Investigation of the potential off-target effects on Munc 18 (p67) involved in synaptic vesical transport due to the interaction with peptide p5

SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins and SM (Sec1/Munc-18 like) proteins are involved in the docking of vesicles with the target membranes followed by the release of neurotransmitters in the brain. The Syntaxin protein plays a crucial role in the SNARE complex formation. Munc 18 (p67) is known to regulate the different functions of these SNARE complexes by binding with different conformations of Syntaxin. It has also been established that the absence of p67 results in neuronal death. Our previous work studied the effect of the peptide p5, a promising drug candidate, on CDK5-p25, an established Alzheimer's disease pathological complex. In vivo and in vitro data shows that p5 selectively inhibits the pathological complex CDK5-p25 without affecting CDK5 physiology in presence of p67. This study focuses on p67-p5 interaction and on the characterization of any conformational changes induced by it, especially in the Syntaxin binding site (the cleft region between domains 1 and 3a). This provides insights into the potential off-target effects caused by p5 due to a potential inhibition of SNARE complex formation. Our Monte Carlo/Molecular dynamics method (MCMD) predicted nine different binding modes, four of which were analyzed previously and indicated conformational changes induced in the Syntaxin binding site at the important functional domains 3a and 2. Herein we investigate the remaining five p67-p5 modes in order to fully understand the interaction dynamics, and the relevant results are presented.