The design and delivery of a thermally responsive peptide to inhibit S100B-mediated neurodegeneration

Abstract S100B, a glial-secreted protein, is believed to play a major role in neurodegeneration in Alzheimer's disease, Down syndrome, traumatic brain injury, and spinocerebellar ataxia type 1 (SCA1). SCA1 is a trinucleotide repeat disorder in which the expanded polyglutamine mutation in the protein ataxin-1 primarily targets Purkinje cells of the cerebellum. Currently, the exact mechanism of S100B-mediated Purkinje cell damage in SCA1 is not clear. However, here we show that S100B may act via the activation of the receptor for advanced glycation end product (RAGE) signaling pathway, resulting in oxidative stress-mediated injury to mutant ataxin-1-expressing neurons. To combat S100B-mediated neurodegeneration, we have designed a selective thermally responsive S100B inhibitory peptide, Synb1-ELP-TRTK. Our therapeutic polypeptide was developed using three key elements: (1) the elastin-like polypeptide (ELP), a thermally responsive polypeptide, (2) the TRTK12 peptide, a known S100B inhibitory peptide, and (3) a cell-penetrating peptide, Synb1, to enhance intracellular delivery. Binding studies revealed that our peptide, Synb1-ELP-TRTK, interacts with its molecular target S100B and maintains a high S100B binding affinity as comparable with the TRTK12 peptide alone. In addition, in vitro studies revealed that Synb1-ELP-TRTK treatment reduces S100B uptake in SHSY5Y cells. Furthermore, the Synb1-ELP-TRTK peptide decreased S100B-induced oxidative damage to mutant ataxin-1-expressing neurons. To test the delivery capabilities of ELP-based therapeutic peptides to the cerebellum, we treated mice with fluorescently labeled Synb1-ELP and observed that thermal targeting enhanced peptide delivery to the cerebellum. Here, we have laid the framework for thermal-based therapeutic targeting to regions of the brain, particularly the cerebellum. Overall, our data suggest that thermal targeting of ELP-based therapeutic peptides to the cerebellum is a novel treatment strategy for cerebellar neurodegenerative disorders.