Marek Magdalena, Silvestro Daniele, Fredslund Maria D, Andersen Tonni G, Pomorski Thomas G
Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
FEMS Yeast Res. 2014 Dec;14(8):1223-33. doi: 10.1111/1567-1364.12219. Epub 2014 Nov 17.
Sterol uptake in fungi is a multistep process that involves interaction between external sterols and the cell wall, incorporation of sterol molecules into the plasma membrane, and subsequent integration into intracellular membranes for turnover. ATP-binding cassette (ABC) transporters have been implicated in sterol uptake, but key features of their activity remain to be elucidated. Here, we apply fluorescent cholesterol (NBD-cholesterol) to monitor sterol uptake under anaerobic and aerobic conditions in two fungal species, Candida glabrata (Cg) and Saccharomyces cerevisiae (Sc). We found that in both fungal species, ABC transporter-dependent uptake of cholesterol under anaerobic conditions and in mutants lacking HEM1 gene is promoted in the presence of the serum protein albumin that is able to bind the sterol molecule. Furthermore, the C. glabrata ABC transporter CgAus1p expressed in S. cerevisiae requires the presence of serum or albumin for efficient cholesterol uptake. These results suggest that albumin can serve as sterol donor in ABC transporter-dependent sterol uptake, a process potentially important for growth of C. glabrata inside infected humans.
真菌中的甾醇摄取是一个多步骤过程，涉及外部甾醇与细胞壁之间的相互作用、甾醇分子掺入质膜以及随后整合到细胞内膜中进行周转。ATP结合盒（ABC）转运蛋白与甾醇摄取有关，但其活性的关键特征仍有待阐明。在这里，我们应用荧光胆固醇（NBD-胆固醇）来监测两种真菌，光滑念珠菌（Cg）和酿酒酵母（Sc）在厌氧和好氧条件下的甾醇摄取。我们发现，在这两种真菌中，在能够结合甾醇分子的血清蛋白白蛋白存在的情况下，厌氧条件下以及缺乏HEM1基因的突变体中，ABC转运蛋白依赖性胆固醇摄取会增加。此外，在酿酒酵母中表达的光滑念珠菌ABC转运蛋白CgAus1p需要血清或白蛋白的存在才能有效摄取胆固醇。这些结果表明，白蛋白可以作为ABC转运蛋白依赖性甾醇摄取中的甾醇供体，这一过程可能对感染人类体内的光滑念珠菌生长具有重要意义。
