- Email: [email protected]
Fish liver adrenoceptors - An update
s3 Sl-5
Molecular evolution of estrogen and beta subtypes in teleosts
receptor
alpha
Yu KI,_‘, Ma CH’, Nong Gls2, He ML’, Chow CH’, Chik FC’, Da HN’ and Cheng CHK2. Department of $.oology, The University of Hong Kong, Hong Kong and Department of Biochemistry, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
redefined the vertebrates. In
Symposium 2: Antifreeze proteins: evolution, regulation and mechanisms of action. Chair: G. Fletcher (Canada) s2-1 Antifreeze
protein structure
and function
K.Vanva Ewart NRC Institute for Marine Biosciences 1411 Oxford St., Halifax NS, Canada B3H 321 Antifreeze proteins (AFPs) bind to ice crystals and inhibit their growth. Structurally diverse AFPs are found in a number of animals, plants, bacteria and fungi from cold environments. Although several of the antifreezes have been shown to bind to different molecular surfaces of ice crystals, they all share the capacity to slow or stop ice growth and cause a non-colligative solution freezing point depression. The mechanism by which AFPs adsorb to ice surfaces has been the focus of intense study. However, the challenge of studying ice as a protein l&and together with the sheer diversity of AFP structures have made AFP-ice interaction an elusive process to define at the molecular level. In spite of these obstacles, significant developments have taken place in determining the interactions that lead to protein binding to ice. This seminar will summarise recent findings in AFP research and will highlight some of the discoveries that have been made. Delineating the mechanism of AFP-ice interaction will, in turn, provide new perspectives on the emergence, functions and roles of these proteins in nature and their applications in biotechnology. s2-2
Sl-6
Fish liver adrenoceptors - An update. Moon TW, Dugan S, Nickerson J and Drouin G Department of Biology, University of Ottawa, Ottawa, Ontario, Canada KIN 6N5. We have clearly demonstrated the presence of a- and j3adrenoceptors (ARs) and their signal transduction pathways in hepatic membranes of trout, bullhead and eels. The physiological role of this dual receptor system, however, is not clear. Using primers designed from mammalian AR sequences, we have cloned and sequenced putative ARs from trout and bullhead. The expression of these receptors in various tissues of trout exposed to various environmental insults is being undertaken. The regulation of the AR subtypes present on fish hepatocytes is being characterized using competitive ligand binding and enzyme assays. Cultured bullhead hepatocytes exposed to P-AR agonists marginally altered membrane receptor numbers and apparent affinities for the mixed agonist CGP 12177 suggesting limited down-regulation. Displacement studies support CGP-binding is to receptors with characteristics of both the mammalian PI- and &ARs, consistent with molecular studies that point towards the P-AR of trout not being clearly either a PI- or j&AR. Southern blot analyses indicate the presence of two P-AR genes in both trout and bullhead. These studies indicate that the three fish species studied retain an AR system that is qualitatively different from that reported in mammals.
Molecular
evolution of fish antifreeze
proteins.
Cheng C-HC Department of Ecology, Ethology and Evolution, University of Illinois, Urbana, Illinois 61801, USA. Evolution of the antifreeze (AF) proteins in teleost fishes to survive in freezing marine habitats is an elegant illustration of a direct link between natural selection, new gene genesis, phenotypic expression, and organismal success. The environmental selective force was the onset of the Tertiary glaciation of the polar and subpolar waters, where endemic fish must either evolve a protective function to survive, or succumb to freezing death. Drawing on pre-existing ancestral genes, new AF genes were derived. Expressing the ice-binding protein in abundance singularly ensured the freeze-avoidance phenotype, and thus the continuation of a fish lineage. For the Antarctic notothenioid fishes captive in the oceanographically isolated Southern Ocean, creation of their AF glycoproteins had in addition empowered their adaptive radiation and diversification into all icy ecological niches vacated by the extinction of unprotected fish, to become the foremost Antarctic fish taxon and the only known marine flock today. Fish AFs have evolved independently multiple times leading to 5 (and counting) different structural types, promising a rich trove of yet to be unveiled molecular mechanisms of novel gene genesis. Already demonstrated are the rare protein sequence convergence of near-identical AFGPs in the unrelated Antarctic notothenioids and northern cods, and the de nova creation of notothenioid AFGP gene by expanding a rudimentruy short sequence from a functionally unrelated serine protease. The recency of the latter has in fact permitted us to capture the evolutionary transition from protease to AFGP in form of lingering chimeric protease-AFGP intermediates in the contemporary notothenioid genomes.
Molecular evolution of estrogen and beta subtypes in teleosts
receptor
alpha
Yu KI,_‘, Ma CH’, Nong Gls2, He ML’, Chow CH’, Chik FC’, Da HN’ and Cheng CHK2. Department of $.oology, The University of Hong Kong, Hong Kong and Department of Biochemistry, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
redefined the vertebrates. In
Symposium 2: Antifreeze proteins: evolution, regulation and mechanisms of action. Chair: G. Fletcher (Canada) s2-1 Antifreeze
protein structure
and function
K.Vanva Ewart NRC Institute for Marine Biosciences 1411 Oxford St., Halifax NS, Canada B3H 321 Antifreeze proteins (AFPs) bind to ice crystals and inhibit their growth. Structurally diverse AFPs are found in a number of animals, plants, bacteria and fungi from cold environments. Although several of the antifreezes have been shown to bind to different molecular surfaces of ice crystals, they all share the capacity to slow or stop ice growth and cause a non-colligative solution freezing point depression. The mechanism by which AFPs adsorb to ice surfaces has been the focus of intense study. However, the challenge of studying ice as a protein l&and together with the sheer diversity of AFP structures have made AFP-ice interaction an elusive process to define at the molecular level. In spite of these obstacles, significant developments have taken place in determining the interactions that lead to protein binding to ice. This seminar will summarise recent findings in AFP research and will highlight some of the discoveries that have been made. Delineating the mechanism of AFP-ice interaction will, in turn, provide new perspectives on the emergence, functions and roles of these proteins in nature and their applications in biotechnology. s2-2
Sl-6
Fish liver adrenoceptors - An update. Moon TW, Dugan S, Nickerson J and Drouin G Department of Biology, University of Ottawa, Ottawa, Ontario, Canada KIN 6N5. We have clearly demonstrated the presence of a- and j3adrenoceptors (ARs) and their signal transduction pathways in hepatic membranes of trout, bullhead and eels. The physiological role of this dual receptor system, however, is not clear. Using primers designed from mammalian AR sequences, we have cloned and sequenced putative ARs from trout and bullhead. The expression of these receptors in various tissues of trout exposed to various environmental insults is being undertaken. The regulation of the AR subtypes present on fish hepatocytes is being characterized using competitive ligand binding and enzyme assays. Cultured bullhead hepatocytes exposed to P-AR agonists marginally altered membrane receptor numbers and apparent affinities for the mixed agonist CGP 12177 suggesting limited down-regulation. Displacement studies support CGP-binding is to receptors with characteristics of both the mammalian PI- and &ARs, consistent with molecular studies that point towards the P-AR of trout not being clearly either a PI- or j&AR. Southern blot analyses indicate the presence of two P-AR genes in both trout and bullhead. These studies indicate that the three fish species studied retain an AR system that is qualitatively different from that reported in mammals.
Molecular
evolution of fish antifreeze
proteins.
Cheng C-HC Department of Ecology, Ethology and Evolution, University of Illinois, Urbana, Illinois 61801, USA. Evolution of the antifreeze (AF) proteins in teleost fishes to survive in freezing marine habitats is an elegant illustration of a direct link between natural selection, new gene genesis, phenotypic expression, and organismal success. The environmental selective force was the onset of the Tertiary glaciation of the polar and subpolar waters, where endemic fish must either evolve a protective function to survive, or succumb to freezing death. Drawing on pre-existing ancestral genes, new AF genes were derived. Expressing the ice-binding protein in abundance singularly ensured the freeze-avoidance phenotype, and thus the continuation of a fish lineage. For the Antarctic notothenioid fishes captive in the oceanographically isolated Southern Ocean, creation of their AF glycoproteins had in addition empowered their adaptive radiation and diversification into all icy ecological niches vacated by the extinction of unprotected fish, to become the foremost Antarctic fish taxon and the only known marine flock today. Fish AFs have evolved independently multiple times leading to 5 (and counting) different structural types, promising a rich trove of yet to be unveiled molecular mechanisms of novel gene genesis. Already demonstrated are the rare protein sequence convergence of near-identical AFGPs in the unrelated Antarctic notothenioids and northern cods, and the de nova creation of notothenioid AFGP gene by expanding a rudimentruy short sequence from a functionally unrelated serine protease. The recency of the latter has in fact permitted us to capture the evolutionary transition from protease to AFGP in form of lingering chimeric protease-AFGP intermediates in the contemporary notothenioid genomes.