title: Autographa californica multiple nucleopolyhedrovirus and Choristoneura fumiferana multiple nucleopolyhedrovirus v-cath genes are expressed as pre-proenzymes.
abstract: Intracellular processing and trafficking of the baculovirus v-cath expressed cathepsin (V-CATH), which lacks canonical targeting signals, are poorly understood. The cathepsins of Autographa californica multiple nucleopolyhedrovirus (AcMNPV), Choristoneura fumiferana multiple nucleopolyhedrovirus (CfMNPV) and most other alphabaculovirus group I nucleopolyhedroviruses have well-conserved N-termini containing overlapping chymotrypsin-cleavage (Y(11)) and myristoylation (G(12)) motifs, which are suggestive of proteolytic signal-peptide cleavage to generate proV-CATH and subsequent acylation. To determine proteolytic N-terminal processing of V-CATH, haemagglutinin epitope-coding tags were fused to the 5' and/or 3' ends of AcMNPV and CfMNPV v-cath. Immunoblot analysis suggested that a small N-terminal peptide is cleaved for both viruses, indicating that v-cath is expressed as a pre-proenzyme. The two viral homologues undergo similar proteolytic processing, but have different glycosylation or other post-translational modifications. An AcMNPV V-CATH-DsRED fusion protein co-localized to the endoplasmic reticulum with an HDEL motif-containing green fluorescent protein. Based on these findings, pre-proV-CATH processing and trafficking mechanisms are postulated.
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Hodgson
authors.affiliation: Laboratory for Molecular Virology, Great Lakes Forestry Centre, Sault Ste Marie, ON P6A 2E5, Canada.
authors.forename: Basil M
authors.initials: BM
authors.lastname: Arif
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Krell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002403:Cathepsins / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004792:Enzyme Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D007915:Lepidoptera / Q000821:virology*; D008969:Molecular Sequence Data; D009036:Moths / Q000821:virology*; D017924:Nucleopolyhedroviruses / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004792:Enzyme Precursors; D014764:Viral Proteins; D002403:Cathepsins; D003546:Cysteine Endopeptidases; C417028:V-CATH protein, Autographa californica nucleopolyhedrovirus