Disorder in the Human Skp1 Structure is the Key to its Adaptability to Bind Many Different Proteins in the SCF Complex Assembly

Mercuric sulfide nanoparticles suppress the neurobehavioral functions of Caenorhabditis elegans through a Skp1-dependent mechanism

Cinnabar is the naturally occurring mercuric sulfide (HgS) and concerns about its safety have been grown. However, the molecular mechanism of HgS-related neurotoxicity remains unclear. S-phase kinase-associated protein 1 (Skp1), identified as the target protein of HgS, plays a crucial role in the development of neurological diseases. This study aims to investigate the neurotoxic effects and molecular mechanism of HgS based on Skp1 using the Caenorhabditis elegans (C. elegans) model. We prepared the HgS nanoparticles and conducted a comparative analysis of neurobehavioral differences in both wild-type C. elegans (N2) and a transgenic strain of C. elegans (VC1241) with a knockout of the SKP1 homologous gene after exposure to HgS nanoparticles. Our results showed that HgS nanoparticles could suppress locomotion, defecation, egg-laying, and associative learning behaviors in N2 C. elegans, while no significant alterations were observed in the VC1241 C. elegans. Furthermore, we conducted a 4D label-free proteomics analysis and screened 504 key proteins significantly affected by HgS nanoparticles through Skp1. These proteins play pivotal roles in various pathways, including SNARE interactions in vesicular transport, TGF-beta signaling pathway, calcium signaling pathway, FoxO signaling pathway, etc. In summary, HgS nanoparticles at high doses suppress the neurobehavioral functions of C. elegans through a Skp1-dependent mechanism.

Identification of Skp1 as a target of mercury sulfide for neuroprotection

Mercury sulfide (HgS) exerts extensive biological effects on neuronal function. To investigate the direct target of HgS in neuronal cells, we developed a biotin-tagged HgS probe (bio-HgS) and employed an affinity purification technique to capture its target proteins. Then, we identified S-phase kinase-associated protein 1 (Skp1) as a potential target of HgS. Unexpectedly, we discovered that HgS covalently binds to Skp1 through a "Cys62-HgS-Cys120" mode. Moreover, our findings revealed that HgS inhibits the ubiquitin-protease system through Skp1 to up-regulate SNAP-25 expression, thereby triggering synaptic vesicle exocytosis to regulate locomotion ability in C. elegans. Collectively, our findings may promote a comprehensive interpretation of the pharmacological mechanism of mercury sulfide on neuroprotective function.