O- GlcNAc reports ambient temperature and confers heat resistance on ectotherm development

Abstract

Effects of temperature on biological processes are complex. Diffusion is less affected than the diverse enzymatic reactions that have distinct individual temperature profiles. Hence thermal fluctuations pose a formidable challenge to ectothermic organisms in which body temperature is largely dictated by the ambient temperature. How cells in ectotherms cope with the myriad disruptive effects of temperature variation is poorly understood at the molecular level. Here we show that nucleocytoplasmic posttranslational modification of proteins with O-linked GlcNAc (O-GlcNAc) is closely correlated with ambient temperature during development of distantly related ectotherms ranging from the insect Drosophila melanogaster to the nematode Caenorhabditis elegans to the fish Danio rerio. Regulation seems to occur at the level of activity of the only two enzymes, O-GlcNAc transferase and O-GlcNAcase, that add and remove, respectively, this posttranslational modification in nucleus and cytoplasm. With genetic approaches in D. melanogaster and C. elegans, we demonstrate the importance of high levels of this posttranslational modification for successful development at elevated temperatures. Because many cytoplasmic and nuclear proteins in diverse pathways are O-GlcNAc targets, temperature-dependent regulation of this modification might contribute to an efficient coordinate adjustment of cellular processes in response to thermal change.O-GlcNAcylation | temperature acclimation A mbient temperature can fluctuate over various time scales and degrees in different ecological niches. Organisms cope with thermal fluctuations using alternative strategies. Endotherms like humans rely primarily on internally generated heat in combination with intricate regulation for maintenance of a relatively high and constant core body temperature. In contrast, the majority of organisms are ectotherms that produce far less heat. Their internal temperature is primarily dictated by the environment. Cells in some ectotherms are able to acclimate over a remarkable range of ambient temperatures even though temperature change has pervasive effects. All biological processes depend on temperature, but notably not in a uniform manner. Compensation of the myriad disruptive effects of temperature change at the cellular level necessitates extremely complex regulation. Our understanding of the responsible molecular mechanisms is still remarkably poor, even though ambient temperature is often the major ecological determinant of species range.Beyond advanced genetics, Drosophila melanogaster embryos provide additional advantages for studies at the cellular and molecular level, because behavioral responses to temperature change do not yet occur during the immotile early stages. Our characterization of temperature effects on early D. melanogaster development has revealed a unique temperature sensitivity of posttranslational modification of nucleocytoplasmic proteins with O-linked GlcNAc (O-GlcNAc). O-GlcNAc modification is known to occur on thousands of proteins involve...

O-GlcNAc occurs cotranslationally to stabilize nascent polypeptide chains

“…Answering such questions will depend on time-resolved mapping of O-GlcNAcylation sites on both coand post-translationally O-GlcNAcylated proteins. On a more functional level, O-GlcNAc is a cellular stress response 6,35 that is also nutrient responsive [39][40][41] , and so it seems likely that cotranslational O-GlcNAcylation is an adaptive response enabling protection of nascent chains during times of stress or high metabolic flux, a view that is consistent with the protective effects of increased O-GlcNAc in various models 42 and the effects of altered O-GlcNAc levels on the levels of some proteins [7][8][9]37 .…”

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

“…The C. elegans homolog of OGT (OGT-1) is not essential for cellular viability or fertility under normal growth conditions (110), although it does appear to play a role in allowing embryogenesis at elevated temperatures (114). 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).…”

O-GlcNAc-ylation in the Nuclear Pore Complex

“…One of the most widely studied processes affected by O-GlcNAc-ylation is the cellular stress response. In model organisms, such as Drosophila, C. elegans , and D. rerio , intracellular O-GlcNAc levels have been shown to increase in response to oxidative stress, osmotic stress, ethanol, UV light, and heat shock 2,15,16,17,18 as well as improve cell survival during the normal life cycle 15 and during development 17 . Furthermore, dysregulated O-GlcNAc-ylation has also been linked to diabetes, cardiovascular disease, neurodegenerative disorders, and cancer 19,20,21,22,23,24 .…”