O-GlcNAc-modification of SNAP-29 regulates autophagosome maturation

Abstract

The mechanism by which nutrient status regulates the fusion of autophagosomes with endosomes/lysosomes is poorly understood. Here, we report that O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (OGT) mediates O-GlcNAcylation of the SNARE protein SNAP-29 and regulates autophagy in a nutrient-dependent manner. In mammalian cells, OGT knockdown, or mutating the O-GlcNAc sites in SNAP-29, promotes the formation of a SNAP-29-containing SNARE complex, increases fusion between autophagosomes and endosomes/lysosomes, and promotes autophagic flux. In Caenorhabditis elegans, depletion of ogt-1 has a similar effect on autophagy; moreover, expression of an O-GlcNAc-defective SNAP-29 mutant facilitates autophagic degradation of protein aggregates. O-GlcNAcylated SNAP-29 levels are reduced during starvation in mammalian cells and in C. elegans. Our study reveals a mechanism by which O-GlcNAc-modification integrates nutrient status with autophagosome maturation.

The Biochemistry of O-GlcNAc Transferase: Which Functions Make It Essential in Mammalian Cells?

“…ogt-1 null nematodes are developmentally normal, and despite showing no detectable O-GlcNAc on their nuclear pores, they appear to have normal nuclear translocation of transcription factors (110). The primary perturbations seen in these knockouts relate to metabolism and longevity, with organisms showing a reduced ability to enter the dauer state as well as reduced glycogen and lipid stores (110), reduced life span (115,116), and increased autophagy (117,118). These phenotypes can all be linked to changes in insulin signaling in mutant nematodes (110,116), which suggest that regulating insulin signaling is a conserved role for OGT from C. elegans to mammals (15).…”

“…Regulation of several biological processes, including autophagy (117,118), insulin signaling (14,115,116,(140)(141)(142)(143), stress response (12,116,144,145), proteasomal degradation of proteins (16-18, 146, 147), and polycomb repression (5,124), is conserved across species. Although conserved targets provide insight into the ancestral functions of OGT, they do not explain its greater importance in mammalian cells unless an essential function for glycosylation of one or more of these targets has been gained since evolutionary divergence.…”

New insights into autophagosome–lysosome fusion

“…Similar machineries and mechanisms are also used for autophagosome-lysosome fusion in Drosophila (Takats et al, 2013). Furthermore, the O-linked N-acetylglucosamine (O-GlcNAc) modification of SNAP29 negatively regulates SNARE-dependent fusion between autophagosomes and lysosomes (Guo et al, 2014). Consequently, knockdown of OGlcNAc transferase or mutating SNAP29 O-GlcNAc sites promotes formation of the SNAP29-containing SNARE complex and increases fusion between autophagosomes and lysosomes (Fig.…”

Phosphorylated Presenilin 1 decreases β-amyloid by facilitating autophagosome–lysosome fusion

“…In addition to providing the core machinery for membrane fusion, SNARE-interacting proteins can facilitate complex formation. For instance, SNAP29 and Atg14 stabilize Stx17-Vamp8 interaction and promote autophagosome-lysosome fusion (13)(14)(15).…”