Alternative splicing creates sex-specific transcripts and truncated forms of the furin protease in the parasite Dirofilaria immitis
Molecular Parasitology Division, New England Biolabs Inc., Beverly, MA 01915, USA. Gene
(Impact Factor: 2.14).
10/1999; 237(1):161-75. DOI: 10.1016/S0378-1119(99)00282-6
Many extracellular proteins are activated by specific cleavage with an endoprotease. In nematodes, several proteins are cleaved after RX(K/R)R, the recognition site for the subtilisin-like proprotein convertases, furin and blisterase. To characterize furin in the parasitic nematode Dirofilaria immitis, we determined the sequence of the difur gene and its multiple transcripts. The gene spans 11 kb; encodes 16 exons and has a complex pattern of alternative splicing which generates at least 16 distinct mRNAs. The major transcript is a 4.4 kb mRNA which codes for a protein of 834 aa with an unusually long prodomain of 254 aa. Sex-specific splice variants of difur were observed by RT-PCR. The three female-specific and five male-specific transcripts are the first reported examples of sex-specific splicing in parasitic nematodes. This suggests that nematodes have sex-specific factors which regulate RNA splicing. Other splice variants are predicted to alter the phosphorylation and localization of the protease. Alternative splicing after the prodomain encodes a truncated protein that may be an inhibitor and/or substrate of Difurin.
Available from: usda.gov
- "In contrast, examples of AS are only scarcely reported in the parasitic nematodes. The fur gene of Dirofilaria immitis  and the glutathione S-transferase 3 gene of Onchocerca volvulus  are among the few examples of alternatively spliced genes identified in animal-parasitic nematodes. However, studies on the functional consequences of AS are still lacking in this group of nematodes. "
[Show abstract] [Hide abstract]
ABSTRACT: Chorismate mutase (CM) secreted from the stylet of plant-parasitic nematodes plays an important role in plant parasitism. We isolated and characterized a new nematode CM gene (Gr-cm-1) from the potato cyst nematode, Globodera rostochiensis. The Gr-cm-1 gene was found to exist in the nematode genome as a single-copy gene that has two different alleles, Gr-cm-1A and Gr-cm-1B, both of which could give rise to two different mRNA transcripts of Gr-cm-1 and Gr-cm-1-IRII. In situ mRNA hybridization showed that the Gr-cm-1 gene was exclusively expressed within the subventral oesophageal gland cells of the nematode. Gr-cm-1 was demonstrated to encode a functional CM (GR-CM-1) potentially having a dimeric structure as the secreted bacterial *AroQ CMs. Gr-cm-1-IRII, generated by retention of intron 2 of the Gr-cm-1 pre-mRNA through alternative splicing (AS), would encode a truncated protein (GR-CM-1t) lacking the CM domain with no CM activity. The quantitative real-time reverse transcription-PCR assay revealed that splicing of the Gr-cm-1 gene was developmentally regulated; Gr-cm-1 was up-regulated whereas Gr-cm-1-IRII was down-regulated in early nematode parasitic stages compared to the preparasitic juvenile stage. Low-temperature SDS-PAGE analysis revealed that GR-CM-1 could form homodimers when expressed in Escherichia coli and the dimerization domain was retained in the truncated GR-CM-1t protein. The specific interaction between the two proteins was demonstrated in yeast. Our data suggested that the novel splice variant might function as a dominant negative isoform through heterodimerization with the full-length GR-CM-1 protein and that AS may represent an important mechanism for regulating CM activity during nematode parasitism.
[Show abstract] [Hide abstract]
ABSTRACT: Vapor phase catalytic hydrodechlorination of 1,1,1-trichloroethane (TCA) has been studied using various supported platinum catalysts in a plug microflow reactor. The reactor was operated at temperatures ranging from 250 to 350°C, a H2:TCA:He ratio of 10:1:89, a space velocity of 24 L/g cat-h, and atmospheric pressure. To study the deactivation process, tests were carried out by dividing the catalyst bed into three segments (inlet, middle, outlet) separated by glass wool plugs. Although the catalysts showed high initial activity, rapid deactivation was also observed. For example, when using a Pt/η-alumina catalyst at 250°C, essentially complete TCA conversion was observed initially; however, after 15 h TCA conversion had declined to < 25 percent. To understand the deactivation process, surface acidity and basicity, coke content, chlorine content, and platinum content were measured for both the fresh and the used catalysts. These measurements showed that up to 40 wt% coke formed on the supported platinum catalyst and that the acidity changed significantly during the reaction at 350°C.
[Show abstract] [Hide abstract]
ABSTRACT: Significant advances have recently been made in our understanding of the mechanisms of activation of proteins that require processing. Often this involves endoproteolytic cleavage of precursor forms at basic residues, and is carried out by a group of serine endoproteinases, termed the proprotein convertases. In mammals, seven different convertases have been identified to date. These act in both the regulated secretory pathway for the processing of prohormones and proneuropeptides and in the constitutive secretory pathway, in which a variety of proproteins are activated endoproteolytically. The recently completed sequence of the nematode Caenorhabditis elegans genome affords a unique opportunity to examine the entire proprotein convertase family in a multicellular organism. Here we review the nature of the family, emphasising the structural features, characteristic of the four nematode genes, that supply all of the necessary functions unique to this group of serine endoproteinases. Studies of the C. elegans genes not only provide important information about the evaluation of this gene family but should help to illuminate the roles of these proteins in mammalian systems. BioEssays 22:545-553, 2000.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.