Transcriptome profiling identifies p53 as a key player during calreticulin deficiency: Implications in lipid...

Area of Science:

• Biochemistry
• Molecular Biology
• Hepatology

Background:

• Calreticulin (CRT) is an endoplasmic reticulum calcium-binding protein involved in diverse cellular functions.
• Hepatic lipid accumulation, a hallmark of fatty liver disease, involves complex regulatory pathways.

Purpose of the Study:

• To investigate the role of calreticulin (CRT) in regulating hepatic lipid metabolism and its connection to the p53 pathway.
• To identify molecular mechanisms linking CRT deficiency to increased hepatic lipid accumulation.

Main Methods:

• Transcriptome analysis in CRT-knockdown HepG2 cells to identify altered genes.
• In silico protein-protein interaction network and MCODE clustering to identify key regulatory nodes.
• siRNA-mediated knockdown of CRT and p53 in HepG2 cells and primary mouse hepatocytes.
• Analysis of p53 binding to the SREBP-1c promoter using chromatin immunoprecipitation assays.
• Assessment of SREBP-1c promoter activity and hepatic lipid levels.
• Validation in a diabetic mouse model (db/db).

Main Results:

• CRT knockdown led to reduced p53 protein levels and promoted hepatic lipid accumulation, with elevated SREBP-1c and FAS.
• p53 binds to the SREBP-1c promoter at -219 bp; CRT knockdown decreased p53 occupancy at this site.
• Reduced p53 binding correlated with increased SREBP-1c promoter activity and lipid accumulation.
• CRT and p53 levels were decreased, while SREBP-1c was elevated in fatty livers of diabetic db/db mice.

Conclusions:

• CRT negatively regulates hepatic lipid accumulation by facilitating p53 binding to the SREBP-1c promoter.
• Decreased CRT levels may contribute to fatty liver development by impairing p53-mediated repression of SREBP-1c.
• The CRT-p53-SREBP-1c axis represents a potential therapeutic target for managing hepatic steatosis.