Impact of mannosylation on structure and functionality of ER and Golgi

ABSTRACT: Many proteins undergo glycosylation in the endoplasmic reticulum (ER) and the Golgi apparatus. Altered glycosylation can manifest in serious, sometimes fatal malfunctions. We recently showed that mutations in the cytoplasmic protein GDP-mannose pyrophosphorylase A (GMPPA) cause a syndrome characterized by alacrima, achalasia, mental retardation and myopathic alterations. GMPPA acts as feedback inhibitor of GDP-mannose pyrophosphorylase B (GMPPB), which provides GDP-mannose as a substrate for protein glycosylation. Loss of GMPPA enhances incorporation of mannose into glycochains of various proteins, including α-dystroglycan (α-DG), a protein that links the extracellular matrix with the cytoskeleton. Here, we show that loss of GMPPA affects the functionality of the Golgi apparatus using different approaches. First, we show a fragmentation of the Golgi apparatus in skeletal muscle fibers and in neurons of GMPPA KO mice. A major reorganization is also evident by mass spectrometry of KO tissues with a regulation of several ER- and Golgi-resident proteins. We further show that loss of GMPPA increases the retention of α-DG in the ER. Notably, mannose supplementation can mimic changes in ER and Golgi structure and function in WT cells. In summary, our data underline the importance of a balanced mannose homeostasis for structure and function of the secretory pathway.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Brain, Skeletal Muscle

SUBMITTER: Emilio Cirri  

LAB HEAD: Christian A. Hübner

PROVIDER: PXD037129 | Pride | 2023-03-11

REPOSITORIES: Pride