M1 muscarinic agonist treatment reverses cognitive and cholinergic impairments of apolipoprotein E-deficient mice

Complete sequence of a novel protein containing a femtomolar-activity-dependent neuroprotective peptide

The vulnerability of neurons and the irreversibility of loss make discoveries of neuroprotective compounds fundamentally important. Here, the complete coding sequence of a novel protein (828 amino acids, pI 5.99), derived from mouse neuroglial cells, is revealed. The sequence contained (1) a neuroprotective peptide, NAPVSIPQ, sharing structural and immunological homologies with the previously reported, activity-dependent neurotrophic factor; (2) a glutaredoxin active site; and (3) a zinc binding domain. Gene expression was enriched in the mouse hippocampus and cerebellum and augmented in the presence of the neuropeptide vasoactive intestinal peptide, in cerebral cortical astrocytes. In mixed neuron-astrocyte cultures, NAPVSIPQ provided neuroprotection at subfemtomolar concentrations against toxicity associated with tetrodotoxin (electrical blockade), the beta-amyloid peptide (the Alzheimer's disease neurotoxin), N-methyl-D-aspartate (excitotoxicity), and the human immunodeficiency virus envelope protein. Daily NAPVSIPQ injections to newborn apolipoprotein E-deficient mice accelerated the acquisition of developmental reflexes and prevented short-term memory deficits. Comparative studies suggested that NAPVSIPQ was more efficacious than other neuroprotective peptides in the apolipoprotein E-deficiency model. A potential basis for rational drug design against neurodegeneration is suggested with NAPVSIPQ as a lead compound. The relative enrichment of the novel mRNA transcripts in the brain and the increases found in the presence of vasoactive intestinal peptide, an established neuroprotective substance, imply a role for the cloned protein in neuronal function.

Site-specific dephosphorylation of tau of apolipoprotein E-deficient and control mice by M1 muscarinic agonist treatment

Apolipoprotein E (apoE)-deficient mice have memory deficits that are associated with synaptic loss of basal forebrain cholinergic projections and with hyperphosphorylation of distinct epitopes of the microtubule-associated protein tau. Furthermore, treatment of apoE-deficient mice with the M1 selective agonist 1-methylpiperidine-4-spiro-(2'-methylthiazoline) [AF150(S)] abolishes their memory deficits and results in recovery of their brain cholinergic markers. In the present study, we used a panel of anti-tau monoclonal antibodies to further map the tau epitopes that are hyperphosphorylated in apoE-deficient mice and examined the effects of prolonged treatment with AF150(S). This revealed that tau of apoE-deficient mice contains a distinct, hyperphosphorylated "hot spot" domain which is localized N-terminally to the microtubule binding domain of tau, and that AF150(S) has an epitope-specific tau dephosphorylating effect whose magnitude is affected by apoE deficiency. Accordingly, epitopes which reside in the hyperphosphorylated "hot spot" are dephosphorylated by AF150(S) in apoE-deficient mice but are almost unaffected in the controls, whereas epitopes which flank this tau domain are dephosphorylated by AF150(S) in both mice groups. In contrast, epitopes located at the N and C terminals of tau are unaffected by AF150(S) in both groups of mice. These findings suggest that apoE deficiency results in hyperphosphorylation of a distinct tau domain whose excess phosphorylation can be reduced by muscarinic treatment.

Novel m1 muscarinic agonists in treatment and delaying the progression of Alzheimer's disease: an unifying hypothesis

M1 selective agonists from the AF series (e.g. AF102B, AF150(S)), via m1 muscarinic receptors, activate distinct signal transductions, enhance amyloid precursors proteins secretion from transfected cells and primary cell cultures, show neurotrophic effects and are beneficial in a variety of animal models for Alzheimer's disease. Such m1 agonists may be effective in the treatment and therapy of Alzheimer's disease.