Department of Molecular Genetics, The Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, 1 Efron St. Bat-Galim, Haifa 31096, Israel.
Biochem J. 2011 Jun 15;436(3):661-9. doi: 10.1042/BJ20101031.
JDP2 (c-Jun dimerization protein 2) is a member of the basic leucine zipper family of transcription factors that is ubiquitously expressed in all examined cell types. JDP2 is phosphorylated on Thr148 by JNK (c-Jun N-terminal kinase) and p38 kinase, although the functional role of its phosphorylation is unknown. In the present paper we show that the JDP2 protein level is dramatically reduced in response to serum stimulation, anisomycin treatment, ultraviolet light irradiation and cycloheximide treatment, all of which activate the JNK pathway. In addition, endogenous and overexpressed JDP2 are phosphorylated in response to these stimuli. Replacement of Thr148 with an alanine residue stabilizes ectopically expressed JDP2 in the presence of the stimuli; conversely, substitution with glutamic acid destabilizes it. Serum-induced phosphorylation and degradation of JDP2 are specific to JNK activation since a JNK inhibitor (SP600125) abolishes these effects, whereas p38 and MEK inhibitors (SB203580 and UO126) have no effect. In the presence of cycloheximide, JDP2 is rapidly phosphorylated and degraded due to the combined effects of protein synthesis inhibition and activation of JNK. Pre-treatment of cells with SP600125 prior to cycloheximide treatment significantly prolongs the half-life of JDP2 that is found mainly in the unphosphorylated form. Lastly, the proteasome inhibitor (MG132) rescues JDP2 degradation following cycloheximide treatment and increases the expression of the JDP2 phospho-mimetic T148E mutant. Collectively, these results suggest that phosphorylation of JDP2 on thr148 by JNK targets it to the proteasome for degradation.
JDP2（c-Jun 二聚化蛋白 2）是一种普遍存在于所有被检测细胞类型中的碱性亮氨酸拉链家族转录因子成员。JDP2 可被 JNK（c-Jun N 端激酶）和 p38 激酶磷酸化在 Thr148 上，尽管其磷酸化的功能作用尚不清楚。在本文中，我们表明 JDP2 蛋白水平在血清刺激、anisomycin 处理、紫外线照射和环己酰亚胺处理后显著降低，所有这些都激活了 JNK 途径。此外，内源性和过表达的 JDP2 在这些刺激下发生磷酸化。用丙氨酸取代 Thr148 可稳定在刺激存在下异位表达的 JDP2；相反，用谷氨酸取代会使其不稳定。血清诱导的 JDP2 磷酸化和降解是 JNK 激活特异性的，因为 JNK 抑制剂（SP600125）可消除这些作用，而 p38 和 MEK 抑制剂（SB203580 和 UO126）则没有作用。在环己酰亚胺存在下，由于蛋白合成抑制和 JNK 激活的综合作用，JDP2 迅速被磷酸化和降解。在环己酰亚胺处理前用 SP600125 预处理细胞可显著延长 JDP2 的半衰期，其主要以未磷酸化形式存在。最后，蛋白酶体抑制剂（MG132）可挽救环己酰亚胺处理后 JDP2 的降解，并增加 JDP2 磷酸模拟突变体 T148E 的表达。总的来说，这些结果表明 JNK 在 Thr148 上对 JDP2 的磷酸化将其靶向蛋白酶体进行降解。
