The last enzyme of the de novo purine synthesis pathway 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC) plays a central role in insulin signaling and the Golgi/endosomes protein network.

TitleThe last enzyme of the de novo purine synthesis pathway 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC) plays a central role in insulin signaling and the Golgi/endosomes protein network.
Publication TypeJournal Article
Year of Publication2015
AuteursBoutchueng-Djidjou, M, Collard-Simard, G, Fortier, S, Hébert, SS, Kelly, I, Landry, CR, Faure, RL
JournalMol Cell Proteomics
Volume14
Issue4
Pagination1079-92
Date Published2015 Apr
ISSN1535-9484
KeywordsAdenylate Kinase, Aminoimidazole Carboxamide, Animals, Biosynthetic Pathways, Cell Membrane, Computational Biology, Endocytosis, Endosomes, Female, Gene Knockdown Techniques, Golgi Apparatus, HEK293 Cells, Humans, Insulin, Intracellular Signaling Peptides and Proteins, Kinetics, Liver, Mass Spectrometry, Nucleotide Deaminases, Phosphorylation, Proteomics, Purines, Rats, Sprague-Dawley, Receptor, Insulin, Ribonucleotides, Signal Transduction, Sus scrofa
Abstract

Insulin is internalized with its cognate receptor into the endosomal apparatus rapidly after binding to hepatocytes. We performed a bioinformatic screen of Golgi/endosome hepatic protein fractions and found that ATIC, which is a rate-limiting enzyme in the de novo purine biosynthesis pathway, and PTPLAD1 are associated with insulin receptor (IR) internalization. The IR interactome (IRGEN) connects ATIC to AMPK within the Golgi/endosome protein network (GEN). Forty-five percent of the IR Golgi/endosome protein network have common heritable variants associated with type 2 diabetes, including ATIC and AMPK. We show that PTPLAD1 and AMPK are rapidly compartmentalized within the plasma membrane (PM) and Golgi/endosome fractions after insulin stimulation and that ATIC later accumulates in the Golgi/endosome fraction. Using an in vitro reconstitution system and siRNA-mediated partial knockdown of ATIC and PTPLAD1 in HEK293 cells, we show that both ATIC and PTPLAD1 affect IR tyrosine phosphorylation and endocytosis. We further show that insulin stimulation and ATIC knockdown readily increase the level of AMPK-Thr172 phosphorylation in IR complexes. We observed that IR internalization was markedly decreased after AMPKα2 knockdown, and treatment with the ATIC substrate AICAR, which is an allosteric activator of AMPK, increased IR endocytosis in cultured cells and in the liver. These results suggest the presence of a signaling mechanism that senses adenylate synthesis, ATP levels, and IR activation states and that acts in regulating IR autophosphorylation and endocytosis.

DOI10.1074/mcp.M114.047159
Alternate JournalMol. Cell Proteomics
PubMed ID25687571
PubMed Central IDPMC4390253
Grant ListGMX-299432 / / Canadian Institutes of Health Research / Canada
GMX-324265 / / Canadian Institutes of Health Research / Canada