Chen Daliang, Janganan Thamarai K, Chen Gongyou, Marques Everaldo R, Kress Marcia R, Goldman Gustavo H, Walmsley Adrian R, Borges-Walmsley M Inês
Centre for Infectious Diseases, Wolfson Research Institute, School of Biological and Biomedical Sciences, University of Durham - Queen's Campus, Stockton-on-Tees TS17 6BH, UK.
Mol Microbiol. 2007 Aug;65(3):761-79. doi: 10.1111/j.1365-2958.2007.05824.x.
Paracoccidioides brasiliensis is a human pathogenic fungus that switches from a saprobic mycelium to a pathogenic yeast. Consistent with the morphological transition being regulated by the cAMP-signalling pathway, there is an increase in cellular cAMP levels both transiently at the onset (< 24 h) and progressively in the later stages (> 120 h) of the transition to the yeast form, and this transition can be modulated by exogenous cAMP. We have cloned the cyr1 gene encoding adenylate cyclase (AC) and established that its transcript levels correlate with cAMP levels. In addition, we have cloned the genes encoding three Galpha (Gpa1-3), Gbeta (Gpb1) and Ggamma (Gpg1) G proteins. Gpa1 and Gpb1 interact with one another and the N-terminus of AC, but neither Gpa2 nor Gpa3 interacted with Gpb1 or AC. The interaction of Gpa1 with Gpb1 was blocked by GTP, but its interaction with AC was independent of bound nucleotide. The transcript levels for gpa1, gpb1 and gpg1 were similar in mycelium, but there was a transient excess of gpb1 during the transition, and an excess of gpa1 in yeast. We have interpreted our findings in terms of a novel signalling mechanism in which the activity of AC is differentially modulated by Gpa1 and Gpb1 to maintain the signal over the 10 days needed for the morphological switch.
巴西副球孢子菌是一种人类致病真菌，可从腐生菌丝体转变为致病酵母。与形态转变受cAMP信号通路调控一致，在向酵母形态转变的起始阶段（<24小时）细胞内cAMP水平短暂升高，在后期阶段（>120小时）则逐渐升高，并且这种转变可被外源性cAMP调节。我们克隆了编码腺苷酸环化酶（AC）的cyr1基因，并确定其转录水平与cAMP水平相关。此外，我们还克隆了编码三种Gα（Gpa1 - 3）、Gβ（Gpb1）和Gγ（Gpg1）G蛋白的基因。Gpa1和Gpb1相互作用，且与AC的N端相互作用，但Gpa2和Gpa3均不与Gpb1或AC相互作用。Gpa1与Gpb1的相互作用被GTP阻断，但其与AC的相互作用不依赖于结合的核苷酸。gpa1、gpb1和gpg1的转录水平在菌丝体中相似，但在转变过程中Gpb1短暂过量，在酵母中Gpa1过量。我们根据一种新的信号传导机制来解释我们的发现，即AC的活性受到Gpa1和Gpb1的差异调节，以在形态转变所需的10天内维持信号。
