Regulation of inositol 1,3,4-trisphosphate 5/6-kinase (ITPK1) by reversible lysine acetylation.
The enzyme inositol 1,3,4-trisphosphate 5/6-kinase (ITPK1) catalyzes the rate-limiting step in the formation of higher phosphorylated forms of inositol in mammalian cells. Because it sits at a key regulatory point in the inositol metabolic pathway, its activity is likely to be regulated. We have previously shown that ITPK1 is phosphorylated, a posttranslational modification used by cells to regulate enzyme activity. We show here that ITPK1 is modified by acetylation of internal lysine residues. The acetylation sites, as determined by mass spectrometry, were found to be lysines 340, 383, and 410, which are all located on the surface of this protein. Overexpression of the acetyltransferases CREB-binding protein or p300 resulted in the acetylation of ITPK1, whereas overexpression of mammalian silent information regulator 2 resulted in the deacetylation of ITPK1. Functionally, ITPK1 acetylation regulates its stability. CREB-binding protein dramatically decreased the half-life of ITPK1. We further found that ITPK1 acetylation down-regulated its enzyme activity. HEK293 cells stably expressing acetylated ITPK1 had reduced levels of the higher phosphorylated forms of inositol, compared with the levels seen in cells expressing unacetylated ITPK1. These results demonstrate that lysine acetylation alters both the stability as well as the activity of ITPK1 in cells.
Departments of Internal Medicine and Biochemistry, Washington University School of Medicine, St Louis, MO 63110, USA.
Chunfen
C
Zhang
Philip W
PW
Majerus
Monita P
MP
Wilson
D000107:Acetylation; D000595:Amino Acid Sequence; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D015536:Down-Regulation; D004795:Enzyme Stability; D006207:Half-Life; D006801:Humans; D008239:Lysine / Q000378:metabolism*; D008969:Molecular Sequence Data; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D056564:Sirtuin 1 / Q000378:metabolism; D050880:p300-CBP Transcription Factors / Q000378:metabolism
D050880:p300-CBP Transcription Factors; D017853:Phosphotransferases (Alcohol Group Acceptor); C056875:myo-inositol-trisphosphate 6-kinase; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D008239:Lysine