Functional analysis of the scaffold protein JSAP1 in the developing mouse cerebellum

哺乳动物MAPK级联的支架蛋白被认为通过将信号组件组织成功能模块而在这些通路的时空调节中发挥作用。我们研究了c-Jun氨基末端激酶(JNK)/应激激活蛋白激酶相关蛋白1(JSAP1)的功能，这是一种参与墨水MAPK级联反应的支架蛋白。我们的研究结果总结如下：1)我们首次建立了携带LOX-P侧翼(狐狸)JSAP 1基因的基因工程小鼠，并将狐狸JSAP 1缺失突变体特异性地引入神经谱系。JSAP 1条件性基因敲除小鼠表现出与JSAP1缺失小鼠基本相同的表型，这表明JSAP 1缺陷小鼠的新生儿死亡是由神经系统(Neurosci)缺陷引起的。2)我们发现JSAP1支架在神经生长因子诱导的信号通路中特定地调节PC12h细胞的细胞间相互作用，并通过调节N-cad…来实现更多的Herin(Biochem.生物群落。3)我们还研究了JSAP1和JNK在小鼠脑内的表达。我们通过原位杂交和免疫组织化学分析得到的结果有力地表明JSAP1-JNK信号在发育和成年小鼠脑中发挥着重要作用(J.Neurothe.，2006)。4)在小脑发育过程中，颗粒细胞前体(GCP)大量克隆性扩张发生在外部颗粒层(EGL)的外部。我们提供的证据表明，JSAP1和激活的JNK在发育中的小脑中优先表达于有丝分裂后的内EGL前体细胞。此外，JSAP-1缺乏导致小鼠胚胎中GCP的数量增加。此外，在培养的GCP中过表达JSAP1导致NeuN阳性细胞数量增加，同时JNK被激活。总之，这些数据有力地表明，JSAP1通过调节小脑发育中的JNK活性来促进GCP的细胞周期退出和分化(准备中)。较少

Scaffold proteins of the mammalian MAP kinase (MAPK) cascades are thought to function in the spatio-temporal regulation of these pathways by organizing the signaling components into functional modules. We have examined the functions of c-Jun NH,-terminal kinase (JNK)/stress-activated protein kinase-associated protein 1 (JSAP1), a scaffold protein that are involved in INK MAPK cascades. Our findings are summarized as follows:1) We first generated genetically engineered mice carrying a lox-P-flanked (foxed) Jsap 1 gene, and introduced the foxed Jsap 1 deletion mutant specifically into the neural lineage. The Jsap 1 conditional knockout mice showed essentially the same phenotypes as the JSAP1-null mice, suggesting that the neonatal death of Jsap 1-deficient mice is caused by defects in the nervous system (Neurosci. Lett., 2007).2) We showed that JSAP1 scaffold regulates cell-cell interactions in PC12h cells specifically in the NGF-induced signaling pathway, and does so by modulating N-cad … More herin (Biochem. Biophys. Res. Commun., 2007) through the knock down experiments in PC12h cells.3) We also studied JSAP1 and JNK expression in mouse brains. Our results obtained by in situ hybridization and immunohistochemical analyses strongly suggested that JSAP1-JNK signaling plays important roles in developing and adult mouse brains (J. Neurothem., 2006).4) During the development of the cerebellum, massive clonal expansion of granule cell precursors (GCPs) occurs in the outer part of the external granular layer (EGL). We have provided evidence that JSAP1 and active JNK were expressed preferentially in the post-mitotic inner EGL progenitors in the developing cerebellum. Moreover, Jsap 1 deficiency resulted in increasing numbers of proliferating GCPs in mouse embryos. Besides, overexpression of JSAP1 in cultured GCPs led to increased numbers of NeuN-positive cells together with the activation of JNK. Together, these data strongly indicated that JSAP1 promotes the cell-cycle exit and differentiation of GCPs by modulating JNK activity in cerebellar development (in preparation). Less