Extracellular acidification enhances DNA binding activity of MafG‐FosB heterodimer
Extracellular acidification enhances DNA binding activity of MafG‐FosB heterodimer
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DOI：
10.1002/jcp.20369
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发表时间：
2005-10
影响因子：
5.6
通讯作者：
N. Shimokawa;I. Kumaki;Chun-Hong Qiu;Y. Ohmiya;K. Takayama;N. Koibuchi
中科院分区：
文献类型：
--
作者：
N. Shimokawa;I. Kumaki;Chun-Hong Qiu;Y. Ohmiya;K. Takayama;N. Koibuchi
细胞对细胞外 pH 值的变化非常敏感，并通过检测细胞外液中的 H+/HCO 3− 水平来做出反应。然而，人们对酸中毒引起的分子细节知之甚少，例如细胞内途径和基因表达。在这里，我们描述了细胞外酸化过程中碱性区亮氨酸拉链 (bZIP) 转录因子 Maf 和 FosB 的基因表达、蛋白质相互作用和 DNA 结合活性的特性。当细胞在低pH培养基中孵育时，小Maf蛋白（MafG、MafK和MafF）和FosB的表达以细胞外pH依赖的方式明显增加，并在刺激后1-2小时后瞬时表达达到峰值。免疫荧光和蛋白质结合研究表明，MafG 在细胞核中与 FosB 部分共定位，并且在细胞外 pH 7.40 下，MafG 可以与 FosB 形成异二聚体。此外，我们发现 MafG-FosB 复合物能够与 AP-1 共有序列 TGACTCA 结合。为了研究细胞外酸化是否影响 MafG 和 FosB 的二聚化和 DNA 结合活性，将培养细胞的细胞外 pH 从 7.40 降低至 6.80。细胞外 pH 值的降低导致 MafG 与 FosB 的二聚化增强，从而增强异二聚体与 AP-1 共有序列的 DNA 结合活性。此外，细胞外酸化会诱导基质金属蛋白酶-1（受 AP-1 调节的基因之一）的 mRNA 表达。这些结果表明 MafG-FosB 复合物参与响应细胞外酸化的转录调节。 © 2005 Wiley-Liss, Inc.
Cells are quite sensitive to a change of the extracellular pH and respond to it through detection of the H+/HCO 3− level in extracellular fluid. However, little is known about molecular details induced by acidosis, such as intracellular pathways and gene expression. Here 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 the genes that are regulated by AP‐1. These results suggest that MafG–FosB complexes are involved in transcriptional regulation in response to extracellular acidification. © 2005 Wiley‐Liss, Inc.