2Department of Biochemistry and Molecular Biology, Basic Medical College, China Medical University, Shenyang 110001, China; E-mail: email@example.com
3Laboratory of Molecular Genetics and Genomics, School of Biological Sciences, Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Korea; E-mail: firstname.lastname@example.org
4School of Pharmaceutical Science, Liaoning University, Shenyang 110036, China; E-mail: email@example.com
* To whom correspondence should be addressed.
Received February 6, 2011; Revision received April 12, 2011
dSelK (G-rich), a homolog of human and mouse SelK, is one of three selenoproteins in Drosophila melanogaster. It is the only trans-membrane selenoprotein in D. melanogaster integrated into both the endoplasmic reticulum (ER) membrane and the Golgi apparatus. The gene expression profile of Drosophila Schneider 2 (S2) cells after the dsRNA interference (dsRNAi) targeting of dSelK was examined with the GeneChip Drosophila Genome 2.0 Array (Affymetrix), a high-density oligonucleotide microarray encompassing nearly the full Drosophila genome. The results showed that the transcriptional expression of eight genes whose proteins are located on (or related to) the ER or the Golgi apparatus was highly induced or repressed by the dsRNAi treatment. The mRNA levels of the inositol 1,4,5-tris-phosphate receptor (IP3 receptor), whose gene product is integrated into the ER membrane and regulates the release of Ca2+ from the ER to the cytosol, were significantly downregulated. In contrast, the expression of inositol 1,4,5-tris-phosphate kinase 1, which is a cytosolic protein with opposing functions to the IP3 receptor, was significantly upregulated. Quantitative real-time PCR verified these results. The concentration of intracellular free Ca2+ of the Drosophila S2 cells was significantly decreased after the knockdown of dSelK, whereas overexpression of dSelK significantly increased the intracellular free Ca2+ concentration. These results indicate that dSelK in D. melanogaster is involved in regulating the release of Ca2+ from the ER to the cytosol and may play important roles in the signal transduction pathways involving Ca2+ mobilization.
KEY WORDS: Drosophila melanogaster, selenoprotein, dSelK, dsRNAi, inositol 1,4,5-tris-phosphate receptor, Ca2+