title: Characterisation and expression analysis of cathepsins and ubiquitin-proteasome genes in gilthead sea bream (Sparus aurata) skeletal muscle.
abstract: BACKGROUND
  The proteolytic enzymes involved in normal protein turnover in fish muscle are also responsible for post-mortem softening of the flesh and are therefore potential determinants of product quality. The main enzyme systems involved are calpains, cathepsins, and the ubiquitin-proteasome (UbP). In this study on Sparus aurata (Sa), the coding sequences of cathepsins (SaCTSB and SaCTSDb) and UbP family members (SaN3 and SaUb) were cloned from fast skeletal muscle, and their expression patterns were examined during ontogeny and in a fasting/re-feeding experiment.
  
  
  RESULTS
  The amino acid sequences identified shared 66-100% overall identity with their orthologues in other vertebrates, with well conserved characteristic functional domains and catalytic residues. SaCTSDb showed phylogenetic, sequence and tissue distribution differences with respect to its paralogue SaCTSDa, previously identified in the ovary. Expression of gilthead sea bream cathepsins (B, L, Da, Db) and UbP members (N3, Ub, MuRF1 and MAFbx) in fast skeletal muscle was determined at three different life-history stages and in response to fasting and re-feeding in juveniles. Most of the proteolytic genes analysed were significantly up-regulated during fasting, and down-regulated with re-feeding and, between the fingerling (15 g) and juvenile/adult stages (~50/500 g), consistent with a decrease in muscle proteolysis in both later contexts. In contrast, SaCTSDa and SaMuRF1 expression was relatively stable with ontogeny and SaUb had higher expression in fingerlings and adults than juveniles.
  
  
  CONCLUSIONS
  The data obtained in the present study suggest that cathepsins and UbP genes in gilthead sea bream are co-ordinately regulated during ontogeny to control muscle growth, and indicate that feeding regimes can modulate their expression, providing a potential dietary method of influencing post-mortem fillet tenderisation, and hence, product quality.
authors.affiliation: Department of Physiology and Immunology, Faculty of Biology, University of Barcelona, Av. Diagonal 643, Barcelona, 08028, Spain. csalmeron@ub.edu.
authors.forename: Cristina
authors.initials: C
authors.lastname: Salmerón
authors.affiliation: Department of Physiology and Immunology, Faculty of Biology, University of Barcelona, Av. Diagonal 643, Barcelona, 08028, Spain. mnavarro@ub.edu.
authors.forename: Isabel
authors.initials: I
authors.lastname: Navarro
authors.affiliation: Scottish Oceans Institute, School of Biology, University of St Andrews, St Andrews Fife, KY16 8LB, Scotland, UK. iaj@st-andrews.ac.uk.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Johnston
authors.affiliation: Department of Physiology and Immunology, Faculty of Biology, University of Barcelona, Av. Diagonal 643, Barcelona, 08028, Spain. jgutierrez@ub.edu.
authors.forename: Joaquim
authors.initials: J
authors.lastname: Gutiérrez
authors.affiliation: Department of Physiology and Immunology, Faculty of Biology, University of Barcelona, Av. Diagonal 643, Barcelona, 08028, Spain. ecapilla@ub.edu.
authors.forename: Encarnación
authors.initials: E
authors.lastname: Capilla
mesh_terms: D000367:Age Factors; D000595:Amino Acid Sequence; D000818:Animals; D002154:Calpain / Q000235:genetics* / Q000378:metabolism; D002403:Cathepsins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005396:Fish Products / Q000032:analysis; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism*; D010802:Phylogeny; D046988:Proteasome Endopeptidase Complex / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D021541:Sea Bream / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D025801:Ubiquitin / Q000235:genetics* / Q000378:metabolism
chemical_list: D029941:Fish Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D025801:Ubiquitin; D002403:Cathepsins; D002154:Calpain; D046988:Proteasome Endopeptidase Complex