Similarities between UDP-Glucose and Adenine Nucleotide Release in Yeast: Involvement of the Secretory Pathway
详细信息 查看全文
- 作者：Charles R. Esther ; ; Henrik G. Dohlman ; Addison D. Ault ; Marié ; n L. Clas ; Eduardo R. Lazarowski ; Richard C. Boucher
- 刊名：Biochemistry
- 出版年：2008
- 出版时间：September 2, 2008
- 年：2008
- 卷：47
- 期：35
- 页码：9269-9278
- 全文大小：288K
- 年卷期：v.47,no.35(September 2, 2008)
- ISSN：1520-4995
文摘
Extracellular UDP-glucose is a natural purinergic receptor agonist, but its mechanisms of cellular release remain unclear. We studied these mechanisms in Saccharomyces cerevisiae, a simple model organism that releases ATP, another purinergic agonist. Similar to ATP, UDP-glucose was released by S. cerevisiae at a rate that was linear over time. However, unlike ATP release, UDP-glucose release was not dependent on glucose stimulation. This discrepancy was resolved by demonstrating the apparent glucose stimulation of ATP release reflected glucose-dependent changes in the intracellular pattern of adenine nucleotides, with AMP release dominating in the absence of glucose. Indeed, total adenine nucleotide release, like UDP-glucose release, did not vary with glucose concentration over the short term. The genetic basis of UDP-glucose release was explored through analysis of deletion mutants, aided by development of a novel bioassay for UDP-glucose based on signaling through heterologously expressed human P2Y14 receptors. Using this assay, an elevated rate of UDP-glucose release was demonstrated in mutants lacking the putative Golgi nucleotide sugar transporter YMD8. An increased rate of UDP-glucose release in ymd8Δ was reduced by deletion of the YEA4 UDP-N-acetylglucosamine or the HUT1 UDP-galactose transporters, and overexpression of YEA4 or HUT1 increased the rate of UDP-glucose release. These findings suggest an exocytotic release mechanism similar to that of ATP, a conclusion supported by decreased rates of ATP, AMP, and UDP-glucose release in response to the secretory inhibitor Brefeldin A. These studies demonstrate the involvement of the secretory pathway in nucleotide and nucleotide sugar efflux in yeast and offer a powerful model system for further investigation.