AKR1A1 Human

What is the primary catalytic function of AKR1A1 in human cells?

AKR1A1 catalyzes the NADPH-dependent reduction of a wide variety of carbonyl-containing compounds to their corresponding alcohols. It displays enzymatic activity towards endogenous metabolites such as aromatic and aliphatic aldehydes, ketones, monosaccharides, and bile acids, with a notable preference for negatively charged substrates including glucuronate and succinic semialdehyde. The enzyme functions primarily as a detoxifying agent by reducing toxic aldehydes including methylglyoxal and 3-deoxyglucosone, compounds that accumulate under hyperglycemic conditions .

Which protein partners does AKR1A1 interact with most significantly?

Research using protein interaction databases reveals that AKR1A1 forms functional partnerships with several key proteins involved in aldehyde metabolism. The most significant interactions include:

These interactions suggest AKR1A1 functions within a network of enzymes involved in detoxification pathways and aldehyde metabolism .

What are effective approaches for recombinant expression of active AKR1A1?

For high-quality recombinant expression of AKR1A1, the intein strategy has proven particularly effective. This method involves expressing AKR1A1 as a thioester, which can then be selectively modified through expressed protein ligation techniques. For optimal results, researchers should utilize bacterial expression systems (typically E. coli BL21 strains) with temperature-controlled induction protocols to maximize protein solubility. Purification should employ affinity chromatography followed by size exclusion chromatography to ensure enzyme homogeneity. Activity assays using model substrates should be performed immediately after purification to confirm functional integrity .

How can researchers optimize site-specific immobilization of AKR1A1 to enhance stability and activity?

Site-specific immobilization dramatically improves AKR1A1 performance compared to random immobilization methods. The most effective approach utilizes expressed protein ligation methodology, where AKR1A1 is recombinantly expressed as a thioester via the intein strategy. The thioester can then be selectively modified with a biotin label through expressed protein ligation and subsequently immobilized on streptavidin templates. This method produces remarkably improved enzymatic activity comparable to the wild-type enzyme in solution and 60–300-fold greater than randomly immobilized enzymes. Furthermore, the site-specifically immobilized enzyme demonstrates exceptional stability, with no activity loss observed for over a week and more than 35% activity maintained even after 50 days .

How does AKR1A1 regulate energy metabolism during mesenchymal stem cell differentiation?

AKR1A1 functions as a master metabolic regulator during mesenchymal stem cell (MSC) differentiation, with differential expression patterns that determine cell fate. The enzyme's activity creates a metabolic switch between glycolysis and oxidative phosphorylation pathways:

This metabolic reprogramming is central to determining whether MSCs differentiate into osteoblasts or adipocytes, with AKR1A1 promoting adipogenesis while inhibiting osteogenesis .

What molecular mechanisms connect AKR1A1 to the SIRT1-PGC-1α pathway?

AKR1A1 regulates MSC differentiation through a molecular cascade involving the SIRT1-PGC-1α-TAZ axis. In adipocyte-committed MSCs, increased AKR1A1 expression inhibits the SIRT1-dependent pathway, resulting in decreased expression of PGC-1α and TAZ while increasing PPARγ. This promotes glycolytic metabolism that favors adipogenesis. Conversely, in osteoblast-committed cells, reduced AKR1A1 expression relieves its inhibitory effect on SIRT1, enabling SIRT1-mediated activation of PGC-1α and TAZ, which facilitates osteogenesis and mitochondrial oxidative phosphorylation. These findings establish AKR1A1 as a key upstream regulator of metabolic pathways that determine stem cell fate .

What evidence links AKR1A1 to diabetic kidney disease pathophysiology?

Multiomics analyses have identified AKR1A1 as a significant biomarker for diabetic kidney disease (DKD), the leading cause of end-stage kidney disease. By integrating single-cell RNA-sequencing data from the Kidney Precision Medicine Project, proteomics of human kidney cortex biopsies, protein quantitative trait loci, genome-wide association study results, and plasma metabolomics, researchers revealed AKR1A1 as a molecular hub for DKD cellular dysfunction. Specifically, differential expression analysis identified 790 differentially expressed genes in proximal tubule cells, with AKR1A1 emerging as a central node in several cross-linked pathways characterized by deficiency of this enzyme. The findings suggest that impaired AKR1A1 function contributes to the metabolic dysregulation observed in diabetic kidney disease .

How do genetic variants of AKR1A1 contribute to schizophrenia?

A silent variant of AKR1A1, c.753G > A (rs745484618, p. Arg251Arg) located at the first position of exon 8, has been linked to schizophrenia through a mechanism involving exon skipping. This variant leads to a loss of gene expression and enzymatic activity, resulting in the accumulation of glucuronate (GlucA) in serum. Elevated GlucA levels are significant in treatment-resistant schizophrenia because GlucA promotes drug excretion by forming conjugates with medications, potentially reducing their therapeutic efficacy. The genetic loss of AKR1A1 function thus provides a mechanistic explanation for both biochemical abnormalities in schizophrenia and the reduced effectiveness of antipsychotic medications in certain patients .

What connections exist between AKR1A1 and cancer biology?

AKR1A1 plays complex roles in cancer development and progression. Several AKRs, including AKR1A1, are involved in tobacco-carcinogenesis while simultaneously catalyzing the detoxification of nicotine-derived nitrosamino ketones. This dual function highlights the context-dependent nature of AKR1A1's effects in different tissues and cancer types. Additionally, the enzyme's role in detoxifying reactive aldehydes suggests it may influence cellular responses to oxidative stress, a key factor in cancer development. Research into AKR1A1 expression patterns in different tumor types and its interactions with carcinogens and chemotherapeutic agents is essential for understanding its contribution to cancer biology and potential as a therapeutic target .

How can multi-omics approaches identify AKR1A1-related biomarkers and therapeutic targets?

Multi-omics approaches offer powerful frameworks for investigating AKR1A1's role in complex diseases. Such methodologies involve:

• Transcriptomics: Single-cell RNA-sequencing to identify cell-type-specific expression patterns of AKR1A1 and co-regulated genes

• Proteomics: Mass spectrometry analysis of tissue samples to quantify AKR1A1 protein levels and post-translational modifications

• Metabolomics: Identification of AKR1A1 substrates and products in biological samples

• Genomics: Analysis of genetic variants affecting AKR1A1 expression or function

• Integration: Computational methods to correlate findings across multiple datasets

This integrated approach has successfully identified AKR1A1 as a biomarker for diabetic kidney disease, revealing it as a hub in multiple disease-associated pathways. Similar strategies could uncover AKR1A1's role in other conditions and guide the development of targeted therapeutics .

What therapeutic potential exists for AKR1A1 inhibitors in treating bone disorders?

AKR1A1 inhibition represents a promising therapeutic approach for conditions characterized by excessive bone marrow adipogenesis and bone loss, such as senile osteoporosis. The GSNOR inhibitor N6022 has been investigated for its ability to inhibit AKR1A1 and potentially reverse pathological adipo-osteogenic differentiation of bone marrow stem cells. By suppressing AKR1A1 activity, such inhibitors could relieve the enzyme's inhibition of the SIRT1-dependent pathway, thereby increasing PGC-1α and TAZ expression to promote osteogenesis while suppressing adipogenesis. Therapeutic development should focus on optimizing selectivity, bioavailability, and tissue distribution of AKR1A1 inhibitors while monitoring potential off-target effects on related AKR family members .

How does AKR1A1 function in detoxification pathways across different tissues?

AKR1A1 contributes to detoxification of endogenous and exogenous compounds across multiple tissues. The enzyme catalyzes the reduction of various toxic aldehydes, including those generated during lipid peroxidation and glycation reactions. In the liver, AKR1A1 participates in aldehyde detoxification pathways alongside aldehyde dehydrogenases. In the kidney, it contributes to the metabolism of glucuronate and may influence drug clearance. The tissue-specific expression patterns of AKR1A1 correlate with detoxification requirements, with higher expression in metabolically active tissues exposed to xenobiotics. Research methods to study tissue-specific functions include tissue-specific knockout models, ex vivo tissue slice cultures, and targeted proteomics to quantify AKR1A1 abundance across different organs and cell types .