22The microtubule (MT) associated protein Tau is instrumental for the regulation of MT 23 assembly and dynamic instability, orchestrating MT-dependent cellular processes. 24 Aberration in Tau post-translational modifications ratio deviation of spliced Tau isoforms 25 3 or 4 MT binding repeats (3R/4R) have been implicated in neurodegenerative tauopathies.
26Activity-dependent neuroprotective protein (ADNP) is vital for brain formation and 27 cognitive function. ADNP deficiency in mice causes pathological Tau 28 hyperphosphorylation and aggregation, correlated with impaired cognitive functions. It has 29 been previously shown that the ADNP-derived peptide NAP protects against ADNP 30 deficiency, exhibiting neuroprotection, MT interaction and memory protection. NAP 31 prevents MT degradation by recruitment of Tau and end-binding proteins to MTs and 32 expression of these proteins is required for NAP activity. Clinically, NAP (davunetide, 33 CP201) exhibited efficacy in prodromal Alzheimer's disease patients (Tau3R/4R 34 tauopathy) but not in progressive supranuclear palsy (increased Tau4R tauopathy). Here, 35we examined the potential preferential interaction of NAP with 3R vs. 4R Tau, toward 36 personalized treatment of tauopathies. Affinity-chromatography showed that NAP 37 preferentially interacted with Tau3R protein from rat brain extracts and fluorescence 38 recovery after photobleaching assay indicated that NAP induced increased recruitment of 39 human Tau3R to MTs under zinc intoxication, in comparison to Tau4R. Furthermore, we 40 showed that NAP interaction with tubulin (MTs) was inhibited by obstruction of Tau-41 binding sites on MTs, confirming the requirement of Tau-MT interaction for NAP activity.
42The preferential interaction of NAP with Tau3R may explain clinical efficacy in mixed vs.
43Tau4R pathologies, and suggest effectiveness in Tau3R neurodevelopmental disorders. 44 45 Microtubules (MTs) are the major component of the neuronal cytoskeleton, and MT 46 stability and organization play a critical regulatory role during axonal transport and 47 synaptic transmission (1). The MT-associated protein Tau is widely expressed in neurons 48 and serves as a primary protein marker for axons (2, 3). Tau promotes MT assembly and 49 regulates MT dynamic instability, which is essential for establishing neuronal polarity, 50 axonal elongation, and neural outgrowth (4). Neurodegenerative disorders with Tau 51 involvement are referred to as tauopathies (5). The Tau protein consists of an N-terminus 52 region projecting outward from the MTs and a C-terminus part directly interacting with the 53 MTs through MT-binding domains (6). Tau3R and 4R (containing either three or four MT-54 tubulin -binding repeats, respectively) are produced by alternative splicing around exon 55 10 of the Tau transcript (7). The healthy human brain exhibits a 1/1 ratio of Tau3R/4R and 56 deviation from this ratio are the pathological feature of several tauopathies (8).
57Phosphorylation of Tau protein controls its binding to MT and is assoc...