Unveiling the Potential of a New β‐Cyclodextrin‐Suxibuzone Conjugate in Proteasome Regulation

The proteasome is a central component of the cellular machinery responsible for degrading misfolded or damaged proteins, thereby maintaining protein homeostasis. Dysregulation of proteasome activity has been implicated in various diseases, including neurodegenerative disorders and cancer. In this article, a new β-cyclodextrin conjugate of suxibuzone (SB-CD) is designed and its proteasome activity on purified human 20S core particle and in differentiated human neuroblastoma SH-SY5Y cells (dSHSY5Y) is investigated. This conjugate enhances the proteolytic activity of the 20S proteasome in a dose-dependent manner, with an increase observed at concentrations as low as 5 µM. The EC50 values for SB-CD are determined to be 0.6 ± 0.1 µM for chymotrypsin-like activity and 1.1 ± 0.3 µM for trypsin-like activity, indicating higher efficacy compared to suxibuzone alone. In dSH-SY5Y cells, a decrease in the accumulation of ubiquitinated proteins is observed, consistent with the activation of the proteasome. High-resolution electrospray ionization mass spectrometry investigations confirmed the internalization of SB-CD in cells and verified the stability of the conjugate in response to cellular protease effects, after incubation for up to 24 h. These promising results suggest that the new conjugate is an effective enhancer of proteasome activity, holding significant promise for therapeutic applications targeting proteasome-related pathologies.