A novel equation for cooperativity of the allosteric state function.
Ontology highlight
ABSTRACT:
SUBMITTER: Edelstein SJ
PROVIDER: S-EPMC3898861 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The muscarinic M1 receptor (M1R) is a promising target for treating cognitive impairment associated with cholinergic deficits in disorders such as Alzheimer's disease and schizophrenia. We previously reported that cooperativity (?-value) was key to lowering the risk of diarrhea by M1R positive allosteric modulators (M1 PAMs). Based on this, we discovered a low ?-value M1 PAM, TAK-071 (?-value: 199), and characterized TAK-071 using T-662 as a reference M1 PAM with high ?-value of 1786. Both TAK-071 and T-662 were potent and highly selective M1 PAMs, with inflection points of 2.7 and 0.62?nM, respectively. However, T-662 but not TAK-071 augmented isolated ileum motility. TAK-071 and T-662 increased hippocampal inositol monophosphate production through M1R activation and improved scopolamine-induced cognitive deficits in rats at 0.3 and 0.1?mg/kg, respectively. TAK-071 and T-662 also induced diarrhea at 10 and 0.1?mg/kg, respectively, in rats. Thus, taking into consideration the fourfold lower brain penetration ratio of T-662, TAK-071 had a wider margin between cognitive improvement and diarrhea induction than T-662. Activation of M1R increases neural excitability via membrane depolarization, reduced afterhyperpolarization, and generation of afterdepolarization in prefrontal cortical pyramidal neurons. T-662 induced all three processes, whereas TAK-071 selectively induced afterdepolarization. Combining sub-effective doses of TAK-071, but not T-662, with an acetylcholinesterase inhibitor, significantly ameliorated scopolamine-induced cognitive deficits in rats. TAK-071 may therefore provide therapeutic opportunities for cognitive dysfunction related to cholinergic deficits or reduced M1R expression, while minimizing peripheral cholinergic side effects.
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Project description:Conformational cooperativity is a universal molecular effect mechanism and plays a critical role in signaling pathways. However, it remains a challenge to develop artificial molecular networks regulated by conformational cooperativity, due to the difficulties in programming and controlling multiple structural interactions. Herein, we develop a cooperative strategy by programming multiple conformational signals, rather than chemical signals, to regulate protein-oligonucleotide signal transduction, taking advantage of the programmability of allosteric DNA constructs. We generate a cooperative regulation mechanism, by which increasing the loop lengths at two different structural modules induced the opposite effects manifesting as down- and up-regulation. We implement allosteric logic operations by using two different proteins. Further, in cell culture we demonstrate the feasibility of this strategy to cooperatively regulate gene expression of PLK1 to inhibit tumor cell proliferation, responding to orthogonal protein-signal stimulation. This programmable conformational cooperativity paradigm has potential applications in the related fields.
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