1. The N-terminal Region of Comparative Gene Identification-58 (CGI-58) Is Important for Lipid Droplet Binding and Activation of Adipose Triglyceride Lipase
- Author
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Margret Poeschl, Martina Schweiger, Sepp D. Kohlwein, Christina Eder, Heimo Wolinski, Manju Kumari, Achim Lass, Irina Cornaciu, Robert Zimmermann, Gabriele Schoiswohl, Monika Oberer, Rudolf Zechner, and Astrid Gruber
- Subjects
Models, Molecular ,Molecular Sequence Data ,Protein domain ,White adipose tissue ,Biology ,Transfection ,Biochemistry ,Mice ,Protein structure ,health services administration ,Lipid droplet ,Chlorocebus aethiops ,mental disorders ,Animals ,Humans ,Protein Interaction Domains and Motifs ,Amino Acid Sequence ,Molecular Biology ,Peptide sequence ,chemistry.chemical_classification ,Lipid metabolism ,Lipase ,Cell Biology ,1-Acylglycerol-3-Phosphate O-Acyltransferase ,Lipid Metabolism ,Recombinant Proteins ,humanities ,Protein Structure, Tertiary ,Amino acid ,Enzyme Activation ,Metabolism ,chemistry ,Structural Homology, Protein ,COS Cells ,Adipose triglyceride lipase ,Mutagenesis, Site-Directed ,Carboxylic Ester Hydrolases - Abstract
In mammals, excess energy is stored in the form of triacylglycerol primarily in lipid droplets of white adipose tissue. The first step of lipolysis (i.e. the mobilization of fat stores) is catalyzed by adipose triglyceride lipase (ATGL). The enzymatic activity of ATGL is strongly enhanced by CGI-58 (comparative gene identification-58), and the loss of either ATGL or CGI-58 function causes systemic triglyceride accumulation in humans and mice. However, the mechanism by which CGI-58 stimulates ATGL activity is unknown. To gain insight into CGI-58 function using structural features of the protein, we generated a three-dimensional homology model based on sequence similarity with other proteins. Interestingly, the model of CGI-58 revealed that the N terminus forms an extension of the otherwise compact structure of the protein. This N-terminal region (amino acids 1-30) harbors a lipophilic tryptophan-rich stretch, which affects the localization of the protein. (1)H NMR experiments revealed strong interaction between the N-terminal peptide and dodecylphosphocholine micelles as a lipid droplet-mimicking system. A role for this N-terminal region of CGI-58 in lipid droplet binding was further strengthened by localization studies in cultured cells. Although wild-type CGI-58 localizes to the lipid droplet, the N-terminally truncated fragments of CGI-58 are dispersed in the cytoplasm. Moreover, CGI-58 lacking the N-terminal extension loses the ability to stimulate ATGL, implying that the ability of CGI-58 to activate ATGL is linked to correct localization. In summary, our study shows that the N-terminal, Trp-rich region of CGI-58 is essential for correct localization and ATGL-activating function of CGI-58.
- Published
- 2010
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