Tauopathies are neurodegenerative disorders with increasing incidence and still without cure. The extensive time required for development and approval of novel therapeutics highlights the need for testing and repurposing known safe molecules. Since doxycycline impacts α-synuclein aggregation and toxicity, herein we tested its effect on tau. We found that doxycycline reduces amyloid aggregation of the 2N4R and K18 isoforms of tau protein in a dose-dependent manner. Furthermore, in a cell free system doxycycline also prevents tau seeding and in cell culture reduces toxicity of tau aggregates. Overall, our results expand the spectrum of action of doxycycline against aggregation-prone proteins, opening novel perspectives for its repurposing as a disease-modifying drug for tauopathies.

The oviductal sperm reservoir of South American camelids is formed when sperm bind to N-acetylgalactosamine (GalNAc) on the surface of oviductal epithelium. The aim of this study was to characterize the GalNAc-binding proteins on llama sperm, and to establish their origin. Sperm-adsorbed proteins were extracted with 0.5 M KCl in Hepes-balanced salts. Sperm-adsorbed and seminal plasma proteins were then subjected to ligand blotting for their GalNAc affinity, and the labeled bands were identified by mass spectrometry. Three proteins were identified in seminal plasma versus only one in the sperm-adsorbed population; SL15, a seminal lectin, was common to both. SL15 is a homologue of Zymogen granule protein 16, homolog B-like, which belongs to the Jacalin-related lectin family. This lectin is likely presented to sperm via seminal plasma since epididymal sperm are not capable of binding GalNAc, whereas ejaculated sperm does, and its transcript was enriched predominantly in the prostate and bulbourethral glands. This is the first report of a seminal lectin in South American camelids that originates in the male reproductive tract, and is probably involved in sperm reservoir formation.

Tauopathies are neurodegenerative disorders with increasing incidence and still without cure. The extensive time required for development and approval of novel therapeutics highlights the need for testing and repurposing known safe molecules. Since doxycycline impacts α-synuclein aggregation and toxicity, herein we tested its effect on tau. We found that doxycycline reduces amyloid aggregation of the different isoforms of tau protein in a dose-dependent manner, remodeling the resultant species. Furthermore, doxycycline interacts with tau microtubule-binding domain preventing its aggregation. In a cell free system doxycycline also prevents tau seeding and in cell culture reduces toxicity of tau aggregates. Overall, our results expand the spectrum of action of doxycycline against aggregation-prone proteins, opening novel perspectives for its repurposing as a disease-modifying drug for tauopathies.