Molecular and Cellular Biochemistry

, Volume 378, Issue 1–2, pp 83–89 | Cite as

Rat brain myo-inositol 3-phosphate synthase is a phosphoprotein

  • R. N. Parthasarathy
  • J. Lakshmanan
  • M. Thangavel
  • R. S. Seelan
  • J. I. Stagner
  • A. J. Janckila
  • R. E. Vadnal
  • M. F. Casanova
  • L. K. Parthasarathy


The therapeutic effects of lithium in bipolar disorder are poorly understood. Lithium decreases free inositol levels by inhibiting inositol monophosphatase 1 and myo-inositol 3-phosphate synthase (IPS). In this study, we demonstrate for the first time that IPS can be phosphorylated. This was evident when purified rat IPS was dephosphorylated by lambda protein phosphatase and analyzed by phospho-specific ProQ-Diamond staining and Western blot analysis. These techniques demonstrated a mobility shift consistent with IPS being phosphorylated. Mass spectral analysis revealed that Serine-524 (S524), which resides in the hinge region derived from exon 11 of the gene, is the site for phosphorylation. Further, an antibody generated against a synthetic peptide of IPS containing monophosphorylated-S524, was able to discriminate the phosphorylated and non-phosphorylated forms of IPS. The phosphoprotein is found in the brain and testis, but not in the intestine. The intestinal IPS isoform lacks the peptide bearing S524, and hence, cannot be phosphorylated. Evidences suggest that IPS is monophosphorylated at S524 and that the removal of this phosphate does not alter its enzymatic activity. These observations suggest a novel function for IPS in brain and other tissues. Future studies should resolve the functional role of phospho-IPS in brain inositol signaling.


Bipolar disorder Inositol phosphate synthase Myo-inositol Serine phosphorylation 

Supplementary material

11010_2013_1597_MOESM1_ESM.doc (22 kb)
Supplementary material 1 (DOC 22 kb)


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Copyright information

© Springer Science+Business Media New York (outside the USA) 2013

Authors and Affiliations

  • R. N. Parthasarathy
    • 1
    • 2
    • 3
  • J. Lakshmanan
    • 1
    • 3
    • 4
  • M. Thangavel
    • 1
    • 3
  • R. S. Seelan
    • 1
    • 3
    • 5
  • J. I. Stagner
    • 6
  • A. J. Janckila
    • 7
    • 8
  • R. E. Vadnal
    • 9
  • M. F. Casanova
    • 1
  • L. K. Parthasarathy
    • 1
    • 3
  1. 1.Molecular Neuroscience and Bioinformatics Laboratories, Mental Health, Behavioral Science and Research ServicesRobley Rex Veterans Affairs Medical CenterLouisvilleUSA
  2. 2.Department of Biochemistry and Molecular BiologyUniversity of LouisvilleLouisvilleUSA
  3. 3.Department of Psychiatry and Behavioral SciencesUniversity of LouisvilleLouisvilleUSA
  4. 4.Price Institute of Surgical Research, Department of Surgery, School of MedicineUniversity of LouisvilleLouisvilleUSA
  5. 5.Department of Molecular, Cellular & Craniofacial Biology, School of DentistryUniversity of LouisvilleLouisvilleUSA
  6. 6.Research ServicesRobley Rex Veterans Affairs Medical CenterLouisvilleUSA
  7. 7.Special Hematology LabRobley Rex Veterans Affairs Medical CenterLouisvilleUSA
  8. 8.Department of Microbiology and Immunology, School of MedicineUniversity of LouisvilleLouisvilleUSA
  9. 9.Eastern Colorado Health Care SystemDepartment of Veterans AffairsPuebloUSA

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