Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America.
PLoS One. 2010 Sep 2;5(9):e12503. doi: 10.1371/journal.pone.0012503.
Cryptococcus neoformans is a human opportunistic fungal pathogen responsible for approximately 1/3 of HIV/AIDS deaths worldwide. This budding yeast expresses a polysaccharide capsule necessary for virulence. Capsule production inhibits phagocytosis by macrophages. Here we describe results that link copper homeostasis to capsule production and the inhibition of phagocytosis. Specifically, using Agrobacterium-mediated insertional mutagenesis, we identified an insertion in the promoter region of the putative copper transporter-encoding gene CTR2 that results in reduced expression of CTR2 and increased phagocytosis by murine RAW264.7 macrophages. The mutant also displayed sensitivity to copper starvation and defects in polysaccharide capsule production and melanization. These defects were all reversed by genetic correction of the promoter insertion by homologous targeting. Several melanization-defective mutants identified previously, those in the RIM20, RIM101, and VPS25 genes, also display sensitivity to copper starvation, reduced capsule production and increased phagocytosis. Together these results indicate a previously undescribed link between copper homeostasis to polysaccharide capsule production and phagocytosis inhibition in Cryptococcus neoformans.
新生隐球菌是一种人类机会致病性真菌病原体，导致全球约 1/3 的艾滋病相关死亡。这种出芽酵母表达一种多糖荚膜，这对于其毒力是必需的。荚膜的产生抑制了巨噬细胞的吞噬作用。在这里，我们描述了将铜稳态与荚膜产生和吞噬作用抑制联系起来的结果。具体来说，我们使用农杆菌介导的插入突变，在假定的铜转运蛋白编码基因 CTR2 的启动子区域发现了一个插入，导致 CTR2 的表达减少，以及对鼠 RAW264.7 巨噬细胞的吞噬作用增加。该突变体还对铜饥饿敏感，并表现出多糖荚膜产生和黑色素形成缺陷。通过同源靶向对启动子插入进行基因校正，这些缺陷都得到了逆转。以前鉴定的几个黑色素形成缺陷突变体，如 RIM20、RIM101 和 VPS25 基因，也表现出对铜饥饿敏感、荚膜产生减少和吞噬作用增加。这些结果表明，在新生隐球菌中，铜稳态与多糖荚膜产生和吞噬作用抑制之间存在以前未描述的联系。
