Molecular & Cellular Proteomics最新文献

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.

Emerging evidence shows that translation from noncanonical ORFs produces a diverse set of biologically active proteins. These ORFs reside in 5' and 3' UTRs, long noncoding RNAs, overlapping frames within annotated genes (dual coding), or pseudogenes and can initiate at non-AUG start codons. The resulting products, variously termed microproteins, small proteins, small ORF-encoded peptides, and alternative proteins, modulate fundamental cellular processes, including metabolic flux and epigenetic regulation. We consolidate these entities under the umbrella of the ghost proteome, a functional proteome arising from the genome's presumed "dark matter." This concept is distinct from the dark proteome, which refers to regions of canonical proteins lacking structural, functional, or experimental annotation and is not necessarily derived from noncanonical loci. Recognizing the ghost proteome expands the boundary of what is considered protein coding, demands harmonized nomenclature and database integration, and motivates systematic discovery and functional characterization. By reframing sequences once dismissed as noncoding or "junk," the ghost proteome compels a re-evaluation of genome annotation and reveals new opportunities to interrogate biology and disease.

Variants in the human β-N-acetylglucosamine (O-GlcNAc) transferase (OGT) gene give rise to an intellectual disability (ID) syndrome termed OGT congenital disorder of glycosylation (OGT-CDG). The mechanisms by which loss of OGT and/or protein O-GlcNAcylation leads to this syndrome are not understood, but symptoms associated with the syndrome suggest a developmental origin. Here, we establish and characterize two lines of mouse embryonic stem cells carrying different patient mutations and show that these mutations lead to disrupted O-GlcNAc homeostasis. Using quantitative proteomics on these cells in the pluripotent state, we identify candidate proteins/pathways that could underpin this syndrome. In addition to the increased levels of OGT and decreased levels of OGA reflecting disrupted O-GlcNAc homeostasis, we find that expression of the ID gene Zscan4 is upregulated. This is associated with increased levels of the OGT:10 Eleven (Tet) - protein complex that regulates DNA methylation and Zscan4 expression. These data uncover a potential mechanism contributing to the developmental aspects of OGT-CDG.

Tetrahymena thermophila (T. thermophila), a well-established model organism, has been instrumental in advancing our understanding of evolutionarily conserved biological processes. A key biological feature of this unicellular eukaryote is its life cycle strategy, marked by three major stages: growth, starvation, and conjugation. Despite its prominence as a model system, functional genomic studies of T. thermophila have been constrained by limitations in the accuracy and completeness of gene discovery since the initial genome assembly in 2006. To address this gap, we performed a multi-stage proteogenomic analysis, combining genomic sequencing with high-resolution mass spectrometry (MS)-based proteomic profiling across 10 strategically selected life cycle states. This integrative approach enabled a comprehensive reassessment of gene discovery, leading to the validation of 24,319 previously predicted protein-coding genes and the identification of 383 novel genes. Additionally, our investigation systematically identified a diverse repertoire of post-translational modifications (PTMs), including 7123 modification sites distributed across 4705 proteins. These PTMs are postulated to exert critical regulatory functions during developmental phase transitions. Collectively, this work not only refines the T. thermophila gene catalog and enhances its utility as a robust genetic toolkit for advancing biological research but also offers new mechanistic insights into the molecular regulation of its life cycle progression.