FAT10 differentially stabilizes MYPT2 isoforms.

Myosin phosphatase (MP) is an enzyme complex that regulates muscle contraction and plays important roles in various physiological and pathological conditions. Myosin phosphatase targeting subunit (MYPT) 2, a subunit of MP, interacts with protein phosphatase 1c to regulate its phosphatase activity. MYPT2 exists in various isoforms that differ in the composition of essential motifs that contribute to its function. However, regulatory mechanisms underlying these isoforms are poorly understood. Human leukocyte antigen-F adjacent transcript 10 (FAT10) is a ubiquitin-like modifier that not only targets proteins for proteasomal degradation but also stabilizes its interacting proteins. In this study, we investigated the effect of the interaction between FAT10 and MYPT2 isoform a (the canonical full-length form of MYPT2) or MYPT2 isoform f (the natural truncated form of MYPT2). FAT10 interacted with both MYPT2 isoforms a and f; however, only MYPT2 isoform f was increased by FAT10, whereas MYPT2 isoform a remained unaffected by FAT10. We further confirmed that, in contrast to MYPT2 isoform a, MYPT2 isoform f undergoes rapid degradation via the ubiquitin-proteasome pathway and that FAT10 stabilizes MYPT2 isoform f by inhibiting its ubiquitination. Therefore, our findings suggest that the interaction between FAT10 and MYPT2 isoforms leads to distinct stabilization effects on each isoform, potentially modulating MP activity.

FAT10 Induces cancer cell migration by stabilizing phosphorylated ABI3/NESH.

The WAVE regulatory complex (WRC) is involved in various cellular processes by regulating actin polymerization. The dysregulation of WRC components is associated with cancer development. ABI family member 3 (ABI3)/new molecule including SH3 (NESH) is one of the WRC components and it has been reported that ABI3 phosphorylation can affect WRC function. Although several residues of ABI3 have been reported to be possible phosphorylation sites, it is still unclear which residues are important for the function of ABI3. Furthermore, it is unclear how the phosphorylated form of ABI3 is regulated. Here, we demonstrate that ABI3 is stabilized by its interaction with human leukocyte antigen-F adjacent transcript 10 (FAT10). Using phospho-dead or phospho-mimetic mutants of ABI3, we showed that serine 213 and 216 are important phosphorylation sites of ABI3. In particular, FAT10 has a higher affinity for the phosphorylated form of ABI3 than the non-phosphorylated form, and it stabilizes the phosphorylated form more than the non-phosphorylated form through this differential affinity. The interaction between FAT10 and the phosphorylated form of ABI3 promoted cancer cell migration. Therefore, our results suggest that FAT10 stabilizes the phosphorylated form of ABI3, which may lead to WRC activation, thereby promoting cancer cell migration.

DNA Methylation and Transcription of HLA-F and Serum Cytokines Relate to Chinese Medicine Syndrome Classification in Patients with Chronic Hepatitis B.

OBJECTIVE: To explore the molecular bases of Chinese medicine (CM) syndrome classification in chronic hepatitis B (CHB) patients in terms of DNA methylation, transcription and cytokines. METHODS: Genome-wide DNA methylation and 48 serum cytokines were detected in CHB patients (DNA methylation: 15 cases; serum cytokines: 62 cases) with different CM syndromes, including dampness and heat of Gan (Liver) and gallbladder (CHB1, DNA methylation: 5 cases, serum cytokines: 15 cases), Gan stagnation and Pi (Spleen) deficiency (CHB2, DNA methylation: 5 cases, serum cytokines: 15 cases), Gan and Shen (Kidney) yin deficiency (CHB3, DNA methylation: 5 cases, serum cytokines: 16 cases), CHB with hidden symptoms (HS, serum cytokines:16 cases) and healthy controls (DNA methylation: 6 cases). DNA methylation of a critical gene was further validated and its mRNA expression was detected on enlarged samples. Genome-wide DNA methylation was detected using Human Methylation 450K Assay and furthered verified using pyrosequencing. Cytokines and mRNA expression of gene were evaluated using multiplex biometric enzyme-linked immunosorbent assay (ELISA)-based immunoassay and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), respectively. RESULTS: Totally 28,667 loci, covering 18,403 genes were differently methylated among CHB1, CHB2 and CHB3 (P<0.05 and |Δß value| > 0.17). Further validation showed that compared with HS, the hg19 CHR6: 29691140 and its closely surrounded 2 CpG loci were demethylated and its mRNA expressions were significantly up-regulated in CHB1 (P<0.05). However, they remained unaltered in CHB2 (P>0.05). Levels of Interleukin (IL)-12 were higher in CHB3 and HS than that in CHB1 and CHB2 groups (P<0.05). Levels of macrophage inflammatory protein (MIP)-1α and MIP-1ß were higher in CHB3 than other groups and leukemia inhibitory factor level was higher in CHB1 and HS than CHB2 and CHB3 groups (P<0.05). IL-12, MIP-1α and MIP-1ß concentrations were positively correlated with human leukocyte antigen F (HLA-F) mRNA expression (R2=0.238, P<0.05; R2=0.224, P<0.05; R=0.447, P<0.01; respectively). Furthermore, combination of HLA-F mRNA and differential cytokines greatly improved the differentiating accuracy among CHB1, CHB2 and HS. CONCLUSIONS: Demethylation of CpG loci in 5' UTR of HLA-F may up-regulate its mRNA expression and HLA-F expression was associated with IL-12, MIP-1α and MIP-1ß levels, indicating that HLA-F and the differential cytokines might jointly involve in the classification of CM syndromes in CHB. REGISTRATION NO: ChiCTR-RCS-13004001.

DNA Methylation and Transcription of HLA-F and Serum Cytokines Relate to Chinese Medicine Syndrome Classification in Patients with Chronic Hepatitis B / 中国结合医学杂志

OBJECTIVE@#To explore the molecular bases of Chinese medicine (CM) syndrome classification in chronic hepatitis B (CHB) patients in terms of DNA methylation, transcription and cytokines.@*METHODS@#Genome-wide DNA methylation and 48 serum cytokines were detected in CHB patients (DNA methylation: 15 cases; serum cytokines: 62 cases) with different CM syndromes, including dampness and heat of Gan (Liver) and gallbladder (CHB1, DNA methylation: 5 cases, serum cytokines: 15 cases), Gan stagnation and Pi (Spleen) deficiency (CHB2, DNA methylation: 5 cases, serum cytokines: 15 cases), Gan and Shen (Kidney) yin deficiency (CHB3, DNA methylation: 5 cases, serum cytokines: 16 cases), CHB with hidden symptoms (HS, serum cytokines:16 cases) and healthy controls (DNA methylation: 6 cases). DNA methylation of a critical gene was further validated and its mRNA expression was detected on enlarged samples. Genome-wide DNA methylation was detected using Human Methylation 450K Assay and furthered verified using pyrosequencing. Cytokines and mRNA expression of gene were evaluated using multiplex biometric enzyme-linked immunosorbent assay (ELISA)-based immunoassay and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), respectively.@*RESULTS@#Totally 28,667 loci, covering 18,403 genes were differently methylated among CHB1, CHB2 and CHB3 (P<0.05 and |Δβ value| > 0.17). Further validation showed that compared with HS, the hg19 CHR6: 29691140 and its closely surrounded 2 CpG loci were demethylated and its mRNA expressions were significantly up-regulated in CHB1 (P<0.05). However, they remained unaltered in CHB2 (P>0.05). Levels of Interleukin (IL)-12 were higher in CHB3 and HS than that in CHB1 and CHB2 groups (P<0.05). Levels of macrophage inflammatory protein (MIP)-1α and MIP-1β were higher in CHB3 than other groups and leukemia inhibitory factor level was higher in CHB1 and HS than CHB2 and CHB3 groups (P<0.05). IL-12, MIP-1α and MIP-1β concentrations were positively correlated with human leukocyte antigen F (HLA-F) mRNA expression (R2=0.238, P<0.05; R2=0.224, P<0.05; R=0.447, P<0.01; respectively). Furthermore, combination of HLA-F mRNA and differential cytokines greatly improved the differentiating accuracy among CHB1, CHB2 and HS.@*CONCLUSIONS@#Demethylation of CpG loci in 5' UTR of HLA-F may up-regulate its mRNA expression and HLA-F expression was associated with IL-12, MIP-1α and MIP-1β levels, indicating that HLA-F and the differential cytokines might jointly involve in the classification of CM syndromes in CHB.@*REGISTRATION NO@#ChiCTR-RCS-13004001.

The Emerging Roles of Human Leukocyte Antigen-F in Immune Modulation and Viral Infection.

Human leukocyte antigens (HLAs) play various critical roles in both innate and adaptive immunity through processes such as presenting antigens to T cells and serving as ligands for receptors expressed on natural killer (NK) cells. Among the HLA class I family, the clinical significance and biological function of HLA-F have been the least investigated and have remained elusive for a long period of time. Previous studies have revealed that HLA-F expression might be involved in various physiological and pathological processes, such as pregnancy, viral infection, cancer, transplantation, and autoimmune diseases. However, recent data have shown that, akin to other HLA family members, HLA-F molecules can interact with both activating and inhibitory receptors on immune cells, such as NK cells, and can present a diverse panel of peptides. These important findings pave new avenues for investigations regarding the functions of HLA-F as an important immune regulatory molecule. In the present review, we summarize the studies on the role of HLA-F in immune modulation, with a special emphasis placed on the roles of HLA-F and KIR3DS1 interactions in viral infection.

Clinicopathological significance of human leukocyte antigen F-associated transcript 10 expression in colorectal cancer.

BACKGROUND: Colorectal cancer (CRC) is a common malignancy of the gastrointestinal tract. The worldwide mortality rate of CRC is about one half of its morbidity. Ubiquitin is a key regulatory factor in the cell cycle and widely exists in eukaryotes. Human leukocyte antigen F-associated transcript 10 (FAT10), known as diubiquitin, is an 18 kDa protein with 29% and 36% homology with the N and C termini of ubiquitin. The function of FAT10 has not been fully elucidated, and some studies have shown that it plays an important role in various cell processes. AIM: To examine FAT10 expression and to analyze the relationship between FAT10 expression and the clinicopathological parameters of CRC. METHODS: FAT10 expression in 61 cases of CRC and para-cancer colorectal tissues was measured by immunohistochemistry and Western blotting. The relationship between FAT10 expression and clinicopathological parameters of CRC was statistically analyzed. RESULTS: Immunohistochemical analysis showed that the positive rate of FAT10 expression in CRC (63.93%) was significantly higher than that in tumor-adjacent tissues (9.84%, P < 0.05) and normal colorectal mucosal tissue (1.64%, P < 0.05). Western blotting also indicated that FAT10 expression was significantly higher in CRC than in tumor-adjacent tissue (P < 0.05). FAT10 expression was closely associated with clinical stage and lymphatic spread of CRC. FAT10 expression also positively correlated with p53 expression. CONCLUSION: FAT10 expression is highly upregulated in CRC. FAT10 expression is closely associated with clinical stage and lymphatic spread of CRC.

Human leukocyte antigen (HLA-F) polymorphism is associated with chronic HBV infection.

Human leukocyte antigen (HLA)-F has been involved in immune regulation of infectious diseases. However, the role of HLA-F polymorphisms in hepatitis B infection outcomes remains unclear. Here, we aimed to determine HLA-F polymorphism implication in chronic HBV. Genotype analysis was performed for three single nucleotide polymorphisms (SNPs) of HLA-F and one SNP of HLA-E using PCR-SSP, in 252 Tunisian patients with chronic HBV infection stratified according to their HBV DNA levels (140 patients with low HBV DNA levels < 2000 IU/mL and 112 patients with high HBV DNA levels ≥ 2000 IU/mL) and 240 healthy controls (CTRL). The three HLA-F SNPs (HLA-F*01:02, -F*01:03 and -F*01:04) have the same allelic and genotypic frequencies in patients and in CTRL. We reported a low HLA-F*01:02 and F*01:04 allelic frequencies in the Tunisian population; however, high HLA-F*01:03 allele frequencies were observed (17%). A significant association was found between the HLA-F*01:03 allele and decreased level of HBV DNA (P = 0.02 OR 0.56, 95% CI 0.35-0.92). No significant differences were observed in haplotype distribution between patients and CTRL. A significant association of HLA-F*01:03 with the level of HBV DNA suggests an important role of HLA-F in HBV replication control.

Natural Killer Cell Interactions with Classical and Non-Classical Human Leukocyte Antigen Class I in HIV-1 Infection.

Natural killer (NK) cells are effector lymphocytes of the innate immune system that are able to mount a multifaceted antiviral response within hours following infection. This is achieved through an array of cell surface receptors surveilling host cells for alterations in human leukocyte antigen class I (HLA-I) expression and other ligands as signs of viral infection, malignant transformation, and cellular stress. This interaction between HLA-I ligands and NK-cell receptor is not only important for recognition of diseased cells but also mediates tuning of NK-cell-effector functions. HIV-1 alters the expression of HLA-I ligands on infected cells, rendering them susceptible to NK cell-mediated killing. However, over the past years, various HIV-1 evasion strategies have been discovered to target NK-cell-receptor ligands and allow the virus to escape from NK cell-mediated immunity. While studies have been mainly focusing on the role of polymorphic HLA-A, -B, and -C molecules, less is known about how HIV-1 affects the more conserved, non-classical HLA-I molecules HLA-E, -G, and -F. In this review, we will focus on the recent progress in understanding the role of non-classical HLA-I ligands in NK cell-mediated recognition of HIV-1-infected cells.

Lesion human leukocyte antigen-F expression is associated with a poor prognosis in patients with hepatocellular carcinoma.

Human leukocyte antigen (HLA)-F, a non-classical HLA-class I molecule, has attracted attention as an important immunosuppressive molecule in recent years, although the clinical relevance of HLA-F expression in cancer patients remains unclear. In the present study, HLA-F expression in 90 primary hepatocellular carcinoma (HCC) lesions and 55 corresponding adjacent normal liver tissues was analyzed by immunohistochemistry, and the associations between HLA-F expression and clinicopathological parameters and patient survival times were analyzed. Positive HLA-F expression was observed in 47.8% (43/90) of the HCC lesions and in 10.9% (6/55) of the normal liver tissues. HLA-F expression in HCC lesions was significantly correlated with patient gender (P=0.02), and venous or lymphatic invasion (P=0.02). Patients who were HLA-F-positive had worse survival times than those who were HLA-F-negative (P=0.04). The mean overall survival times for HLA-F-negative and -positive patients were 44.2 months [95% confidence interval (CI), 37.7-50.7] and 33.0 months (95% CI, 25.1-40.8), respectively. Multivariate analysis revealed that HLA-F was an independent prognostic factor for HCC patients with a hazard ratio of 2.1 (95% CI, 1.0-4.4). In conclusion, the present study demonstrated that HLA-F expression was associated with poor survival in HCC patients, and is correlated with tumor cell invasion and metastasis.