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Activation of sterol regulatory element-binding protein by the caspase Drice in Drosophila larvae.

ABSTRACT: During larval development in Drosophila melanogaster, transcriptional activation of target genes by sterol regulatory element-binding protein (dSREBP) is essential for survival. In all cases studied to date, activation of SREBPs requires sequential proteolysis of the membrane-bound precursor by site-1 protease (S1P) and site-2 protease (S2P). Cleavage by S2P, within the first membrane-spanning helix of SREBP, releases the transcription factor. In contrast to flies lacking dSREBP, flies lacking dS2P are viable. The Drosophila effector caspase Drice cleaves dSREBP, and cleavage requires an Asp residue at position 386, in the cytoplasmic juxtamembrane stalk. The initiator caspase Dronc does not cleave dSREBP, but animals lacking dS2P require both drice and dronc to complete development. They do not require Dcp1, although this effector caspase also can cleave dSREBP in vitro. Cleavage of dSREBP by Drice releases the amino-terminal transcription factor domain of dSREBP to travel to the nucleus where it mediates the increased transcription of target genes needed for lipid synthesis and uptake. Drice-dependent activation of dSREBP explains why flies lacking dS2P are viable, and flies lacking dSREBP itself are not.

SUBMITTER: Amarneh B

PROVIDER: S-EPMC2665088 | biostudies-other | 2009 Apr

REPOSITORIES: biostudies-other

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Activation of sterol regulatory element-binding protein by the caspase Drice in Drosophila larvae.

Amarneh Bilal B Matthews Krista A KA Rawson Robert B RB

The Journal of biological chemistry 20090217 15

During larval development in Drosophila melanogaster, transcriptional activation of target genes by sterol regulatory element-binding protein (dSREBP) is essential for survival. In all cases studied to date, activation of SREBPs requires sequential proteolysis of the membrane-bound precursor by site-1 protease (S1P) and site-2 protease (S2P). Cleavage by S2P, within the first membrane-spanning helix of SREBP, releases the transcription factor. In contrast to flies lacking dSREBP, flies lacking d ...[more]

PMID: 19224859

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Project description:BackgroundAberrantly elevated sterol regulatory element binding protein (SREBP), the lipogenic transcription factor, contributes to the development of fatty liver and insulin resistance in animals. Our recent studies have discovered that AMP-activated protein kinase (AMPK) phosphorylates SREBP at Ser-327 and inhibits its activity, represses SREBP-dependent lipogenesis, and thereby ameliorates hepatic steatosis and atherosclerosis in insulin-resistant LDLR(-/-) mice. Chronic inflammation and activation of NLRP3 inflammasome have been implicated in atherosclerosis and fatty liver disease. However, whether SREBP is involved in vascular lipid accumulation and inflammation in atherosclerosis remains largely unknown.Principal findingsThe preclinical study with aortic pouch biopsy specimens from humans with atherosclerosis and diabetes shows intense immunostaining for SREBP-1 and the inflammatory marker VCAM-1 in atherosclerotic plaques. The cleavage processing of SREBP-1 and -2 and expression of their target genes are increased in the well-established porcine model of diabetes and atherosclerosis, which develops human-like, complex atherosclerotic plaques. Immunostaining analysis indicates an elevation in SREBP-1 that is primarily localized in endothelial cells and in infiltrated macrophages within fatty streaks, fibrous caps with necrotic cores, and cholesterol crystals in advanced lesions. Moreover, concomitant suppression of NAD-dependent deacetylase SIRT1 and AMPK is observed in atherosclerotic pigs, which leads to the proteolytic activation of SREBP-1 by diminishing the deacetylation and Ser-372 phosphorylation of SREBP-1. Aberrantly elevated NLRP3 inflammasome markers are evidenced by increased expression of inflammasome components including NLPR3, ASC, and IL-1?. The increase in SREBP-1 activity and IL-1? production in lesions is associated with vascular inflammation and endothelial dysfunction in atherosclerotic pig aorta, as demonstrated by the induction of NF-?B, VCAM-1, iNOS, and COX-2, as well as by the repression of eNOS.ConclusionsThese translational studies provide in vivo evidence that the dysregulation of SIRT1-AMPK-SREBP and stimulation of NLRP3 inflammasome may contribute to vascular lipid deposition and inflammation in atherosclerosis.

Dataset Information

Activation of sterol regulatory element-binding protein by the caspase Drice in Drosophila larvae.

Publications

Activation of sterol regulatory element-binding protein by the caspase Drice in Drosophila larvae.

Similar Datasets

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