ALOX12B

Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer worldwide. Solanine is a phytochemical extracted from traditional Chinese medicine with widely reported anticancer effects. Here, we investigated the potential role of solanine in regulating ferroptosis in CRC cells and scrutinized the molecular mechanism.

Cell growth and cytotoxicity were examined using CCK-8 proliferation assay and lactate dehydrogenase assay. Oxidative stress was determined by measuring glutathione (GSH), malondialdehyde, and reactive oxygen species (ROS) levels. Subcellular changes in mitochondria were examined by transmission electron microscopy. Gene and protein expression levels were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Protein-protein interaction was determined by co-immunoprecipitation.

Solanine arrested cell proliferation in CRC cells and induced typical ferroptotic changes. Solanine treatment promoted ROS production, lipid peroxidation, and cell membrane disruption, while the cellular level of antioxidant GSH was reduced upon solanine treatment. ALOX12B was identified as a molecular mediator of solanine to promote ferroptosis. Solanine treatment upregulated ALOX12B levels and silencing ALOX12B could suppress solanine-induced ferroptosis. Further, ADCY4 was found to physically associate with ALOX12B and maintain ALOX12B protein stability. Silencing ADCY4 destabilized ALOX12B and attenuated solanine-induced ferroptosis.

Our data demonstrated the ferroptosis-inducing effect of solanine in CRC cells, and revealed ALOX12B/ADCY4 molecular axis as the ferroptosis mediator of solanine. Solanine may synergize with existing ferroptosis inducer as an anticancer strategy in CRC, which warrants further validation in animal experiments.

Hereditary ichthyosis is a clinically and genetically heterogeneous disorder associated with more than 50 genes with TGM1, ALOX12B, and ALOXE3 being the most prevalent. Establishing an accurate diagnosis is important for effective genetic counseling and optimal patient management.

We studied the diagnostic value of whole exome sequencing (WES) in a small case series with hereditary ichthyosis.

During a 1-year period, index cases of 5 unrelated families clinically diagnosed with hereditary ichthyosis went through WES, followed by extensive segregation analysis. Prenatal diagnosis (PND) was conducted where indicated.

We identified 4 homozygous variants-2 in TGM1 (c.655A > G and c.797A > G) and 2 in ALOX12B (c.527 + 2 T > G and c.1654G > T)-alongside a heterozygous variant in TGM1 (c.428G > A) in 5 families. The variants were all pathogenic/likely pathogenic according to the ACMG classification and segregation analysis, except for c.797A > G in TGM1 which remained a variant of unknown clinical significance. Four variants were novel. All families were referred either during pregnancy or before reproductive planning; 4 benefited from WES as it identified the mutation in the probands and enabled carrier detection in at-risk relatives; PND was conducted in 2 families.

Our findings further support WES is a powerful tool for the comprehensive, accurate, and rapid molecular diagnosis of hereditary ichthyosis and can offer opportunities for reproductive planning, carrier screening and prenatal diagnosis to at-risk families.

The human genome involves six functional arachidonic acid lipoxygenase (ALOX) genes and the corresponding enzymes (ALOX15, ALOX15B, ALOX12, ALOX12B, ALOXE3, ALOX5) have been implicated in cell differentiation and in the pathogenesis of inflammatory, hyperproliferative, metabolic, and neurological disorders. In other vertebrates, ALOX-isoforms have also been identified, but they occur less frequently. Since bony fish represent the most abundant subclass of vertebrates, we recently expressed and characterized putative ALOX15 orthologs of three different bony fish species (Nothobranchius furzeri, Pundamilia nyererei, Scleropages formosus). To explore whether these enzymes represent functional equivalents of mammalian ALOX15 orthologs, we here compared a number of structural and functional characteristics of these ALOX-isoforms with those of mammalian enzymes. We found that in contrast to mammalian ALOX15 orthologs, which exhibit a broad substrate specificity, a membrane oxygenase activity, and a special type of dual reaction specificity, the putative bony fish ALOX15 orthologs strongly prefer C₂₀ fatty acids, lack any membrane oxygenase activity and exhibit a different type of dual reaction specificity with arachidonic acid. Moreover, mutagenesis studies indicated that the Triad Concept, which explains the reaction specificity of all mammalian ALOX15 orthologs, is not applicable for the putative bony fish enzymes. The observed functional differences between putative bony fish ALOX15 orthologs and corresponding mammalian enzymes suggest a targeted optimization of the catalytic properties of ALOX15 orthologs during vertebrate development.