Effects of stress-associated endoplasmic reticulum protein 1 on endoplasmic stress induced by the tunicamycin in HepG2 cells

doi:10.3877/cma.j.issn.2095-655X.2014.01.006

Abstract

Abstract:

Backgroud

Endoplasmic reticulum stress was induced by the accumulation and aggregation of unfolded proteins due to stresses that disturbed the cellular energy levels, the redox state, or Ca²⁺ concentration, and leading to the unfolded protein response (UPR) pathway. The hepatic UPR was activated in several forms of liver disease. Recent data showed that the role of the UPR in hepatic cells have identified molecular mechanisms that may underlie the association between UPR activation and liver disease. SERP1 was known as ribosome-associated membrane protein 4 (RAMP4), was homologous to yeast suppressor of SecY 6 protein (YSY6p) which suggested a role in pathways controlling membrane protein biogenesis at the ER level. Expression of SERP1 was enhanced during cellular stress, causing accumulation of unfolded proteins in the ER.By interaction with the molecular chaperone calnexin, SERP1/RAMP4 could control biogenesis of membrane proteins and take participate in the endoplasmic reticulum stress.Objective To study the effects of stress-associated endoplasmic reticulum protein 1(SERP1) on the endoplasmic reticulum stress induced by the tunicamycin in HepG2 cells.

Methods

The tunicamycin was used to induce endoplasmic reticulum stress in the HepG2 cells.We divided the cells into 5 groups: normal control group, tunicamycin treated group, tunicamycin + 0.25μg/μl SERP1 transfected group, tunicamycin + 0.25μg/μl SERP1 transfected group, tunicamycin + 0.5μg/μl SERP1 transfected group, tunicamycin + 1μg/μl SERP1 transfected group. Each experiment was repeated three times.MTT was used to detect the effect on the survival rate of the HepG2 cells and selected the optimal concentration and time of tunicamycin treatment.Western blot was used to detect the standard of expression of endoplasmic reticulum stress spcific mark proteins, glucose-regulated protein 78(GRP78), C/EBP homologous protein (CHOP) and calnexin.

Results

Compared with the control group, the expression levels of GRP78, CHOP and calnexin were significantly increased in the tunicaymicin treated group, which were 3.8 times, 1.3 times and 1.4 times respectively. With the increasing amount of transfection, SERP1 over expression was found to relieve the expression of GRP78 12%(1.838±0.29, 1.6±0.132, P>0.05), 24% and 30%(1.838±0.29, 1.40±0.11, 1.27±0.21, F=50.56, P<0.01)compared with the tunicamycin group, the expression of CHOP were decreased by 23%, 29% and 34%(1.0±0.15, 0.79±0.07, 0.72±0.55, 0.67±0.14, F=9.532, P<0.01)respectively and calnexin were decreased by 5%(1.20±0.18, 1.15±0.13, P>0.05)、24%和28%(1.20±0.18, 0.92±0.07, 0.87±0.18, F=8.116, P<0.01)respectively, which were induced by tunicamycin treatment.

Conclusion

SERP1 overexpression could attenuate the ER stress induced by tunicamycin, and may reduce the cell damage mediated by the ER stress.

Key words: Endopasmic reticulum stress, Stress-associated Endoplasmic Reticulum Protein 1, Glucose-regulated protein 78, C/EBP homologous protein, Calnexin

Yuanyuan Xiao, Yueqin Mao, Qianqian Wang, Meilin Wei, Junfeng Han, jun Yin, Jinwei Huang, Li Wei. Effects of stress-associated endoplasmic reticulum protein 1 on endoplasmic stress induced by the tunicamycin in HepG2 cells[J]. Chinese Journal of Diagnostics(Electronic Edition), 2014, 02(01): 32-37.

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References 21

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组别	GRP78	CHOP	Calnexin
对照组	0.48±0.04	0.78±0.07	0.88±0.08
衣霉素组	1.83±0.29^a	1.01±0.15^a	1.20±0.18^a
衣霉素＋0.25mg/L SERP1组	1.61±0.13^a	0.79±0.07^c	1.15±0.13^b
衣霉素＋0. 5mg/L SERP1组	1.40±0.11^ac	0.72±0.06^c	0.92±0.07^c
衣霉素＋1mg/L SERP1组	1.27±0.21^ac	0.67±0.14^c	0.88±0.18^c
F值	50.56	9.53	8.12
P值	<0.05	<0.05	<0.05

组别	GRP78	CHOP	Calnexin
对照组	0.48±0.04	0.78±0.07	0.88±0.08
衣霉素组	1.83±0.29^a	1.01±0.15^a	1.20±0.18^a
衣霉素＋0.25mg/L SERP1组	1.61±0.13^a	0.79±0.07^c	1.15±0.13^b
衣霉素＋0. 5mg/L SERP1组	1.40±0.11^ac	0.72±0.06^c	0.92±0.07^c
衣霉素＋1mg/L SERP1组	1.27±0.21^ac	0.67±0.14^c	0.88±0.18^c
F值	50.56	9.53	8.12
P值	<0.05	<0.05	<0.05

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