RESUMEN
BACKGROUND: Snake venom metalloproteinases (SVMPs) are widely distributed in snake venoms and are versatile toxins, targeting many important elements involved in hemostasis, such as basement membrane proteins, clotting proteins, platelets, endothelial and inflammatory cells. The functional diversity of SVMPs is in part due to the structural organization of different combinations of catalytic, disintegrin, disintegrin-like and cysteine-rich domains, which categorizes SVMPs in 3 classes of precursor molecules (PI, PII and PIII) further divided in 11 subclasses, 6 of them belonging to PII group. This heterogeneity is currently correlated to genetic accelerated evolution and post-translational modifications. RESULTS: Thirty-one SVMP cDNAs were full length cloned from a single specimen of Bothrops neuwiedi snake, sequenced and grouped in eleven distinct sequences and further analyzed by cladistic analysis. Class P-I and class P-III sequences presented the expected tree topology for fibrinolytic and hemorrhagic SVMPs, respectively. In opposition, three distinct segregations were observed for class P-II sequences. P-IIb showed the typical segregation of class P-II SVMPs. However, P-IIa grouped with class P-I cDNAs presenting a 100% identity in the 365 bp at their 5' ends, suggesting post-transcription events for interclass recombination. In addition, catalytic domain of P-IIx sequences segregated with non-hemorrhagic class P-III SVMPs while their disintegrin domain grouped with other class P-II disintegrin domains suggesting independent evolution of catalytic and disintegrin domains. Complementary regions within cDNA sequences were noted and may participate in recombination either at DNA or RNA levels. Proteins predicted by these cDNAs show the main features of the correspondent classes of SVMP, but P-IIb and P-IIx included two additional cysteines cysteines at the C-termini of the disintegrin domains in positions not yet described. CONCLUSIONS: In B. neuwiedi venom gland, class P-II SVMPs were represented by three different types of transcripts that may have arisen by interclass recombination with P-I and P-III sequences after the divergence of the different classes of SVMPs. Our observations indicate that exon shuffling or post-transcriptional mechanisms may be driving these recombinations generating new functional possibilities for this complex group of snake toxins.
Asunto(s)
Bothrops/genética , Variación Genética , Metaloproteasas/genética , Venenos de Serpiente/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Dominio Catalítico/genética , Clonación Molecular , ADN Complementario , Metaloproteasas/química , Metaloproteasas/metabolismo , Filogenia , Procesamiento Proteico-Postraduccional , Recombinación Genética , Alineación de Secuencia , Análisis de Secuencia de ADN , Venenos de Serpiente/metabolismoRESUMEN
Snake venom metalloproteinases (SVMPs) are widely distributed in snake venoms and are versatiletoxins, targeting many important elements involved in hemostasis, such as basement membrane proteins, clottingproteins, platelets, endothelial and inflammatory cells. The functional diversity of SVMPs is in part due to thestructural organization of different combinations of catalytic, disintegrin, disintegrin-like and cysteine-rich domains,which categorizes SVMPs in 3 classes of precursor molecules (PI, PII and PIII) further divided in 11 subclasses, 6 ofthem belonging to PII group. This heterogeneity is currently correlated to genetic accelerated evolution and posttranslationalmodifications. Thirty-one SVMP cDNAs were full length cloned from a single specimen of Bothrops neuwiedi snake,sequenced and grouped in eleven distinct sequences and further analyzed by cladistic analysis. Class P-I and classP-III sequences presented the expected tree topology for fibrinolytic and hemorrhagic SVMPs, respectively. Inopposition, three distinct segregations were observed for class P-II sequences. P-IIb showed the typical segregationof class P-II SVMPs. However, P-IIa grouped with class P-I cDNAs presenting a 100% identity in the 365 bp at their5 ends, suggesting post-transcription events for interclass recombination. In addition, catalytic domain of P-IIxsequences segregated with non-hemorrhagic class P-III SVMPs while their disintegrin domain grouped with otherclass P-II disintegrin domains suggesting independent evolution of catalytic and disintegrin domains.Complementary regions within cDNA sequences were noted and may participate in recombination either at DNAor RNA levels.
Asunto(s)
Animales , Metaloproteasas/clasificación , Serpientes/clasificación , Venenos de SerpienteRESUMEN
Pteridium aquilinum (bracken fern) is one of the most common plants. Epidemiological studies have revealed a higher risk of certain types of cancers (i.e., esophageal, gastric) in people who consume bracken fern directly (as crosiers or rhizomes) or indirectly through the consumption of milk from livestock that fed on the plant. In animals, evidence exists regarding the associations between chronic bracken fern intoxication, papilloma virus infection, and the development of carcinomas. While it is possible that some carcinogens in bracken fern could be responsible for these cancers in both humans and animals, it is equally plausible that the observed increases in cancers could be related to induction of an overall immunosuppression by the plant/its various constituents. Under the latter scenario, normal tumor surveillance responses against nascent (non-bracken-induced) cancers or responses against viral infections (specifically those linked to induction of cancers) might be adversely impacted by continuous dietary exposure to this plant. Therefore, the overall objective of this study was to evaluate the immunomodulatory effects of bracken fern following daily ingestion of its extract by a murine host over a period of 14 (or up to 30) days. In C57BL/6 mice administered (by gavage) the extract, histological analyses revealed a significant reduction in splenic white pulp area. Among a variety of immune response parameters/functions assessed in these hosts and isolated cells, both delayed-type hypersensitivity (DTH) analysis and evaluation of IFNgamma production by NK cells during T(H)1 priming were also reduced. Lastly, the innate response in these hosts-assessed by analysis of NK cell cytotoxic functionality-was also diminished. The results here clearly showed the immunosuppressive effects of P. aquilinum and that many of the functions that were modulated could contribute to the increased risk of cancer formation in exposed hosts.