The Calbindin-D28k binding site on inositol monophosphatase may allow inhibition independent of the lithium site of action

Among numerous reported biochemical effects the lithium-inhibitable enzyme inositol-monophosphatase (IMPase) remains a viable target for lithium's therapeutic mechanism of action. Calbindin-D28k (calbindin) interacts with IMPase enhancing its activity. In the present study in silico modeling of IMPase-calbindin binding using the program MolFit 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). The model further suggested that the Lys-Glu-Lys motif interacts with residues Asp24 and Asp26 of calbindin. Indeed, 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 peptide with the sequence of amino acids 58-63 of IMPase (peptide 1) and by six amino-acid peptides including at least part of the Lys-Glu-Lys motif. The three amino-acid peptide Lys-Glu-Lys or five amino-acid peptides containing this motif were ineffective. Intracerebroventricular administration of peptide 1 resulted in a significant antidepressant-like reduced immobility in the Porsolt forced swim test (FST) compared with mice treated with a scrambled peptide or artificial cerebrospinal fluid. 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 and one linear pre-cyclic analog peptides exhibited an inhibitory effect on calbindin-activated brain IMPase activity in vitro. These findings may lead to the development of molecules capable of inhibiting IMPase activity at an alternative site than that of lithium

Carbamoylphosphonates inhibit autotaxin and metastasis formation in vivo

Autotaxin is an extracellular, two zinc-centered enzyme that hydrolyzes lysophosphatidyl choline to lysophosphatidic acid, involved in various cancerous processes, e.g. migration, proliferation and tumor progression. We examined the autotaxin inhibitory properties of extended structure carbamoylphosphonates (CPOs) PhOC(6)H(4)SO(2)NH(CH(2))nNHCOPO(3)H(2), with increasing lengths of methylene chains, (CH(2))(n), n = 4-8. Carbamoylphosphonates having n = 6, 7, 8 inhibited autotaxin in vitro with IC(50) ≈ 1.5 µM. Using an imaging probe we demonstrated that compound n = 6 inhibits recombinant autotaxin activity in vitro and in vivo, following oral CPO administration. Additionally, daily oral administration of compound n = 7 inhibited over 90% of lung metastases in a murine melanoma metastasis model. Both the carbamoylphosphonates and the enzymes reside and interact in the extracellular space expecting minimal toxic side effects, and presenting a novel approach for inhibiting tumor proliferation and metastasis dissemination

The Authors

DOI: 10.2165/0019053-200826100-00009Clinical-trial-design, Cost-effectiveness