Quantitative phosphoproteomic analysis of soft and firm grass carp muscle

Correlation analysis of phosphorylation of myofibrillar protein and muscle quality of tilapia during storage in ice

In this study, the correlation between protein phosphorylation and deterioration in the quality of tilapia during storage in ice was examined by assessing changes in texture, water-holding capacity (WHC), and biochemical characteristics of myofibrillar protein throughout 7 days of storage. The hardness significantly decreased from 471.50 to 252.17 g, whereas cooking and drip losses significantly increased from 26.5% to 32.6% and 2.9% to 9.1%, respectively (P < 0.05). Myofibril fragmentation increased, while myofibrillar protein sulfhydryl content and Ca2+-ATPase activity decreased from 119.33 to 89.29 μmol/g prot and 0.85 to 0.46 μmolPi/mg prot/h, respectively (P < 0.05). Correlation analysis revealed that the myofibrillar protein phosphorylation level was positively correlated with hardness and Ca2+-ATPase activity but negatively correlated with WHC. Myofibrillar protein phosphorylation affects muscle contraction by influencing the dissociation of actomyosin, thereby regulating hardness and WHC. This study provides novel insights for the establishment of quality control strategies for tilapia storage based on protein phosphorylation.

Quantitative Phosphoproteomics Analysis Reveals the Protective Mechanism of Chlorogenic Acid on Immunologically Stressed Broiler Meat Quality

Modern poultry production is stressful for the birds, and this stress is recognized as a major cause of inferior meat quality. Chlorogenic acid (CGA), a plant phenolic acid, has excellent antioxidant and anti-inflammatory properties. The antioxidant capacity and phosphoproteomics of immunologically stressed broiler breast muscle were assessed to elucidate the mechanism of the beneficial effects of CGA on meat quality. Dietary CGA decreased drip and cooking loss, postmortem pH and antioxidant capacity of breast muscle from stressed broilers, and increased MyHC-I mRNA levels. Quantitative phosphoproteomics revealed that CGA supplementation downregulated the phosphorylation of myofibrillar proteins, glycolytic enzymes, and endoplasmic reticulum proteins involved in homeostasis, which contributed to improving the meat quality of broilers. Moreover, 14 phosphorylation sites (e.g., P13538-Ser1236 and F1NN63-Ser117) in 13 phosphoproteins were identified as key regulators of processes related to broiler meat quality. Together, these findings provide novel regulatory targets and nutritional strategies for improving the stressed broiler meat quality.

Effects of Five Lipid Sources on Growth, Hematological Parameters, Immunity and Muscle Quality in Juvenile Largemouth Bass (Micropterus salmoides)

This study investigated the effects of fish oil (FO), soybean oil (SO), rapeseed oil (RO), peanut oil (PO) and lard oil (LO) on growth, immunity and muscle quality in juvenile largemouth bass. After 8 weeks, the results showed that FO and RO could increase weight gain and serum alkaline phosphatase and apelin values compared with LO (p < 0.05). Except lower crude lipid contents, higher amounts of n-3 polyunsaturated fatty acids (15.83% and 14.64%) were present in the dorsal muscle of the FO and RO groups. Meanwhile, FO and RO could heighten mRNA levels of immune defense molecules (lysozyme, hepcidin, and transforming growth factor β1) compared with PO (p < 0.05). While SO could increase potential inflammatory risk via rising counts of white blood cells, platelets, neutrophils and monocytes, and mRNA levels of interleukins (IL-1β, IL-8, IL-12 and IL-15), FO and RO could improve hardness, chewiness and springiness through increasing amounts of hydroxyproline, collagen and lysyl oxidase, and mRNA levels of collagen 1α2 and prolyl hydroxylase in the fish dorsal muscle. Moreover, FO and RO could improve firmness through increasing glycogen and glycogen synthase 1 levels when compared with LO (p < 0.05). Therefore, these results could provide dietary lipid source references during the feeding process of adult largemouth bass.

Restoration of energy homeostasis under oxidative stress: Duo synergistic AMPK pathways regulating arginine kinases

Rapid depletion of cellular ATP can occur by oxidative stress induced by reactive oxygen species (ROS). Maintaining energy homeostasis requires the key molecular components AMP-activated protein kinase (AMPK) and arginine kinase (AK), an invertebrate orthologue of the mammalian creatine kinase (CK). Here, we deciphered two independent and synergistic pathways of AMPK acting on AK by using the beetle Tribolium castaneum as a model system. First, AMPK acts on transcriptional factor forkhead box O (FOXO) leading to phosphorylation and nuclear translocation of the FOXO. The phospho-FOXO directly promotes the expression of AK upon oxidative stress. Concomitantly, AMPK directly phosphorylates the AK to switch the direction of enzymatic catalysis for rapid production of ATP from the phosphoarginine-arginine pool. Further in vitro assays revealed that Sf9 cells expressing phospho-deficient AK mutants displayed the lower ATP/ADP ratio and cell viability under paraquat-induced oxidative stress conditions when compared with Sf9 cells expressing wild-type AKs. Additionally, the AMPK-FOXO-CK pathway is also involved in the restoration of ATP homeostasis under oxidative stress in mammalian HEK293 cells. Overall, we provide evidence that two distinct AMPK-AK pathways, transcriptional and post-translational regulations, are coherent responders to acute oxidative stresses and distinguished from classical AMPK-mediated long-term metabolic adaptations to energy challenge.

N-glycosylomic analysis provides new insight into the molecular mechanism of firmness of fish fillet

Post-translational protein modification affects muscle physiochemistry. To understand the roles of N-glycosylation in this process, the muscle N-glycoproteomes of crisp grass carp (CGC) and ordinary grass carp (GC) were analyzed and compared. We identified 325 N-glycosylated sites with the NxT motif, classified 177 proteins, and identified 10 upregulated and 19 downregulated differentially glycosylated proteins (DGPs). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes annotations revealed that these DGPs participate in myogenesis, extracellular matrix content formation, and muscle function. The DGPs partially accounted for the molecular mechanisms associated with the relatively smaller fiber diameter and higher collagen content observed in CGC. Though the DGPs diverged from the identified differentially phosphorylated proteins and differentially expressed proteins detected in previous study, they all shared similar metabolic and signaling pathways. Thus, they might independently alter fish muscle texture. Overall, the present study provides novel insights into the mechanisms underlying fillet quality.

Phosphoproteomic insight into the changes in structural proteins of muscle architecture associated with texture softening of grass carp (Ctenopharyngodon idella) fillets during chilling storage

Texture is an important sensory attribute of fish affected by modifications of structural proteins in muscle architecture. To investigate the changes in protein phosphorylation during texture softening of fish, the proteins of grass carp muscle after chilling storage of 0 day and 6 days were compared by phosphoproteomics, and their association with texture was analyzed. Totally 1026 unique phosphopeptides on 656 phosphoproteins were identified as differential. They were mainly classified as intracellular myofibril and cytoskeleton, and extracellular matrix, of which the molecular function and biological process were binding into supramolecular assembly and myofilament contraction. The concomitant dephosphorylation of kinases and assembly regulators indicated dephosphorylation and disassembly tendency of sarcomeric architecture. Correlation analysis defined the relation between texture and dephosphorylation of myosin light chain, actin, collagen and cytoskeleton. This study revealed that protein phosphorylation may affect the texture of fish muscle through regulating sarcomeric assembly of structural proteins in muscle architecture.

Mechanisms of Mitochondrial Apoptosis-Mediated Meat Tenderization Based on Quantitative Phosphoproteomic Analysis

This study investigates the mechanism of phosphorylation in the regulation of apoptosis-mediated meat tenderization during postmortem aging. The results found that the pork muscle exhibited apoptotic potential at early postmortem (48 h) and showed more tenderness at late postmortem, as evidenced by the increase in mitochondrial membrane permeability (MMP), Ca2+ level, reactive oxygen species (ROS) content, and caspases activity at 0 h to 48 h, and decreases in ATP level at 0 h to 24 h and shear force at 12 h to 120 h (p < 0.05). Phosphoproteomic analysis revealed that phosphorylation regulated apoptosis by modulating ATP and calcium bindings as well as apoptotic signaling, which occurred within early 12 h and mainly occurred at 12 h to 48 h postmortem. Moreover, differential expression of phosphoproteins demonstrated that phosphorylation regulated oxidative stress-induced apoptosis and rigor mortis, thereby promoting the development of meat tenderness. Our results provide insights into the roles of phosphorylation in various physiological processes that affect meat tenderness.

Comparative phosphoproteomic provides insights into meat quality differences between slow- and fast-growing broilers

The selection of broilers for augmented growth rate and breast yield has been accompanied by deterioration in meat quality. To characterise the meat quality differences between slow- (SG) and fast-growing broilers (FG), Xueshan and Ross 308 chickens were employed to determine the mechanisms causing these differences. SG meat was found to display more redness and yellowness, higher shear force, pH_24h, and protein content, with lower intramuscular fat (IMF) content than FG meat. Further, based on comparative phosphoproteomic analysis (SG/FG), upregulated phosphorylated myofibrillar proteins resulted in larger fibres, which contributed to lower pressing loss and tenderness. The phosphoproteins of glycolytic enzymes, phosphorylase kinases, and calcium-related proteins were significantly downregulated, which reduced the acidity of the meat. SLC7A5 at Ser21, MRC2 at Ser1359 and CRAT at Ser341, AUP1 at Ser377 positively affected protein and IMF deposition, respectively. Together, these phosphoproteins elicit vital information for the genetic improvement of chicken meat quality.

Identification and characterization of phosphoproteins in the striated and smooth adductor muscles of Yesso scallop Patinopecten yessoensis

Many proteins are known to be phosphorylated, affecting important regulatory factors of muscle quality in the aquatic animals. The striated and smooth adductor muscles of Yesso scallop Patinopecten yessoensis were used to investigate muscle texture and identify phosphoproteins by histological methods and phosphoproteomic analysis. Our present study reveals that muscle fiber density is in relation to meat texture of the striated and smooth adductor muscles. The phosphoproteomic analysis has identified 764 down-regulated and 569 up-regulated phosphosites on 743 phosphoproteins in the smooth muscle compared to the striated part. The identification of unique phosphorylation sites in glycolytic enzymes may increase the activity of glycolytic enzymes and the rate of glycolysis in the striated adductor muscle. The present findings will provide new evidences on the role of muscle structure and protein phosphorylation in scallop muscle quality and thus help to develop strategies for improving meat quality of scallop products.

Textural quality, growth parameters and oxidative responses in Nile tilapia (Oreochromis niloticus) fed faba bean water extract diet

Texture is one of the key quality attributes used in the fresh and processed fish industry to assess product quality and consumer acceptability. To improve the textural quality of tilapia, we formulated the expanded pellet diet (EPD) and pellet diet (PD), both containing faba bean (Vicia faba, FB) water extract, a previously reported potential aquafeed additive to increase flesh texture. The common diet was used as a control. After Nile tilapia (Oreochromis niloticus) were fed three kinds of experimental diet for 120 days, muscle textural quality, growth parameters, oxidative response and immune parameters were analyzed. The results showed that there was no significant difference in the growth parameters between the three groups (P > 0.05). The highest measure of textural quality (hardness and chewiness) was found for the PD group, followed by the EPD and the control (P < 0.05). Less oxidative damage to the hepatopancreas and intestine was found in the EPD compared with the PD group, as demonstrated by the decreased levels of reactive oxygen species and increased levels of nicotinamide adenine dinucleotide and intestinal digestive enzyme activity (amylase and lipase). Taken together, this study highlights the potential usefulness in commercial settings of FB water extract for improving the textural quality of tilapia, and EPD containing faba bean water extract could be more advanced substitute for faba bean in tilapia culture in term of both effectiveness in textural quality improvement and health status enhancement compared with PD.

Phosphorylated Protein Levels in Animal-Sourced Food Muscles Based on Fe3+ and UV/Vis Spectrometry

Protein phosphorylation, a post-translational modification of proteins, is important in biological regulation. The quantity of phosphorylated proteins is a key requirement for the quality change of animal muscle foods. In the present study, a new approach to quantify phosphorylated proteins and/or peptides was developed based on ferric ions (Fe³⁺) and UV/vis spectrometry. This method is proved to be ultra-effective in discriminating phosphopeptides and non-phosphopeptides with the assistance of Fe³⁺. The protocol of extracting proteins with 0.1% trifluoroacetic acid (TFA) solution from animal muscle samples coupled with Fe³⁺ was verified by using an artificial mixture of peptides with different phosphorylation sites and was successfully used to characterize the phosphorylation quantity in the samples via UV/vis spectrometry. A peptide with one phosphorylated site was taken as a reference standard and successfully utilized for the absolute quantification of phosphorylated proteins in caprine muscles during frozen storage and in fish muscle food samples. This present study paves a new way for the evaluation of phosphorylated protein quantitative levels in bio-samples.

Organ-Based Proteome and Post-Translational Modification Profiling of a Widely Cultivated Tropical Water Fish, Labeo rohita

Proteomics has enormous applications in human and animal research. However, proteomic studies in fisheries science are quite scanty particularly for economically important species. Few proteomic studies have been carried out in model fish species, but comprehensive proteomics of aquaculture species are still scarce. This study aimed to perform a comprehensive organ-based protein profiling of important tissue samples for one of the most important aquaculture species,Labeo rohita.Deep proteomic profiling of 17 histologically normal tissues, blood plasma, and embryo provided mass-spectrometric evidence for 8498 proteins at 1% false discovery rate that make up about 26% of the total annotated protein-coding sequences in Rohu. Tissue-wise expression analysis was performed, and the presence of several biologically important proteins was also verified using a targeted proteomic approach. We identified the global post-translational modifications (PTMs) in terms of acetylation (N-terminus and lysine), methylation (N-terminus, lysine, and arginine), and phosphorylation (serine, threonine, and tyrosine) to present a comprehensive proteome resource. An interactive web-based portal has been developed for an overall landscape of protein expression across the studied tissues of Labeo rohita (www.fishprot.org). This draft proteome map of Labeo rohita would advance basic and applied research in aquaculture to meet the most critical challenge of providing food and nutritional security to an increasing world population.

Quantitative phosphoproteomic analysis unveil the effect of marketable ages on meat quality in geese

The quality of poultry goose meat is closely related to its marketable ages, with meat quality varying with increasing marketable age. Geese of two marketable ages (70-day and 120-day) were selected to understand the mechanisms behind this effect. Darker and redder meat; chewier and higher water-holding capacity (WHC) as well as greater protein and intramuscular fat (IMF) content were observed in the breast muscle (BM) of 120-day-old geese as compared to 70-day-old geese. Quantitative phosphoproteomics revealed up-regulated phosphorylated myofibrillar proteins and glycolytic enzymes in 120BM contributed to chewier meat with higher WHC. Redder meat might be attributed to phosphorylated mitochondrial proteins interacting with glycolytic enzymes in energy metabolism. Additionally, phosphorylation of PLIN1 and PERM1 might positively affect IMF deposition. Taken together, these data provided a phosphoproteomics perspective for the effect of marketable ages on meat quality and a theoretical strategy for improving meat quality in geese of younger marketable age.

Comparative Phosphoproteomics Reveals a Role for AMPK in Hypoxia Signaling in Testes of Oriental River Prawn (Macrobrachium nipponense)

Hypoxia is one of the major stresses in aquaculture animals. Recently, we reported that hypoxia disrupts the endocrine system and inhibits testicular function of oriental river prawns (Macrobrachium nipponense), but the molecular mechanism of testes responded to hypoxia remains largely unknown. In the present study, we aimed to integrate whole phosphoproteomic profiles of hypoxia-treated testes of the oriental river prawn (Macrobrachium nipponense). We successfully isolated sperm cells and evaluated the mitochondrial morphology and function using laser confocal microscopy, flow cytometry, and biochemical analyses. Quantitative proteomics identified 117 differentially abundant phosphorylated proteins, and these proteins are mainly involved in the pathways related to cellular processes, including autophagy, apoptosis, and the FoxO signaling pathway. Protein-protein interaction analysis clustered these phosphoproteins into three groups, many of which have been suggested to impact carbohydrate metabolism, autophagy, and signal regulation in testes. Western blotting confirmed that phosphorylated proteins including AMPK, ULK1, and TP53 (of the AMPK pathway) may contribute to testicular dysfunction caused by hypoxia. Further, we investigated the potential roles of AMP-activated protein kinase (AMPK)'s in testes mitochondrial autophagy and apoptosis in M. nipponense as induced by hypoxia. Simultaneous knockdown of AMPKα in sperm cells led to a decrease in FOXO3a phosphorylation at Ser413, upregulation of caspase-3 and caspase-9 activities, and an increased apoptosis rate. These results improve our understanding of hypoxia-induced energy metabolism disorders in the testes of M. nipponense.

Slight Increases in Salinity Improve Muscle Quality of Grass Carp (Ctenopharyngodon idellus)

Fish muscle quality is an important parameter in the aquaculture industry. In this study, we analyzed and compared the muscle quality of grass carp (Ctenopharyngodon idellus) cultured at salinities of 0‰, 3‰, and 6‰ (GC0, GC3, GC6). There was no significant difference in crude protein and crude fat content of muscle between GC0 and GC3. Crude fat was significantly lower in GC6 compared to the other groups. GC3 and GC6 had higher hydroxyproline content, which suggested that these groups had higher collagen content. GC3 and GC6 had higher contents of free amino acids and umami amino acids than GC0, but there was no significant difference in sweet or sour amino-acid content among groups. GC3 and GC6 had better texture properties, including hardness, gumminess, chewiness, resilience, and springiness, than GC0. GC3 had the highest water-holding capacity among the groups. As the salinity increased, the diameter of muscle fibers decreased and the sarcolemma showed a thickening trend. These results suggest that a slight increase in salinity (i.e., 3‰) can effectively improve the muscle quality of grass carp.