Ablation of MEKK4 kinase activity causes neurulation and skeletal patterning defects in the mouse embryo
Ablation of MEKK4 kinase activity causes neurulation and skeletal patterning defects in the mouse embryo
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DOI：
10.1128/mcb.25.20.8948-8959.2005
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发表时间：
2005-10-01
影响因子：
5.3
通讯作者：
Johnson, GL
中科院分区：
文献类型：
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作者：
Abell, AN;Rivera-Perez, JA;Johnson, GL
骨骼疾病和神经管闭合缺陷代表临床上显著的人类畸形。调节正常骨骼模式和神经形成的信号网络在很大程度上是未知的。MEK激酶4（MEKK 4）活性位点赖氨酸的靶向突变产生激酶失活的MEKK 4蛋白（MEKK 4（K1361 R））。这种突变的纯合子胚胎在出生时由于骨骼畸形和神经管缺陷而死亡。外脑MEKK 4（K1361 R）胚胎的后脑显示出神经上皮细胞凋亡的显著增加和由MEKK 4在p38通路中调节的MKK 3和-6，丝裂原活化蛋白激酶（MKK）的磷酸化的显著丧失。MAPK激活的蛋白激酶2（p38底物）的磷酸化也受到抑制，表明MEKK 4（K1361 R）胚胎中p38活性丧失。相反，MEK 1/2-细胞外信号调节激酶1（ERK 1）/ERK 2和MKK 4-Jun N-末端蛋白激酶途径不受影响。p38通路已经显示出调节小的热休克蛋白HSP 27的磷酸化和表达。与野生型相比，MEKK 4（K1361 R）成纤维细胞显示出p38和HSP 27的磷酸化显著减少，并具有相应的热休克诱导的肌动蛋白细胞骨架的不稳定性。总之，这些数据证明了MEKK 4对p38的调节以及p38下游的底物控制细胞内稳态。这些发现首次证明MEKK 4调节的p38活性对神经形成至关重要。
Skeletal disorders and neural tube closure defects represent clinically significant human malformations. The signaling networks regulating normal skeletal patterning and neurulation are largely unknown. Targeted mutation of the active site lysine of MEK kinase 4 (MEKK4) produces a kinase-inactive MEKK4 protein (MEKK4(K1361R)). Embryos homozygous for this mutation die at birth as a result of skeletal malformations and neural tube defects. Hindbrains of exencephalic MEKK4(K1361R) embryos show a striking increase in neuroepithelial cell apoptosis and a dramatic loss of phosphorylation of MKK3 and -6, mitogen-activated protein kinase kinases (MKKs) regulated by MEKK4 in the p38 pathway. Phosphorylation of MAPK-activated protein kinase 2, a p38 substrate, is also inhibited, demonstrating a loss of p38 activity in MEKK4(K1361R) embryos. in contrast, the MEK1/2-extracellular signal-regulated kinase 1 (ERK1)/ERK2 and MKK4-Jun N-terminal protein kinase pathways were unaffected. The p38 pathway has been shown to regulate the phosphorylation and expression of the small heat shock protein HSP27. Compared to the wild type, MEKK4(K1361R) fibroblasts showed significantly reduced phosphoryllation of p38 and HSP27, with a corresponding heat shock-induced instability of the actin cytoskeleton. Together, these data demonstrate MEKK4 regulation of p38 and that substrates downstream of p38 control cellular homeostasis. The findings are the first demonstration that MEKK4-regulated p38 activity is critical for neurulation.