engleski

Tissue distribution and gene expression regulation of MRP9 (abcc12) in rainbow trout and zebrafish

MRP9 is the last discovered member of the MRP subfamily. It has predicted topology of 12 transmembrane helices arranged in two membrane spanning domains and is similar in structure to short MRP’s sharing the highest degree of amino acid sequences identity (42%) with MRP5 (ABCC5). In human, MRP9 is expressed in various tumor tissues and cell lines, with negligible expression in normal tissues while in mice dominant expression is in testis with modest expression in other tissues. No physiological substrates of MRP9 have been identified so far. MRP9 has not been studied in fish and its possible role in aquatic species is not known. Main goals of our work were to determine the gene expression levels in different tissues of two fish species and to obtain first insights into regulation of Mrp9 gene expression. Using the qPCR we found ubiquitous expression of abcc9 with the same tissue distribution pattern in both fish species. High expression was found in intestine while the expression in other tissues was moderate to low (intestine >> testis/ovaries > kidney > liver >> brain > gills > muscle). We found no sex related differences in abcc9 mRNA levels. In addition, to study regulation of abcc9 in fish we used rainbow trout liver cell line R1 which showed high expression of various nuclear receptors. R1 cells were exposed for 24 h to 30 different model ligands of nuclear receptors. We found that fibrates, dexamethasone and fluoxetine induce abcc9, suggesting the involvement of peroxisome proliferator-activated receptors (PPARs) and glucocorticoid receptor (GR) in regulation of abcc9. Furthermore, we found that aryl hydrocarbon receptor (AhR) ligands like TCDD and benzo[a]pyren significantly elicit expression of abcc9. In conclusion, our results showed that abcc9 is under complex regulation of both, physiological as well as receptors related to xenobiotic metabolism. Determination of substrate specificity of Mrp9 will be focus of our further research.

abcc12 ; tissue distribution ; regulation

nije evidentirano