Snyder Nathan A, Stefan Christopher P, Soroudi Camille T, Kim Adam, Evangelista Carlos, Cunningham Kyle W
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218
G3 (Bethesda). 2017 Dec 4;7(12):3913-3924. doi: 10.1534/g3.117.300339.
Glycosylation reactions in the Golgi complex and the endoplasmic reticulum utilize nucleotide sugars as donors and produce inorganic phosphate (Pi) and acid (H) as byproducts. Here we show that homologs of mammalian XPR1 and TMEM165 (termed Erd1 and Gdt1) recycle luminal Pi and exchange luminal H for cytoplasmic Ca, respectively, thereby promoting growth of yeast cells in low Pi and low Ca environments. As expected for reversible H/Ca exchangers, Gdt1 also promoted growth in high Ca environments when the Golgi-localized V-ATPase was operational but had the opposite effect when the V-ATPase was eliminated. Gdt1 activities were negatively regulated by calcineurin signaling and by Erd1, which recycled the Pi byproduct of glycosylation reactions and prevented the loss of this nutrient to the environment via exocytosis. Thus, Erd1 transports Pi in the opposite direction from XPR1 and other EXS family proteins and facilitates byproduct removal from the Golgi complex together with Gdt1.
高尔基体复合体和内质网中的糖基化反应利用核苷酸糖作为供体,并产生无机磷酸(Pi)和酸(H)作为副产物。在这里,我们表明哺乳动物XPR1和TMEM165的同源物(分别称为Erd1和Gdt1)分别回收腔内的Pi并将腔内的H与细胞质中的Ca交换,从而促进酵母细胞在低Pi和低Ca环境中的生长。正如对可逆H/Ca交换器的预期,当高尔基体定位的V-ATP酶起作用时,Gdt1也促进了在高Ca环境中的生长,但当V-ATP酶被消除时则产生相反的效果。Gdt1的活性受到钙调磷酸酶信号传导和Erd1的负调控,Erd1回收糖基化反应的Pi副产物,并通过胞吐作用防止这种营养物质流失到环境中。因此,Erd1与XPR1和其他EXS家族蛋白在相反方向运输Pi,并与Gdt1一起促进从高尔基体复合体中去除副产物。