Titin, the largest known protein in the body expressed in three isoforms (N2A, N2BA and N2B), is essential for muscle structure, force generation, conduction and regulation. Since the 1950s, muscle contraction mechanisms have been explained by the sliding filament theory involving thin and thick muscle filaments, while the contribution of cytoskeleton in force generation and conduction was ignored. With the discovery of insoluble protein residues and large molecular weight proteins in muscle fibers, the third myofilament, titin, has been identified and attracted a lot of interests. The development of single molecule mechanics and gene sequencing technology further contributed to the extensive studies on the arrangement, structure, elastic properties and components of titin in sarcomere. Therefore, this paper reviews the structure, isforms classification, elastic function and regulatory factors of titin, to provide better understanding of titin.
Connectin/genetics* ; Muscle Proteins/metabolism* ; Protein Isoforms/genetics* ; Sarcomeres/metabolism* ; Muscle Fibers, Skeletal/metabolism*

Wnt5a is a secreted Wnt ligand that plays a critical role in cellular pathways and inflammatory diseases. The WNT5A gene encodes two protein isoforms, Wnt5a-long and Wnt5a-short, which differ based on different promoter methylation and have distinct functions. However, the mechanisms of the promoter methylation are unclear. Depending on the extent of promoter methylation, Wnt5a exerts both anti-inflammatory and pro-inflammatory effects in inflammatory diseases, which may be involved in different Wnt5a isoforms. Therefore, the Wnt5a isoforms may be potential diagnostic markers for inflammatory diseases and the mechanisms of the WNT5A gene promoter methylation need to be further investigated.
DNA Methylation ; Wnt-5a Protein ; Promoter Regions, Genetic ; Protein Isoforms/genetics*

Vascular endothelial growth factor-A (VEGF-A) is a critical angiogenic factor which is mainly secreted from podocytes and epithelial cells in kidney and plays an important role in renal pathophysiology. In recent years, functions of different isoforms of VEGF-A and the new secretion approach via extracellular vesicles (EVs) have been identified. Thus, further understanding are needed for the role of VEGF-A and its isoforms in renal injury and repair. In this review, we summarized the expression, secretion and regulation of VEGF-A, its biological function, and the role of different isoforms of VEGF-A in the development of different renal diseases. Meanwhile, the research progress of VEGF-A as diagnostic marker and therapeutic target for renal diseases were discussed.
Humans ; Kidney/metabolism* ; Kidney Diseases ; Protein Isoforms/metabolism* ; Vascular Endothelial Growth Factor A/physiology*

OBJECTIVE: To explore the clinical value of serum isoform [-2] proprostate-specific antigen (p2PSA) and its derivatives %p2PSA and prostate health index (PHI) in predicting aggressive prostate cancer (PCa). METHODS: The pre-operation serum and basic clinical data of 322 patients with PCa (including 143 patients diagnosed with PCa by transrectal ultrasound-guided prostate biopsy and 179 patients undergoing radical prostatectomy) in Peking University First Hospital were collected from August 2015 to May 2018. Serum total prostate-specific antigen (tPSA), free prostate antigen (fPSA) and fPSA/tPSA (f/t) and the p2PSA level of all these patients were measured on automatic immune analyzers DxI800, and then %p2PSA and PHI were calculated. The prostate pathologic result was considered as the gold standard to evaluate the Gleason score of the patients with PCa. Receiver operator curves (ROC) were used to assess the ability of p2PSA, %p2PSA and PHI to predict aggressive PCa (pathologic Gleason score≥7) compared with those traditional markers tPSA, fPSA and f/t. RESULTS: Among these patients, the p2PSA, %p2PSA and PHI median levels were significantly higher in patients with pathologic Gleason score≥7 than those with Gleason score<7 (p2PSA: 30.22 ng/L vs. 18.33 ng/L; %p2PSA: 2.50 vs. 1.27; PHI: 91.81 vs. 35.44; all P<0.01). The area under curve (AUC) of %p2PSA and PHI (0.770, 0.760) in predicting Gleason score≥7 were higher than those of the traditional indicators tPSA, fPSA and f/t (AUC were 0.648, 0.536 and 0.693, respectively). Among those patients diagnosed with PCa by transrectal ultrasound-guided prostate biopsy, the AUC of %p2PSA and PHI (AUC were 0.808 and 0.801, respectively) in predicting Gleason score≥7 were higher than those of the traditional indicators tPSA, fPSA and f/t (AUC were 0.729, 0.655 and 0.665 respectively). Among those patients undergoing radical prostatectomy, PHI and %p2PSA also had the trend of higher predictive value than those of the traditional indicators. The AUC of %p2PSA and PHI were 0.798 and 0.744, respectively while the AUC of tPSA, fPSA and f/t were 0.625, 0.507 and 0.697, respectively. CONCLUSION Compared with traditional markers tPSA, fPSA and f/t, %p2PSA and PHI had much higher predictive value for aggressive PCa, which may help clinicians to evaluate the therapeutic regime and make more appropriate management plan for the patients.
Humans ; Male ; Neoplasm Grading ; Prostate-Specific Antigen ; Prostatectomy ; Prostatic Neoplasms ; Protein Isoforms ; ROC Curve

Peroxiredoxins (Prxs) are antioxidant enzymes that protect cells from oxidative stress by reducing intracellular accumulation of reactive oxygen species (ROS). In mammalian cells, the six Prx isoforms are ubiquitously expressed in diverse intracellular locations. They are involved in the regulation of various physiological processes including cell growth, differentiation, apoptosis, immune response and metabolism as well as intracellular ROS homeostasis. Although there are increasing evidences that Prxs are involved in carcinogenesis of many cancers, their role in cancer is controversial. The ROS levels in cancer cells are increased compared to normal cells, thus promoting cancer development. Nevertheless, for various cancer types, an overexpression of Prxs has been found to be associated with poor patient prognosis, and an increasing number of studies have reported that tumorigenesis is either facilitated or inhibited by regulation of cancer-associated signaling pathways. This review summarizes Prx isoforms and their basic functions, the relationship between the expression level and the physiological role of Prxs in cancer cells, and their roles in regulating cancer-associated signaling pathways.
Apoptosis ; Carcinogenesis ; Homeostasis ; Humans ; Metabolism ; Oxidative Stress ; Peroxiredoxins ; Physiological Processes ; Prognosis ; Protein Isoforms ; Reactive Oxygen Species

Two proteins of similar molecular weight (named as ASPR-C-1 and ASPR-C-2) from the crude drug of Angelica sinensis were purified and characterized by 80% ammonium sulfate precipitation, Sephadex G-50 gel filtration chromatography, and DEAE-Sepharose anion exchange chromatography. The molecular weight of ASPR-C-1 and ASPR-C-2 on SDS-PAGE was 17.33 kDa and 17.18 kDa, respectively. They were mainly monomeric in solution, but partially formed dimers and they were glycoproteins with glycosyl content of 2.6% and 8.2%, respectively. Both ASPR-C-1 and ASPR-C-2 were identified to be members of pathogenesis-related 10 family of proteins by matrix-assisted laser desorption ionization time-of-flight mass spectrometry and have ribonuclease activities with the specific activity of 73.60 U/mg and 146.76 U/mg, respectively. The optimum pH of the two isoforms was similar, at about 5.6, while their optimum temperatures were different. The optimum temperature of ASPR-C-1 was 50 ℃, and that of ASPR-C-2 was 60 ℃. Both isoforms presented highest thermal stability at 60 ℃. However, ASPR-C-2 was more thermotolerant than ASPR-C-1. The latter was rapidly inactivated and retained only about 20% residual activity while the former still maintained about 80% of its original activity at a higher treatment temperature (80 to 100 ℃). In addition, Fe²⁺ had an activating effect on the ribonuclease activities of two isoforms while Ca²⁺, Mg²⁺, Zn²⁺, Mn²⁺, Ag⁺, Cu²⁺, EDTA (Elhylene diamine tetraacetic acid), dithiothreitol and sodium dodecylsulphate showed different degrees of inhibition of the enzyme activities. Our findings provide a foundation for further research on the biological function of PR-10 protein from Angelica sinensis.
Angelica sinensis ; Chromatography, Gel ; Chromatography, Ion Exchange ; Electrophoresis, Polyacrylamide Gel ; Enzyme Stability ; Hydrogen-Ion Concentration ; Kinetics ; Molecular Weight ; Protein Isoforms ; Temperature

PURPOSE: The p38 mitogen-activated protein kinase (MAPKs) play a crucial role in the production of pro-inflammatory cytokines and over-expression of it increase cytokines which promote cancer. Among four isoforms, p38α has been well studied in head and neck squamous cell carcinoma (HNSCC) and other cancers as a therapeutic target. p38δ has recently emerged as a potential disease-specific drug target. Elevated serum p38α level in HNSCC was reported earlier from our lab. This study aims to estimate the levels of p38 MAPK-isoforms in the serum of HNSCC and design peptide inhibitor targeting the same. MATERIALS AND METHODS: Levels of p38 MAPK isoforms in the serum of HNSCC and healthy controls were quantified by surface plasmon resonance technology. The peptide inhibitor for p38 MAPK was designed by molecular modeling using Grid-based Ligand Docking with Energetics tools and compared with known specific inhibitors. RESULTS: We have observed highly elevated levels of all four isoforms of p38 MAPK in serum of HNSCC patients compared to the control group. Further, serum p38α, p38β, and p38δ levels were down regulated after therapy in follow-up patients, while p38γ showed no response to the therapy. Present study screened designed peptide WFYH as a specific inhibitor against p38δ. The specific inhibitor of p38δ was found to have no effect on p38α due to great structural difference at ATP binding pocket. CONCLUSION: In this study, first time estimated the levels of p38 MAPK isoforms in the serum of HNSCC. It can be concluded that p38 MAPK isoforms can be a diagnostic and prognostic marker for HNSCC and p38δ as a therapeutic target.
Adenosine Triphosphate ; Carcinoma, Squamous Cell* ; Cytokines ; Epithelial Cells* ; Follow-Up Studies ; Head* ; Humans ; Models, Molecular ; Neck* ; p38 Mitogen-Activated Protein Kinases ; Protein Isoforms* ; Protein Kinases ; Surface Plasmon Resonance

DNA double-stranded break (DSB) is one of the most catastrophic damages of genotoxic insult. Inappropriate repair of DNA DSBs results in the loss of genetic information, mutation, and the generation of harmful genomic rearrangements, which predisposes an organism to immunodeficiency, neurological damage, and cancer. The tumor repressor p53 plays a key role in DNA damage response, and has been found to be mutated in 50% of human cancer. p53, p63, and p73 are three members of the p53 gene family. Recent discoveries have shown that human p53 gene encodes at least 12 isoforms. Different p53 members and isoforms play various roles in orchestrating DNA damage response to maintain genomic integrity. This review briefly explores the functions of p53 and its isoforms in DNA DSB repair.
Animals ; DNA Breaks, Double-Stranded ; DNA Repair ; Humans ; Mice ; Protein Isoforms ; physiology ; Tumor Protein p73 ; physiology ; Tumor Suppressor Protein p53 ; genetics ; physiology

OBJECTIVE: To establish a method for detecting the exosomal PML-RARA fusion gene expression by droplet digital PCR (ddPCR). METHODS: By using Taqman probe-based ddPCR technique, the method that able to detect both long and short isoforms of PML-RARA fusion gene transcripts was established. RNA from PML-RARA negative cell line HL-60 as negative control was used to set the limit of blank (LOB), while the RNA from PML-RARA positive cell line NB4 and the recombinant plasmid pSG5-PML-RARA(S) were used to set the limit of detection (LOD) for long and short PML-RARA transcripts, respectively. Furtherly, the expression of exosomal PML-RARA fusion gene in NB4 cell culture supernatant and serum of patients with acute promyelocytic leukemia (APL) was analyzed by ddPCR technique. RESULTS: The LOB of ddPCR assay for long and short PML-RARA transcripts were 0.0725 and 0.083 copies per microliter of PCR reaction system, respectively, while the LOD of long and short PML-RARA transcripts were 0.19 and 0.21 copies per microliter of PCR reaction system, respectively. In addition, the expression of exosomal PML-RARA fusion gene derived from both NB4 cell culture supernatant and serum of APL patients was successfully detected. CONCLUSION A ddPCR-based technique for detecting fusion gene transcripts has been established, which can be used to analyze absolute quantification in the minimal quantity of PML-RARA transcripts derived from exosomes. It suggests the possibility of this technique to non-invasively and dynamicly monitore the exosomal PML-RARA transcripts from APL patients' serum.
Exosomes ; Gene Expression ; Humans ; Leukemia, Promyelocytic, Acute ; Oncogene Proteins, Fusion ; analysis ; Polymerase Chain Reaction ; Protein Isoforms

OBJECTIVE: To explore the possible molecular mechanism of Ikaros regulation on FUT4 expression by analyzing the correlation of the functional state of Ikaros with level of FUT4 expression, so as to provide the theoretical basis for personalized treatment in children with ALL. METHODS: The subtypes of Ikaros were identified by nested PCR and sequencing. The expression level of FUT4 was detected by quantitative PCR and analyzed by ΔΔCt method in the early stage of treatment, remission and relapse of ALL. RESULTS: Ik1 and Ik2 were the main functional subtypes, and the dominant negative Ikaros was Ik6; the Ik6 was detected in 23 patients with ALL. It was found that 2.73% patients expressing Ik6 alone and 18.18% patients with heterozygous expression were detected. The expression of FUT4 in the newly diagnosed ALL was higher than that in the control group, and the functional Ikaros negatively correlated with the FUT4 expression(r=-0.6329). CONCLUSION Dominant negative Ikaros closely correlated with the relapse of acute lymphoblastic leukemia in children. The functional Ikaros negatively correlated with FUT4 expression. Ikaros inhibit the transcriptional activity of FUT4, that may be the molecular mechanism of Ikaros regulating the expression of FUT4.
Acute Disease ; Child ; Fucosyltransferases ; metabolism ; Humans ; Ikaros Transcription Factor ; metabolism ; Lewis X Antigen ; metabolism ; Precursor Cell Lymphoblastic Leukemia-Lymphoma ; Protein Isoforms ; Recurrence