The Impact of ZIP8 Disease-Associated Variants G38R, C113S, G204C, and S335T on Selenium and Cadmium Accumulations: The First Characterization

Abstract

The metal cation symporter ZIP8 (SLC39A8) is a transmembrane protein that imports the essential micronutrients iron, manganese, and zinc, as well as heavy toxic metal cadmium (Cd). It has been recently suggested that selenium (Se), another essential micronutrient that has long been known for its role in human health and cancer risk, may also be transported by the ZIP8 protein. Several mutations in the ZIP8 gene are associated with the aberrant ion homeostasis of cells and can lead to human diseases. However, the intricate relationships between ZIP8 mutations, cellular Se homeostasis, and human diseases (including cancers and illnesses associated with Cd exposure) have not been explored. To further verify if ZIP8 is involved in cellular Se transportation, we first knockout (KO) the endogenous expression of ZIP8 in the HeLa cells using the CRISPR/Cas9 system. The elimination of ZIP8 expression was examined by PCR, DNA sequencing, immunoblot, and immunofluorescence analyses. Inductively coupled plasma mass spectrometry indicated that reduced uptake of Se, along with other micronutrients and Cd, was observed in the ZIP8-KO cells. In contrast, when ZIP8 was overexpressed, increased Se uptake could be detected in the ZIP8-overexpressing cells. Additionally, we found that ZIP8 with disease-associated single-point mutations G38R, G204C, and S335T, but not C113S, showed reduced Se transport ability. We then evaluated the potential of Se on Cd cytotoxicity prevention and therapy of cancers. Results indicated that Se could suppress Cd-induced cytotoxicity via decreasing the intracellular Cd transported by ZIP8, and Se exhibited excellent anticancer activity against not all but only selected cancer cell lines, under restricted experimental conditions. Moreover, clinical-based bioinformatic analyses revealed that up-regulated ZIP8 gene expression was common across multiple cancer types, and selenoproteins that were significantly co-expressed with ZIP8 in these cancers had been identified. Taken together, this study concludes that ZIP8 is an important protein in modulating cellular Se levels and provides insights into the roles of ZIP8 and Se in disease prevention and therapy.

Single-gene knockout-coupled omics analysis identifies C9orf85 and CXorf38 as two uncharacterized human proteins associated with ZIP8 malfunction

“…Human cervical cancer (HeLa) cell line was purchased from the American Type Culture Collection (ATCC) (Rockville, MD, United States). A ZIP8 single-gene KO HeLa cell model was established using the CRISPR/Cas9 genome editing technology, as described in Liang et al (2021) . All cell lines used in the current study were routinely cultured in MEM medium containing 10% fetal bovine serum and 1% penicillin/streptomycin at 37°C in a 5% CO 2 incubator as recommended by ATCC.…”

“…Recently, we used CRISPR/Cas9 genome editing technology to knockout (KO) the SLC39A8 gene in the human cervical cancer HeLa cell line ( Liang et al, 2021 ). We then studied the micronutrient transport ability of the single-gene KO cell model and discovered that the elimination of ZIP8 could result in not only the reduced cellular uptake of the above-mentioned metals, but also reduced uptake of another essential micronutrient, selenium (Se) ( Liang et al, 2021 ).…”

“…Recently, we used CRISPR/Cas9 genome editing technology to knockout (KO) the SLC39A8 gene in the human cervical cancer HeLa cell line ( Liang et al, 2021 ). We then studied the micronutrient transport ability of the single-gene KO cell model and discovered that the elimination of ZIP8 could result in not only the reduced cellular uptake of the above-mentioned metals, but also reduced uptake of another essential micronutrient, selenium (Se) ( Liang et al, 2021 ). Furthermore, by utilizing clinical datasets of 40 different types of cancers from The Cancer Genome Atlas (TCGA) database, we showed that SLC39A8 gene expressions tend to be upregulated in a great number of tumor types ( Liang et al, 2021 ).…”

“…We then studied the micronutrient transport ability of the single-gene KO cell model and discovered that the elimination of ZIP8 could result in not only the reduced cellular uptake of the above-mentioned metals, but also reduced uptake of another essential micronutrient, selenium (Se) ( Liang et al, 2021 ). Furthermore, by utilizing clinical datasets of 40 different types of cancers from The Cancer Genome Atlas (TCGA) database, we showed that SLC39A8 gene expressions tend to be upregulated in a great number of tumor types ( Liang et al, 2021 ). This data suggested that ZIP8 could be a novel molecular target in preventing or treating human cancers and/or illnesses related to Cd exposure.…”

Editorial to Special Issue Molecular Biology of Selenium in Health and Disease

“…Many of the most important subjects in the selenium field are covered. These include a historical perspective of the roles of selenium and selenoproteins in health and development, including its beneficial and detrimental aspects [ 2 ], the role of selenium in redox signaling in macrophages [ 3 ], as well as in bacterial and human selenoprotein biosynthesis [ 4 ], and its proposed cellular transport via a metal cation symporter [ 5 ]. Furthermore, selenium deficiency is discussed in the setting of cardiovascular function [ 6 ] and as a trigger for autoimmune diseases [ 7 ].…”