Crystal structure of human aldehyde dehydrogenase 1A3 complexed with NAD+ and retinoic acid

Abstract

The aldehyde dehydrogenase family 1 member A3 (ALDH1A3) catalyzes the oxidation of retinal to the pleiotropic factor retinoic acid using NAD+. The level of ALDHs enzymatic activity has been used as a cancer stem cell marker and seems to correlate with tumour aggressiveness. Elevated ALDH1A3 expression in mesenchymal glioma stem cells highlights the potential of this isozyme as a prognosis marker and drug target. Here we report the first crystal structure of human ALDH1A3 complexed with NAD+ and the product all-trans retinoic acid (REA). The tetrameric ALDH1A3 folds into a three domain-based architecture highly conserved along the ALDHs family. The structural analysis revealed two different and coupled conformations for NAD+ and REA that we propose to represent two snapshots along the catalytic cycle. Indeed, the isoprenic moiety of REA points either toward the active site cysteine, or moves away adopting the product release conformation. Although ALDH1A3 shares high sequence identity with other members of the ALDH1A family, our structural analysis revealed few peculiar residues in the 1A3 isozyme active site. Our data provide information into the ALDH1As catalytic process and can be used for the structure-based design of selective inhibitors of potential medical interest.

NAD+ promotes assembly of the active tetramer of aldehyde dehydrogenase 7A1

“…Initial structural studies revealed ALDH7A1 forms a dimerof-dimers tetramer both in crystallo [6][7][8] and in solution [7]. Many other ALDHs form the same tetramer, including ALDH1 [9][10][11][12], ALDH2 [13,14], ALDH5A1 [15], methylmalonate semialdehyde dehydrogenase [16], ALDH21 [17], 2-aminomuconate-6-semialdehyde dehydrogenase [18], betaine aldehyde dehydrogenase [19], lactaldehyde dehydrogenase [20], indole-3-acetaldehyde Abbreviations ALDH, aldehyde dehydrogenase; EM, electron microscopy; PDE, pyridoxine-dependent epilepsy; PLP, pyridoxal-5 0 -phosphate. dehydrogenase [21], a-ketoglutarate-semialdehyde dehydrogenase [22], propionaldehyde dehydrogenase [23], and salicylaldehyde dehydrogenase [24].…”

Novel mutations in ALDH1A3 associated with autosomal recessive anophthalmia/microphthalmia, and review of the literature

“…a Schematic representation of exons of the ALDH1A3 gene highlighting the positions of all disease causing mutations identified to date. b Domains of predicted protein product as described by Moretti and colleagues [11], highlighting the positions of all disease associated variants identified to date. Discrete color pattern of variants shows type of phenotype (red: anophthalmia, blue: micophthalmia and a combination of red and blue: both anophthalmia and microphthlamia…”

“…ALDH1A3 assembles as a tetramer, however, each of its monomeric units is independently able to oxidize retinaldehyde into retinoic acid using NAD as a cofactor. Each monomeric unit folds into 13 α-helices, 19 β-sheets and the connecting loops, arranged into three functional domains: the NAD-binding domains (L20-D149 and I171–G282), the catalytic domain (G283–M482), and the C-terminal oligomerization domains (K150–P170 and S483–L507), [11]. …”

“…The Cys174Tyr, Lys190*, Gly237Arg and Gly282Ala variants are located at the foot of the NAD-binding domain (Ile171- Gly282). Variants in this region are important, may directly affect NAD binding by altering the conformation of ALDH1A3 in NAD binding pockets [11], leading to proteasome degradation [5, 21]. A homozygous splice site mutation (c.204 + 1G > A) was found by Abouzeid et al [17] in the head of NAD binding domain of the ALDH1A3 protein that was predicted to lead to an improperly spliced product by affecting the donor splice site of intron 2.…”

“…Retinoic acid functions as a ligand for DNA-binding retinoid receptors that directly regulate transcription of specific target genes in the retinoic-acid signaling pathway in vertebrates [9], and promotes neuronal differentiation in the embryonic nervous system [10]. It also has an important function in the normal early embryonic development of ocular and nasal regions [11]. …”