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KMID : 0613820140240101039
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Journal of Life Science
2014 Volume.24 No. 10 p.1039 ~ p.1045
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hCG-induced Endoplasmic Reticulum Stress Leads to Activation of the IRE1/XBP1 Pathway in Mouse Leydig Tumor Cells (mLTC-1)
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Park Sun-Ji
Kim Tae-Shin
Lee Dong-Seok
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Abstract
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This study analyzed whether human chorionic gonadotropin (hCG) induces ER stress via the IRE/XBP1 pathway in mouse Leydig tumor (mLTC-1) cells. In a previous study, we demonstrated that the unfolding protein response (UPR) plays an important role in the expression of steroidogenic enzymes by modulating the ATF6 pathway, as well as ER stress-mediated apoptosis in hCG-stimulated Leydig cells. Although UPR signaling has been reported to regulate the IRE1/XBP1 pathway, it is not known whether hCG-induced ER stress in Leydig cells can activate the pathway. To investigate the activation of the IRE1/XBP1 pathway in mLTC-1 cells after hCG treatment, we performed a Western blot analysis to detect the phospho-IRE1 protein and an RT-PCR analysis to validate splicing of XBP1 mRNA. We used ER stress-activated indicator (ERAI) constructs for monitoring the activity of IRE1 and then analyzed by fluorescence microscopy and flow cytometry. The expression levels of the phospho-IRE1 protein markedly increased in response to the hCG treatment. In the mLTC-1 cells transfected with an F-XBP1-venus/F-XBP1△DBD-venus construct, the hCG treatment led to the appearance of green fluorescent cells and detectable fluorescence in the nucleus and cytosol, respectively. In addition, splicing of XBP1 mRNA significantly increased after the hCG treatment. Taken together, these results indicate that hCG-induced ER stress leads to activation of the IRE1/XBP pathway in Leydig cells.
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KEYWORD
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ER stress, hCG (human chorionic gonadotropin), IRE1, leydig cells, XBP1
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