title: Chaperone roles for TMAO and HSP70 during hyposmotic stress in the spiny dogfish shark (Squalus acanthias).
abstract: Salinity decreases are experienced by many marine elasmobranchs. To understand how these fishes cope with hyposmotic stress on a cellular level, we used the spiny dogfish shark (Squalus acanthias) as a model to test whether a reciprocal relationship exists between the cell's two primary protein protection mechanisms, the chemical (e.g., trimethylamine oxide, TMAO) and molecular (e.g., heat shock protein 70, HSP70) chaperone systems. This relationship is interesting given that many elasmobranchs are expected to gain water and lose osmolytes, chemical chaperones, and ions as they osmoconform to new, lowered salinity. Dogfish were cannulated for repeated blood sampling and exposed to 70% seawater (SW) for 48 h. These hyposmotic conditions had no effect on red blood cell (RBC) and white muscle TMAO concentrations, and did not result in HSP70 induction or signs of protein damage (i.e., increased ubiquitin), suggesting that TMAO levels were sufficiently protective in these tissues. However, in the gill, we observed a significant decrease in TMAO concentration and a significant induction of HSP70 as well as signs of protein damage. In the face of this cellular stress response, gill Na(+)/K(+)-ATPase (NKA) activity significantly increased during hyposmotic conditions, as expected. We suggest that this functional preservation in the gill is partly the result of HSP70 induction with lowered salinity. We conclude a reciprocal relationship between TMAO and HSP70 in the gills of dogfish as a result of in vivo hyposmotic stress. When osmotically induced protein damage surpasses the protective capacity of remaining TMAO, HSP70 is induced to preserve tissue and organismal function.
authors.affiliation: Department of Biochemistry, Mount Allison University, Sackville, NB, Canada.
authors.forename: Robyn J
authors.initials: RJ
authors.lastname: MacLellan
authors.affiliation: Department of Biology, Mount Allison University, Sackville, NB, E4L 1G7, Canada.
authors.forename: Louise
authors.initials: L
authors.lastname: Tunnah
authors.affiliation: Atlantic Cancer Research Institute, Moncton, NB, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Barnett
authors.affiliation: Department of Integrative Biology, University of Guelph, Guelph, ON, Canada.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Wright
authors.affiliation: Department of Biochemistry, Mount Allison University, Sackville, NB, Canada.
authors.forename: Tyson
authors.initials: T
authors.lastname: MacCormack
authors.affiliation: Department of Biology, Mount Allison University, Sackville, NB, E4L 1G7, Canada. scurrie@mta.ca.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Currie
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D029941:Fish Proteins / Q000378:metabolism*; D005880:Gills / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D008297:Male; D008744:Methylamines / Q000097:blood / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D009997:Osmotic Pressure; D054712:Salinity; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D048251:Squalus acanthias / Q000097:blood / Q000378:metabolism*; D013997:Time Factors; D014508:Urea / Q000097:blood
chemical_list: D029941:Fish Proteins; D018840:HSP70 Heat-Shock Proteins; D008744:Methylamines; D014508:Urea; D000254:Sodium-Potassium-Exchanging ATPase; C005855:trimethyloxamine
keywords: Chemical chaperone; Elasmobranch; Gill; Heat shock proteins; Trimethylamine oxide; Ubiquitin