CGI‐58 regulates triacylglycerol metabolism and lipid signaling pathways in plant cells

Abstract

CGI‐58 (Comparative Gene Identification‐58) encodes an α/β hydrolase‐type protein that is involved in multiple aspects of lipid metabolism in mammals, including the breakdown of triacylglycerols (TAGs) and formation of the hydrophobic barrier of the skin. Mutations in CGI‐58 result not only in aberrant skin formation, but also in accumulation of lipid droplets (LDs) in non‐lipid‐storing tissues such as skin, liver, and blood cells. The activity of CGI‐58 is determined at least in part by its interaction with other proteins including perilipin, which serves to anchor CGI‐58 to the surface of LDs. Phosphorylation of perilipin releases CGI‐58 and allows it to interact with Adipose Triglyceride Lipase (ATGL), thereby stimulating TAG breakdown. Interestingly, disruption of the CGI‐58 homolog in Arabidopsis results also in the accumulation of LDs in tissues that do not normally store lipids (e.g., leaves and stems), but plants lack any apparent homologs to perilipin or ATGL. In an effort to better understand the function of CGI‐58 in plants, we conducted a yeast 2‐hybrid assay using Arabidopsis CGI‐58 as bait. Although we did not identify any obvious LD‐associated proteins or lipases, we did identify several proteins known to be involved in distinct aspects of plant lipid metabolism. Evidence will be presented showing that CGI‐58 modulates the level of linolenic acid as well as lipid signaling pathways in plant cells.