X-box binding protein 1 regulates brain natriuretic peptide through a novel AP1/CRE-like element in cardiomyocytes.
The unfolded protein response (UPR) is triggered to assist protein folding when endoplasmic reticulum (ER) function is impaired. Recent studies demonstrated that ER stress can also induce cell-specific genes. In this study, we examined whether X-box binding protein 1 (XBP1), a major UPR-linked transcriptional factor, regulates the expression of brain natriuretic peptide (BNP) in cardiomyocytes. In samples from failing human hearts, extensive splicing of XBP1 was observed along with increased expression of glucose-regulated protein of 78 kDa (GRP78), a target of spliced XBP1 (sXBP1), suggesting that the UPR was induced in heart failure in humans. Interestingly, quantitative real-time PCR revealed a positive correlation between cardiac expression of GRP78 and BNP, leading us to test the hypothesis that sXBP1 regulates BNP as well as GRP78 in cardiomyocytes. A pharmacological ER stressor caused a dose-dependent increase in the expression of sXBP1 and BNP by cultured cardiomyocytes. Short interfering RNA targeting XBP1 suppressed the induction of BNP expression by a pharmacological ER stressor or norepinephrine, which was rescued by the adenovirus-mediated overexpression of sXBP1. The promoter assay with overexpression of sXBP1 or norepinephrine showed that the proximal AP1/CRE-like element in the promoter region of BNP was critical for transcriptional regulation of BNP by sXBP1. Direct binding of sXBP1 to this element was confirmed by the chromatin immunoprecipitation assay. These findings suggest that ER stress observed in failing hearts regulates cardiac BNP expression through a novel promoter region of the AP1/CRE-like element.
Sawada
Tamaki
T
Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
Minamino
Tetsuo
T
Fu
Hai Ying
HY
Asai
Mitsutoshi
M
Okuda
Keiji
K
Isomura
Tadashi
T
Yamazaki
Satoru
S
Asano
Yoshihiro
Y
Okada
Ken-ichiro
K
Tsukamoto
Osamu
O
Sanada
Shoji
S
Asanuma
Hiroshi
H
Asakura
Masanori
M
Takashima
Seiji
S
Kitakaze
Masafumi
M
Komuro
Issei
I
D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D018613:Microscopy, Confocal / Q000379:methods; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology*; D020097:Natriuretic Peptide, Brain / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D051381:Rats; D000071701:Regulatory Factor X Transcription Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D000071717:X-Box Binding Protein 1
D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C051684:GRP78 protein, rat; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D000071701:Regulatory Factor X Transcription Factors; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C000605545:Xbp1 protein, rat; D020097:Natriuretic Peptide, Brain