Molecular cloning and characterization of a nuclear androgen receptor activated by 11-ketotestosterone

Abstract

Although 11-ketotestosterone is a potent androgen and induces male secondary sex characteristics in many teleosts, androgen receptors with high binding affinity for 11-ketotestosterone or preferential activation by 11-ketotestosterone have not been identified. So, the mechanism by which 11-ketotestosterone exhibits such high potency remains unclear. Recently we cloned the cDNA of an 11-ketotestosterone regulated protein, spiggin, from three-spined stickleback renal tissue. As spiggin is the only identified gene product regulated by 11-ketotestosterone, the stickleback kidney is ideal for determination of the mechanism of 11-ketotestosterone gene regulation. A single androgen receptor gene with two splicing variants, belonging to the androgen receptor-β subfamily was cloned from stickleback kidney. A high affinity, saturable, single class of androgen specific binding sites, with the characteristics of an androgen receptor, was identified in renal cytosolic and nuclear fractions. Measurement of ligand binding moieties in the cytosolic and nuclear fractions as well as to the recombinant receptor revealed lower affinity for 11-ketotestosterone than for dihydrotestosterone. Treatment with different androgens did not upregulate androgen receptor mRNA level or increase receptor abundance, suggesting that autoregulation is not involved in differential ligand activation. However, comparison of the transactivation potential of the stickleback androgen receptor with the human androgen receptor, in both human HepG2 cells and zebrafish ZFL cells, revealed preferential activation by 11-ketotestosterone of the stickleback receptor, but not of the human receptor. These findings demonstrate the presence of a receptor preferentially activated by 11-ketotestosterone in the three-spined stickleback, so far the only one known in any animal.

Diastereomers of the Brominated Flame Retardant 1,2-Dibromo-4-(1,2 dibromoethyl)cyclohexane Induce Androgen Receptor Activation in the HepG2 Hepatocellular Carcinoma Cell Line and the LNCaP Prostate Cancer Cell Line

“…Furthermore, as the modeling experiments are in agreement with results obtained from the in vitro studies, this demonstrates that modeling is a powerful tool when identifying potential endocrine disruptors. However, it remains unknown how TBECH interacts with AR in other species, such as three-spined stickleback and zebrafish, that both have 11-ketotestoterone as their most potent activator of the AR ( Hossain et al 2008 ; Olsson et al 2005 ). Therefore, future studies are needed to determine the interaction of TBECH with AR from other species in order to determine its effects on species present in the environment.…”

An amphioxus orthologue of the estrogen receptor that does not bind estradiol: Insights into estrogen receptor evolution

“…Glucocorticoids differ in mouse (cortisol) and in human (corticosterone), with both hormones being GR ligands [ 77 ]. There are several androgens in teleost fishes, with 11-ketotestosterone being teleost-specific [ 78 ]. As there are 2 androgen receptors (ARs) in teleost fishes, from a whole genome duplication [ 79 ], the study of the ligand-binding ability of those ARs is a potentially interesting case for the evolution of endocrine systems.…”

Steroid Transport, Local Synthesis, and Signaling within the Brain: Roles in Neurogenesis, Neuroprotection, and Sexual Behaviors

“…Two ar genes ( ar 1 and ar 2) were isolated and characterized in several fish species including the Japanese eel ( Anguilla japonica ), the rainbow trout, the kelp bass ( Paralabrax clathratus ), the Atlantic croaker, and cichlids (Ikeuchi et al, 1999 ; Sperry and Thomas, 1999a , b ; Takeo and Yamashita, 1999 , 2000 ; Harbott et al, 2007 ). More recently, only one ar isoform was described in the stickleback (Olsson et al, 2005 ), the wrasse ( Halichoeres trimaculatus ) (Kim et al, 2002 ), the zebrafish (Jorgensen et al, 2007 ; de Waal et al, 2008 ; Gorelick et al, 2008 ; Hossain et al, 2008 ), and in the plainfish midshipman (Forlano et al, 2010 ).…”