P58 Expression Research Articles

Mitochondrial dysfunction and pancreatic islet β-cell failure (Review).

Pancreatic β-cells are the only source of insulin in humans. Mitochondria uses pyruvate to produce ATP as an intermediate link between glucose intake and insulin secretion in β-cells, in a process known as glucose-stimulated insulin secretion (GSIS). Previous studies have demonstrated that GSIS is negatively regulated by various factors in the mitochondria, including tRNALeu mutations, high p58 expression, reduced nicotinamide nucleotide transhydrogenase activity, abnormal levels of uncoupling proteins and reduced expression levels of transcription factors A, B1 and B2. Additionally, oxidative stress damages mitochondria and impairs antioxidant defense mechanisms, leading to the increased production of reactive oxygen species, which induces β-cell dysfunction. Inflammation in islets can also damage β-cell physiology. Inflammatory cytokines trigger the release of cytochrome c from the mitochondria via the NF-κB pathway. The present review examined the potential factors underlying mitochondrial dysfunction and their association with islet β-cell failure, which may offer novel insights regarding future strategies for the preservation of mitochondrial function and enhancement of antioxidant activity for individuals with diabetes mellitus.

P58IPKinhibits coxsackievirus-induced apoptosis via the PI3K/Akt pathway requiring activation of ATF6a and subsequent upregulation of mitofusin 2

Previously we found that prolonged endoplasmic reticulum (ER) stress caused by coxsackievirus B3 (CVB3) infection led to p58(IPK) downregulation and subsequent cell apoptosis. This finding implies that p58(IPK) expression benefits cell survival and counteracts CVB3-induced apoptosis. In testing this hypothesis, we first found that PI3K/Akt survival pathway is more sensitive than ERK1/2 in response to p58(IPK) expression. This finding was further verified by silencing p58(IPK) with specific siRNAs, which led to the significant suppression of phosphorylation of Akt (p-Akt) but not ERK1/2. Further, using CVB3-infected cell line expressing dominant negative ATF6a (DN-ATF6a), we found that expression of p58(IPK) and p-Akt was significantly reduced, which led to the decreased cell viability. However, when the DN-ATF6a cells were transiently transfected with p58(IPK) , an opposite result was obtained. Finally, by CVB3 infection of cells stably expressing p58(IPK) , we found that CVB3-induced mitochondria-mediated apoptosis was suppressed, which was evidenced by the reduced cytochrome c release and upregulation of the mitochondrial membrane protein mitofusin 2. However, silencing p58(IPK) with either specific siRNAs or DN-ATF6a sensitized cells to CVB3-induced apoptosis. These results suggest that p58(IPK) suppresses CVB3-induced apoptosis through selective activation of PI3K/Akt pathway that requires activation of ATF6a and subsequently upregulates mitofusin 2.

P58 Expression of Nischarin in human breast-cancer tissue

P58 Expression of Nischarin in human breast-cancer tissue

Expression of chemokine and inhibitory receptors on natural killer cells: effect of immune activation and HIV viremia.

We examined the cell-surface expression of chemokine and natural killer (NK) cell inhibitory receptors (iNKRs) on NK cells from individuals with human immunodeficiency virus (HIV) infection, chronic hepatitis C infection, and Wegener's granulomatosis (WG), an inflammatory, granulomatous vasculitis. The expression of CCR5 on NK cells was up-regulated in individuals with HIV viremia and in individuals with active WG, indicating that expression of this receptor is modulated by states of immune activation associated with viral infection and inflammatory or immune-mediated diseases. In contrast, iNKRs were shown to be up-regulated only on NK cells of individuals with HIV viremia, and they returned to a normal level when viremia was controlled with effective antiviral therapy. In individuals with HIV-1 viremia, there was a direct correlation between the level of expression of p58.1, p58.2, and CD94 receptors and plasma HIV viremia, suggesting that ongoing active HIV replication has an effect on the expression of such receptors on NK cells. These results suggest that immune activation leads to abnormal cell-surface expression of chemokine receptors on NK cells, whereas HIV-specific processes account for the up-regulation of iNKRs on NK cells; this may explain the NK cell-functional defects seen in HIV infection.

Expression of p58.2 or CD94/NKG2A inhibitory receptors in an NK-like cell line, YTINDY, leads to HLA Class I-mediated inhibition of cytotoxicity in the p58.2- but not the CD94/NKG2A-expressing transfectant

Natural killer cytotoxicity is down-regulated by HLA Class I-specific inhibitory receptors classified as killer inhibitory receptors (KIRs) or C-type lectins. The regulation of their inhibitory signaling pathways is not completely understood. The YTINDY NK-like cell line was transfected to express p58.2 KIR (YT/C143 transfectant) or CD94/NKG2A C-type lectin (YT/CD94 transfectant); and YT/C143, but not YT/CD94, cytotoxicity was down-regulated by Class I. YT/C143 and YT/CD94 expressed equally low p56 lck levels, suggesting that p56 lck is not absolutely required for p58.2 signaling but may be required for CD94/NKG2A signaling. Lower SHP-1 levels and activity were observed in YT/CD94 compared to YT/C143. However, increasing SHP-1 to equivalent levels in YT/C143 did not restore inhibition in YT/CD94. Our results suggest that the combination of low p56 lck and SHP-1 levels may be responsible for the absent inhibitory signal in YT/CD94. In addition, the possible expression of CD94/NKG2C activating receptor may override inhibitory signals transduced through CD94/NKG2A.

Expression of Inhibitory Receptors in Natural Killer (CD3−CD56+) Cells and CD3+CD56+ Cells in the Peripheral Blood Lymphocytes and Tumor Infiltrating Lymphocytes in Patients with Primary Hepatocellular Carcinoma

The cytolytic responses of NK (CD3−CD56+) and CD3+CD56+ cells are inhibited by the engagement of the killer inhibitory receptors (p58.1, p58.2, and CD94) with respective ligands on the target cell. The expression of these receptors in peripheral blood lymphocytes (PBLs) (n = 18) and tumor infiltrating lymphocytes (TILs) (n = 7) was examined in patients with primary hepatocellular carcinoma (HCC). There were no differences in the expression of the three inhibitory receptors by both NK and CD3+CD56+ PBLs in patients with HCC compared to that of control NK and CD3+CD56+ PBLs, respectively (all P = NS). However, the expression of p58.1 by NK TILs and by CD3+CD56+ TILs in patients with HCC was significantly decreased compared to that of hepatic lymphocytes of the control subjects (8.9% vs 37.85%, P = 0.047; 4.1% vs 25.2%, P = 0.049, respectively). The expression of p58.2 by CD3+CD56+ TILs and CD94 by NK TILs was also decreased compared to that of hepatic lymphocytes of the control subjects (16.9% vs 73.1%, P = 0.047; 21% vs 49.95%, P = 0.037, respectively). These changes were limited to hepatic TILs, and this observation may reflect an adaptive anti-tumor phenomenon occurring in the microenvironment of HCC.

Phenotypic and cytokine analysis of human peripheral blood gamma delta T cells expressing NK cell receptors.

The presence of NK receptors (NKR) on populations of T cells has been proposed to play a regulatory role in T cell function, fine tuning the response to Ag, and influencing the nature of the immune response through rapid secretion of large amounts of cytokines. In this study, we assessed the nature and distribution of NKR on human peripheral blood gamma delta T cells and established clones to study cytokine release. In circulating gamma delta T cells, approximately 80% expressed CD94, approximately 25% expressed NKR-P1A, and approximately 20% expressed p58, values substantially higher than those found on alpha beta T cells from the same donors. When cloned for specific NKR expression, most cells in culture were NKR-P1A+ whereas p58 expression was variable, suggesting that the NKR-P1A phenotype can be acquired in culture whereas expression of p58 is more stable. Some clones were triple positive for CD94, NKR-P1A, and p58. V delta 2+ cells generally expressed a wider range of NKR than V delta 1+ cells. Following activation through CD3, all gamma delta T cell clones released large amounts of IFN-gamma, commencing as early as 4 h postactivation. Some clones also released TNF-alpha and IL-4, but no correlation with specific NKR expression was noted. Activation through NKR-P1A induced moderate levels of IFN-gamma without inducing IL-4. The results suggest that activation of most gamma delta T cells is regulated by signaling events occurring via both the TCR and the NKR. They further show that peripheral blood gamma delta T cells may function as a source of the proinflammatory cytokines IFN-gamma and TNF-alpha.

Cloning, expression, and cellular localization of the oncogenic 58-kDa inhibitor of the RNA-activated human and mouse protein kinase

The 58-kDa inhibitor of the interferon-induced double-stranded RNA-activated protein kinase (PKR) is a cellular protein that is activated during influenza virus infection to down-regulate the activity of PKR. This study was initiated to further our understanding of the inhibitor which, when overproduced, has the capacity to malignantly transform cells. We report here the isolation and characterization of cDNA clones encoding the inhibitor, designated p58, from human HeLa and mouse NIH 3T3 cells. The human and mouse p58 cDNAs were 6.5 and 1.6 kb in length, respectively. Surprisingly, the deduced amino acid sequences of the human and mouse p58 were 96% identical, indicating a remarkably high degree of conservation between species. An examination of p58 mRNA expression in human tissues revealed a 6.5-kb transcript in all tissues examined, with a particularly high level of expression present in the pancreas and liver, and also in certain leukemic cell lines. Similarly, p58 expression was detected in all mouse tissues examined, with the highest level of expression found in liver. In contrast to human tissues, three p58 transcripts of approximately 1.7, 3.3 and 5.4 kb were observed in mouse tissues, suggesting that p58 expression may be regulated differently in human and mouse cells. Western blot analysis of subcellular fractions and indirect immunofluorescence analysis of intact cells revealed that p58 was found predominantly in the cytoplasm, consistent with its function as an inhibitor of PKR, which is also a predominantly cytoplasmic protein.

Factors necessary for restoring an evolutionary change in an anural ascidian embryo

The ascidian Molgula oculata has a tailed (or urodele) larva, whereas Molgula occulta develops directly via a tailless (or anural) embryo. Interspecific hybrid embryos produced by fertilizing M. occulta eggs with M. oculata sperm ( M. occulta × M. oculata hybrids) can develop urodele larval structures, including a brain pigment cell and a short tail containing a small notochord. Development of larval features differs in individual M. occulta clutches: some eggs develop into hybrids with both a brain pigment cell and a tail, some into hybrids with either a brain pigment cell or a tail, and others into hybrids without urodele features. The expression of a 58-kDa protein (p58), which is present in eggs and embryos of urodele ascidians but lacking in those of most anural species, also varies in expression between different clutches of M. occulta eggs. Western blot and immunofluorescence studies show that p58 expression is correlated with the ability of hybrid embryos to express urodele features. For example, clutches of M. occulta eggs containing relatively high levels of p58 produce many hybrids with both a brain pigment cell and a tail. Differential expression of p58 occurs during oogenesis in M. occulta individuals: p58 is found at similar levels in previtellogenic oocytes, but in some animals it disappears during vitellogenesis, while in others it persists throughout oogenesis and is present in mature eggs. When M. occulta eggs are extracted with Triton X-100, p58 remains in the detergent-insoluble fraction, suggesting that it is associated with the cytoskeleton. In most unfertilized M. occulta eggs, p58 is uniformly distributed, but after fertilization it is localized in the uncleaved zygote and then concentrated in embryonic ectoderm, notochord, and muscle lineage cells. Despite containing high levels of p58, gynogenetic hybrid embryos, produced by fertilizing M. occulta eggs with uv-irradiated M. oculata sperm, develop into hybrids without a brain pigment cell or a tail. The results suggest that both a functional paternal genome and p58 are necessary for restoration of larval features in M. occulta × M. oculata hybrids. The cytoskeletal complex containing p58 may mediate the localization of key maternal factors in the egg or may be involved in cellular interactions during embryogenesis which are responsible for development of urodele cell fates.

Increased expression of a 58-kDa protein kinase leads to changes in the CHO cell cycle.

We have isolated and characterized cDNA encoding a human 58-kDa protein kinase that is homologous to the cell division control (CDC) protein kinases. This protein kinase also contains a unique N-terminal domain that may potentially regulate its function. Due to its relatedness to p34CDC2, the human p58 cDNA was overexpressed in CHO cells to determine the effect on the cell cycle. Elevated expression of p58 in these cells resulted in prolonged late telophase and early G1 phase of the cell cycle. These p58 overexpressors showed a significantly increased frequency of tubulin midbodies as well as significant increases in mitotic abnormalities. Thus, proper regulation of p58 protein kinase is essential for normal cell cycle progression in these cells.