Role of S-palmitoylation on IFITM5 for the interaction with FKBP11 in osteoblast cells.
Recently, one of the interferon-induced transmembrane (IFITM) family proteins, IFITM3, has become an important target for the activity against influenza A (H1N1) virus infection. In this protein, a post-translational modification by fatty acids covalently attached to cysteine, termed S-palmitoylation, plays a crucial role for the antiviral activity. IFITM3 possesses three cysteine residues for the S-palmitoylation in the first transmembrane (TM1) domain and in the cytoplasmic (CP) loop. Because these cysteines are well conserved in the mammalian IFITM family proteins, the S-palmitoylation on these cysteines is significant for their functions. IFITM5 is another IFITM family protein and interacts with the FK506-binding protein 11 (FKBP11) to form a higher-order complex in osteoblast cells, which induces the expression of immunologically relevant genes. In this study, we investigated the role played by S-palmitoylation of IFITM5 in its interaction with FKBP11 in the cells, because this interaction is a key process for the gene expression. Our investigations using an established reporter, 17-octadecynoic acid (17-ODYA), and an inhibitor for the S-palmitoylation, 2-bromopalmitic acid (2BP), revealed that IFITM5 was S-palmitoylated in addition to IFITM3. Specifically, we found that cysteine residues in the TM1 domain and in the CP loop were S-palmitoylated in IFITM5. Then, we revealed by immunoprecipitation and western blot analyses that the interaction of IFITM5 with FKBP11 was inhibited in the presence of 2BP. The mutant lacking the S-palmitoylation site in the TM1 domain lost the interaction with FKBP11. These results indicate that the S-palmitoylation on IFITM5 promotes the interaction with FKBP11. Finally, we investigated bone nodule formation in osteoblast cells in the presence of 2BP, because IFITM5 was originally identified as a bone formation factor. The experiment resulted in a morphological aberration of the bone nodule. This also indicated that the S-palmitoylation contributes to bone formation.
Graduate School of Life Science, Hokkaido University, Sapporo, Japan ; Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan.
Takashi
T
Tsukamoto
Xianglan
X
Li
Hiromi
H
Morita
Takashi
T
Minowa
Tomoyasu
T
Aizawa
Nobutaka
N
Hanagata
Makoto
M
Demura
D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D054878:Lipoylation / Q000187:drug effects / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D022021:Tacrolimus Binding Proteins / Q000235:genetics / Q000378:metabolism*
D004791:Enzyme Inhibitors; C560216:FKBP11 protein, mouse; C532488:IFITM5 protein, mouse; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D022021:Tacrolimus Binding Proteins