S-Nitrosohemoglobin: an allosteric mediator of NO group function in mammalian vasculature

Since the discovery of NO as the endothelium-derived relaxing factor, there has been considerable interest in how NO interacts with hemoglobin (Hb). Numerous investigations have highlighted the possibility that rather than operating as a sink to consume NO, the vasculature can operate as a delivery mechanism for NO. The principal hypothesis proposed to explain this phenomenon is that Hb can transport NO on the conserved cysteine residue beta93 and deliver that NO to the tissues in an allosterically dependent manner. This proposal has been termed the S-Nitrosohemoglobin (SNO-Hb) Hypothesis. This review addresses the experimental evidence that led to development of this hypothesis and examines much of the research that resulted from its generation. Specifically it covers the evidence concerning NO in the vasculature, the SNO-Hb Hypothesis itself, the biochemical and biophysical data relating to NO and Hb interactions, SNO-Hb in human physiology, and alternative vascular forms of NO. Finally a model of NO in the vasculature in which SNO-Hb forms the central core is proposed.     

S-Nitrosohemoglobin is unstable in the reductive erythrocyte environment and lacks O2/NO-linked allosteric function

Our previous results run counter to the hypothesis that S-nitrosohemoglobin (SNO-Hb) serves as an in vivo reservoir for NO from which NO release is allosterically linked to oxygen release. We show here that SNO-Hb undergoes reductive decomposition in erythrocytes, whereas it is stable in purified solutions and in erythrocyte lysates treated with an oxidant such as ferricyanide. Using an extensively validated methodology that eliminates background nitrite and stabilizes erythrocyte S-nitrosothiols, we find the levels of SNO-Hb in the basal human circulation, including red cell membrane fractions, were 46 +/- 17 nm in human arterial erythrocytes and 69 +/- 11 nm in venous erythrocytes, incompatible with the postulated reservoir function of SNO-Hb. Moreover, we performed experiments on human red blood cells in which we elevated the levels of SNO-Hb to 10,000 times the normal in vivo levels. The elevated levels of intra-erythrocytic SNO-Hb fell rapidly, independent of oxygen tension and hemoglobin saturation. Most of the NO released during this process was oxidized to nitrate. A fraction (25%) was exported as S-nitrosothiol, but this fraction was not increased at low oxygen tensions that favor the deoxy (T-state) conformation of Hb. Results of these studies show that, within the redox-active erythrocyte environment, the beta-globin cysteine 93 is maintained in a reduced state, necessary for normal oxygen affinity, and incapable of oxygen-linked NO storage and delivery.     

Fitness landscape of human immunodeficiency virus type 1 protease quasispecies

Here we show, at a high resolution (1%), the human immunodeficiency virus type 1 (HIV-1) protease gene quasispecies landscape from three infected na?ve individuals. A huge range of genetic configurations was found (67%, 71%, and 80% of the nucleotide clones from the three individuals, respectively, were different), and these configurations created a dense net that linked different parts of the viral population. Similarly, a vast diversity of different protease activities was also found. Importantly, 65% of the analyzed enzymes had detectable protease activity, and 11% of the minority individual variants showed similar or better fitness than the master (most abundant) enzyme, suggesting that the viral complexity in this genomic region does not exclusively depend on the enzyme's catalytic efficiency. Several high-fitness minority variants had only one substitution compared to the master sequence, supporting the possibility that the rugged HIV-1 protease quasispecies fitness landscape may be formed by a continuous network that can be traversed by single mutational steps without passing through defective or less-adapted proteins.     

Heterozygous Reelin Mutations Cause Autosomal-Dominant Lateral Temporal Epilepsy

Autosomal-dominant lateral temporal epilepsy (ADLTE) is a genetic epilepsy syndrome clinically characterized by focal seizures with prominent auditory symptoms. ADLTE is genetically heterogeneous, and mutations in LGI1 account for fewer than 50% of affected families. Here, we report the identification of causal mutations in reelin (RELN) in seven ADLTE-affected families without LGI1 mutations. We initially investigated 13 ADLTE-affected families by performing SNP-array linkage analysis and whole-exome sequencing and identified three heterozygous missense mutations co-segregating with the syndrome. Subsequent analysis of 15 small ADLTE-affected families revealed four additional missense mutations. 3D modeling predicted that all mutations have structural effects on protein-domain folding. Overall, RELN mutations occurred in 7/40 (17.5%) ADLTE-affected families. RELN encodes a secreted protein, Reelin, which has important functions in both the developing and adult brain and is also found in the blood serum. We show that ADLTE-related mutations significantly decrease serum levels of Reelin, suggesting an inhibitory effect of mutations on protein secretion. We also show that Reelin and LGI1 co-localize in a subset of rat brain neurons, supporting an involvement of both proteins in a common molecular pathway underlying ADLTE. Homozygous RELN mutations are known to cause lissencephaly with cerebellar hypoplasia. Our findings extend the spectrum of neurological disorders associated with RELN mutations and establish a link between RELN and LGI1, which play key regulatory roles in both the developing and adult brain.     

Grooming coercion and the post-conflict trading of social services in wild Barbary macaques

In animal and human societies, social services such as protection from predators are often exchanged between group members. The tactics that individuals display to obtain a service depend on its value and on differences between individuals in their capacity to aggressively obtain it. Here we analysed the exchange of valuable social services (i.e. grooming and relationship repair) in the aftermath of a conflict, in wild Barbary macaques (Macaca sylvanus). The relationship repair function of post-conflict affiliation (i.e. reconciliation) was apparent in the victim but not in the aggressor. Conversely, we found evidence for grooming coercion by the aggressor; when the victim failed to give grooming soon after a conflict they received renewed aggression from the aggressor. We argue that post-conflict affiliation between former opponents can be better described as a trading of social services rather than coercion alone, as both animals obtain some benefits (i.e. grooming for the aggressor and relationship repair for the victim). Our study is the first to test the importance of social coercion in the aftermath of a conflict. Differences in competitive abilities can affect the exchange of services and the occurrence of social coercion in animal societies. This may also help explain the variance between populations and species in their social behaviour and conflict management strategies.     

Phenotypic hypersusceptibility to multiple protease inhibitors and low replicative capacity in patients who are chronically infected with human immunodeficiency virus type 1

Increased susceptibility to the protease inhibitors saquinavir and amprenavir has been observed in human immunodeficiency virus type 1 (HIV-1) with specific mutations in protease (V82T and N88S). Increased susceptibility to ritonavir has also been described in some viruses from antiretroviral agent-naive patients with primary HIV-1 infection in association with combinations of amino acid changes at polymorphic sites in the protease. Many of the viruses displaying increased susceptibility to protease inhibitors also had low replication capacity. In this retrospective study, we analyze the drug susceptibility phenotype and the replication capacity of virus isolates obtained at the peaks of viremia during five consecutive structured treatment interruptions in 12 chronically HIV-1-infected patients. Ten out of 12 patients had at least one sample with protease inhibitor hypersusceptibility (change 相似文献