Sexual divergence in microtubule function: the novel intranasal microtubule targeting SKIP normalizes axonal transport and enhances memory

Abstract

Activity-dependent neuroprotective protein (ADNP), essential for brain formation, is a frequent autism spectrum disorder (ASD)-mutated gene. ADNP associates with microtubule end-binding proteins (EBs) through its SxIP motif, to regulate dendritic spine formation and brain plasticity. Here, we reveal SKIP, a novel four-amino-acid peptide representing an EB-binding site, as a replacement therapy in an outbred Adnp-deficient mouse model. We discovered, for the first time, axonal transport deficits in Adnp(+/-) mice (measured by manganese-enhanced magnetic resonance imaging), with significant male-female differences. RNA sequencing evaluations showed major age, sex and genotype differences. Function enrichment and focus on major gene expression changes further implicated channel/transporter function and the cytoskeleton. In particular, a significant maturation change (1 month-five months) was observed in beta1 tubulin (Tubb1) mRNA, only in Adnp(+/+) males, and sex-dependent increase in calcium channel mRNA (Cacna1e) in Adnp(+/+) males compared with females. At the protein level, the Adnp(+/-) mice exhibited impaired hippocampal expression of the calcium channel (voltage-dependent calcium channel, Cacnb1) as well as other key ASD-linked genes including the serotonin transporter (Slc6a4), and the autophagy regulator, BECN1 (Beclin1), in a sex-dependent manner. Intranasal SKIP treatment normalized social memory in 8- to 9-month-old Adnp(+/-)-treated mice to placebo-control levels, while protecting axonal transport and ameliorating changes in ASD-like gene expression. The control, all d-amino analog D-SKIP, did not mimic SKIP activity. SKIP presents a novel prototype for potential ASD drug development, a prevalent unmet medical need.

Microtubule stabilising peptides rescue tau phenotypes in-vivo

“…Substitution of proline (P) with alanine (A) abolishes neuroprotection against oxidative stress (H 2 O 2 ) in pheochromocytoma (PC12) cells64. Indeed, the SIP motif of NAP and SAL is essential for neuroprotection and interaction with key MT end-binding proteins EB1 and EB3, promoting MT assembly and neuronal plasticity1826. Collectively, our data and the studies discussed imply that SAL acts in a similar manner as NAP to confer neuroprotection.…”

“…Furthermore, silencing of EB3 in primary cortical neurons inhibits NAP-mediated dendritic spine formation18. A novel NAP analogue, SKIP, is reported to bind NAP and enhance axonal transport in ADNP-deficient mice26. It is therefore conceivable that NAP restores MT integrity and function in our Drosophila model of tauopathy by interacting with EB’s via its SIP domain.…”

Premature primary tooth eruption in cognitive/motor-delayed ADNP-mutated children

“…4 The data have been uploaded to GEO, GSE81268. Further details are in the Supplementary Information.…”

“…Activity-dependent neuroprotective protein (ADNP) was discovered in the Gozes laboratory 2 as a protein-protecting nerve cells against electrical blockade. 3 Recent studies identified ADNP as a regulator of axonal transport, 4 dendritic spine plasticity 5 and autophagy. 6 Complete Adnp deficiency in mice results in inability to form a brain.…”

“…10 Throughout postnatal brain maturation and adulthood, Adnp regulates multiple key genes associated with synaptic transmission including tubulin, ion channel and autophagy-controlling genes in an age/sex/genotype-dependent manner. 4 …”