Regulation of G0/G1 Switch Gene 2 (G0S2) Protein Ubiquitination and Stability by Triglyceride Accumulation and ATGL Interaction
Authors: Bradlee L Heckmann
Jun Liu
Xiaodong Zhang
Alicia M Saarinen
Journal: PloS one (2016)
Discipline: Multidisciplinary
Keywords: Intracellular triglyceride; lipolysis; adipose triglyceride lipase; G0/G1 Switch Gene 2; protein degradation
Affiliations: Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Scottsdale, Arizona, United States of America., Metabolic HEALth Program, Mayo Clinic, Scottsdale, Arizona, United States of America., Mayo Graduate School, Rochester, Minnesota, United States of America.

Abstract:  Intracellular triglyceride (TG) hydrolysis or lipolysis is catalyzed by the key intracellular triglyceride hydrolase, adipose triglyceride lipase (ATGL). The G0/G1 Switch Gene 2 (G0S2) was recently identified as the major selective inhibitor of ATGL and its hydrolase function. Since G0S2 levels are dynamically linked and rapidly responsive to nutrient status or metabolic requirements, the identification of its regulation at the protein level is of significant value. Earlier evidence from our laboratory demonstrated that G0S2 is a short-lived protein degraded through the proteasomal pathway. However, little is currently known regarding the underlying mechanisms. In the current study we find that 1) protein degradation is initiated by K48-linked polyubiquitination of the lysine- 25 in G0S2; and 2) G0S2 protein is stabilized in response to ATGL expression and TG accumulation. Mutation of lysine-25 of G0S2 abolished ubiquitination and increased protein stability. More importantly, G0S2 was stabilized via different mechanisms in the presence of ATGL vs. in response to fatty acid (FA)-induced TG accumulation. Furthermore, G0S2 protein but not mRNA levels were reduced in the adipose tissue of ATGL-deficient mice, corroborating the involvement of ATGL in the stabilization of G0S2. Taken together our data illustrate for the first time a crucial multifaceted mechanism for the stabilization of G0S2 at the protein level. 

Retracted: No

PubPeer comments:
 There seems to be re-use of of western blotting data that has been stretched and re-labeled to represent 2 different experiments in figures 1 and 3. There are some bubbles in the western blot that makes it possible to spot the duplicated blots. If you stretch and enhance the contrast the last look identical. Here s the images as they re shown in the paper with the similar lanes in red boxes: https: imgur.com odKB0Yt And here s the same panels after a stretch and contrast adjust. They look remarkably similar. https: imgur.com fhb2XjH , 
 There appears to be another instance of blot re-use and stretching. It involves the same blot shown above in figure 3D and a blot presented in figure 2D. It appears that the same part of the blot in 3D (and in Fig 1A, see above) was stretched and re-labelled. Here s the 2 blots direct from the publication, with the similar part boxed n red: https: imgur.com UjaZqH0 Here s the same two blots with Fig 3D stretched vertically. There are some small imperfections in the blots that makes them identifiable (circled in blue): https: imgur.com tQCkuup Odd that the same blot appears 3 different times labelled as 3 different samples. ,