scholarly journals Generation of an Unbiased Interactome for the Tetratricopeptide Repeat Domain of O-GlcNAc Transferase Indicates a Role for the Enzyme in Intellectual Disability

2020 ◽  
Author(s):  
Hannah M Stephen ◽  
Jeremy L Praissman ◽  
Lance Wells
Keyword(s):  
Intellectual Disability ◽  
Missense Mutations ◽  
Substantial Impact ◽  
Cellular Survival ◽  
Cellular Processes ◽  
Disease States ◽  
Tetratricopeptide Repeat Domain ◽  
Nucleocytoplasmic Proteins ◽  
Glcnac Transferase ◽  
Tpr Domain

The O-GlcNActransferase (OGT) is localized to the nucleus and cytoplasm where it regulates nucleocytoplasmic proteins by modifying serine and threonine residues with a non-extended monosaccharide, b-N-Acetyl-Glucosamine (O-GlcNAc). With thousands ofknown O-GlcNAcmodifiedproteinsbut only oneOGTencoded in the mammalian genome, a prevailing question is howOGTselects its substrates. Prior work has indicated that theN-terminaltetratricopeptide repeat (TPR) domain of OGT, rather than itsC-terminalcatalytic domain, is responsible forsubcellular targeting andsubstrate selection.An additional impetus for exploring the OGT TPR domain interactome is the fact that missense mutations inOGTassociated with X-linked intellectual disability (XLID) are primarily localized to the TPR domain without substantial impact on activity or stability of the enzyme.Therefore, we adapted theBioIDlabeling method to identify interactors of a TPR-BirA* fusion protein in HeLa cells. We identified 115high confidenceinteractors representing both known and novel O-GlcNAcmodified proteins and OGT interactors. The TPR interactors are highly enriched in processes in which OGT has a known role (e.g. chromatin remodeling, cellular survival of heat stress, circadian rhythm), as well as processesin which OGT has yet to be implicated (e.g. pre-mRNA processing). Importantly,the identified TPR interactors are involved in several disease states but most notably are highly enriched in pathologies featuring intellectual disability.Theseproteinsrepresent candidateinteractors that may underlie the mechanismby which mutations in OGT lead to XLID. Furthermore, the identified interactors provide additional evidence of the importance of the TPR domain for OGT targeting and/or substrate selection.Thus, this defined interactome for the TPR domain of OGT serves as ajumping off point for future researchexploringthe role of OGT, the TPR domain, and its protein interactorsin multiple cellular processes and disease mechanisms, including intellectual disability.

scholarly journals Catalytic deficiency of O-GlcNAc transferase leads to X-linked intellectual disability

2019 ◽  
Vol 116 (30) ◽  
pp. 14961-14970 ◽  
Author(s):  
Veronica M. Pravata ◽  
Villo Muha ◽  
Mehmet Gundogdu ◽  
Andrew T. Ferenbach ◽  
Poonam S. Kakade ◽  
...  
Keyword(s):  
Intellectual Disability ◽  
Protein Interactions ◽  
Catalytic Domain ◽  
Embryonic Stem ◽  
Global Changes ◽  
Missense Mutations ◽  
Protein Protein Interactions ◽  
Delayed Differentiation ◽  
Nucleocytoplasmic Proteins ◽  
Glcnac Transferase

O-GlcNAc transferase (OGT) is an X-linked gene product that is essential for normal development of the vertebrate embryo. It catalyses the O-GlcNAc posttranslational modification of nucleocytoplasmic proteins and proteolytic maturation of the transcriptional coregulator Host cell factor 1 (HCF1). Recent studies have suggested that conservative missense mutations distal to the OGT catalytic domain lead to X-linked intellectual disability in boys, but it is not clear if this is through changes in the O-GlcNAc proteome, loss of protein–protein interactions, or misprocessing of HCF1. Here, we report an OGT catalytic domain missense mutation in monozygotic female twins (c. X:70779215 T > A, p. N567K) with intellectual disability that allows dissection of these effects. The patients show limited IQ with developmental delay and skewed X-inactivation. Molecular analyses revealed decreased OGT stability and disruption of the substrate binding site, resulting in loss of catalytic activity. Editing this mutation into the Drosophila genome results in global changes in the O-GlcNAc proteome, while in mouse embryonic stem cells it leads to loss of O-GlcNAcase and delayed differentiation down the neuronal lineage. These data imply that catalytic deficiency of OGT could contribute to X-linked intellectual disability.

scholarly journals Intellectual disability-associated disruption of O-GlcNAcylation impairs neuronal development and cognitive function in Drosophila

2022 ◽  
Author(s):  
Michaela Fenckova ◽  
Villo Muha ◽  
Daniel Mariyappa ◽  
Marica Catinozzi ◽  
Ignacy Czajewski ◽  
...  
Keyword(s):  
Intellectual Disability ◽  
Cognitive Function ◽  
Neuronal Development ◽  
Critical Role ◽  
Patient Specific ◽  
Transferase Activity ◽  
Missense Mutations ◽  
Post Translational Modification ◽  
Larval Neuromuscular Junction ◽  
Glcnac Transferase

O-GlcNAcylation is a reversible co-/post-translational modification involved in a multitude of cellular processes. The addition and removal of O-GlcNAc modification is controlled by two conserved enzymes, O-GlcNAc transferase (OGT) and O-GlcNAc hydrolase (OGA). Mutations in OGT have recently been discovered to cause a novel Congenital Disorder of Glycosylation (OGT-CDG) that is characterized by intellectual disability. The mechanisms by which OGT-CDG mutations affect cognition remain unclear. We manipulated O-GlcNAc transferase and O-GlcNAc hydrolase activity in Drosophila and demonstrate an important role of O-GlcNAcylation in habituation learning and synaptic development at the larval neuromuscular junction. Introduction of patient-specific missense mutations into Drosophila O-GlcNAc transferase using CRISPR/Cas9 gene editing, leads to deficits in locomotor function and habituation learning. The habituation deficit can be corrected by blocking O-GlcNAc hydrolysis, indicating that OGT-CDG mutations affect cognitive function via reduced protein O-GlcNAcylation. This study establishes a critical role for O-GlcNAc cycling and disrupted O-GlcNAc transferase activity in cognitive dysfunction. These findings suggest that blocking O-GlcNAc hydrolysis is a potential treatment strategy for OGT-CDG.

scholarly journals On the Need to Tell Apart Fraternal Twins eEF1A1 and eEF1A2, and Their Respective Outfits

2021 ◽  
Vol 22 (13) ◽  
pp. 6973
Author(s):  
Alberto Mills ◽  
Federico Gago
Keyword(s):  
De Novo ◽  
Elongation Factor ◽  
Missense Mutations ◽  
Developmentally Regulated ◽  
High Sequence Identity ◽  
80S Ribosome ◽  
Cellular Effects ◽  
Cellular Processes ◽  
Eukaryotic Elongation Factor ◽  
A Site

eEF1A1 and eEF1A2 are paralogous proteins whose presence in most normal eukaryotic cells is mutually exclusive and developmentally regulated. Often described in the scientific literature under the collective name eEF1A, which stands for eukaryotic elongation factor 1A, their best known activity (in a monomeric, GTP-bound conformation) is to bind aminoacyl-tRNAs and deliver them to the A-site of the 80S ribosome. However, both eEF1A1 and eEF1A2 are endowed with multitasking abilities (sometimes performed by homo- and heterodimers) and can be located in different subcellular compartments, from the plasma membrane to the nucleus. Given the high sequence identity of these two sister proteins and the large number of post-translational modifications they can undergo, we are often confronted with the dilemma of discerning which is the particular proteoform that is actually responsible for the ascribed biochemical or cellular effects. We argue in this review that acquiring this knowledge is essential to help clarify, in molecular and structural terms, the mechanistic involvement of these two ancestral and abundant G proteins in a variety of fundamental cellular processes other than translation elongation. Of particular importance for this special issue is the fact that several de novo heterozygous missense mutations in the human EEF1A2 gene are associated with a subset of rare but severe neurological syndromes and cardiomyopathies.

scholarly journals Regulating the Regulators: Mechanisms of Substrate Selection of the O-GlcNAc Cycling Enzymes OGT and OGA

Glycobiology ◽  
2021 ◽  
Author(s):  
Hannah M Stephen ◽  
Trevor M Adams ◽  
Lance Wells
Keyword(s):  
Nutrient Sensing ◽  
Substrate Selection ◽  
Disease States ◽  
Dynamic Modification ◽  
Selection For ◽  
Outstanding Question ◽  
Glcnac Transferase ◽  
Future Work ◽  
Partner Proteins ◽  
Selection Of

Abstract Thousands of nuclear and cytosolic proteins are modified with a single β-N-acetylglucosamine on serine and threonine residues in mammals, a modification termed O-GlcNAc. This modification is essential for normal development and plays important roles in virtually all intracellular processes. Additionally, O-GlcNAc is involved in many disease states, including cancer, diabetes, and X-linked intellectual disability. Given the myriad of functions of the O-GlcNAc modification, it is therefore somewhat surprising that O-GlcNAc cycling is mediated by only two enzymes: the O-GlcNAc transferase (OGT), which adds O-GlcNAc, and the O-GlcNAcase (OGA), which removes it. A significant outstanding question in the O-GlcNAc field is how do only two enzymes mediate such an abundant and dynamic modification. In this review, we explore the current understanding of mechanisms for substrate selection for the O-GlcNAc cycling enzymes. These mechanisms include direct substrate interaction with specific domains of OGT or OGA, selection of interactors via partner proteins, posttranslational modification of OGT or OGA, nutrient sensing, and localization alteration. Altogether, current research paints a picture of an exquisitely regulated and complex system by which OGT and OGA select substrates. We also make recommendations for future work, toward the goal of identifying interaction mechanisms for specific substrates that may be able to be exploited for various research and medical treatment goals.

scholarly journals Intracellular Ionic Strength Sensing Using NanoLuc

2021 ◽  
Vol 22 (2) ◽  
pp. 677
Author(s):  
Tausif Altamash ◽  
Wesam Ahmed ◽  
Saad Rasool ◽  
Kabir H. Biswas
Keyword(s):  
Thermal Stability ◽  
Phase Separation ◽  
Drug Discovery ◽  
Ionic Strength ◽  
Cellular Signaling ◽  
Live Cells ◽  
Protein Activity ◽  
Cellular Survival ◽  
Cellular Processes ◽  
Wide Range

Intracellular ionic strength regulates myriad cellular processes that are fundamental to cellular survival and proliferation, including protein activity, aggregation, phase separation, and cell volume. It could be altered by changes in the activity of cellular signaling pathways, such as those that impact the activity of membrane-localized ion channels or by alterations in the microenvironmental osmolarity. Therefore, there is a demand for the development of sensitive tools for real-time monitoring of intracellular ionic strength. Here, we developed a bioluminescence-based intracellular ionic strength sensing strategy using the Nano Luciferase (NanoLuc) protein that has gained tremendous utility due to its high, long-lived bioluminescence output and thermal stability. Biochemical experiments using a recombinantly purified protein showed that NanoLuc bioluminescence is dependent on the ionic strength of the reaction buffer for a wide range of ionic strength conditions. Importantly, the decrease in the NanoLuc activity observed at higher ionic strengths could be reversed by decreasing the ionic strength of the reaction, thus making it suitable for sensing intracellular ionic strength alterations. Finally, we used an mNeonGreen–NanoLuc fusion protein to successfully monitor ionic strength alterations in a ratiometric manner through independent fluorescence and bioluminescence measurements in cell lysates and live cells. We envisage that the biosensing strategy developed here for detecting alterations in intracellular ionic strength will be applicable in a wide range of experiments, including high throughput cellular signaling, ion channel functional genomics, and drug discovery.

scholarly journals The Putative Eukaryote-LikeO-GlcNAc Transferase of the Cyanobacterium Synechococcus elongatus PCC 7942 Hydrolyzes UDP-GlcNAc and Is Involved in Multiple Cellular Processes

2014 ◽  
Vol 197 (2) ◽  
pp. 354-361 ◽  
Author(s):  
Kerry A. Sokol ◽  
Neil E. Olszewski
Keyword(s):  
Deletion Mutant ◽  
Bacterial Species ◽  
Synechococcus Elongatus ◽  
Single Amino Acid ◽  
Content Type ◽  
Cellular Processes ◽  
Mutant Phenotypes ◽  
Glcnac Transferase ◽  
Pcc 7942 ◽  
Mutant Cells

The posttranslational addition of a single O-linked β-N-acetylglucosamine (O-GlcNAc) to serine or threonine residues regulates numerous metazoan cellular processes. The enzyme responsible for this modification,O-GlcNAc transferase (OGT), is conserved among a wide variety of organisms and is critical for the viability of many eukaryotes. Although OGTs with domain structures similar to those of eukaryotic OGTs are predicted for many bacterial species, the cellular roles of these OGTs are unknown. We have identified a putative OGT in the cyanobacteriumSynechococcus elongatusPCC 7942 that shows active-site homology and similar domain structure to eukaryotic OGTs. An OGT deletion mutant was created and found to exhibit several phenotypes. Without agitation, mutant cells aggregate and settle out of the medium. The mutant cells have higher free inorganic phosphate levels, wider thylakoid lumen, and differential accumulation of electron-dense inclusion bodies. These phenotypes are rescued by reintroduction of the wild-type OGT but are not fully rescued by OGTs with single amino acid substitutions corresponding to mutations that reduce eukaryotic OGT activity.S. elongatusOGT purified fromEscherichia colihydrolyzed the sugar donor, UDP-GlcNAc, while the mutant OGTs that did not fully rescue the deletion mutant phenotypes had reduced or no activity. These results suggest that bacterial eukaryote-like OGTs, like their eukaryotic counterparts, influence multiple processes.

SMARCA4-mutated lung adenocarcinoma, a distinctive non-small cell lung cancer with worse prognosis.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e20548-e20548
Author(s):  
Longfeng Zhang ◽  
Weijin Xiao ◽  
Fangjun Wu ◽  
Ran Peng ◽  
Jialong Shi ◽  
...  
Keyword(s):  
Protein Expression ◽  
Lung Adenocarcinoma ◽  
Copy Number ◽  
Enrichment Analysis ◽  
Outcome Data ◽  
Copy Number Loss ◽  
Missense Mutations ◽  
Cellular Processes ◽  
Pathological Characteristics ◽  
Worse Prognosis

e20548 Background: SMARCA4 gene is one of the catalytic subunits of the SWI/SNF chromosomal remodeling complex, which can regulate important cellular processes and functions and is closely associated to tumors. The clinical features, therapeutic efficacy, prognosis and pathological features of lung adenocarcinoma with this genetic variation are still unknown and controversial. Methods: The study recruited 274 patients (pts) with lung adenocarcinoma whose samples were sent to perform parallel hybridization-based next-generation sequencing. Two categories of SMARCA4 mutations were divided into Type1 mutations (frameshift mutations, nonsense mutations, splice-3 mutations, copy number amplification) and Type2 mutations (missense mutations and copy number loss) based on whether the mutation may result in defective protein. Furthermore, comparative analysis by using the clinical outcome data, the genomic and pathological characteristics were be performed in SMARCA4 Type 1 alterations corhort and Type 2 alterations corhort. Results: Among 274 pts were recruited, the mutation rate of SMARCA4 gene in lung adenocarcinoma was 9.1%. Furthermore, the presence of SMARCA4 alteration was associated with smoking (P＜0.05). Missense, nonsense, frameshift and splice were the most common types of mutations (92%). The pts with SMARCA4 Type1 alterations which probably lead to defective protein expression, had a worse prognosis compared with pts with SMARCA4 Type1 alterations (The role leading to defective protein expression is uncertain) and SMARCA4 Wild groups (P＜0.05). In addition, EGFR alterations were strongly associated with SMARCA4 Wild corhort compared to SMARCA4 Type1 alterations corhort (67% vs. 31% ), and SMARCA4 Type1 alterations was more associated with the absence of TP53, RB1, and Robo3 alterations. GO enrichment analysis suggested that the differentiated mutated genes between SMARCA4 Type1 alterations corhort and SMARCA4 Wild corhort were mainly enriched in cell cycle regulation. Pathologically, The SMARCA4 Type1 alterations was mostly poorly or moderately differentiated and strongly accompanied by the loss of expression of TTF-1(83.3%) and BRG1(80%) in immunohistochemistry. Conclusions: SMARCA4 Type1 alterations which probably lead to abnormality of protein was associated with poor prognosis and having different the genomic and pathological characteristics.

Sign in / Sign up

Export Citation Format

Share Document