A direct interaction between NQO1 and a chemotherapeutic dimeric naphthoquinone

Background

Multimeric naphthoquinones are redox-active compounds that exhibit antineoplastic, antiprotozoal, and antiviral activities. Due to their multimodal effect on perturbation of cellular oxidative state, these compounds hold great potential as therapeutic agents against highly proliferative neoplastic cells. In our previous work, we developed a series of novel dimeric naphthoquinones and showed that they were selectively cytotoxic to human acute myeloid leukemia (AML), breast and prostate cancer cell lines. We subsequently identified the oxidoreductase NAD(P)H dehydrogenase, quinone 1 (NQO1) as the major target of dimeric naphthoquinones and proposed a mechanism of action that entailed induction of a futile redox cycling.

Results

Here, for the first time, we describe a direct physical interaction between the bromohydroxy dimeric naphthoquinone E6a and NQO1. Moreover, our studies reveal an extensive binding interface between E6a and the isoalloxazine ring of the flavin adenine dinucleotide (FAD) cofactor of NQO1 in addition to interactions with protein side chains in the active site. We also present biochemical evidence that dimeric naphthoquinones affect the redox state of the FAD cofactor of NQO1. Comparison of the mode of binding of E6a with those of other chemotherapeutics reveals unique characteristics of the interaction that can be leveraged in future drug optimization efforts.

Conclusion

The first structure of a dimeric naphthoquinone-NQO1 complex was reported, which can be used for design and synthesis of more potent next generation dimeric naphthoquinones to target NQO1 with higher affinity and specificity.

     

Localization of the von Hippel-Lindau disease gene to a small region of chromosome 3

We studied 25 families with von Hippel-Lindau disease (VHL) to locate VHL more precisely on chromosome 3. We found that VHL was linked to RAF1, confirming previous observations, and to two polymorphic DNA markers, D3S18 and D3S191. Multipoint linkage analysis indicated that the most likely location for VHL was in the interval between RAF1 and D3S18. D3S18 was located at 3p26. Genetic heterogeneity was not detected in this panel of von Hippel-Lindau disease families. The polymorphic markers RAF1, D3S18, and D3S191 should be useful in identifying asymptomatic gene carriers in VHL families and in guiding efforts at gene isolation.     

Endotoxin, epinephrine, and ellagic acid effects on the radiation-sensitized walker 256 rat carcinosarcoma

A radiation exposure of 1500 R to the Walker 256 rat tumor was found to sensitize this tumor to the effect of a sublethal dose of endotoxin (Sarratia marcescens lipopolysaccharide) given 2 days later so that complete or almost complete destruction of the tumor resulted. Histological. study showed rapidly developing massive necrosis of tumor tissue. Tracer experiments with 131I-labeled antibody to rat fibrin indicated an absence of blood circulation in the treated tumor. These results suggest that the lesion may be secondary to blood coagulation occurring in the vascular bed of the tumor. Apparently identical lesions were also produced by epinephrine and ellagic acid, alone or in combination. It is known that even untreated tumors are often the site of fibrin deposition. Presumably radiation, by injury to tumor cells, enhances the release of coagulation-producing substances into the vascular bed. It is postulated that the effect of subsequent treatment with the drugs listed above is produced by circulatory stasis induced in the tumor. This may be associated with Hageman factor activation or release of platelet factor 3.     

Herbivory in global climate change research: direct effects of rising temperature on insect herbivores

This review examines the direct effects of climate change on insect herbivores. Temperature is identified as the dominant abiotic factor directly affecting herbivorous insects. There is little evidence of any direct effects of CO₂ or UVB. Direct impacts of precipitation have been largely neglected in current research on climate change. Temperature directly affects development, survival, range and abundance. Species with a large geographical range will tend to be less affected. The main effect of temperature in temperate regions is to influence winter survival; at more northerly latitudes, higher temperatures extend the summer season, increasing the available thermal budget for growth and reproduction. Photoperiod is the dominant cue for the seasonal synchrony of temperate insects, but their thermal requirements may differ at different times of year. Interactions between photoperiod and temperature determine phenology; the two factors do not necessarily operate in tandem. Insect herbivores show a number of distinct life‐history strategies to exploit plants with different growth forms and strategies, which will be differentially affected by climate warming. There are still many challenges facing biologists in predicting and monitoring the impacts of climate change. Future research needs to consider insect herbivore phenotypic and genotypic flexibility, their responses to global change parameters operating in concert, and awareness that some patterns may only become apparent in the longer term.     

HIV-1 Receptor Binding Site-Directed Antibodies Using a VH1-2 Gene Segment Orthologue Are Activated by Env Trimer Immunization

Broadly neutralizing antibodies (bNAbs) isolated from chronically HIV-1 infected individuals reveal important information regarding how antibodies target conserved determinants of the envelope glycoprotein (Env) spike such as the primary receptor CD4 binding site (CD4bs). Many CD4bs-directed bNAbs use the same heavy (H) chain variable (V) gene segment, VH1-2*02, suggesting that activation of B cells expressing this allele is linked to the generation of this type of Ab. Here, we identify the rhesus macaque VH1.23 gene segment to be the closest macaque orthologue to the human VH1-2 gene segment, with 92% homology to VH1-2*02. Of the three amino acids in the VH1-2*02 gene segment that define a motif for VRC01-like antibodies (W50, N58, flanking the HCDR2 region, and R71), the two identified macaque VH1.23 alleles described here encode two. We demonstrate that immunization with soluble Env trimers induced CD4bs-specific VH1.23-using Abs with restricted neutralization breadth. Through alanine scanning and structural studies of one such monoclonal Ab (MAb), GE356, we demonstrate that all three HCDRs are involved in neutralization. This contrasts to the highly potent CD4bs-directed VRC01 class of bNAb, which bind Env predominantly through the HCDR2. Also unlike VRC01, GE356 was minimally modified by somatic hypermutation, its light (L) chain CDRs were of average lengths and it displayed a binding footprint proximal to the trimer axis. These results illustrate that the Env trimer immunogen used here activates B cells encoding a VH1-2 gene segment orthologue, but that the resulting Abs interact distinctly differently with the HIV-1 Env spike compared to VRC01.     

Human CYP1A1 gene: cosegregation of the enzyme inducibility phenotype and an RFLP.

The human CYP1A1 (cytochrome P1450) gene encodes an enzyme involved in the activation of procarcinogens, such as benzo[a]pyrene, to the ultimate reactive intermediate. Approximately 10% of the human population exhibit high CYP1A1 inducibility, and Kouri et al. reported that the high-inducibility phenotype might be at greater risk than low-inducibility individuals for cigarette smoke-induced bronchogenic carcinoma. In one 3-generation family of 15 individuals, we show here that the high-CYP1A1-inducibility phenotype segregates concordantly with an infrequent polymorphic site located 450 bases downstream from the CYP1A1 gene. Our findings are consistent with the study of Kawajiri et al., who demonstrated an association between this polymorphism and an increased incidence of squamous-cell lung cancer. Our data suggest that the CYP1A1 structural gene, or a region near this gene, might be correlated with the inducibility phenotype.     

Temperature and the hygropreference of the Arctic Collembolan Onychiurus arcticus and mite Lauroppia translamellata

The hygropreference of adult Onychiurus arcticus (Tullberg) was investigated over 2 h at 0, 10 and 20°C, along humidity gradients (12–98% RH) established using different salt solutions. At all temperatures O. arcticus preferred the highest humidity (98% RH). At 0 and 20°C, saturated conditions were preferred to 98% RH. The hygropreference of the mite Lauroppia translamellata (Willmann) was also assessed at 20°C, and no clear RH preference was observed. This species survived the loss of 24.9 ± 2.1% of its initial water content when held for 24 h at 20°C and 12% RH. A range of assays designed to eliminate the influence of thigmotactic behaviour and population clumping permit exclusion of these factors as being responsible for the observed results. The mean initial water content of O. arcticus samples (71.7 ± 10.9, 73.4 ± 4.0 and 73.8 ± 23.5% at 0, 10 and 20°C, respectively) did not differ significantly between temperatures, indicating that the results were not influenced by differences in initial hydrated state. The percentage water loss of individuals within the gradient increased with temperature, and differed significantly between regimes. The ecological significance of the observed humidity preferences are discussed.