Aldehyde dehydrogenase

About: Aldehyde dehydrogenase is a research topic. Over the lifetime, 3365 publications have been published within this topic receiving 107683 citations.

Structural Basis of Substrate Recognition by Aldehyde Dehydrogenase 7A1

Abstract: Aldehyde dehydrogenase 7A1 (ALDH7A1) is part of lysine catabolism and catalyzes the NAD(+)-dependent oxidation of α-aminoadipate semialdehyde to α-aminoadipate. Herein, we describe a structural study of human ALDH7A1 focused on substrate recognition. Five crystal structures and small-angle X-ray scattering data are reported, including the first crystal structure of any ALDH7 family member complexed with α-aminoadipate. The product binds with the e-carboxylate in the oxyanion hole, the aliphatic chain packed into an aromatic box, and the distal end of the product anchored by electrostatic interactions with five conserved residues. This binding mode resembles that of glutamate bound to the proline catabolic enzyme ALDH4A1. Analysis of ALDH7A1 and ALDH4A1 structures suggests key interactions that underlie substrate discrimination. Structures of apo ALDH7A1 reveal dramatic conformational differences from the product complex. Product binding is associated with a 16 A movement of the C-terminus into the active site, which stabilizes the active conformation of the aldehyde substrate anchor loop. The fact that the C-terminus is part of the active site was hitherto unknown. Interestingly, the C-terminus and aldehyde anchor loop are disordered in a new tetragonal crystal form of the apoenzyme, implying that these parts of the enzyme are highly flexible. Our results suggest that the active site of ALDH7A1 is disassembled when the aldehyde site is vacant, and the C-terminus is a mobile element that forms quaternary structural interactions that aid aldehyde binding. These results are relevant to the c.1512delG genetic deletion associated with pyridoxine-dependent epilepsy, which alters the C-terminus of ALDH7A1.

High expression of octamer-binding transcription factor 4A, prominin-1 and aldehyde dehydrogenase strongly indicates involvement in the initiation of lung adenocarcinoma resulting in shorter disease-free intervals.

Abstract: OBJECTIVES: The increasing relevance of the cancer stem cell (CSC) hypothesis and the impact of CSC-associated markers in the carcinogenesis of solid tumours may provide potential prognostic implications in lung cancer. We propose that a collective genetic analysis of established CSC-related markers will generate data to better define the role of putative CSCs in lung adenocarcinoma (LAC). METHODS: Sixty-four paired tumour and non-tumour biopsies from LAC patients were included in this study. Using the quantitative reverse transcriptase–polymerase chain reaction, we assessed the expression profiles of established CSC-related biomarkers: octamerbinding transcription factor 4 (OCT4A), CD133, aldehyde dehydrogenase (ALDH), BMI-1, ATP-binding cassette subfamily G, member 2 (ABCG2), SRY (sex-determining region Y)-box 2 (SOX2) and uPAR, and evaluated their relation to clinicopathological parameters and disease prognosis. RESULTS: All of the above-mentioned CSC-related markers were detectable in both tumour and corresponding normal tissues. Importantly, expression levels of OCT4A, CD133, BMI-1, SOX2 and uPAR were significantly higher (OCT4A, P= 0.0003; CD133, P= 0.002; BMI-1, P= 0.04; SOX2, P= 0.0003; uPAR, P= 0.03) in the tumour compared with those in the non-tumour tissues. By contrast, the quantities of ACBG2 and ALDH were markedly reduced (ACBG2, P= 0.0006; ALDH, P= 0.007) in the tumour relative to those in the normal biopsies. Using multivariate analysis, elevated ALDH and CD133 revealed significant associations in tumour stage (ALDH, P= 0.03; CD133, P= 0.007) and differentiation (ALDH, P= 0.03; CD133, P= 0.018). We observed that ALDH and OCT4A were associated with nodal status (ALDH, P= 0.05; OCT4A, P= 0.03) having lower mRNA levels in tumours with lymph node metastasis, N+, compared with that in N0. High OCT4A levels were significantly correlated with tumour size of 3 cm (P= 0.03). Kaplan–Meier correlation analyses, showed that OCT4A and CD133 were correlated to short disease-free intervals (OCT4A, P= 0.047; CD133, P= 0.033) over a period of 29 months. CONCLUSIONS: Our study reveals that CSC-associated markers: OCT4A, CD133 and ALDH are involved in the initial phase of carcinogenesis of LAC, and can be used as predictors of early stage LAC and poor disease-free intervals. In addition, this work validates the relevance of the CSC hypothesis in LAC.

ALDH1A3 upregulation and spontaneous metastasis formation is associated with acquired chemoresistance in colorectal cancer cells

Abstract: Efficiency of colorectal carcinoma treatment by chemotherapy is diminished as the resistance develops over time in patients. The same holds true for 5-fluorouracil, the drug used in first line chemotherapy of colorectal carcinoma. Chemoresistant derivative of HT-29 cells was prepared by long-term culturing in increasing concentration of 5-fluorouracil. Cells were characterized by viability assays, flow cytometry, gene expression arrays and kinetic imaging. Immunomagnetic separation was used for isolation of subpopulations positive for cancer stem cells-related surface markers. Aldehyde dehydrogenase expression was attenuated by siRNA. In vivo studies were performed on SCID/bg mice. The prepared chemoresistant cell line labeled as HT-29/EGFP/FUR is assigned with different morphology, decreased proliferation rate and 135-fold increased IC50 value for 5-fluorouracil in comparison to parental counterparts HT-29/EGFP. The capability of chemoresistant cells to form tumor xenografts, when injected subcutaneously into SCID/bg mice, was strongly compromised, however, they formed distant metastases in mouse lungs spontaneously. Derived cells preserved their resistance in vitro and in vivo even without the 5-fluorouracil selection pressure. More importantly, they were resistant to cisplatin, oxaliplatin and cyclophosphamide exhibiting high cross-resistance along with alterations in expression of cancer-stem cell markers such as CD133, CD166, CD24, CD26, CXCR4, CD271 and CD274. We also detected increased aldehyde dehydrogenase (ALDH) activity associated with overexpression of specific ALDH isoform 1A3. Its inhibition by siRNA approach partially sensitized cells to various agents, thus linking for the first time the ALDH1A3 and chemoresistance in colorectal cancer. Our study demonstrated that acquired chemoresistance goes along with metastatic and migratory phenotype and can be accompanied with increased activity of aldehyde dehydrogenase. We describe here the valuable model to study molecular link between resistance to chemotherapy and metastatic dissemination.