Biology subjects

Gygi, S. P.

Publications and source records attributed to Gygi, S. P..

At least 55 records · Page 3Linked to original sources

bioRxiv2023

Multi-omics characterization of partial chemical reprogramming reveals evidence of cell rejuvenation

Partial reprogramming by cyclic short-term expression of Yamanaka factors holds promise for shifting cells to younger states and consequently delaying the onset of many diseases of aging. However, the delivery of transgenes and potential risk of teratoma formation present challenges for in vivo applications. Recent advances include the use of cocktails of compounds to reprogram somatic cells, but the characteristics and mechanisms of partial cellular reprogramming by chemicals remain unclear. Here, we report a multi-omics characterization of partial chemical reprogramming in fibroblasts from young and aged mice. We measured the effects of partial chemical reprogramming on the epigenome, transcriptome, proteome, phosphoproteome, and metabolome. At the transcriptome, proteome, and phosphoproteome levels, we saw widescale changes induced by this treatment, with the most notable signature being an upregulation of mitochondrial oxidative phosphorylation. Furthermore, at the metabolome level, we observed a reduction in the accumulation of aging-related metabolites. Using both transcriptomic and epigenetic clock-based analyses, we show that partial chemical reprogramming reduces the biological age of mouse fibroblasts. We demonstrate that these changes have functional impacts, as evidenced by changes in cellular respiration and mitochondrial membrane potential. Taken together, these results illuminate the potential for chemical reprogramming reagents to rejuvenate aged biological systems and warrant further investigation into adapting these approaches for in vivo age reversal.

molecular biology↗

bioRxiv2023

Fission yeast CK1 promotes DNA double-strand break repair through both homologous recombination and non-homologous end joining

The CK1 family are conserved serine/threonine kinases with numerous substrates and cellular functions. The fission yeast CK1 orthologues Hhp1 and Hhp2 were first characterized as regulators of DNA repair, but the mechanism(s) by which CK1 activity promotes DNA repair had not been investigated. Here, we found that deleting Hhp1 and Hhp2 or inhibiting CK1 catalytic activities in yeast or in human cells activated the DNA damage checkpoint due to persistent double-strand breaks (DSBs). The primary pathways to repair DSBs, homologous recombination and non-homologous end joining, were both less efficient in cells lacking Hhp1 and Hhp2 activity. In order to understand how Hhp1 and Hhp2 promote DSB repair, we identified new substrates using quantitative phosphoproteomics. We confirmed that Arp8, a component of the INO80 chromatin remodeling complex, is a bona fide substrate of Hhp1 and Hhp2 that is important for DSB repair. Our data suggest that Hhp1 and Hhp2 facilitate DSB repair by phosphorylating multiple substrates, including Arp8.

cell biology↗

bioRxiv2023

Proteostasis and lysosomal quality control deficits in Alzheimer's disease neurons

Aging is the most prominent risk factor for Alzheimers disease (AD). However, the cellular mechanisms linking neuronal proteostasis decline to the characteristic aberrant protein deposits in AD brains remain elusive. Here, we develop transdifferentiated neurons (tNeurons) from human dermal fibroblasts as a neuronal model that retains aging hallmarks and exhibits AD-linked vulnerabilities. Remarkably, AD tNeurons accumulate proteotoxic deposits, including phospho-Tau and A{beta}, resembling those in AD patient and APP mouse brains. Quantitative tNeuron proteomics identify aging and AD-linked deficits in proteostasis and organelle homeostasis, most notably in endosome-lysosomal components. Lysosomal deficits in aged tNeurons, including constitutive lysosomal damage and ESCRT-mediated lysosomal repair defects, are exacerbated in AD tNeurons and linked to inflammatory cytokine secretion and cell death. Supporting lysosomal deficits centrality in AD, compounds ameliorating lysosomal function reduce A{beta} deposits and cytokine secretion. Thus, the tNeuron model system reveals impaired lysosomal homeostasis as an early event of aging and AD.

cell biology↗

bioRxiv2022

UBXN1 maintains ER proteostasis and represses UPR activation by modulating translation independently of the p97 ATPase

Endoplasmic reticulum (ER) protein homeostasis (proteostasis) is essential to facilitate proper folding and maturation of proteins in the secretory pathway. Loss of ER proteostasis due to cell stress or mutations in ER proteins can lead to the accumulation of misfolded or aberrant proteins in the ER and triggers the unfolded protein response (UPR). In this study we find that the p97 adaptor UBXN1 is an important negative regulator of the UPR. Loss of UBXN1 significantly sensitizes cells to ER stress and activates canonical UPR signaling pathways. This in turn leads to widespread upregulation of the ER stress transcriptional program. Using comparative, quantitative proteomics we show that deletion of UBXN1 results in a significant enrichment of proteins belonging to ER-quality control processes including those involved in protein folding and import. Notably, we find that loss of UBXN1 does not perturb p97-dependent ER associated degradation (ERAD). Our studies indicate that loss of UBXN1 increases translation in both resting and ER-stressed cells. Surprisingly, this process is independent of p97 function. Taken together, our studies have identified a new role for UBXN1 in repressing translation and maintaining ER proteostasis in a p97 independent manner.

cell biology↗

bioRxiv2022

Phosphate Starvation Signaling Increases Mitochondrial Membrane Potential through Respiration-independent Mechanisms

Mitochondrial membrane potential directly powers many critical functions of mitochondria, including ATP production, mitochondrial protein import, and metabolite transport. Its loss is a cardinal feature of aging and mitochondrial diseases, and cells closely monitor membrane potential as an indicator of mitochondrial health. Given its central importance, it is logical that cells would modulate mitochondrial membrane potential in response to demand and environmental cues, but there has been little exploration of this question. We report that loss of the Sit4 protein phosphatase in yeast increases mitochondrial membrane potential, both through inducing the electron transport chain and the phosphate starvation response. Indeed, a similarly elevated mitochondrial membrane potential is also elicited simply by phosphate starvation or by abrogation of the Pho85-dependent phosphate sensing pathway. This enhanced membrane potential is primarily driven by an unexpected activity of the ADP/ATP carrier. We also demonstrate that this connection between phosphate limitation and enhancement of the mitochondrial membrane potential is also observed in primary and immortalized mammalian cells as well as in Drosophila. These data suggest that mitochondrial membrane potential is subject to environmental stimuli and intracellular signaling regulation and raise the possibility for therapeutic enhancement of mitochondrial functions even with defective mitochondria.

cell biology↗

bioRxiv2022

Global proteome metastability response in isogenic animals to missense mutations and polyglutamine expansions in aging

The conformational stability of the proteome has tremendous implications for the health of the cell and its capacity to determine longevity or susceptibility to age-associated degenerative diseases. For humans, this question of proteome conformational stability has the additional complexity from non-synonymous mutations in thousands of protein coding genes challenging the capacity of the proteostasis network to properly fold, transport, assemble and degrade proteins. Here, we quantify the proteome-wide capacity to such challenges using the isogenic organism Caenorhabditis elegans by examining the dynamics of global proteome conformational stability in animals expressing different temperature-sensitive (ts) proteins or short polyglutamine (polyQ) expansions in the context of biological aging. Using limited proteolysis of native extracts together with tandem mass tag-based quantitative proteomics, we identify proteins that become metastable under these conditions and monitor the effects on proteome solubility and abundance. Expression of different mutant proteins in the same tissue identifies hundreds to a thousand proteins that become metastable affecting multiple compartments and processes in a cell autonomous and non-autonomous manner. Comparison of the network of metastable proteins, however, reveals only a small number of common proteins. The most dramatic effects on global proteome dynamics occur in aging with one-third of the proteome undergoing conformational changes in early adulthood. These age-dependent metastable proteins overlap substantially with ts proteins and polyQ; moreover, expression of polyQ accelerates the aging phenotype. Together, these results reveal that the proteome responds to misfolding one-at-a-time to generate a metastable sub-proteome network with features of a fingerprint for which aging is the dominant determinant of proteome metastability.

biochemistry↗

bioRxiv2022

Mapping the GALNT1 substrate landscape with versatile proteomics tools

O-GalNAc type glycosylation is a common post-translational modification (PTM) of proteins catalyzed by polypeptide GalNAc transferases, but the substrate specificity of these transferases is poorly understood. Here we develop a strategy based on integral thermal proteome solubility profiling to identify and prioritize the protein substrates of polypeptide N-acetylgalactosaminyltransferase 1 (GALNT1). Combined with glycoprotein enrichment followed by HCD and soft EThcD gas-phase fragmentation technique, we uncover hundreds of novel GALNT1 substrates in two model human cell lines. GALNT1-mediated O-glycosylation is more common on Thr than Ser residues, with a strong preference for Pro at positions +3 and +4 in respect to O-glycosylation. These results implicate GALNT1 in potentially regulating proteins in several diverse pathways, including some unexpected processes, such as TCA cycle and DNA transcription. This study depicts a roadmap for identification of functional substrates for glycosyltransferases, facilitating fundamental insight into the role of glycosylation in homeostasis and disease.

biochemistry↗

bioRxiv2022

Large-scale proteomic analysis of T. spiralis muscle-stage ESPs identifies a novel upstream motif for in silico prediction of secreted products

The Trichinella genus contains parasitic nematodes capable of infecting a wide range of hosts including mammals, birds and reptiles. Like other helminths, T. spiralis secretes a complex mixture of bioactive molecules capable of modulating its immediate surroundings and creating a hospitable environment for growth, survival and ultimately transmission. The constitution of these excretory-secretory products (ESPs) changes depending on the tissue niche and the specific stage of parasite development. Unique to T. spiralis is a true intracellular stage wherein larvae develop inside striated myotubes. Remarkably, the parasite larvae do not destroy the host cell but rather reprogram it to support their presence and growth. This transformation is largely mediated through stage-specific secretions released into the host cell cytoplasm. In this study, we apply state of the art proteomics and computational approaches to elucidate the composition and functions of muscle-stage T. spiralis ESPs. Moreover, we define a commonly-occurring, upstream motif that we believe is associated with the stichosome, the main secretory organ of this worm, and can thus be used to predict secreted proteins across experimentally less tractable T. spiralis life cycle stages. Author SummaryTrichinella spiralis is the only helminth parasite with a true intracellular stage. Newborn larvae penetrate the intestinal wall of the host, enter the circulation and preferentially infect muscle cells. Remarkably, they do not destroy the host cell but rather initiate a series of modulatory events that transform it into a nurse cell complex, a collagenated cyst that can persist for years. Each stage of T. spiralis development is guided by host-targeted secretions released by the worm directly into its immediate environment, mediating events such as immunoregulation, cell cycle control and angiogenesis. As such, these worm effectors hold therapeutic potential for chronic and autoimmune diseases. The composition of excretory-secretory products (ESPs) changes according to what the worm needs to accomplish and what tissue niche it is occupying at the time, with many deriving from the stichosome, the worms dedicated secretory organ. In this study, we characterise ESPs of muscle-stage T. spiralis larvae using proteomic and bioinformatic approaches and we define a regulatory motif associated with stichosome-derived proteins.

cell biology↗

bioRxiv2022

The role of an unusual cyclin in control of cell cycle entry and cell size in budding yeast

Entry into the cell cycle in late G1 phase occurs only when sufficient growth has occurred. In budding yeast, a cyclin called Cln3 is thought to link cell cycle entry to cell growth. Cln3 accumulates during growth in early G1 phase and eventually triggers accumulation of late G1 phase cyclins that drive cell cycle entry. All current models for cell cycle entry assume that expression of late G1 phase cyclins is initiated at the transcriptional level. Current models also assume that the sole function of Cln3 in cell cycle entry is to promote transcription of late G1 phase cyclins, and that Cln3 works solely in G1 phase. Here, we show that cell cycle-dependent expression of late G1 phase cyclins does not require cell cycle-dependent transcription. Moreover, Cln3 can influence accumulation of late G1 phase cyclin proteins via post-transcriptional mechanisms. Finally, we show that Cln3 has functions in mitosis that strongly influence cell size. Together, these discoveries reveal surprising new functions for Cln3 that challenge current models for control of cell cycle entry and cell size.

cell biology↗

bioRxiv2022

Multi-omics analysis identifies drivers of protein phosphorylation

Phosphorylation of proteins is a key step in the regulation of many cellular processes including activation of enzymes and signaling cascades. The abundance of a phosphorylated peptide (phosphopeptide) is determined by the abundance of its parent protein and the proportion of target sites that are phosphorylated. We quantified phosphopeptides, proteins, and transcripts in heart, liver, and kidney tissue samples of mice from 58 strains of the Collaborative Cross strain panel. We mapped [~]700 phosphorylation quantitative trait loci (phQTL) across the three tissues and applied genetic mediation analysis to identify causal drivers of phosphorylation. We identified kinases, phosphatases, cytokines, and other factors, including both known and potentially novel interactions between target proteins and genes that regulate site-specific phosphorylation. Our analysis highlights multiple targets of pyruvate dehydrogenase kinase 1 (PDK1), a regulator of mitochondrial function that shows reduced activity in the NZO/HILtJ mouse, a polygenic model of obesity and type 2 diabetes.

genomics↗

bioRxiv2022

Three ALS genes regulate expression of the MHC class II antigen presentation pathway

Here we report that the major histocompatibility complex II (MHC II) antigen presentation pathway is regulated by the ALS-causative genes, FUS, TAF15, or MATR3. Of >6000 proteins detected by quantitative mass spectrometry, the subunits of the MHC II heterodimer, HLA-DR, were the top 2 downregulated proteins in HeLa knock outs (KO) of these ALS genes, but not the related gene, EWSR1. Moreover, CD74, which is the 3rd essential component of HLA-DR, was downregulated in the 3 KOs. We show that the downregulations are due to loss of CIITA, a transcription factor dedicated to expression of MHC II genes. Thus, our results reveal the 1st shared cellular pathway regulated by multiple ALS genes, and this pathway is ALS genes -> CIITA -> MHC II genes. We obtained the same results in HMC3 cells, a microglia cell line, showing that loss of the MHC II pathway extends to an ALS-relevant cell type in the central nervous system (CNS). Furthermore, the MHC II pathway is downregulated in hematopoietic progenitor cells (HPCs) bearing the ALS FUSR495X mutation. This observation may be highly significant to ALS pathogenesis as HPCs give rise to a multitude of CNS-specific and systemic immune cells, both of which have known or suspected roles in ALS. Together, our data raise the possibility that loss of the MHC II pathway in a large range of immune cells results in global failure of the immune system to protect motor neurons from damage that leads to the disease. Consequently, CIITA and the other genes in the MHC II pathway may be important new therapeutic targets for the disease.

molecular biology↗

bioRxiv2022

An anaphase switch in astral microtubule dynamics specifically requires the APC/C-Cdc20-dependent degradation of the mitotic cyclin Clb4

Key for accurate chromosome partitioning to the offspring is the ability of mitotic spindle microtubules to respond to different molecular signals and remodel their dynamics accordingly. Spindle microtubules are conventionally divided into three classes: kinetochore, interpolar and astral microtubules (kMTs, iMTs and aMTs, respectively), among all aMT regulation remains elusive. Here, we show that aMT dynamics are tightly regulated. aMTs remain unstable up to metaphase and are stabilized at anaphase onset. This switch in aMT dynamics, crucial for proper spindle orientation, specifically requires the degradation of the mitotic cyclin Clb4 by the Anaphase Promoting Complex bound to its activator subunit Cdc20 (APC/CCdc20). These data highlight a unique role for mitotic cyclin Clb4, provide a framework to understand aMT regulation in vertebrates and uncover mechanistic principles of how the APC/CCdc20 choreographs the timing of late mitotic events by sequentially impacting on the three classes of spindle microtubules.

cell biology↗

bioRxiv2022

The relaxin receptor RXFP1 signals through a mechanism of autoinhibition

The relaxin family peptide receptor 1 (RXFP1) is the receptor for relaxin-2, an important regulator of reproductive and cardiovascular physiology. RXFP1 is a multi-domain G protein-coupled receptor (GPCR) with an ectodomain consisting of an LDLa module and leucine-rich repeats. The mechanism of RXFP1 signal transduction is clearly distinct from that of other GPCRs, but remains very poorly understood. Here, we present the cryo-electron microscopy structure of active-state human RXFP1, bound to a single-chain version of the endogenous agonist relaxin-2 and to the heterotrimeric Gs protein. Evolutionary coupling analysis and structure-guided functional experiments reveal that RXFP1 signals through a mechanism of autoinhibition, wherein the receptors extracellular loop 2 occupies the orthosteric site in the active state but is inhibited by the ectodomain in the absence of relaxin-2. Our results explain how an unusual GPCR family functions, providing a path to rational drug development targeting the relaxin receptors.

pharmacology and toxicology↗

bioRxiv2022

Time-resolved proximity labeling of protein networks associated with ligand-activated EGFR

Ligand binding to the EGF receptor (EGFR) triggers multiple signal transduction processes and promotes endocytosis of the receptor. The mechanisms of EGFR endocytosis and its crosstalk with signaling are poorly understood. Here, we combined peroxidase-catalyzed proximity labeling, isobaric peptide tagging and quantitative mass-spectrometry to define the dynamics of the proximity proteome of ligand-activated EGFR. Using this approach, we identified a network of signaling proteins, which remain associated with the receptor during its internalization and trafficking through the endosomal system. We showed that Trk-fused gene (TFG), a protein known to function at the endoplasmic reticulum exit sites, was enriched in the proximity proteome of EGFR in early/sorting endosomes and localized in these endosomes, and demonstrated that TFG regulates endosomal sorting of EGFR. This study provides a comprehensive resource of time-dependent nanoscale environment of EGFR, thus opening avenues to discovering new regulatory mechanisms of signaling and intracellular trafficking of receptor tyrosine kinases.

systems biology↗

bioRxiv2021

Self-assembling short immunostimulatory duplex RNAs with broad spectrum antiviral activity

The current COVID-19 pandemic highlights the need for broad-spectrum antiviral therapeutics. Here we describe a new class of self-assembling immunostimulatory short duplex RNAs that potently induce production of type I and type III interferon (IFN-I and IFN-III), in a wide range of human cell types. These RNAs require a minimum of 20 base pairs, lack any sequence or structural characteristics of known immunostimulatory RNAs, and instead require a unique conserved sequence motif (sense strand: 5-C, antisense strand: 3-GGG) that mediates end-to-end dimer self-assembly of these RNAs by Hoogsteen G-G base-pairing. The presence of terminal hydroxyl or monophosphate groups, blunt or overhanging ends, or terminal RNA or DNA bases did not affect their ability to induce IFN. Unlike previously described immunostimulatory siRNAs, their activity is independent of TLR7/8, but requires the RIG-I/IRF3 pathway that induces a more restricted antiviral response with a lower proinflammatory signature compared with poly(I:C). Immune stimulation mediated by these duplex RNAs results in broad spectrum inhibition of infections by many respiratory viruses with pandemic potential, including SARS-CoV-2, SARS-CoV, MERS-CoV, and influenza A, as well as the common cold virus HCoV-NL63 in both cell lines and human Lung Chips that mimic organ-level lung pathophysiology. These short dsRNAs can be manufactured easily, and thus potentially could be harnessed to produce broad-spectrum antiviral therapeutics at low cost.

immunology↗

bioRxiv2021

Assessing target engagement using proteome-wide solvent shift assays

Recent advances in mass spectrometry (MS) have enabled quantitative proteomics to become a powerful tool in the field of drug discovery, especially when applied toward proteome-wide target engagement studies. Similar to temperature gradients, increasing concentrations of organic solvents stimulate unfolding and precipitation of the cellular proteome. This property can be influenced by physical association with ligands and other molecules, making individual proteins more or less susceptible to solvent-induced denaturation. Herein, we report the development of proteome-wide solvent shift assays by combining the principles of solvent-induced precipitation (Zhang et al., 2020) with modern quantitative proteomics. Using this approach, we developed solvent proteome profiling (SPP), which is capable of establishing target engagement through analysis of SPP denaturation curves. We readily identified the specific targets of compounds with known mechanisms of action. As a further efficiency boost, we applied the concept of area-under-the-curve analysis to develop solvent proteome integral solubility alteration (solvent-PISA) and demonstrate that this approach can serve as a reliable surrogate for SPP. We propose that by combining SPP with alternative methods, like thermal proteome profiling, it will be possible to increase the absolute number of high-quality melting curves that are attainable by either approach individually thereby increasing the fraction of the proteome that can be screened for evidence of ligand binding.

biochemistry↗

bioRxiv2021

Aging predisposes B cells to malignancy by activating c-Myc and perturbing the genome and epigenome

While cancer is an age-related disease, many cancer studies utilize younger animal models. Here, we uncover how a cancer, B-cell lymphoma, develops as a consequence of a naturally aged system. We show that this malignancy is associated with increased cell size, splenomegaly, and a newly discovered age-associated clonal B-cell (ACBC) population. Driven by exogenous c-Myc activation, hypermethylated promoters and somatic mutations, ACBC cells clonally expand independent of germinal centers (IgM+) and show increased biological age and hypomethylation in partially methylated domains related to mitotic solo-CpGs. Epigenetic changes in transformed mouse B cells are enriched for changes observed in human B-cell lymphomas. Mechanistically, the data suggest that cancerous ACBC cells originate from age-associated B cells, in part involving CD22 protein signaling fostered by the aging microenvironment. Transplantation assays demonstrate that ACBC evolve to become self-sufficient and support malignancy when transferred into young recipients. Inhibition of mTOR or c-Myc in old mice attenuates premalignant changes in B cells during aging and emerges as a therapeutic strategy to delay the onset of age-related lymphoma. Together, we show how aging contributes to B-cell lymphoma through a previously unrecognized mechanism involving cell-intrinsic changes and the aged microenvironment, characterize a model that captures the origin and progression of spontaneous cancer during aging and identify candidate interventions against age-associated lymphoma.

cancer biology↗

bioRxiv2020

Enrichment of neurodegenerative microglia signature in brain-derived extracellular vesicles isolated from Alzheimer's disease mouse model

Extracellular vesicles (EVs) are secreted by any neuronal cells in the central nervous system (CNS) for molecular clearance, cellular communications and disease spread in multiple neurodegenerative diseases, including Alzheimers disease (AD), although their exact molecular mechanism is poorly understood. We hypothesize that high-resolution proteomic profiling of EVs separated from animal models of AD would determine the composition of EV contents and their cellular origin. Here, we examined recently developed transgenic mice (CAST.APP/PS1), which express familial AD-linked mutations of amyloid precursor protein (APP) and presenilin-1 (PS1) in the CAST/EiJ mouse strain and develop hippocampal neurodegeneration. Quantitative proteomics analysis of EVs separated from CAST.APP/PS1 and age-matched control mice by tandem mass tag-mass spectrometry identified a total of 3,444 unique proteins, which are enriched in neuron, astrocyte, oligodendrocyte and microglia-specific molecules. CAST.APP/PS1-derived EVs show significant enrichment of Psen1, APP, Itgax, and reduction of Wdr61, Pmpca, Aldh1a2, Calu, Anp32b, Actn4 and Ndufv2 compared to WT-derived EVs, suggesting the involvement of A{beta}-processing complex and disease-associated / neurodegenerative microglia (DAM/MGnD) in EV secretion. In addition, Itgax and Apoe, the DAM/MGnD markers, in EV show a positive correlation with Itgax and Apoe mRNA expression from brain tissue in CAST.APP/PS1 mice. These datasets indicate the significant contribution of A{beta} plaque and neurodegeneration-induced DAM/MGnD microglia for EV secretion in CAST.APP/PS1 mice and shed light on understanding the AD pathogenesis.

neuroscience↗