Cell Proliferation and Motility Are Inhibited by G1 Phase Arrest in 15-kDa Selenoprotein-Deficient Chang Liver Cells

Abstract

The 15-kDa selenoprotein (Sep15) is a selenoprotein residing in the lumen of the endoplasmic reticulum (ER) and implicated in quality control of protein folding. Herein, we established an inducible RNAi cell line that targets Sep15 mRNA in Chang liver cells. RNAi-induced Sep15 deficiency led to inhibition of cell proliferation, whereas cell growth was resumed after removal of the knockdown inducer. Sep15-deficient cells were arrested at the G1 phase by upregulating p21 and p27, and these cells were also characterized by ER stress. In addition, Sep15 deficiency led to the relocation of focal adhesions to the periphery of the cell basement and to the decrease of the migratory and invasive ability. All these changes were reversible depending on Sep15 status. Rescuing the knockdown state by expressing a silent mutant Sep15 mRNA that is resistant to siRNA also reversed the phenotypic changes. Our results suggest that SEP15 plays important roles in the regulation of the G1 phase during the cell cycle as well as in cell motility in Chang liver cells, and that this selenoprotein offers a novel functional link between the cell cycle and cell motility.

Modulation of ERQC and ERAD: A Broad-Spectrum Spanner in the Works of Cancer Cells?

“…The expression levels of Sep15 were investigated in various cancer models: downregulation of the protein was found in hepatocarcinomas and colorectal, gastric, and prostate cancers [53, 54, 60, 61]. On the other hand, decreased expression of Sep15 reduces proliferation and growth of liver and colon cancer cell lines, pointing to a role of Sep15 in tumour progression [60, 62–64]. Single-nucleotide polymorphisms in the Sep15 gene have been studied in conjunction with differential levels of selenocysteine insertion [65] and susceptibility to lung and breast cancer [66–68], highlighting the need for a stratified medicine approach in the development of Sep15 modulators as anticancer therapeutics.…”

Selenophosphate synthetase 1 is an essential protein with roles in regulation of redox homoeostasis in mammals

“…To construct a knockdown-resistant (rescue) SPS1 expression vector, three silent point mutations were introduced into the shRNA target sequence by two-step PCR [22]. In the first step, two DNA fragments (the 5′-half and the 3′-half) were amplified from the mouse F9 cell cDNA using two sets of primers: the SPS1 KI-F1 and the SPS1 KI-R1 for the 5′-half, and the SPS1 KI-F2 and the SPS1 KI-R2 for the 3′-half (Table S1; altered bases are under-lined).…”

Association of Selenium and Risk of Esophageal Cancer: A Review

“…SELENOH is a selenium-sensitive SePs with a disturbed expression under suboptimal selenium concentrations. Unlike GPx2, TXNRD1 and SELENOF, knockdown of SELENOH improves cell proliferation in vitro and promotes tumor growth in vivo, indicating that SELENOH may suppress tumor progression (79)(80)(81)(82). SELENOH affect cell cycle through inhibition of G1/S transition by modulating p21 and CCNE1 expression (83,84).…”

“…The 15-kDa selenoprotein (Sep15) can also contribute to cancer progression (85)(86)(87)(88)(89). A study reported that Sep15-deficient Chang liver cells are arrested at the G1 phase by upregulation of p21 and p27 (82). Both p21 and p27 inhibit cell cycle progression by interacting with cyclins and CDKs (90).…”