管疾病、神经退行性病变等有密切的联系,却未提及Cdc42与纤维化之间存在的直接联系。该文总结最新的研究成果,讨论了Cdc42与肝、肾、肺以及心血管纤维化的关系。除此之外,该文也阐述了Cdc42通过细胞黏附迁移、上皮–间质转化等途径导致纤维化的具体机制,以及Cdc42介导的信号通路在纤维化过程中发挥的作用,同时还致力于研究各类关键因子之间的联系及与Rho蛋白质家族的"交谈(crosstalk)",更进一步完善了纤维化发生机制,并提出针对Cdc42的靶向治疗方式,以拓宽纤维化的治疗方案。展开更多
基金supported by the Natural Science Foundation of China(U23A20225)the Key Research and Development Program of the Ningxia Hui Autonomous Region(2023BCF01035)+1 种基金the Agriculture Science and Technology Innovation Program(ASTIPIAS-17)International Atomic Energy Agency Technical Co-Operation and Assistance Programme(No.CPR5029).
文摘Amino acids(AA),including methionine(Met)and leucine(Leu),stimulate milk synthesis in bovine mammary epithelial cells(BMEC)via activation of protein kinase mechanistic target of rapamycin(mTOR).In this study,we further explored the potential role of myotonic dystrophy-related CDC42-binding kinase alpha(MRCKα),previously identified as a critical mediator of prolactin-stimulated milk synthesis in BMEC.Administering different doses(0,0.2,0.4,0.6,0.8 mM)of Met or Leu to a primary BMEC culture showed that 0.6 mM was the optimal dose for stimulatingβ-casein production with both AA.At this dose,Met and Leu independently evoked higher(P<0.05)protein levels ofβ-casein,MRCKαand sterol regulatory element-binding protein 1(SREBP1),and increased(P<0.05)phosphorylation of mTOR(Ser2448)and phosphatidylinositol 3-kinase(PI3K)(Tyr317)after 24 h.The stimulatory effects of both AA on relative protein level ofβ-casein,phosphorylation of mTOR,and phosphorylation of protein kinase B(PKB)(Thr308),were blocked by silencing MRCKαexpression(P<0.05).Whereas,that on the phosphorylation of PI3K remained intact(P=0.385).Inhibiting PI3K with LY294002 blocked Met-and Leu-induced protein expression of MRCKαandβ-casein and phosphorylation of mTOR(P<0.05).Overexpression of MRCKαincreased protein levels ofβ-casein and phosphorylation of mTOR,which was prevented by PKB inhibitor MK2206(P<0.05).Our results indicate that MRCKαis a key mediator of the Met-and Leu-induced signaling cascade,acting downstream of PI3K and upstream of PKB to regulateβ-casein synthesis in BMEC.
文摘细胞分裂周期蛋白42(cell division control protein 42 homolog,Cdc42)是一种Rho蛋白家族的小GTPase,可与GTP或GDP结合并在其活性型或失活型之间的转换充当"分子开关",参与了细胞黏附、迁移与极化的过程。纤维化是引起器官功能丧失的重要原因之一,有许多不同的机制可以导致纤维化。以往的研究表明,Cdc42与癌症、心血管疾病、神经退行性病变等有密切的联系,却未提及Cdc42与纤维化之间存在的直接联系。该文总结最新的研究成果,讨论了Cdc42与肝、肾、肺以及心血管纤维化的关系。除此之外,该文也阐述了Cdc42通过细胞黏附迁移、上皮–间质转化等途径导致纤维化的具体机制,以及Cdc42介导的信号通路在纤维化过程中发挥的作用,同时还致力于研究各类关键因子之间的联系及与Rho蛋白质家族的"交谈(crosstalk)",更进一步完善了纤维化发生机制,并提出针对Cdc42的靶向治疗方式,以拓宽纤维化的治疗方案。
