Novel IκBα Proteolytic pathway in WEHI231 immature B cells
Novel IκBα Proteolytic pathway in WEHI231 immature B cells
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DOI：
10.1128/mcb.18.1.19
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发表时间：
1998-01-01
影响因子：
5.3
通讯作者：
Shumway, SD
中科院分区：
文献类型：
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作者：
Miyamoto, S;Seufzer, BJ;Shumway, SD
转录因子的Rel/NF-κ B家族被属于I κ B家族的抑制蛋白隔离在大多数哺乳动物细胞的细胞质中。通过磷酸化依赖性泛素-蛋白酶体（诱导型）途径降解I κ B被认为允许活性Rel/NF-κ B二聚体的核转运。Rel/NF-κ B（p50-c-Rel二聚体）在鼠B细胞（例如WEHI 231细胞）中是组成性核的。在这些细胞中，p50、c-Rel和I κ B α以高水平合成，但仅I κ B α快速降解。我们已经研究了I κ B α降解的机制及其与组成性p50-c-Rel激活的关系。我们证明，所有I κ B α被发现与c-Rel蛋白在细胞质中的复合物。此外，快速I κ B α蛋白水解独立于诱导途径，但与诱导途径共存，并可被钙螯合剂和一些钙蛋白酶抑制剂抑制。阻止I κ B α降解的条件也抑制核p50-c-Rel活性。此外，核c-Rel的半衰期比细胞质形式的半衰期短得多，强调了其连续核转运以维持组成型p50-c-Rel活性的必要性。我们观察到另一种NF-κ B抑制剂I κ B β也与c-Rel复合，但在WEHI 231细胞中通过蛋白酶体依赖性过程缓慢降解。此外，I κ B β是基础磷酸化的，位于细胞质中。因此，我们认为，钙依赖性I κ B α蛋白水解维持p50-c-Rel异二聚体的核转运，这反过来又激活I κ B α、p50和c-Rel的合成，以维持WEHI 231 B细胞中的这种动态过程。
The Rel/NF-kappa B family of transcription factors is sequestered in the cytoplasm of most mammalian cells by inhibitor proteins belonging to the I kappa B family. Degradation of I kappa B by a phosphorylation-dependent ubiquitin-proteasome (inducible) pathway is believed to allow nuclear transport of active Rel/NF-kappa B dimers. Rel/NF-kappa B (a p50-c-Rel dimer) is constitutively nuclear in murine B cells, such as WEHI231 cells. In these cells, p50, c-Rel, and I kappa B alpha are synthesized at high levels but only I kappa B alpha is rapidly degraded. We have examined the mechanism of I kappa B alpha degradation and its relation to constitutive p50-c-Rel activation. We demonstrate that all I kappa B alpha is found complexed with c-Rel protein in the cytoplasm. Additionally, rapid I kappa B alpha proteolysis is independent of but coexistent with the inducible pathway and can be inhibited by calcium chelators and some calpain inhibitors. Conditions that prevent degradation of I kappa B alpha also inhibit nuclear p50-c-Rel activity. Furthermore, the half-life of nuclear c-Rel is much shorter than that of the cytoplasmic form, underscoring the necessity for its continuous nuclear transport to maintain constitutive p50-c-Rel activity. We observed that I kappa B beta, another NF-kappa B inhibitor, is also complexed with c-Rel but slowly degraded by a proteasome-dependent process in WEHI231 cells. In addition, I kappa B beta is basally phosphorylated and cytoplasmic. We thus suggest that calcium-dependent I kappa B alpha proteolysis maintains nuclear transport of a p50-c-Rel heterodimer which in turn activates the synthesis of I kappa B alpha, p50, and c-Rel to sustain this dynamic process in WEHI231 B cells.