Regulated protein degradation controls PKA function and cell-type differentiation in Dictyostelium
Regulated protein degradation controls PKA function and cell-type differentiation in Dictyostelium
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DOI：
10.1101/gad.871101
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发表时间：
2001-06-01
影响因子：
10.5
通讯作者：
Firtel, RA
中科院分区：
文献类型：
--
作者：
Mohanty, S;Lee, S;Firtel, RA
Cullins 作为支架，与含有 F-box/WD40 重复序列的蛋白质一起介导蛋白质的泛素化，以靶向它们被蛋白酶体降解。我们已经确定了盘基网柄菌发育过程中多个阶段所需的 cullin CulA。 culA 无效细胞在诱导细胞类型特异性基因表达方面存在缺陷，并在聚集过程中表现出缺陷，包括趋化性降低。 PKA 是盘基网柄菌发育的重要调节因子。细胞内 cAMP 和 PKA 活性的水平由 cAMP 合成速率及其由 cAMP 特异性磷酸二酯酶 RegA 降解的速率控制。我们发现，PKA 催化亚基 (PKAcat) 的过表达可以挽救许多 culA 无效缺陷以及缺乏 FbxA/ChtA（一种先前描述的包含 F-box/WD40 重复序列的蛋白质）的细胞的缺陷，表明 CulA 和 PbxA 蛋白参与调节 PKA 功能。尽管 RegA 蛋白水平随着野生型菌株中多细胞生物体的形成而下降，但它们在 culA null 和 fbxA null 细胞中仍然保持较高水平。尽管 PKA 可以抑制 culA 和 fbxA 无效发育表型，但它不能抑制改变的 RegA 降解，表明 PKA 位于 RegA、CulA 和 FbxA 的下游。最后，我们发现 CulA、FbxA 和 RegA 在体内存在复合物，并且该复合物的形成依赖于 MAP 激酶 ERK2，这也是 PKA 功能所必需的。我们提出，CulA 和 FbxA 通过需要 ERK2 功能的途径靶向 RegA 降解来调节多细胞发育，从而导致 cAMP 和 PKA 活性增加。
Cullins function as scaffolds that, along with F-box/WD40-repeat-containing proteins, mediate the ubiquitination of proteins to target them for degradation by the proteasome. We have identified a cullin CulA that is required at several stages during Dictyostelium development. culA null cells are defective in inducing cell-type-specific gene expression and exhibit defects during aggregation, including reduced chemotaxis. PKA is an important regulator of Dictyostelium development. The levels of intracellular cAMP and PKA activity are controlled by the rate of synthesis of cAMP and its degradation by the cAMP-specific phosphodiesterase RegA. We show that overexpression of the PKA catalytic subunit (PKAcat) rescues many of the culA null defects and those of cells lacking FbxA/ChtA, a previously described F-box/WD40-repeat-containing protein, suggesting CulA and PbxA proteins are involved in regulating PKA function. Whereas RegA protein levels drop as the multicellular organism forms in the wild-type strain, they remain high in culA null and fbxA null cells. Although PKA can suppress the culA and fbxA null developmental phenotypes, it does not suppress the altered RegA degradation, suggesting that PKA lies downstream of RegA, CulA, and FbxA. Finally, we show that CulA, FbxA, and RegA are found in a complex in vivo, and formation of this complex is dependent on the MAP kinase ERK2, which is also required for PKA function. We propose that CulA and FbxA regulate multicellular development by targeting RegA for degradation via a pathway that requires ERK2 function, leading to an increase in cAMP and PKA activity.