Micellar Choline-Acetyltransferase Complexes Exhibit Ultra-Boosted Catalytic Rate for Acetylcholine Synthesis—Mechanistic Insights for Development of Acetylcholine-Enhancing Micellar Nanotherapeutics
Year: 2024
Type: article
Abstract: Choline acetyltransferase (ChAT) is the key cholinergic enzyme, responsible for biosynthesis of acetylcholine (ACh), a crucial signaling molecule with both canonical neurotransmitter function and the auto- and paracrine signaling activity in non-neuronal cells, like lymphocytes and astroglia. Cholinergic dysfunction is linked to both neurodegenerative and inflammatory diseases. In this study we investigated a serendipitous observation, namely that catalytic rate of human recombinant ChAT (rhChAT) protein greatly differed in buffered solution in presence and absence of Triton X-100 (TX100). At single concentration of 0.05%(v/v), TX100 boosted the specific activity of rhChAT by 4-folds. Dose-response analysis within a TX100 concentration range of 0.8% to 0.008% (accounting for 13.7mM to 0.013mM) resulted in an S-shaped response-curve, indicative of over 10-folds boost in catalytic rate of rhChAT. This dramatic boost was unlikely due to a mere structural stabilization since it remained even after addition of 1.0 mg/mL gelatin to the ChAT solution as a protein stabilizer. Furthermore, we found that the catalytic function of the ACh-degrading enzyme, AChE, was unaffected by TX100, underscoring specificity of the effect for ChAT. Examination of the dose-response curve in relation to the critical micelle concentration (CMC) of TX100 revealed that the boost in ChAT activity occurred when the TX100 concentration passed its CMC, indicating that formation of micelle-ChAT complexes was crucial. We challenged this hypothesis by repeating the experiment on Tween-20 (TW20), another non-ionic surfactant with ~3-folds lower CMC compared to TX100 (0.06 vs 0.2mM). The analysis confirmed that micelle formation is crucial for ultra-boosting the activity of ChAT. In-silico molecular dynamic simulation supported the notion of ChAT-micelle complex formation. We hypothesize that TX100 or TW20 micelles, by mimicking cell-membrane microenvironments, facilitate ChAT in accessing its full catalytic potential by fine-tuning its structural stabilization and/or enhancing its substrate accessibility. These insights is expected to facilitate research toward development of new cholinergic-enhancing therapeutics through formulation of micelle-embedded ChAT nanoparticle.
Institutions: Karolinska Institutet, Indian Institute of Technology BHU
Language: English
Subfield: Pharmacology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,296
OpenAlex ID: W4405577380