Heme-binding-mediated negative regulation of the tryptophan metabolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1) by IDO2.
Indoleamine 2,3-dioxygenases (IDOs) are tryptophan-catabolizing enzymes with immunomodulatory functions. However, the biological role of IDO2 and its relationship with IDO1 are unknown. To assess the relationship between IDO2 and IDO1, we investigated the effects of co-expression of human (h) IDO2 on hIDO1 activity. Cells co-expressing hIDO1 and hIDO2 showed reduced tryptophan metabolic activity compared with those expressing hIDO1 only. In a proteomic analysis, hIDO1-expressing cells exhibited enhanced expression of proteins related to the cell cycle and amino acid metabolism, and decreased expression of proteins related to cell survival. However, cells co-expressing hIDO1 and hIDO2 showed enhanced expression of negative regulators of cell apoptosis compared with those expressing hIDO1 only. Co-expression of hIDO1 and hIDO2 rescued the cell death induced by tryptophan-depletion through hIDO1 activity. Cells expressing only hIDO2 exhibited no marked differences in proteome profiles or cell growth compared with mock-transfectants. Cellular tryptophan metabolic activity and cell death were restored by co-expressing the hIDO2 mutant substituting the histidine 360 residue for alanine. These results demonstrate that hIDO2 plays a novel role as a negative regulator of hIDO1 by competing for heme-binding with hIDO1, and provide information useful for development of therapeutic strategies to control cancer and immunological disorders that target IDO molecules.
Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea.
Young-Kwan
YK
Lee
Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea.
Hoon Bok
HB
Lee
Department of Food and Nutrition, Seoul National University College of Human Ecology, Seoul, Korea.
Dong-Mi
DM
Shin
Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology and College of Medicine or College of Pharmacy, Seoul National University, Seoul, Korea.
Min Jueng
MJ
Kang
Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology and College of Medicine or College of Pharmacy, Seoul National University, Seoul, Korea.
Eugene C
EC
Yi
Department of Chemistry, Seoul National University College of Natural Science, Seoul, Korea.
Seungjoo
S
Noh
Department of Chemistry, Seoul National University College of Natural Science, Seoul, Korea.
Jaewoo
J
Lee
Department of Chemistry, Seoul National University College of Natural Science, Seoul, Korea.
Chulbom
C
Lee
Department of Internal Medicine, Seoul St Mary's Hospital, The Catholic University of Korea, Seoul, Korea.
Chang-Ki
CK
Min
Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea.
Eun Young
EY
Choi
D049109:Cell Proliferation; D002470:Cell Survival; D015870:Gene Expression; D057809:HEK293 Cells; D006418:Heme / Q000378:metabolism*; D006801:Humans; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014364:Tryptophan / Q000378:metabolism*; D015854:Up-Regulation
C576710:IDO1 protein, human; C576711:IDO2 protein, human; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D006418:Heme; D014364:Tryptophan