title: Inhibition of inositol monophosphatase (IMPase) at the calbindin-D28k binding site: molecular and behavioral aspects.
abstract: Bipolar-disorder (manic-depressive illness) is a severe chronic illness affecting ∼1% of the adult population. It is treated with mood-stabilizers, the prototypic one being lithium-salts (lithium), but it has life threatening side-effects and a significant number of patients fail to respond. The lithium-inhibitable enzyme inositol-monophosphatase (IMPase) is one of the viable targets for lithium's mechanism of action. Calbindin-D28k (calbindin) up-regulates IMPase activity. The IMPase-calbindincomplex was modeled using the program MolFit. The in-silico model indicated that the 55-66 amino-acid segment of IMPase anchors calbindin via Lys59 and Lys61 with a glutamate in between (Lys-Glu-Lys motif) and that the motif interacts with residues Asp24 and Asp26 of calbindin. We found that differently from wildtype calbindin, IMPase was not activated by mutated calbindin in which Asp24 and Asp26 were replaced by alanine. Calbindin's effect was significantly reduced by a linear peptide with the sequence of amino acids 58-63 of IMPase (peptide 1) and by six amino-acid linear peptides including at least part of the Lys-Glu-Lys motif. The three amino-acid peptide Lys-Glu-Lys or five amino-acid linear peptides containing this motif were ineffective. Mice administered peptide 1 intracerebroventricularly exhibited a significant anti-depressant-like reduced immobility in the forced-swim test. Based on the sequence of peptide 1, and to potentially increase the peptide's stability, cyclic and linear pre-cyclic analog peptides were synthesized. One cyclic peptide and one linear pre-cyclic analog peptide inhibited calbindin-activated brain IMPase activity in-vitro. Our findings may lead to the development of molecules capable of inhibiting IMPase activity at an alternative site than that of lithium.
authors.affiliation: Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel; Psychiatry Research Unit, Mental Health Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Itzhak
authors.initials: I
authors.lastname: Levi
authors.forename: Yael
authors.initials: Y
authors.lastname: Eskira
authors.forename: Miriam
authors.initials: M
authors.lastname: Eisenstein
authors.forename: Chaim
authors.initials: C
authors.lastname: Gilon
authors.forename: Amnon
authors.initials: A
authors.lastname: Hoffman
authors.forename: Yftah
authors.initials: Y
authors.lastname: Tal-Gan
authors.forename: Yiftach
authors.initials: Y
authors.lastname: Talgan
authors.forename: Joseph
authors.initials: J
authors.lastname: Fanous
authors.forename: Yuly
authors.initials: Y
authors.lastname: Bersudsky
authors.forename: R H
authors.initials: RH
authors.lastname: Belmaker
authors.forename: Galila
authors.initials: G
authors.lastname: Agam
authors.forename: Orna
authors.initials: O
authors.lastname: Almog
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D064092:Calbindin 1 / Q000378:metabolism*; D005106:Exploratory Behavior / Q000187:drug effects; D006801:Humans; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology; D013550:Swimming / Q000523:psychology; D016138:Walking / Q000502:physiology
chemical_list: D064092:Calbindin 1; D010455:Peptides; D010456:Peptides, Cyclic; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase
keywords: Bipolar disorder; Calbindin; Inositol monophosphatase; Lithium; Protein–protein docking