Pde1 phosphodiesterase modulates cyclic AMP levels through a protein kinase A-mediated negative feedback loop in Cryptococcus neoformans
Pde1 phosphodiesterase modulates cyclic AMP levels through a protein kinase A-mediated negative feedback loop in Cryptococcus neoformans
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DOI：
10.1128/ec.4.12.1971-1981.2005
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发表时间：
2005-12-01
期刊：
影响因子：
--
通讯作者：
Heitman, J
中科院分区：
文献类型：
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作者：
Hicks, JK;Bahn, YS;Heitman, J
人类致病性真菌新型隐球菌的毒力受环AMP （cAMP）依赖性蛋白激酶a （PKA）信号级联调节，该信号级联促进交配和黑色素和荚膜的产生。在这项研究中，编码酿酒酵母菌低亲和力和高亲和力磷酸二酯酶PDE1和PDE2的同源基因在血清型A株新生酵母中被删除。由此产生的突变体相对于野生型表现出适度升高的黑色素和荚膜生产水平。上位性实验表明，Pde1在Got亚基Gpa1的下游起作用，Gpa1在响应细胞外信号时启动camp依赖性信号传导。先前的研究表明，PKA催化亚基Pka1通过负反馈回路控制cAMP水平。在这里，我们发现pde1 δ pka1 δ突变株的cAMP水平比pka1 δ单突变株显著增加（约15倍），PKA磷酸化位点的位点定向突变降低了pde1的功能。这些数据提供了证据，表明cAMP水平的波动是由pka1依赖的Pde1调控和另一个靶标调节的，该靶标包括一个强大的负反馈回路，以严格约束细胞内cAMP水平。
The virulence of the human pathogenic fungus Cryptococcus neoformans is regulated by a cyclic AMP (cAMP)-dependent protein kinase A (PKA) signaling cascade that promotes mating and the production of melanin and capsule. In this study, genes encoding homologs of the Saccharomyces cerevisiae low- and high-affinity phosphodiesterases, PDE1 and PDE2, respectively, were deleted in serotype A strains of C. neoformans. The resulting mutants exhibited moderately elevated levels of melanin and capsule production relative to the wild type. Epistasis experiments indicate that Pde1 functions downstream of the Got subunit Gpa1, which initiates cAMP-dependent signaling in response to an extracellular signal. Previous work has shown that the PKA catalytic subunit Pka1 governs cAMP levels via a negative feedback loop. Here we show that a pde1 Delta pka1 Delta mutant strain exhibits cAMP levels that are dramatically increased (similar to 15-fold) relative to those in a pka1 Delta single mutant strain and that a site-directed mutation in a consensus PKA phosphorylation site reduces Pde1 function. These data provide evidence that fluctuations in cAMP levels are modulated by both Pka1-dependent regulation of Pde1 and another target that comprise a robust negative feedback loop to tightly constrain intracellular cAMP levels.