ABSTRACT. Outbreaks of a disease causing serious losses among populations of cultured penaeid shrimp, including Penaeus monodon, P japonicus and P penicillatus, in Taiwan are characterized by obvious white spots on the carapace, appendages and the inside surface of the body. For this reason, we propose the name 'white spot syndrome' (WSS). Healthy juvenile kuruma shrimp P japonjcus were exposed by immersion to epidermal filtrate from diseased P japonicus and L? monodon which exhibited marked white spot signs. These experimentally infected shrimp resembled the spontaneously infected ones. Cumulative mortalities reached 100% within 5 to 7 d and were significantly affected by catching and temperature stress. A non-occluded rod-shaped viral particle was found by electron microscopy in the epidermis of both spontaneously and experimentally infected kuruma shrimp. Virions were enveloped, 330 + 20 nm in length and 87 * 7 nm in diameter. The close resemblance in external signs and viral morphology between spontaneously diseased and experimentally infected shrimp indicated that the rod-shaped virus may be the main causative agent of the disease characterized by white spot syndrome in Taiwan.

Ribonucleotide reductase from Escherichia coli consists of two dissociable, nonidentical homodimeric proteins called R1 and R2. The role of the C-terminal region of R2 in forming the R1R2 active complex has been studied. A heterodimeric R2 form with a full-length polypeptide chain and a truncated one missing the last 30 carboxyl-terminal residues was engineered by site-directed mutagenesis. Kinetic analysis of the binding of this protein to R1, compared with full-length or truncated homodimer, revealed that the C-terminal end of R2 accounts for all of its interactions with R1. The intrinsic dissociation constant of the heterodimeric R2 form, with only one contact to R1, 13 microM, is of the same magnitude as that obtained previously [Climent, I., Sjöberg, B.-M.,& Huang, C. Y. (1991) Biochemistry 30, 5164-5171] for synthetic C-terminal peptides, 15-18 microM. We have also mutagenized the only two invariant residues localized at the C-terminal region of R2, glutamic acid-350 and tyrosine-356, to alanine. The binding of these mutant proteins to R1 remains tight, but their catalytic activity is severely affected. While E350A protein exhibits a low (240 times less active than the wild-type) but definitive activity, Y356A is completely inactive. A catalytic rather than structural role for these residues is discussed.

One striking clinical feature of hepatitis C virus (HCV) infection is that more than 50% of patients with acute hepatitis C will develop chronic infection. To investigate its possible mechanisms, we examined the activation of type 2‐like T‐helper (Th2‐like) cells relating to the development of chronicity. Peripheral blood CD4+ T‐cell proliferation and cytokine secretion in response to a panel of recombinant HCV antigens including core (C22), envelope 1 (E1), E2, nonstructural (NS) protein 4 (C100), fusion protein of NS3 and NS4 (C200), and NS5 were assayed in 17 patients with acute hepatitis C. All six patients with self‐limited disease had a significant CD4+ T‐cell proliferation to C22, E1, C100, C200, and NS5, running parallel with the antigen‐stimulated secretion of interleukin (IL)‐2 and interferon γ (IFN‐γ), but not with interleukin (IL)‐4 and IL‐10, indicating predominant Th1 responses. Among the remaining 11 patients who developed chronicity, 6, 2, and 9 cases showed a specific CD4+ T‐cell response to C22, C100, and C200, respectively, and the responses were significantly lower than those of cases with recovery in terms of stimulation index (SI) (P < .05) and of antigen‐stimulated IL‐2 and IFN‐γ production. Importantly, IL‐4 and IL‐10 (Th2 responses) were detectable, and C22‐specific Th2‐like T‐cell clones could be generated from patients with chronicity. The data suggested that activation of Th2 responses in acute hepatitis C patients may play a role in the development of chronicity.

Cancer cells may survive under oxygen and nutrient deprivation by metabolic reprogramming for high levels of anaerobic glycolysis, which contributes to tumor growth and drug resistance. Abnormally expressed glucose transporters (GLUTs) are colocalized with hypoxia (Hx) inducible factor (HIF)1α in peri-necrotic regions in human colorectal carcinoma. However, the underlying mechanisms of anti-necrotic resistance conferred by glucose metabolism in hypoxic cancer cells remain poorly understood. Our aim was to investigate signaling pathways of Hx-induced necroptosis and explore the role of glucose pyruvate metabolite in mechanisms of death resistance. Human colorectal carcinoma cells were Hx exposed with or without glucose, and cell necroptosis was examined by receptor-interacting protein (RIP)1/3 kinase immunoprecipitation and 32P kinase assays. Our results showed increased RIP1/3 complex formation and phosphorylation in hypoxic, but not normoxic cells in glucose-free media. Blocking RIP1 signaling, by necrostatin-1 or gene silencing, decreased lactodehydrogenase (LDH) leakage and plasma membrane disintegration. Generation of mitochondrial superoxide was noted after hypoxic challenge; its reduction by antioxidants inhibited RIP signaling and cell necrosis. Supplementation of glucose diminished the RIP-dependent LDH leakage and morphological damage in hypoxic cells, whereas non-metabolizable sugar analogs did not. Hypoxic cells given glucose showed nuclear translocation of HIF1α associated with upregulation of GLUT-1 and GLUT-4 expression, as well as increase of intracellular ATP, pyruvate and lactate levels. The glucose-mediated death resistance was ablated by iodoacetate (an inhibitor to glyceraldehyde-3-phosphate dehydrogenase), but not by UK5099 (an inhibitor to mitochondrial pyruvate carrier), suggesting that glycolytic pathway was involved in anti-necrotic mechanism. Lastly, replacing glucose with cell-permeable pyruvate derivative also led to decrease of Hx-induced necroptosis by suppression of mitochondrial superoxide in an energy-independent manner. In conclusion, glycolytic metabolism confers resistance to RIP-dependent necroptosis in hypoxic cancer cells partly through pyruvate scavenging of mitochondrial free radicals.

Matrix metalloproteinase (MMP)-2 plays critical roles in tumor development and in the metastasis of multiple cancers, including human oral cavity squamous cell carcinoma (OCSCC). One of the upstream regulators of MMP-2 is FOXM1, which is overexpressed in a microarray dataset of OCSCC. It is interesting that FLJ10540 exhibits similar gene expression profiles with MMP-2 and FOXM1, raising the possibility that these molecules might participate in MMP-2-elicited cancer progression and metastasis of OCSCC. To examine this connection, we first showed that FLJ10540 was significantly overexpressed in OCSCC. A strong FLJ10540 expression was significantly correlated with an advanced tumor node metastasis stage and the cumulative 5-year survival rate. Thus, an elevated FLJ10540 expression is an indicator of poor survival. Functionally, FLJ10540 had the abilities to stimulate cell migration and invasion in oral cancer cells through increased FOXM1 and MMP-2 expressions. Conversely, the depletion of the FLJ10540 expression by small interefering RNAs suppressed the FOXM1 and MMP-2 protein expressions. The suppression of either FLJ10540 or FOXM1 could cause significant inhibition on cell migratory and invasive ability in oral cancer cells. Finally, the immunohistochemical and western blotting analyses of human aggressive OCSCC specimens showed a significant positive correlation among FLJ10540, FOXM1 and MMP-2 expressions. These findings suggest that FLJ10540 is not only an important prognostic factor but also a new therapeutic target in the FLJ10540/FOXM1/MMP-2 pathway for OCSCC treatment.