Fig 2. CGI-58 interacts with ATGL-1 and tethers it to the lipid droplets. (A) CGI-58::GFP was expressed in the hypodermis and the intestine atcomparable levels in both control
daf-2 and
daf-2; aak(0) mutant dauer larvae. Both strains carry the same ex[Pcgi-58::
cgi-58::GFP;
rol-6(gf)] transgene (SeeMaterials and Methods). Scale bar = 20 um. (B) CGI-58::GFP localizes to the surface of the lipid droplets at dauer day 0 (48 hours after being shifted to 25 degrees C at the L1 stage) in both
daf-2 and
daf-2; aak(0) mutant dauers. Both strains carry the same ex[Pcgi-58::
cgi-58::GFP;
rol-6(gf)] transgene. Scale bar = 10um. Insets (B' and B") were generated by selecting the same size of frame for each image followed by proportionate amplification to the same magnification. (C) Optimal ATGL-1 lipase activity requires
cgi-58. ATGL-1-dependent lipase activity was determined in
daf-2; aak(0) mutant dauer larvae with wild type orcompromised
cgi-58/atgl-1 function. ** indicates statistical significance (P<0.01) compared to all three of the other genotypes. Error bars indicate SD of three independent experiments. (D) Elimination of
cgi-58 resulted in the dissociation of ATGL-1 from the lipid droplets. Both strains carry the same hjIs67[Patgl-1::
atgl-1::GFP] transgene. Scale bar = 10um. Insets (D' and D'') were generated by selecting the same size of frame for each image followed byproportionate amplification to the same final magnification. (E) ATGL-1 association with the lipid droplets is dependent on appropriate CGI-58 levels.Immunoblot analysis was used to determine the levels of ATGL-1 in isolated lipid droplets (L) and cytoplasm (C) obtained from total day 0 dauer extracts ofeach genotype. Protein concentration was measured and 30ug of total protein was loaded in each sample lane. Actin was used as a loading control for thetotal protein level. (F) CGI-58 does not contribute to ATGL-1 stability in AMPK mutant dauers. ATGL-1 levels were determined by immunobloting using antiATGL-1antisera in lysates obtained from AMPK mutants with or without
cgi-58. (G) CGI-58 physically interacts with ATGL-1 in vivo in both control and AMPKmutant dauers. Co-immunoprecipitations were performed with
daf-2 and
daf-2; aak(0) day 0 dauer larvae carrying the same ex[Pcgi-58::
cgi-58::GFP;
rol-6(gf)] transgene using anti-ATGL-1 serum for pull down and blotted with anti-GFP serum.