Analysis of knockout mouse of a brain-specific H^+ transporter ASPT.

我们描述了c-Jun nh_2末端激酶（JNK）在细胞外H^+增加后调控基因转录的作用。当细胞在低pH培养基中孵育时，可以清楚地观察到细胞中JNK磷酸化和c-Jun表达的促进，并以细胞外pH和时间依赖性的方式进行。与JNK相比，p38和细胞外信号调节激酶1/2 （ERK1/2）的激活非常弱。细胞外H^+的增加导致磷酸化JNK的核易位增强，从而增强c-Jun的转录活性。尼莫地平是电压门控Ca^<2+>离子通道的阻滞剂，以剂量依赖性的方式阻止JNK的磷酸化和c-Jun的表达。这些结果提示了一种新的H^+诱导c-Jun表达的细胞内信号通路：细胞外H^+的增加通过电压门控的Ca^<2+>通道部分通过细胞外Ca^<2+>内流诱导JNK磷酸化和c-Jun表达。本文描述了碱性区亮氨酸拉链（bZIP）转录因子Maf和FosB在细胞外酸化过程中的基因表达、蛋白相互作用和DNA结合活性。当细胞在低pH培养基中孵育时，Maf小蛋白（MafG、MafK和MafF）和FosB的表达明显增加，并以细胞外pH依赖的方式表达，并在刺激后1-2 h后短暂表达，达到峰值。免疫荧光和蛋白结合研究表明，MafG在细胞核内与FosB部分共定位，在胞外pH为7.40时，MafG可与FosB形成异源二聚体。此外，我们发现MafG-FosB复合物能够结合AP-1一致序列TGACTCA。为了研究细胞外酸化对MafG和FosB二聚体和DNA结合活性的影响，我们将培养细胞的胞外pH从7.40降低到6.80。胞外pH降低导致MafG与FosB二聚化增强，从而增强了异源二聚体与AP-1一致序列的DNA结合活性。此外，细胞外酸化诱导AP-1调控的基因之一基质金属蛋白酶-1的mRNA表达。这些结果表明，MafG-FosB复合物参与了细胞外酸化反应的转录调控。少

We describe the role of c-Jun NH_2-terminal kinase(JNK) in regulation of gene transcription after an increase in extracellular H^+. When cells were incubated in low pH medium, the promotion of JNK phosphorylation and c-Jun expression was clearly observed in cells in an extracellular pH-and time-dependent manner. Activation of p38 and extracellular signal-regulated kinase 1/2 (ERK1/2) was extremely weak compared with that of JNK. An increase in extracellular H^+ led to enhanced nuclear translocation of phosphorylated JNK leading to augmentation of the transcriptional activity of c-Jun. Nimodipine, a blocker of voltage-gated Ca^<2+> ion channels, prevented the phosphorylation of JNK and expression of c-Jun in a dose-dependent manner. These results suggesta novel intracellular signalling pathway for H^+-induced c-Jun expression : an increase of extracellular H^+ induces JNK phosphorylation and c-Jun expression via partly extracellular Ca^<2+> influx through voltage-gated Ca^<2+> channels. … More We describe properties of gene expression, protein interaction and DNA binding activity of basic region leucine zipper(bZIP) transcription factor Maf and FosB during extracellular acidification. When cells were incubated with low pH medium, the expressions of small Maf proteins (MafG,MafK and MafF) and FosB were clearly increased in an extracellular pH-dependent manner and expressed transiently with a peak after 1-2 h after stimulation. Immunofluorescence and protein binding studies indicated that MafG was partially co-localized with FosB in the nucleus and MafG can form heterodimers with FosB at extracellular pH 7.40. Moreover, we found that MafG-FosB complexes are able to bind to AP-1 consensus sequence, TGACTCA. To investigate whether extracellular acidification influences to dimerization and DNA binding activity of MafG and FosB, extracellular pH of cultured cells was decreased from 7.40 to 6.80. The decrease in extracellular pH led to enhanced dimerization of MafG with FosB leading to augmentation of the DNA binding activity of the heterodimer to AP-1 consensus sequence. Moreover, extracellular acidification induces mRNA expression of matrix metalloproteinase-1, one of genes that are regulated by AP-1. These results suggest that MafG-FosB complexes are involved in transcriptional regulation in response to extracellular acidification. Less