Retinaldehyde is a substrate for human aldo–keto reductases of the 1C subfamily

Abstract

Human AKR (aldo-keto reductase) 1C proteins (AKR1C1-AKR1C4) exhibit relevant activity with steroids, regulating hormone signalling at the pre-receptor level. In the present study, investigate the activity of the four human AKR1C enzymes with retinol and retinaldehyde. All of the enzymes except AKR1C2 showed retinaldehyde reductase activity with low Km values (~1 μM). The kcat values were also low (0.18-0.6 min-1), except for AKR1C3 reduction of 9-cis-retinaldehyde whose kcat was remarkably higher (13 min-1). Structural modelling of the AKR1C complexes with 9-cis-retinaldehyde indicated a distinct conformation of Trp227, caused by changes in residue 226 that may contribute to the activity differences observed. This was partially supported by the kinetics of the AKR1C3 R226P mutant. Retinol/retinaldehyde conversion, combined with the use of the inhibitor flufenamic acid, indicated a relevant role for endogenous AKR1Cs in retinaldehyde reduction in MCF-7 breast cancer cells. Overexpression of AKR1C proteins depleted RA (retinoic acid) transactivation in HeLa cells treated with retinol. Thus AKR1Cs may decrease RA levels in vivo. Finally, by using lithocholic acid as an AKR1C3 inhibitor and UVI2024 as an RA receptor antagonist, we provide evidence that the pro-proliferative action of AKR1C3 in HL-60 cells involves the RA signalling pathway and that this is in part due to the retinaldehyde reductase activity of AKR1C3.

A missense mutation in ALDH1A3 causes isolated microphthalmia/anophthalmia in nine individuals from an inbred Muslim kindred

“…The procedure was based on the QuikChange SiteDirected Mutagenesis Kit method (Stratagene, Leicester, UK). The mutagenic strands were sequence verified and then transformed into Escherichia coli BL21 cells, in which recombinant ALDH1A3 was expressed at 24 1C and purified, as previously described 10 and as follows: cells were lysed by sonication and the homogenate was applied onto a nickel-charged chelating Sepharose Fast Flow (GE Healthcare, Little Chalfont, UK) column (5 ml). After washing with 60 mM imidazole in 20 mM Tris-HCl, 0.5 M NaCl, pH 8.0, the enzyme was eluted with 250 mM imidazole in the same buffer.…”

DHRS3, a retinal reductase, is differentially regulated by retinoic acid and lipopolysaccharide-induced inflammation in THP-1 cells and rat liver

“…Finally, DHRS3 may not be the only enzyme in the liver to catalyze the reduction of retinal to retinol. There may be others, including AKR1B or AKR1C, as well as other retinol dehydrogenases/reductases (29,35,36). Among AKR1B subfamily enzymes, we found that only the AKR1B7 gene is induced by RA in the liver of vitamin A-deficient, but not vitamin A-sufficient, diet-fed rats.…”

“…The conversion of retinal to retinol has been reported to be mediated through several retinol dehydrogenases (29,35,36), of which the well-conserved microsomal protein DHRS3, a member of the classical short-chain dehydrogenase reductase (SDR) superfamily, has been previously identified (15). Although DHRS3 was originally cloned from the retina, it is expressed in several non-ocular human tissues, including the liver, pancreas, heart, kidney, and lung (3,15).…”

Aldo–keto reductases in retinoid metabolism: Search for substrate specificity and inhibitor selectivity

“…Furthermore, the enzyme was active with compounds related to the androgen receptor (AR), estrogen receptor a (ERa), mineralocorticoid receptor (MR), peroxisome proliferator-activated receptor c (PPARc), RAR and RXR (Table 4). Recently, we studied cell proliferation in human promyelocytic leukemia HL-60 cells, which endogenously express AKR1C3, and showed that the pro-proliferative action of AKR1C3 was mediated in part by the RA signaling pathway [51]. The inhibition of AKR1C3 could cause an increased flow in the 9-cis-RA synthesis and, consequently, a lower cell proliferation rate.…”

“…We have previously demonstrated that AKR1B1, 1B10, 1C1, 1C3 and 1C4 are active retinaldehyde reductases which can decrease both retinaldehyde and RA levels in cellular models [44,51], and therefore they may exert pre-receptor regulation of the RAR and RXR nuclear receptors. Additionally, members of the human AKR1A, 1B, and 1D subfamilies are able to act on lipophilic molecules other than retinoids, including steroids, prostaglandins, and polycyclic aromatic hydrocarbons [52].…”