Dataset Information

Functional properties of the four Atlantic salmon (Salmo salar) aryl hydrocarbon receptor type 2 (AHR2) isoforms.

ABSTRACT: The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor through which organochlorine contaminants including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and some polycyclic aromatic hydrocarbons induce toxicity and altered gene expression. Atlantic salmon has multiple AHR genes, of which two belong to the AHR1 clade and four belong to the AHR2 clade. The four AHR2 forms (alpha, beta, gamma, delta) are more highly expressed than the AHR1 (alpha, beta,) forms and all six AHRs are highly similar in pairs, likely originating from a whole-genome duplication in the salmonid ancestor. It has been speculated that having multiple AHRs contributes to the very high sensitivity of salmonid species to TCDD and related chemicals. To test the hypothesis that all four salmon AHR2 proteins are expressed and functional, we measured mRNA transcription for each AHR2 in several tissues, cloned the cDNAs and evaluated the functional properties of the expressed proteins. Analysis by real-time PCR revealed that the receptors showed differences in transcript levels among salmon tissues and that in general AHR2alpha was transcribed at higher levels than the other three AHR2s. Velocity sedimentation analysis showed that all four in vitro-expressed AHR2 proteins exhibit specific, high-affinity binding of [(3)H]TCDD. When expressed in COS-7 cells, all four AHR2 proteins were able to drive the expression of a reporter gene under control of murine CYP1A1 enhancer elements. From EC(50) values determined in TCDD concentration-response experiments, all four salmon AHR2s show similar sensitivity to TCDD. In summary, all four Atlantic salmon AHR2 appear to function in AHR-mediated signaling, suggesting that all four proteins are involved in TCDD-mediated toxicity.

SUBMITTER: Hansson MC

PROVIDER: S-EPMC2264924 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Functional properties of the four Atlantic salmon (Salmo salar) aryl hydrocarbon receptor type 2 (AHR2) isoforms.

Hansson Maria C MC Hahn Mark E ME

Aquatic toxicology (Amsterdam, Netherlands) 20071101 2

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor through which organochlorine contaminants including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and some polycyclic aromatic hydrocarbons induce toxicity and altered gene expression. Atlantic salmon has multiple AHR genes, of which two belong to the AHR1 clade and four belong to the AHR2 clade. The four AHR2 forms (alpha, beta, gamma, delta) are more highly expressed than the AHR1 (alpha, beta,) forms and all six AHRs ...[more]

PMID: 18063141

Similar Datasets

Project description:The high-affinity/low-capacity system Slc15a2 (PepT2) is responsible for the reuptake of di/tripeptides from the renal proximal tubule, but it also operates in many other tissues and organs. Information regarding PepT2 in teleost fish is limited and, to date, functional data are available from the zebrafish (Danio rerio) only. Here, we report the identification of two slc15a2 genes in the Atlantic salmon (Salmo salar) genome, namely slc15a2a and slc15a2b. The two encoded PepT2 proteins share 87% identity and resemble both structurally and functionally the canonical vertebrate PepT2 system. The mRNA tissue distribution analyses reveal a widespread distribution of slc15a2a transcripts, being more abundant in the brain and gills, while slc15a2b transcripts are mainly expressed in the kidney and the distal part of the gastrointestinal tract. The function of the two transporters was investigated by heterologous expression in Xenopus laevis oocytes and two-electrode voltage-clamp recordings of transport and presteady-state currents. Both PepT2a and PepT2b in the presence of Gly-Gln elicit pH-dependent and Na+ independent inward currents. The biophysical and kinetic analysis of the recorded currents defined the transport properties, confirming that the two Atlantic salmon PepT2 proteins behave as high-affinity/low-capacity transporters. The recent structures and the previous kinetic schemes of rat and human PepT2 qualitatively account for the characteristics of the two Atlantic salmon proteins. This study is the first to report on the functional expression of two PepT2-type transporters that operate in the same vertebrate organism as a result of (a) gene duplication process(es). KEY POINTS: Two slc15a2-type genes, slc15a2a and slc15a2b coding for PepT2-type peptide transporters were found in the Atlantic salmon. slc15a2a transcripts, widely distributed in the fish tissues, are abundant in the brain and gills, while slc15a2b transcripts are mainly expressed in the kidney and distal gastrointestinal tract. Amino acids involved in vertebrate Slc15 transport function are conserved in PepT2a and PepT2b proteins. Detailed kinetic analysis indicates that both PepT2a and PepT2b operate as high-affinity transporters. The kinetic schemes and structures proposed for the mammalian models of PepT2 are suitable to explain the function of the two Atlantic salmon transporters.

Project description:BACKGROUND: Hyperthermia has been shown in a number of organisms to induce developmental defects as a result of changes in cell proliferation, differentiation and gene expression. In spite of this, salmon aquaculture commonly uses high water temperature to speed up developmental rate in intensive production systems, resulting in an increased frequency of skeletal deformities. In order to study the molecular pathology of vertebral deformities, Atlantic salmon was subjected to hyperthermic conditions from fertilization until after the juvenile stage. RESULTS: Fish exposed to the high temperature regime showed a markedly higher growth rate and a significant higher percentage of deformities in the spinal column than fish reared at low temperatures. By analyzing phenotypically normal spinal columns from the two temperature regimes, we found that the increased risk of developing vertebral deformities was linked to an altered gene transcription. In particular, down-regulation of extracellular matrix (ECM) genes such as col1a1, osteocalcin, osteonectin and decorin, indicated that maturation and mineralization of osteoblasts were restrained. Moreover, histological staining and in situ hybridization visualized areas with distorted chondrocytes and an increased population of hypertrophic cells. These findings were further confirmed by an up-regulation of mef2c and col10a, genes involved in chondrocyte hypertrophy. CONCLUSION: The presented data strongly indicates that temperature induced fast growth is severely affecting gene transcription in osteoblasts and chondrocytes; hence change in the vertebral tissue structure and composition. A disrupted bone and cartilage production was detected, which most likely is involved in the higher rate of deformities developed in the high intensive group. Our results are of basic interest for bone metabolism and contribute to the understanding of the mechanisms involved in development of temperature induced vertebral pathology. The findings may further conduce to future molecular tools for assessing fish welfare in practical farming.

Dataset Information

Functional properties of the four Atlantic salmon (Salmo salar) aryl hydrocarbon receptor type 2 (AHR2) isoforms.

Publications

Functional properties of the four Atlantic salmon (Salmo salar) aryl hydrocarbon receptor type 2 (AHR2) isoforms.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets