Human AKR1C4 blocking peptide

Four soluble human 3alpha-hydroxysteroid dehydrogenase (HSD) isoforms exist which are aldo-keto reductase (AKR) superfalnily members. They share 86% sequence identity and correspond to: AKR1C1 (20alpha(3alpha)-HSD); AKR1C2 (type 3 3alpha-HSD and bile-acid binding protein); AKRIC3 (type 2 3alpha-HSD and type 5 17beta-HSD); and AKRIC4 (type 1 3alpha-HSD). Each of the homogeneous recombinant enzymes are plastic and display 3-, 17- and 20-ketosteroid reductase and 3alpha- 17beta- and 20alpha-hydroxysteroid oxidase activities with different k(cat)/K-m ratios in vitro. The crystal structure of the AKR1C2(.)NADP(+.)ursodeoxycholate complex provides an explanation for this functional plasticity. Ursodeoxycholate is bound backwards (beta-ring in the A-ring position) and upside down (beta-face of steroid inverted) relative to the position of 3-ketosteroids in the related rat liver 3alpha-HSD (AKR1C9) structure. Transient transfection indicates that in COS-1 cells, AKR1C enzymes function as ketosteroid reductases due to potent inhibition of their oxidase activity by NADPH. By acting as ketosteroid reductases they may regulate the occupancy of the androgen, estrogen and progesterone receptors. RT-PCR showed that AKRs are discretely localized. AKR1C4 is virtually liver specific, while AKR1C2 and AKR1C3 are dominantly expressed in prostate and mammary gland. AKR1C genes are highly conserved in structure and may be transcriptionally regulated by steroid hormones and stress. (C) 2003 Elsevier Ireland Ltd. All rights reserved.

Hypospadias is a common male genital malformation and is regarded as a complex disease affected by multiple genetic as well as environmental factors. In a previous genome-wide scan for familial hypospadias, we reported suggestive linkage in nine chromosomal regions. We have extended this analysis by including new families and additional markers using non-parametric linkage. The fine mapping analysis displayed an increased LOD score on chromosome 8q24.1 and 10p15 in altogether 82 families. On chromosome 10p15, with the highest LOD score, we further studied AKR1C2, AKR1C3 and AKR1C4 involved in steroid metabolism, as well as KLF6 expressed in preputial tissue from hypospadias patients. Mutation analysis of the AKR1C3 gene showed a new mutation, c.643G4>A (p.(Ala215Thr)), in a boy with penile hypospadias. This mutation is predicted to have an impact on protein function and structure and was not found in controls. Altogether, we homed in on four chromosomal regions likely to harbor genes for hypospadias. Future studies will aim for studying regulatory sequence variants in these regions.