title: Functional diversity of secreted cestode Kunitz proteins: Inhibition of serine peptidases and blockade of cation channels.
abstract: We previously reported a multigene family of monodomain Kunitz proteins from Echinococcus granulosus (EgKU-1-EgKU-8), and provided evidence that some EgKUs are secreted by larval worms to the host interface. In addition, functional studies and homology modeling suggested that, similar to monodomain Kunitz families present in animal venoms, the E. granulosus family could include peptidase inhibitors as well as channel blockers. Using enzyme kinetics and whole-cell patch-clamp, we now demonstrate that the EgKUs are indeed functionally diverse. In fact, most of them behaved as high affinity inhibitors of either chymotrypsin (EgKU-2-EgKU-3) or trypsin (EgKU-5-EgKU-8). In contrast, the close paralogs EgKU-1 and EgKU-4 blocked voltage-dependent potassium channels (Kv); and also pH-dependent sodium channels (ASICs), while showing null (EgKU-1) or marginal (EgKU-4) peptidase inhibitory activity. We also confirmed the presence of EgKUs in secretions from other parasite stages, notably from adult worms and metacestodes. Interestingly, data from genome projects reveal that at least eight additional monodomain Kunitz proteins are encoded in the genome; that particular EgKUs are up-regulated in various stages; and that analogous Kunitz families exist in other medically important cestodes, but not in trematodes. Members of this expanded family of secreted cestode proteins thus have the potential to block, through high affinity interactions, the function of host counterparts (either peptidases or cation channels) and contribute to the establishment and persistence of infection. From a more general perspective, our results confirm that multigene families of Kunitz inhibitors from parasite secretions and animal venoms display a similar functional diversity and thus, that host-parasite co-evolution may also drive the emergence of a new function associated with the Kunitz scaffold.
authors.affiliation: Cátedra de Inmunología, Facultad de Química, Universidad de la República, Montevideo, Uruguay.|Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.
authors.forename: Martín
authors.initials: M
authors.lastname: Fló
authors.affiliation: Cátedra de Inmunología, Facultad de Química, Universidad de la República, Montevideo, Uruguay.
authors.forename: Mariana
authors.initials: M
authors.lastname: Margenat
authors.affiliation: Cátedra de Inmunología, Facultad de Química, Universidad de la República, Montevideo, Uruguay.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Pellizza
authors.affiliation: Unidad de Bioinformática, Institut Pasteur de Montevideo, Montevideo, Uruguay.
authors.forename: Martín
authors.identifier: 0000-0003-1182-8236
authors.initials: M
authors.lastname: Graña
authors.affiliation: Unidad de Bioquímica y Proteómica Analíticas, Institut Pasteur de Montevideo and Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay.
authors.forename: Rosario
authors.initials: R
authors.lastname: Durán
authors.affiliation: Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, México.
authors.forename: Adriana
authors.identifier: 0000-0002-3709-8916
authors.initials: A
authors.lastname: Báez
authors.affiliation: Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, México.
authors.forename: Emilio
authors.initials: E
authors.lastname: Salceda
authors.affiliation: Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, México.
authors.forename: Enrique
authors.identifier: 0000-0003-2428-7416
authors.initials: E
authors.lastname: Soto
authors.affiliation: Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Alvarez
authors.affiliation: Cátedra de Inmunología, Facultad de Química, Universidad de la República, Montevideo, Uruguay.
authors.forename: Cecilia
authors.identifier: 0000-0003-1444-211X
authors.initials: C
authors.lastname: Fernández
mesh_terms: D000818:Animals; D004443:Echinococcosis / Q000378:metabolism* / Q000469:parasitology*; D048209:Echinococcus granulosus; D005727:Ganglia, Spinal / Q000187:drug effects; D015801:Helminth Proteins / Q000378:metabolism*; D006790:Host-Parasite Interactions / Q000502:physiology*; D008958:Models, Molecular; D018408:Patch-Clamp Techniques; D010802:Phylogeny; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology / Q000502:physiology*; D061566:Voltage-Gated Sodium Channels / Q000187:drug effects
chemical_list: D015801:Helminth Proteins; D024642:Potassium Channels, Voltage-Gated; D015842:Serine Proteinase Inhibitors; D061566:Voltage-Gated Sodium Channels