title: Two cathepsins B are responsible for the yolk protein hydrolysis in Culex quinquefasciatus.
abstract: Despite the established role of Culex quinquefasciatus as a vector of various neurotropic viruses, such as the Rift Valley and West Nile viruses, as well as lymphatic filariasis, little is known regarding the organism's reproductive physiology. As in other oviparous animals, vitellogenin, the most important source of nutrients for the embryo development, is digested by intracellular proteases. Using mass spectrometry, we have identified two cathepsin B homologues partially purified by self-proteolysis of Cx. quinquefasciatus total egg extract. The transcriptional profile of these two cathepsin B homologues was determined by quantitative RT-PCR, and the enzymatic activity associated with the peptidase was determined in ovaries after female engorgement. According to the VectorBase (vectorbase.org) annotation, both cathepsin B homologues shared approximately 66% identity in their amino acid sequences. The two cathepsin B genes are expressed simultaneously in the fat body of the vitellogenic females, and enzymatic activity was detected within the ovaries, suggesting an extra-ovarian origin. Similar to the transcriptional profile of vitellogenin, cathepsin B transcripts were shown to accumulate post-blood meal and reached their highest expression at 36 h PBM. However, while vitellogenin expression decreased drastically at 48 h PBM, the expression of the cathepsins increased until 84 h PBM, at which time the females of our colony were ready for oviposition. The similarity between their transcriptional profiles strongly suggests a role for the cathepsin B homologues in vitellin degradation.
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: Alexandre S
authors.initials: AS
authors.lastname: Moura
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: André F
authors.initials: AF
authors.lastname: Cardoso
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brasil; Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, INCT-EM, Rio de Janeiro, RJ, Brasil.
authors.forename: André L
authors.initials: AL
authors.lastname: Costa-da-Silva
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Winter
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: A Tania
authors.initials: AT
authors.lastname: Bijovsky
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002401:Cathepsin B / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D003465:Culex / Q000201:enzymology*; D030541:Databases, Genetic; D004527:Egg Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006868:Hydrolysis; D008969:Molecular Sequence Data; D010053:Ovary / Q000378:metabolism; D010063:Ovum / Q000378:metabolism; D010455:Peptides / Q000032:analysis; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D053719:Tandem Mass Spectrometry; D059467:Transcriptome; D014819:Vitellogenins / Q000378:metabolism
chemical_list: D004527:Egg Proteins; D010455:Peptides; D014819:Vitellogenins; D002401:Cathepsin B