Comprehensive Analysis of Low Molecular Weight Serum Proteome Enrichment for Mass Spectrometric Studies

Identification of phosphorylated small ORF-encoded peptides in Hep3B cells by LC/MS/MS

Small ORF-encoded peptides (SEPs) are a class of low molecular weight proteins and peptides comprising <100 amino acids with important functions in various life activities. Although the sequence length is short, SEPs might also have post-translational modification (PTM). Phosphorylation is one of the most essential PTMs of proteins. In this work, we enriched phosphopeptides with IMAC and TiO2 materials and analyzed the phosphorylated SEPs in Hep3B cells. A total of 24 phosphorylated SEPs were identified, and 11 SEPs were coded by ncRNA. For the sequence analysis, we found that the general characteristics of phosphorylated SEPs are roughly the same as canonical proteins. Besides, two phosphorylation SEPs have the Stathmin family signature 2 motif, which can regulate the microtubule cytoskeleton. Some SEPs have domains or signal peptides, indicating their specific functions and subcellular locations. Kinase network analysis found a small number of kinases that may be a clue to the specific functions of some SEPs. However, only one-fifth of the predicted phosphorylation sites were identified by LC/MS/MS, indicating that many SEP PTMs are hidden in the dark, waiting to be uncovered and verified. This study helps expand our understanding of SEP and provides information for further SEP function investigation. SIGNIFICANCE: Small ORF-encoded peptides (SEPs) are important in various life activities. Although the sequence length is short (<100AA), SEPs might also have post-translational modification (PTM). Phosphorylation is one of the most essential PTMs of proteins. We enriched phosphopeptides and analyzed the phosphorylated SEPs in Hep3B cells. That is the first time to explore the PTM of SPEs systematically. Kinase network analysis found a small number of kinases that may be a clue to the specific functions of SEPs. More SEP PTMs are hidden in the dark and waiting to be uncovered and verified. This study helps expand our understanding of SEP and provides information for further SEP function investigation.

V-ATPase subunit C 1 and IKBIP as tandem prospective biomarkers for diabetic nephropathy

AIMS

The appearance of low-molecular-weight (LMW) protein in the urine indicates any disruption in the structural integrity of the glomerular capillary wall; therefore, the presence of LMW protein may be a potential predictive marker for DN.

METHODS

The urine proteomic profiling of T2DM patients (n = 94) and control group (n = 32) was compared by liquid chromatography-tandem mass spectrometry, and the untargeted LMW protein was identified by Progenesis Q1 For Proteomics v4.2.

RESULTS

A total of 73 LMW proteins were identified and quantified, of which, 32 proteins were found to be altered significantly (p < 0.05). Further analysis with heat maps identified two potential proteins with the highest folding alterations in urine. V-ATPase subunit C 1 abundance was significantly inversely correlated with microalbumin and significantly decreased in urine, whereas increased IKBIP was positively correlated with microalbumin. The level of those proteins was significantly different among the control, T2DM, and DN groups, implying an association with the progression of DN.

CONCLUSIONS

The present findings of our study indicate that the decreasing V-ATPase subunit C 1 together with increasing IKBIP in urine, were found to be closely associated with DN complications and signifying their value as biomarkers for predicting the risk of DN at initial diagnosis.

A novel device for swift and efficient CD44 protein digestion of pipette tips in human serum

For molecular diagnostics in modern biomedical research, electrospray ionisation mass spectrometry (ESI-MS) based on proteome profiling is important. Now a days, sample preparation such as proteolysis and protein extraction remain incredibly challenging and inefficient. Recent sample-preparation methods based on micro tips show promising results toward the aim "a proteome in an hour". Proteolysis at the tip, is still infrequently observed and does not represent the processing of complex bio-samples. In this study, we outline a unique technique for detecting and extracting human serum CD44 biomarkers by ligand-protein interactions. This method employs macropores silica particles (MPSP) or (MOSF) modified with hyaluronic acid (HA). In order to assist in the profile of the human serum proteome, we limitations of immunoassays for rapid and multimodal proteolysis. For effective in situ proteolysis, in micropipette tips, MPSP were designed as nanoreactors with variable pore size and surface chemistry. In MS-based bottom-up proteome analysis, the device as-built demonstrated favourable sensitivity (LOD of 0.304 ± 0.007 ng/mL and LOQ of 0.973 ± 0.054 ng/mL), selectivity, durability (at -20 °C for 2 months), reuse (at least 10 times), and minimal memory impact. In addition, we examined into specific surface chemistries of nanoparticles for the absorption of proteins in serum and profiled the HA-binding serum proteome, setting a new preliminary benchmark for future databases. Our study not only helped establish a new platform for extracting/detection of CD44 and identifying the HA-binding proteome, but it also offered design recommendations for ligand affinity-based techniques for the antibody-free study of serum biomarkers with a view towards diagnostic applications.

Serum metabolic profile and metabolome genome-wide association study in chicken

BACKGROUND

Chickens provide globally important livestock products. Understanding the genetic and molecular mechanisms underpinning chicken economic traits is crucial for improving their selective breeding. Influenced by a combination of genetic and environmental factors, metabolites are the ultimate expression of physiological processes and can provide key insights into livestock economic traits. However, the serum metabolite profile and genetic architecture of the metabolome in chickens have not been well studied.

RESULTS

Here, comprehensive metabolome detection was performed using non-targeted LC-MS/MS on serum from a chicken advanced intercross line (AIL). In total, 7,191 metabolites were used to construct a chicken serum metabolomics dataset and to comprehensively characterize the serum metabolism of the chicken AIL population. Regulatory loci affecting metabolites were identified in a metabolome genome-wide association study (mGWAS). There were 10,061 significant SNPs associated with 253 metabolites that were widely distributed across the entire chicken genome. Many functional genes affect metabolite synthesis, metabolism, and regulation. We highlight the key roles of TDH and AASS in amino acids, and ABCB1 and CD36 in lipids.

CONCLUSIONS

We constructed a chicken serum metabolite dataset containing 7,191 metabolites to provide a reference for future chicken metabolome characterization work. Meanwhile, we used mGWAS to analyze the genetic basis of chicken metabolic traits and metabolites and to improve chicken breeding.

Surface-Enhanced Raman Analysis of Uric Acid and Hypoxanthine Analysis in Fractionated Bodily Fluids

In recent years, the disease burden of hyperuricemia has been increasing, especially in high-income countries and the economically developing world with a Western lifestyle. Abnormal levels of uric acid and hypoxanthine are associated with many diseases, and therefore, to demonstrate improved methods of uric acid and hypoxanthine detection, three different bodily fluids were analysed using surface-enhanced Raman spectroscopy (SERS) and high-performance liquid chromatography (HPLC). Gold nanostar suspensions were mixed with series dilutions of uric acid and hypoxanthine, 3 kDa centrifugally filtered human blood serum, urine and saliva. The results show that gold nanostars enable the quantitative detection of the concentration of uric acid and hypoxanthine in the range 5-50 μg/mL and 50-250 ng/mL, respectively. The peak areas of HPLC and maximum peak intensity of SERS have strongly correlated, notably with the peaks of uric acid and hypoxanthine at 1000 and 640 cm^-1, respectively. The r² is 0.975 and 0.959 for uric acid and hypoxanthine, respectively. Each of the three body fluids has a number of spectral features in common with uric acid and hypoxanthine. The large overlap of the spectral bands of the SERS of uric acid against three body fluids at spectra peaks were at 442, 712, 802, 1000, 1086, 1206, 1343, 1436 and 1560 cm^-1. The features at 560, 640, 803, 1206, 1290 and 1620 cm^-1 from hypoxanthine were common to serum, saliva and urine. There is no statistical difference between HPLC and SERS for determination of the concentration of uric acid and hypoxanthine (p > 0.05). For clinical applications, 3 kDa centrifugal filtration followed by SERS can be used for uric acid and hypoxanthine screening is, which can be used to reveal the subtle abnormalities enhancing the great potential of vibrational spectroscopy as an analytical tool. Our work supports the hypnosis that it is possible to obtain the specific concentration of uric acid and hypoxanthine by comparing the SER signals of serum, saliva and urine. In the future, the analysis of other biofluids can be employed to detect biomarkers for the diagnosis of systemic pathologies.

Simultaneous Quantification of Apolipoprotein C-III O-Glycoforms by Protein-MRM

Apolipoprotein C-III (APOC-III) regulates triglyceride levels, associated with a risk of cardiovascular disease. One gene generates several proteoforms, each with a different molecular mass and a unique function. Unlike peptide multiple reaction monitoring (MRM), protein-MRM without digestion is required to analyze clinically relevant individual proteoforms. We developed a protein-MRM method without digestion to individually quantify APOC-III proteoforms in human serum. We optimized the protein-MRM method following 60% acetonitrile extraction with C18 filtration. Bovine serum and myoglobin served as supporting cushions and the internal standard during sample preparation, respectively. Furthermore, we evaluated the LOD, lower limit of quantification, linearity, accuracy, and precision. Good correlation compared with turbidimetric immunoassay (TIA) and peptide-MRM was observed using 30 clinical sera. Individual APOC-III O-glycoforms were identified by top-down proteomics and simultaneously quantified using the protein-MRM method. The sum abundance of APOC-III proteoforms was significantly correlated with TIA and peptide-MRM. Our protein-MRM method provides an affordable and rapid quantification of potential disease-specific proteoforms. Precise quantification of each proteoform allows investigators to identify novel biological roles potentially related to cardiovascular disease or novel biomarkers. We expect our protein-oriented method to be more clinically useful than antibody-based immunoassays and peptide-oriented MRM analysis, especially for quantification of a biomarker proteoform with certain post-translational modifications.

Engineering bone-forming callus organoid implants in a xenogeneic-free differentiation medium

The field of tissue engineering aspires to provide clinically relevant solutions for patients through the integration of developmental engineering principles with a bottom-up manufacturing approach. However, the manufacturing of cell-based advanced therapy medicinal products is hampered by protocol complexity, lack of non-invasive critical quality controls, and dependency on animal-derived components for tissue differentiation. We investigate a serum-free, chemically defined, xeno- and lipid-free chondrogenic differentiation medium to generate bone-forming callus organoids. Our results show an increase in microtissue homogeneity during prolonged differentiation and the high quality of in vivo bone-forming organoids. The low protein content of the culture medium potentially allows for the monitoring of relevant secreted biomarkers as (critical) quality attributes. Together, we envisage that this xeno- and lipid-free chondrogenic medium is compatible with industrial scale-up and automation while facilitating the implementation of non-invasive imaging and the use of quality control parameters based on secreted biomarkers.

Improved profiling of low molecular weight serum proteome for gastric carcinoma by data-independent acquisition

Low molecular weight proteins (LMWPs) in the bloodstream participate in various biological processes and are closely associated with disease status, whereas identification of serous LMWPs remains a great technical challenge due to the wide dynamic range of protein components. In this study, we constructed an integrated LMWP library by combining the LMWPs obtained by three enrichment methods (50% ACN, 20% ACN + 20 mM ABC, and 30 kDa) and their fractions identified by the data-dependent acquisition method. With this newly constructed library, we comprehensively profiled LMWPs in serum using data-independent acquisition and reliably achieved quantitative results for 75% serous LMWPs. When applying this strategy to quantify LMWPs in human serum samples, we could identify 405 proteins on average per sample, of which 136 proteins were with a MW less than 30 kDa and 293 proteins were with a MW less than 65 kDa. Of note, pre- and post-operative gastric carcinoma (GC) patients showed differentially expressed serous LWMPs, which was also different from the pattern of LWMP expression in healthy controls. In conclusion, our results showed that LMWPs could efficiently distinguish GC patients from healthy controls as well as between pre- and post-operative statuses, and more importantly, our newly developed LMWP profiling platform could be used to discover candidate LMWP biomarkers for disease diagnosis and status monitoring.

Separation of Serum and Plasma Proteins for In-Depth Proteomic Analysis

There are probably no biological samples that did more to spur interest in proteomics than serum and plasma. The belief was that comparing the proteomes of these samples obtained from healthy and disease-affected individuals would lead to biomarkers that could be used to diagnose conditions such as cancer. While the continuing development of mass spectrometers with greater sensitivity and resolution has been invaluable, the invention of strategic strategies to separate circulatory proteins has been just as critical. Novel and creative separation techniques were required because serum and plasma probably have the greatest dynamic range of protein concentration of any biological sample. The concentrations of circulating proteins can range over twelve orders of magnitude, making it a challenge to identify low-abundance proteins where the bulk of the useful biomarkers are believed to exist. The major goals of this article are to (i) provide an historical perspective on the rapid development of serum and plasma proteomics; (ii) describe various separation techniques that have made obtaining an in-depth view of the proteome of these biological samples possible; and (iii) describe applications where serum and plasma proteomics have been employed to discover potential biomarkers for pathological conditions.