Identification Of Deletion Mutants Of Inositol Kinases And Phosphatases Hypersensitive To Valproate

ABSTRACT IDENTIFICATION OF DELETION MUTANTS OF INOSITOL KINASES AND PHOSPHATASES HYPERSENSITIVE TO VALPROATE by WELLEWATTA MUDIYANSELAGE MANOJ SENAKA BANDARA MAY 2010 Advisor: Dr. Miriam Greenberg Major: Biological Sciences Degree: Master of Science Bipolar disorder (BD) is a chronic psychiatric illness affecting at least 1% of the world population. BD is ranked as the sixth greatest cause of death or disability globally. The cause of BD is unknown. Although the anticonvulsant valproate (VPA) is widely used as a mood stabilizer to treat BD, VPA is not completely effective and causes numerous side effects. Hence, it is important to develop more effective drugs with fewer side effects to treat BD. However, drug development is hampered by the lack of knowledge of the therapeutic mechanisms of action of current drugs used to treat BD. VPA depletes inositol in yeast and mammals. The current study was undertaken to determine whether genes affecting inositol synthesis lead to VPA sensitivity.1D-myo-inositol-3 phosphate synthase (MIPS) encoded by INO1 converts glucose-6-phosphate to L-myo-inositol-3-phosphate (MIP) in the de novo synthesis of inositol. The activation of INO1 expression is positively regulated by the INO80 complex, which is inhibited by IP6. KCS1 and VIP1 are inositol hexakisphosphate kinases that convert IP6 to IP7. I found that kcs1∆ is an inositol auxotroph and vip1∆ is a partial inositol auxotroph. Both kcs1∆ and vip1∆ mutants exhibited hypersensitivity to VPA. I also found that loss of KCS1 and VIP1 cause decreased INO1expression. The results of the study suggested that perturbation of IP synthesis exacerbates VPA induced inositol depletion. These findings have implications for understanding the mechanisms underlying responsiveness or resistance to VPA in bipolar patients.