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The Causative Gene in Chanarian Dorfman Syndrome Regulates Lipid Droplet Homeostasis in C. elegans.

Xie M, Roy R - PLoS Genet. (2015)

Bottom Line: We found that the compromise of one of the three C. elegans orthologues of human cgi-58 significantly improves the survival of AMPK-deficient dauers.We also provide evidence that C. elegans CGI-58 acts as a co-activator of ATGL-1, while it also functions cooperatively to maintain regular lipid droplet structure.Surprisingly, we show that it also acts independently of ATGL-1 to restrict lipid droplet coalescence by altering the surface abundance and composition of long chain (C20) polyunsaturated fatty acids (PUFAs).

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, McGill University, Penfield, Montreal, Quebec, Canada.

ABSTRACT
AMP-activated kinase (AMPK) is a key regulator of many cellular mechanisms required for adjustment to various stresses induced by the changing environment. In C. elegans dauer larvae AMPK- mutants expire prematurely due to hyperactive Adipose Triglyceride Lipase (ATGL-1) followed by rapid depletion of triglyceride stores. We found that the compromise of one of the three C. elegans orthologues of human cgi-58 significantly improves the survival of AMPK-deficient dauers. We also provide evidence that C. elegans CGI-58 acts as a co-activator of ATGL-1, while it also functions cooperatively to maintain regular lipid droplet structure. Surprisingly, we show that it also acts independently of ATGL-1 to restrict lipid droplet coalescence by altering the surface abundance and composition of long chain (C20) polyunsaturated fatty acids (PUFAs). Our data reveal a novel structural role of CGI-58 in maintaining lipid droplet homeostasis through its effects on droplet composition, morphology and lipid hydrolysis; a conserved function that may account for some of the ATGL-1-independent features unique to Chanarin-Dorfman Syndrome.

No MeSH data available.


Related in: MedlinePlus

CGI-58 affect C20PUFA abundance in the lipid droplet membrane.(A)-(D) Loss of cgi-58 in AMPK mutant (A and B) and control daf-2 (C and D) dauer larvae led to a lipid droplet-specific reduction of C20PUFAs. LD = lipid droplets. Cyto = cytoplasm. Purified lipid droplets and remaining cytoplasm were subjected to fatty acid methyl ester (FAME) extraction followed by GC/MS analysis. Short/branched fatty acids are the combined total percentage of C14:0, C15ISO, C16ISO, C16:0, C17ISO, C16:1n7 and C17Δ. C18 fatty acids are the combined total percentage of C18:0, C18:1n11, C18:1n10, C18:1n9, C18:1n7, C18:2n6 and C18:3n6. C20PUFAs are total percentage of C20:3n6, C20:4n6, C20:4n3 and C20:5n3. ** indicates statistical significance (P<0.01) and error bars indicate SD of three independent experiments in (A)-(I). (E)-(F) The amount of all major C20PUFAs were decreased in the lipid droplets of daf-2; aak(0); cgi-58(E) and daf-2; cgi-58(F) dauer larvae. (G) Long chain fatty acids were decreased in CGI-58 MEF mutants. Total cell lysates were subjected to FAME extraction followed by GC/MS analysis. Long chain fatty acids include fatty acids with a carbon chain longer than 20 and certain aromatic fatty acids. (H) C20PUFAs were lost from the phospholipid portion of the lipid droplets of daf-2; aak(0); cgi-58 dauer larvae. PL = phospholipid. (I) Some C18 fatty acids were completely absent in the triglyceride portion of the lipid droplets of daf-2; aak(0); cgi-58 dauer larvae. TG = triglyceride.
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pgen.1005284.g006: CGI-58 affect C20PUFA abundance in the lipid droplet membrane.(A)-(D) Loss of cgi-58 in AMPK mutant (A and B) and control daf-2 (C and D) dauer larvae led to a lipid droplet-specific reduction of C20PUFAs. LD = lipid droplets. Cyto = cytoplasm. Purified lipid droplets and remaining cytoplasm were subjected to fatty acid methyl ester (FAME) extraction followed by GC/MS analysis. Short/branched fatty acids are the combined total percentage of C14:0, C15ISO, C16ISO, C16:0, C17ISO, C16:1n7 and C17Δ. C18 fatty acids are the combined total percentage of C18:0, C18:1n11, C18:1n10, C18:1n9, C18:1n7, C18:2n6 and C18:3n6. C20PUFAs are total percentage of C20:3n6, C20:4n6, C20:4n3 and C20:5n3. ** indicates statistical significance (P<0.01) and error bars indicate SD of three independent experiments in (A)-(I). (E)-(F) The amount of all major C20PUFAs were decreased in the lipid droplets of daf-2; aak(0); cgi-58(E) and daf-2; cgi-58(F) dauer larvae. (G) Long chain fatty acids were decreased in CGI-58 MEF mutants. Total cell lysates were subjected to FAME extraction followed by GC/MS analysis. Long chain fatty acids include fatty acids with a carbon chain longer than 20 and certain aromatic fatty acids. (H) C20PUFAs were lost from the phospholipid portion of the lipid droplets of daf-2; aak(0); cgi-58 dauer larvae. PL = phospholipid. (I) Some C18 fatty acids were completely absent in the triglyceride portion of the lipid droplets of daf-2; aak(0); cgi-58 dauer larvae. TG = triglyceride.

Mentions: It is not clear how C. elegans CGI-58 might affect the fusion of lipid droplets in vivo based on our current understanding of its function. Several parameters could affect the rate of lipid exchange including membrane fluidity and/or lipid composition. To further understand how C. elegans CGI-58 prevents lipid droplet fusion we determined the lipid composition of isolated lipid droplets from AMPK mutant dauer larvae that were either compromised or competent for C. elegans CGI-58 function using GC/MS analysis. We found that in the absence of C. elegans CGI-58, the relative amount of total C20PUFAs was significantly reduced in the lipid droplets of both AMPK mutant (Fig 6A) and control daf-2 dauers (Fig 6C), due to the general decrease in abundance of all the individual species of C. elegans C20PUFA of varying degrees of saturation (Fig 6E and 6F). Moreover, this reduction was only observed in isolated lipid droplets, but not in the total lysates, suggesting a lipid droplet-specific role of C. elegans CGI-58 in this context (Fig 6B and 6D).


The Causative Gene in Chanarian Dorfman Syndrome Regulates Lipid Droplet Homeostasis in C. elegans.

Xie M, Roy R - PLoS Genet. (2015)

CGI-58 affect C20PUFA abundance in the lipid droplet membrane.(A)-(D) Loss of cgi-58 in AMPK mutant (A and B) and control daf-2 (C and D) dauer larvae led to a lipid droplet-specific reduction of C20PUFAs. LD = lipid droplets. Cyto = cytoplasm. Purified lipid droplets and remaining cytoplasm were subjected to fatty acid methyl ester (FAME) extraction followed by GC/MS analysis. Short/branched fatty acids are the combined total percentage of C14:0, C15ISO, C16ISO, C16:0, C17ISO, C16:1n7 and C17Δ. C18 fatty acids are the combined total percentage of C18:0, C18:1n11, C18:1n10, C18:1n9, C18:1n7, C18:2n6 and C18:3n6. C20PUFAs are total percentage of C20:3n6, C20:4n6, C20:4n3 and C20:5n3. ** indicates statistical significance (P<0.01) and error bars indicate SD of three independent experiments in (A)-(I). (E)-(F) The amount of all major C20PUFAs were decreased in the lipid droplets of daf-2; aak(0); cgi-58(E) and daf-2; cgi-58(F) dauer larvae. (G) Long chain fatty acids were decreased in CGI-58 MEF mutants. Total cell lysates were subjected to FAME extraction followed by GC/MS analysis. Long chain fatty acids include fatty acids with a carbon chain longer than 20 and certain aromatic fatty acids. (H) C20PUFAs were lost from the phospholipid portion of the lipid droplets of daf-2; aak(0); cgi-58 dauer larvae. PL = phospholipid. (I) Some C18 fatty acids were completely absent in the triglyceride portion of the lipid droplets of daf-2; aak(0); cgi-58 dauer larvae. TG = triglyceride.
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pgen.1005284.g006: CGI-58 affect C20PUFA abundance in the lipid droplet membrane.(A)-(D) Loss of cgi-58 in AMPK mutant (A and B) and control daf-2 (C and D) dauer larvae led to a lipid droplet-specific reduction of C20PUFAs. LD = lipid droplets. Cyto = cytoplasm. Purified lipid droplets and remaining cytoplasm were subjected to fatty acid methyl ester (FAME) extraction followed by GC/MS analysis. Short/branched fatty acids are the combined total percentage of C14:0, C15ISO, C16ISO, C16:0, C17ISO, C16:1n7 and C17Δ. C18 fatty acids are the combined total percentage of C18:0, C18:1n11, C18:1n10, C18:1n9, C18:1n7, C18:2n6 and C18:3n6. C20PUFAs are total percentage of C20:3n6, C20:4n6, C20:4n3 and C20:5n3. ** indicates statistical significance (P<0.01) and error bars indicate SD of three independent experiments in (A)-(I). (E)-(F) The amount of all major C20PUFAs were decreased in the lipid droplets of daf-2; aak(0); cgi-58(E) and daf-2; cgi-58(F) dauer larvae. (G) Long chain fatty acids were decreased in CGI-58 MEF mutants. Total cell lysates were subjected to FAME extraction followed by GC/MS analysis. Long chain fatty acids include fatty acids with a carbon chain longer than 20 and certain aromatic fatty acids. (H) C20PUFAs were lost from the phospholipid portion of the lipid droplets of daf-2; aak(0); cgi-58 dauer larvae. PL = phospholipid. (I) Some C18 fatty acids were completely absent in the triglyceride portion of the lipid droplets of daf-2; aak(0); cgi-58 dauer larvae. TG = triglyceride.
Mentions: It is not clear how C. elegans CGI-58 might affect the fusion of lipid droplets in vivo based on our current understanding of its function. Several parameters could affect the rate of lipid exchange including membrane fluidity and/or lipid composition. To further understand how C. elegans CGI-58 prevents lipid droplet fusion we determined the lipid composition of isolated lipid droplets from AMPK mutant dauer larvae that were either compromised or competent for C. elegans CGI-58 function using GC/MS analysis. We found that in the absence of C. elegans CGI-58, the relative amount of total C20PUFAs was significantly reduced in the lipid droplets of both AMPK mutant (Fig 6A) and control daf-2 dauers (Fig 6C), due to the general decrease in abundance of all the individual species of C. elegans C20PUFA of varying degrees of saturation (Fig 6E and 6F). Moreover, this reduction was only observed in isolated lipid droplets, but not in the total lysates, suggesting a lipid droplet-specific role of C. elegans CGI-58 in this context (Fig 6B and 6D).

Bottom Line: We found that the compromise of one of the three C. elegans orthologues of human cgi-58 significantly improves the survival of AMPK-deficient dauers.We also provide evidence that C. elegans CGI-58 acts as a co-activator of ATGL-1, while it also functions cooperatively to maintain regular lipid droplet structure.Surprisingly, we show that it also acts independently of ATGL-1 to restrict lipid droplet coalescence by altering the surface abundance and composition of long chain (C20) polyunsaturated fatty acids (PUFAs).

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, McGill University, Penfield, Montreal, Quebec, Canada.

ABSTRACT
AMP-activated kinase (AMPK) is a key regulator of many cellular mechanisms required for adjustment to various stresses induced by the changing environment. In C. elegans dauer larvae AMPK- mutants expire prematurely due to hyperactive Adipose Triglyceride Lipase (ATGL-1) followed by rapid depletion of triglyceride stores. We found that the compromise of one of the three C. elegans orthologues of human cgi-58 significantly improves the survival of AMPK-deficient dauers. We also provide evidence that C. elegans CGI-58 acts as a co-activator of ATGL-1, while it also functions cooperatively to maintain regular lipid droplet structure. Surprisingly, we show that it also acts independently of ATGL-1 to restrict lipid droplet coalescence by altering the surface abundance and composition of long chain (C20) polyunsaturated fatty acids (PUFAs). Our data reveal a novel structural role of CGI-58 in maintaining lipid droplet homeostasis through its effects on droplet composition, morphology and lipid hydrolysis; a conserved function that may account for some of the ATGL-1-independent features unique to Chanarin-Dorfman Syndrome.

No MeSH data available.


Related in: MedlinePlus