Crosstalk between protein N-glycosylation and lipid metabolism in Saccharomyces cerevisiae

Antonisamy William James,Chidambaram Ravi,Malathi Srinivasan,Vasanthi Nachiappan

doi:10.1038/s41598-019-51054-7

Abstract

The endoplasmic reticulum (ER) is a multi functional organelle and plays a crucial role in protein folding and lipid biosynthesis. The SEC59 gene encodes dolichol kinase, required for protein glycosylation in the ER. The mutation of sec59-1 caused a protein N-glycosylation defect mediated ER stress resulting in increased levels of phospholipid, neutral lipid and sterol, whereas growth was reduced. In the sec59-1∆ cell, the N-glycosylation of vacuolar carboxy peptidase-Y (CPY) was significantly reduced; whereas the ER stress marker Kar2p and unfolded protein response (UPR) were significantly increased. Increased levels of Triacylglycerol (TAG), sterol ester (SE), and lipid droplets (LD) could be attributed to up-regulation of DPP1, LRO1, and ARE2 in the sec 59-1∆ cell. Also, the diacylglycerol (DAG), sterol (STE), and free fatty acids (FFA) levels were significantly increased, whereas the genes involved in peroxisome biogenesis and Pex3-EGFP levels were reduced when compared to the wild-type. The microarray data also revealed increased expression of genes involved in phospholipid, TAG, fatty acid, sterol synthesis, and phospholipid transport resulting in dysregulation of lipid homeostasis in the sec59-1∆ cell. We conclude that SEC59 dependent N-glycosylation is required for lipid homeostasis, peroxisome biogenesis, and ER protein quality control.

Highlights

Proteins synthesized in the endoplasmic reticulum (ER) are post-translationally modified by N-glycosylation and O-glycosylation
The microarray result shows that 1880 genes involved in various functions were upregulated and 1430 genes were down regulated in the sec59-1∆ strain (S1)
The present study reports the link between protein glycosylation and lipid metabolism, and its impact on the ER protein quality control, and peroxisome biogenesis in S. cerevisiae

Summary

Introduction

Proteins synthesized in the ER are post-translationally modified by N-glycosylation and O-glycosylation. Dolichol kinase transfers the phosphoryl group from CTP to dolichol and catalyzes the final step of the de novo pathway for the Dol-P formation. CTP-mediated dolichol kinase is involved in recycling of glycosyl carrier lipid after it is discharged as Dol-P-P in N-glycosylation reactions. Dol-P (Dolichol Monophosphate) serves as a glycosyl carrier lipid in the assembly of N-linked glycoproteins, glycosylphosphatidylinositol anchors, and C and O-mannosylation. The DK is involved in the dolichol monophosphate (Dol-P) synthesis and serves as a carrier lipid in the assembly of N-linked glycoproteins[1]. Www.nature.com/scientificreports associated with human metabolic diseases, congenital disorder of glycosylation (CDG), muscular hypotonia and progressive dilative cardiomyopathy[5]. The impact of the protein glycosylation defect on lipid metabolism (the phospholipid, neutral lipid, sterol, and fatty acid metabolism), and its associated human lipid metabolic disorder remains elusive. The systematic interrogations of cellular pathways will help to identify the crosstalk between protein glycosylation and lipid metabolism

Methods

Results

Conclusion