The NAP motif of activity-dependent neuroprotective protein (ADNP) enhanced memory scores in patients suffering from mild cognitive impairment and protected activities of daily living in schizophrenia patients, while fortifying microtubule (MT)-dependent axonal transport, in mice and flies. The question is how does NAP fortify MTs? Our sequence analysis identified the MT end-binding protein (EB1)-interacting motif SxIP (SIP, Ser-Ile-Pro) in ADNP/NAP and showed specific SxIP binding sites in all members of the EB protein family (EB1-3). Others found that EB1 enhancement of neurite outgrowth is attenuated by EB2, while EB3 interacts with postsynaptic density protein 95 (PSD-95) to modulate dendritic plasticity. Here, NAP increased PSD-95 expression in dendritic spines, which was inhibited by EB3 silencing. EB1 or EB3, but not EB2 silencing inhibited NAP-mediated cell protection, which reflected NAP binding specificity. NAPVSKIPQ (SxIP=SKIP), but not NAPVAAAAQ mimicked NAP activity. ADNP, essential for neuronal differentiation and brain formation in mouse, a member of the SWI/SNF chromatin remodeling complex and a major protein mutated in autism and deregulated in schizophrenia in men, showed similar EB interactions, which were enhanced by NAP treatment. The newly identified shared MT target of NAP/ADNP is directly implicated in synaptic plasticity, explaining the breadth and efficiency of neuroprotective/neurotrophic capacities.

Microtubules (MTs), key cytoskeletal elements in living cells, are critical for axonal transport, synaptic transmission, and maintenance of neuronal morphology. NAP (NAPVSIPQ) is a neuroprotective peptide derived from the essential activity-dependent neuroprotective protein (ADNP). In Alzheimer’s disease models, NAP protects against tauopathy and cognitive decline. Here, we show that NAP treatment significantly affected the alpha tubulin tyrosination cycle in the neuronal differentiation model, rat pheochromocytoma (PC12) and in rat cortical astrocytes. The effect on tubulin tyrosination/detyrosination was coupled to increased MT network area (measured in PC12 cells), which is directly related to neurite outgrowth. Tubulin beta3, a marker for neurite outgrowth/neuronal differentiation significantly increased after NAP treatment. In rat cortical neurons, NAP doubled the area of dynamic MT invasion (Tyr-tubulin) into the neuronal growth cone periphery. NAP was previously shown to protect against zinc-induced MT/neurite destruction and neuronal death, here, in PC12 cells, NAP treatment reversed zinc-decreased tau-tubulin-MT interaction and protected against death. NAP effects on the MT pool, coupled with increased tau engagement on compromised MTs imply an important role in neuronal plasticity, protecting against free tau accumulation leading to tauopathy. With tauopathy representing a major pathological hallmark in Alzheimer's disease and related disorders, the current findings provide a mechanistic basis for further development. NAP (davunetide) is in phase 2/3 clinical trial in progressive supranuclear palsy, a disease presenting MT deficiency and tau pathology.

Background: Axonal transport (AT) impairment has been implicated as a common mechanism of Alzheimer's disease progression. A newly developed microtubule stabilizing agent, TH237-A, is known for protecting neurons against Ab toxicity, decreasing abnormal tau phosphorylation in cultured neurons, and permeating the blood-brain barrier [1]. We have investigated the efficacy of TH237-A in preserving AT integrity in an animal model of AD, 3xTg mice [2], over one year by measuring AT rates in olfactory bulbs using manganese enhanced MRI. Methods: MR studies were performed using a 9.4 T Varian MR system. Three groups of 3xTg mice (TH237-A(n ¼ 4); vehicle(n ¼ 4); no treatment(n ¼ 3)) and age-matched wild type (wt) mice (TH237-A(n ¼ 4); vehicle(n ¼ 4)) were scanned before treatments at 3 months of age (Pre) and following 12 months of treatments (P12mo). MRI data were acquired before, 1h, 6h, and 24h after unilateral and intranasal administration of MnCl2 solution. Results: Bulk AT rates of the olfactory neurons were significantly lower in 3xTg mice compared with those in wt mice at Pre. 3xTg mice showed age-dependent AT deficits at 15 months of age without any treatment (-30%, p ¼ 0.009) compared with treatment groups. TH237-A treated 3xTg mice did not show any AT rate reduction from Pre to P12mo, whereas TH237-A treated wt mice showed a reduction (-38%, p ¼ 0.001). Considering reduction of AT rates in the nontreated 3xTg mice, no changes of AT rates in TH237-A treated 3xTg mice suggest that TH237-A may be effective in preserving AT integrity in 3xTg mice. However, we also noted that the mice treated with the vehicle (capti-solÒ) alone also showed the similar preservation of AT rates following P12mo treatments. Conclusions: Similar treatment effects of TH237-A and captisol suggest that either effect of TH237-A is more subtle than expected or there are unknown effects of captisol to the AT. We also cannot rule out the environmental effect of daily injection given to the mice. Further studies are needed to identify the source of the treatment effect with additional mouse groups with daily injection with saline.[1]Michaelis, Background: Targeting hyperphosphorylated tau by immunotherapy is emerging as a promising approach to treat tauopathies such as Alzheimer's disease (AD) and frontotemporal dementia. We have previously reported that active tau immunization clears tau aggregates from the brain and attenuates or prevents functional impairments in two different tangle model mice. Here we assessed the efficacy of passive immunization with the PHF1 antibody, which targets a phospho-epitope within one of our active immunogens. Methods: Homozygous JNPL3 P301L mice (2-3 months) were injected intraperitoneally once per week with PHF1 or pooled mouse IgG (250 mg/125 ml; n ¼ 10 per group) for a total of 13 injections. Their behavior was assessed at 5-6 months of age and brain tissue subsequently harvested for analysis of treatment efficacy. Results: The treated mice performed better than controls on the traverse beam task (p < 0.03),...

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