Molecular & Cellular Proteomics最新文献

Toxic polyglutamine (polyQ) expansions in ataxin-2 (ATXN2) trigger neurodegenerative processes, causing spinocerebellar ataxia type 2, and enhancing TAR DNA-binding protein 43-dependent pathology in amyotrophic lateral sclerosis/frontotemporal dementia. Primary disease events can be compensated transiently, delaying disease manifestation. To define potential therapy targets, here we studied how cells modify phosphoprotein signals, using preferentially affected nervous tissue from end-stage Atxn2-CAG100-Knockin mice. The spinal cord phosphoproteome revealed massive hyperphosphorylations flanking the polyQ expansion in ATXN2 and for SQSTM1 and moderate hyperphosphorylations also for amyotrophic lateral sclerosis proteins, OPTN (optineurin), UBQLN2 (ubiquilin-2), TNIP1 (TNFAIP3 interacting protein 1), and TBK1-targeted TAX1BP1. Conversely, strong hypophosphorylations of WNK1 (protein kinase with no lysine 1), SPARCL1 (secreted protein acidic and cysteine rich-like 1), and PSMD9 (proteasome 19S regulator non-ATPase assembly chaperone P27) were found. Significant enrichments of SRC-homology domain type 3-containing proteins, autophagy/endocytosis factors, and actin modulators could be explained by N-terminal, polyQ-adjacent, proline-rich motifs in ATXN2, suggesting that spinocerebellar ataxia type 2 pathogenesis is highly similar to Huntington's disease, where neurotoxicity is mediated by abnormal polyQ-proline-rich motif-SRC-homology domain type 3 interactions. Validation of protein and mRNA levels was done in mouse spinal cord and embryonic fibroblasts or patient fibroblasts after bafilomycin or arsenite treatment, observing polyQ-dependent OPTN deficiency and SQSTM1 induction impairment. Overall, this phosphoproteome profile identified and quantified the main cellular efforts in adapting autophagy pathways to the aggregation propensity of the ATXN2-N-term.

A long-standing limitation of Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS) has been the difficulty in accurately measuring amide exchange with single amide resolution. Excitation of peptides or proteins during ionization, ion transmission, or collisional activation rapidly induces intermolecular hydrogen migration, leading to a loss of the deuterium-labeled state; a term commonly known as "scrambling." Electron-based fragmentation methods in conjunction with gentle ion transmission settings can minimize scrambling but often not completely. Levels of scrambling have been shown to vary with ion transmission settings, peptide charge, and size, but the general properties that govern the susceptibility of peptides to scrambling are not well understood. Furthermore, it remains unclear whether scrambling is generally a global process or if local scrambling networks commonly exist within peptides. Here, we examine a panel of peptides using gentle electron transfer dissociation and map the activation thresholds of scrambling to define a relationship between peptide charge density and scrambling propensity. This study suggests that by and large, the scrambling process has a single activation threshold and involves all exchangeable sites within a peptide. For some peptides, the activation energy required for scrambling is surprisingly close to that of amide bond dissociation.

Across the globe, fungi are impacting the lives of millions of people through the development of infections ranging from superficial to systemic with limited treatment options. To effectively combat fungal disease, rapid and reliable diagnostic methods are required, including current methodologies using antigen detection, culturing, microscopy, and molecular tools. However, the flexibility of these platforms to diagnose infection using non-invasive methods and predict the outcome of disease are limited. In this study, we apply state-of-the-art mass spectrometry-based proteomics to perform dual perspective (i.e., host and pathogen) profiling of cryptococcal infection. Whole blood collected over a temporal scale following murine model challenged with the human fungal pathogen, Cryptococcus neoformans, detected >3000 host proteins and 160 fungal proteins. From the host perspective, temporal regulation of known immune-associated proteins, including eosinophil peroxidase and lipocalin-2, along with suppression of lipoproteins, demonstrated infection- and time-dependent host remodeling. Conversely, from the pathogen perspective, known and putative virulence-associated proteins were detected, including proteins associated with fungal extracellular vesicles and host immune modulation. We also observed and validated a new mechanism of immune system response to C. neoformans through modulation of haptoglobin. Furthermore, we assessed the predictive power of dual perspective proteome profiling toward prognostics of cryptococcal infection and report a previously undisclosed integration among virulence factor production, immune system modulation, and individual model survival. Together, our findings pose novel biomarkers of cryptococcal infection from whole blood and highlight the potential of personal proteome profiles to determine the prognosis of cryptococcal infection, a new parameter in fungal disease management.

Myopia is a growing global public health concern. Recent studies have revealed that the regulation of eye growth occurs via a complex signaling cascade, which originates in the retina and across the choroid to the sclera. Identifying key proteins and specific biological processes (BPs) in the retina, choroid, and sclera is crucial for understanding the molecular mechanisms underlying myopia development. We conducted comprehensive proteomic and phosphoproteomic analyses of the retina, choroid, and sclera from form-deprivation myopia guinea pigs using liquid chromatography-tandem mass spectrometry. Differentially expressed proteins and phosphosites were identified, followed by functional annotation and signaling pathway enrichment analyses. The expression of key proteins was assessed using Western blotting and enzyme-linked immunosorbent assay. Distinct proteomic and phosphoproteomic profiles were observed across the three tissues, with 6470, 6708, and 3236 proteins and 9613, 9416, and 3685 phosphosites in the retina, choroid, and sclera, respectively. Proteomic analysis showed that neural signal transduction was enriched in the retina, with downregulation of NTRK2, suggesting impaired neurotrophic signaling. The upregulation of SYK and BTK, along with increased NF-κB, p65, and IL-1β levels in the choroid, indicated enhanced inflammatory responses. TNNT3, TPM2, and ACTN3 were upregulated in the sclera, reflecting cytoskeletal remodeling associated with scleral expansion. Phosphoproteomic analysis indicated key roles of phosphoproteins in BPs, particularly the spliceosome signaling pathway, which was broadly involved across all three tissues. Kinase network analysis revealed PRPF4B as a key kinase for SF3B1, suggesting the potential regulation roles of RNA splicing in myopia progression. The present study systematically elucidates the proteomic and phosphoproteomic characteristics of the retina, choroid, and sclera of form-deprivation myopia in guinea pigs, highlighting significant tissue-specific BPs to myopia. The findings provide a theoretical foundation for understanding that different tissues exhibit distinct biological reactions to myopia, each through specific signaling pathways and regulatory mechanisms.

PKD1 and PKD2 are the most commonly mutated genes in autosomal dominant polycystic kidney disease (ADPKD). However, the precise roles of the encoded polycystin 1/2 (PC1 and PC2) proteins, and how their functions are disrupted in ADPKD, remain unclear. Here, we characterize the protein interaction networks of PC1 and PC2 in cycling and ciliated cells using proximity-dependent biotinylation (BioID), identifying a common set of 172 proteins that interact with the C terminus of PC1 and the full-length PC2 protein, enriched in autophagy regulators, endoplasmic reticulum tethers, endoplasmic reticulum stress proteins, and other proteins previously linked to ADPKD. Notably, we also find that PC1 specifically interacts with ciliary and lysosomal proteins, including components of the biogenesis of lysosome-related organelles complex (BLOC-1) and BLOC-one-related-complex (BORC). BLOC-1/BORC colocalizes with PC1 at lysosomes and cilia and is required for proper ciliary PC1 localization. In addition, PC1 mutant kidney cells derived from an ADPKD patient display defects in BLOC-1/BORC distribution. Renal cells depleted of PC1 exhibit abnormal lysosomal distribution, similar to those depleted of BLOC-1/BORC components. Finally, shRNA knockdown of BLOC-1/BORC components promoted cystogenesis in a 3D in vitro cyst model, and this could be attenuated by heterologous expression of the C terminus of PC1. This rich dataset thus links the BLOC-1/BORC complex to PC1 function and can be further mined for additional mechanistic insights into the PC1/2 ADPKD proteins.

Histone post-translational modifications (PTMs) play a crucial role in regulating gene expression and maintaining DNA integrity, and their aberrations are linked to various diseases, including cancer. While lysine acetylation and methylation have been extensively studied, recent research has uncovered additional PTMs that significantly contribute to chromatin structure and function. Mass spectrometry is the most effective analytical method for studying histone PTMs; however, computational limitations often restrict the analysis to common modifications. Unrestrictive search strategies have the potential to enable a more comprehensive characterization of the histone modification landscape. In this work, we systematically assess the application of unrestrictive search approaches to histone data. After evaluating the limitations of these methods, we develop a novel bioinformatics workflow, named HiP-Frag (histone PTM analysis with FragPipe), which enables the identification of 96 sites decorated with uncommon PTMs on core histones-60 of which were previously unreported-as well as 55 histone marks on linker histones, including 13 novel ones, purified from human cell lines and primary samples. The expanded histone PTM analysis enabled by this strategy is among the first to extract previously unexplored epigenetic information from mass spectrometry raw data. This approach paves the way for a facilitated and more streamlined identification of uncommon and yet unannotated histone modifications, supporting a deeper dissection of the histone code and the understanding of the potential biological role of the novel epigenetic marks.

Cholangiocarcinoma (CCA) comprises intrahepatic (iCCA) and extrahepatic (eCCA) subtypes, each exhibiting distinct molecular characteristics. Understanding these differences is critical for identifying subtype-specific therapeutic targets and advancing precision medicine. Protein glycosylation, a key post-translational modification, regulates immune evasion and metastasis, yet the glycoproteomic difference between iCCA and eCCA remains unexplored. Here we presented the first comprehensive N-glycoproteomic profile of eCCA and compared it with iCCA using a publicly available dataset. Our N-glycoproteomic analysis of paired eCCA tumors and normal adjacent tissues (NATs) identified 8372 N-glycopeptides, 3467 N-glycosites, and 2627 N-glycoproteins. Comparative analysis revealed distinct N-glycosylation signature, with eCCA exhibiting higher fucosylated glycans and iCCA showing increased sialylation. Pathway enrichment analysis of N-glycoproteins revealed a more prominent lysosome-related enrichment in eCCA, whereas pathways related to immune modulation, cytoskeletal components, and the extracellular matrix were significantly enriched in both subtypes. Immune profiling revealed an immunosuppressive microenvironment in both eCCA and iCCA, characterized by reduced natural killer cell infiltration and subtype-specific fibroblast and endothelial cell remodeling. DPM1, a glycosylation enzyme highly expressed in eCCA, was associated with tumor-specific N-glycopeptides and reduced immune cell infiltration. Its knockdown impaired cell migration, and glycoproteomic analysis implicated DPM1 in regulating adhesion, proteostasis, and immune pathways, highlighting its potential as a therapeutic target in eCCA. Our findings provide insights into N-glycosylation alterations in CCA subtypes, underscoring N-glycosylation-related mechanisms as potential biomarkers and therapeutic targets, particularly in eCCA.

Large-scale plasma proteomics studies offer tremendous potential for biomarker discovery but face significant challenges in balancing analytical depth, throughput, and cost-effectiveness. We present an optimized perchloric acid-based workflow with neutralization-PCA-N-that addresses these limitations. By introducing a neutralization step following protein precipitation, PCA-N enables direct enzymatic digestion without additional purification steps, reducing sample volume requirements to only 5 μl of plasma while maintaining deep plasma proteome coverage. The streamlined protocol allows preparation of over 10,000 samples per day using 384-well formats at costs comparable to undepleted plasma analysis (NEAT). Rigorous validation according to the recently introduced CLSI C64 guideline demonstrated that despite somewhat higher technical variability compared to NEAT, PCA-N maintained excellent biological resolution and reproducibility. We confirmed the workflow's exceptional stability through analysis of over 1700 quality control samples systematically interspersed among more than 40,000 plasma samples measured continuously over 353 days. Technical performance remained consistent across multiple instruments, sample preparation batches and nearly a year of measurements. Compared to NEAT plasma proteomics, PCA-N doubled the proteomic depth while maintaining comparable reagent costs and throughput. The minimal sample requirements, operational simplicity while using only common laboratory chemicals and exceptional scalability positions PCA-N as an attractive approach for population-level plasma proteomics, democratizing access to deep plasma proteomics analysis.

Topoisomerases are essential for resolving topological stress in DNA during key cellular processes. In human cells, six topoisomerases perform specialized yet overlapping functions to manage these challenges. To investigate their distinct and shared roles, as well as their involvement in DNA damage repair, we conducted a comprehensive analysis of the human topoisomerase-associated protein landscape. Using tandem affinity purification coupled with mass spectrometry, we mapped the protein-protein interaction networks of five human topoisomerases under both normal and stressed conditions. Our analysis identified several key interactions that may regulate topoisomerase function. Notably, TOP1 interacts with PUM3, which undergoes a similar relocalization from nucleoli to nucleoplasm following treatment with a TOP1 poison. In addition, we uncovered novel interactions of TOP3A with NSMCE4A, YTHDC2, and NDUFAF7, as well as a previously uncharacterized interaction between TOP3B and the mitochondrial membrane protein TDRKH (TDRD2). We further examined dynamic changes in these interactomes in response to TOP1 and TOP2 poisons and replication stress, distinguishing between interactions in chromatin and soluble fractions. These findings provide new insights into the regulation and functional coordination of human topoisomerases, offering potential biomarkers or therapeutic targets for topoisomerase inhibitors in cancer treatment.

Polyclonal antibodies (pAbs) represent nature's approach to robust immunity, targeting multiple sites on pathogens, but their complex mixtures have remained largely unsequenceable, limiting their therapeutic potential. While monoclonal antibodies (mAbs) dominate therapeutics because of their reproducibility, pAbs offer superior resilience against viral mutations and broader target recognition. Current pAb sequencing attempts have shown limitations, requiring germline databases or B-cell sequencing. Due to the highly variable nature of antibodies, as well as the possibility of unavailable B cells, there is a need for a purely mass spectrometry- and de novo sequencing-based solution. Here, we present PolySeq.AI, an automated de novo workflow that combines bottom-up, middle-down, and intact mass analysis, to accurately sequence pAb samples without relying on external databases. PolySeq.AI achieved >99% sequencing accuracy across all tested samples, including an mAb mixture from the HB-95 cell line and a mixture of four mAbs, with complete bottom-up coverage and strong middle-down fragment support. Importantly, recombinant antibodies produced from our de novo sequences of HB-95 antibodies retained full binding capabilities to human leukocyte antigen-I complexes, confirming the accuracy and efficacy of our pAb de novo sequencing workflow.