In Silico and In Vitro Methods for Pharmacokinetic Analysis of Substituted Tryptamines as Microtubule Targeting Agents

Inside every living cell, a vast and intricate network of microscopic rods provides the structural framework that holds the cell together and helps it move. These rods, known as microtubules, are not static beams but dynamic structures that constantly assemble and disassemble, a process essential for cell division, shape, and the transport of materials within the cell. They are built from protein building blocks called tubulin, which snap together to form long filaments. Because these structures are so fundamental to life, scientists have long studied how various molecules interact with them. Some well-known drugs, for instance, work by either locking these filaments in place or preventing them from forming at all. While many people are familiar with a specific class of compounds called tryptamines—molecules that include natural neurotransmitters like serotonin and famous psychoactive substances like psilocybin and LSD—scientists have primarily focused on how these compounds affect chemical signals on the surface of cells. A lingering question has been whether these same molecules might also reach inside the cell to interact directly with the microtubule framework itself, potentially influencing how the cell changes and adapts over time.

A team of researchers at the University of Waterloo set out to answer this question by combining computer modeling with laboratory experiments to see if substituted tryptamines could bind to tubulin and alter the way microtubules form. They began by creating a digital library of 294 different variations of these tryptamine molecules. Using powerful computer simulations, they tested how each of these molecules might fit into seven known docking spots on the tubulin protein where other drugs are known to bind. The results of this massive digital screening suggested that the tryptamines did not bind randomly; instead, they showed a strong preference for a specific region on the tubulin protein, the same area where a drug called colchicine attaches. This finding was significant because it hinted that these psychoactive compounds might share a physical target with established microtubule-targeting agents. To ensure that the molecules selected for further study could realistically reach the brain, the researchers also ran computer predictions on their ability to cross the blood-brain barrier, a protective filter that separates the bloodstream from the central nervous system. Several of the top candidates from the screening were predicted to be able to pass through this barrier, making them viable subjects for deeper investigation.

From the initial pool of 294 compounds, the researchers narrowed their focus to three specific molecules: HIOC, benzotript, and moschamine. These were chosen because they showed the strongest predicted binding in the computer models and were available for physical testing. To understand how these molecules behaved in a more realistic environment, the team ran detailed molecular dynamics simulations. Unlike the static snapshots of the initial screening, these simulations allowed the molecules to move and interact with the protein in a fluid, water-filled environment, mimicking the conditions inside a living cell. The simulations confirmed that the molecules could indeed sit stably within the binding pocket of the tubulin protein, with one of the compounds, moschamine, showing a particularly favorable fit. However, computer models can only suggest possibilities; they cannot prove what happens in a real biological system. To move from prediction to observation, the researchers turned to a test tube experiment designed to watch microtubules assemble in real time.

In the laboratory, the team mixed pure tubulin protein with each of the three selected tryptamines at various concentrations and watched to see if the microtubules would form. They measured the clarity of the solution as the proteins assembled into filaments, a process that changes how light scatters through the liquid. The results showed that the tryptamines did indeed influence the assembly process, but the effect depended heavily on both the specific molecule and its concentration. Among the three, benzotript produced the most dramatic change, altering the formation of the microtubules more strongly than the other two candidates. In some cases, the effect of benzotript was so pronounced that it surpassed even a standard drug known to stabilize microtubules. To ensure that these changes represented the formation of actual, healthy microtubule filaments rather than just a clumping of proteins into useless blobs, the researchers used a high-powered microscope to take pictures of the structures. The images revealed that under the influence of the tryptamines, the proteins formed long, thread-like structures that looked like normal microtubules, rather than amorphous aggregates. This visual confirmation was crucial, as it indicated that the compounds were genuinely interacting with the cellular machinery to change how these filaments were built.

The study concludes that certain substituted tryptamines are capable of interacting directly with the tubulin protein and can change the way microtubules assemble in a test tube. While the computer models suggested a preference for a specific binding site, the laboratory experiments confirmed that this interaction leads to measurable physical changes in the cell's structural framework. The researchers found that these effects are not uniform; they vary depending on which specific chemical variation is used and how much of it is present. The compound benzotript stood out as the most potent in this group, driving the strongest changes in the assembly process. Although the work was conducted outside of living organisms, the findings provide a new layer of understanding for how these psychoactive molecules might function. They suggest that beyond their well-known effects on cell surface receptors, these compounds may also reach inside the cell to influence the very scaffolding that supports cellular structure and movement. This opens the door for further research to determine exactly how these interactions occur and what role they might play in the broader effects these molecules have on the brain and body.