GRASP depletion-mediated Golgi fragmentation impairs glycosaminoglycan synthesis, sulfation, and secretion
Authors:
Erpan Ahat, Yuefan Song, Ke Xia, Whitney Reid, Jie Li, Sarah Bui, Fuming Zhang, Robert J. Linhardt & Yanzhuang Wang
Affiliation:
Department of Molecular, Cellular and Developmental Biology, University of Michigan, 1105 North University Avenue, Ann Arbor, MI, 48109-1085, USA
Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
Department of Neurology, University of Michigan School of Medicine, Ann Arbor, MI, USA
Description:
Synthesis of glycosaminoglycans, such as heparan sulfate (HS) and chondroitin sulfate (CS), occurs in the lumen of the Golgi, but the relationship between Golgi structural integrity and glycosaminoglycan synthesis is not clear. In this study, we disrupted the Golgi structure by knocking out GRASP55 and GRASP65 and determined its effect on the synthesis, sulfation, and secretion of HS and CS. We found that GRASP depletion increased HS synthesis while decreasing CS synthesis in cells, altered HS and CS sulfation, and reduced both HS and CS secretion. Using proteomics, RNA-seq and biochemical approaches, we identified EXTL3, a key enzyme in the HS synthesis pathway, whose level is upregulated in GRASP knockout cells; while GalNAcT1, an essential CS synthesis enzyme, is robustly reduced. In addition, we found that GRASP depletion decreased HS sulfation via the reduction of PAPSS2, a bifunctional enzyme in HS sulfation. Our study provides the first evidence that Golgi structural defect may significantly alter the synthesis and secretion of glycosaminoglycans.