Myricetin Preferentially Binds to Interfacial Regions in Domains 1 – 3 to Inhibit Cholesterol-Dependent Cytolysins: A Molecular Docking Study

<p>Cholesterol-dependent cytolysins (CDCs) are proteinaceous toxins secreted as monomers by some Gram-positive and Gram-negative bacteria that contribute to their pathogenicity. These toxins bind to either cholesterol or human CD59, leading to massive structural changes, toxin oligomerization, formation of very large pores, and ultimately cell death, making these proteins promising targets for inhibition. Myricetin, and its related flavonoids, have been previously identified as a candidate small molecule inhibitor of specific CDCs such as listeriolysin O (LLO) and suilysin (SLY), interfering with their oligomerization. In this work, molecular docking was performed to assess the interaction of myricetin with other CDCs whose crystal structures are already known. Results indicated that although myricetin bound to the hitherto identified cavity in domain 4 (D4), much more efficient and stable binding was obtained in sites along the interfacial regions of domains 1 – 3 (D1 – D3). This was common among the tested CDCs, which was primarily due to much more extensive stabilizing intermolecular interactions, as indicated by post-docking analysis. Specifically, myricetin bound to (1) the interface of the three domains in anthrolysin O (ALO), perfringolysin O (PFO), pneumolysin (PLY), SLY, and vaginolysin (VLY), (2) at/near the D1/D3 interface in LLO and streptolysin O (SLO), and (3) along the D2/D3 interface in intermedilysin (ILY). These findings provide theoretical basis on the possibility of using myricetin and its related compounds as a broad-spectrum inhibitor of CDCs to potentially address the diseases associated with these pathogens.</p>

Myricetin Preferentially Binds to Interfacial Regions in Domains 1 – 3 to Inhibit Cholesterol-Dependent Cytolysins: A Molecular Docking Study

<p>Cholesterol-dependent cytolysins (CDCs) are proteinaceous toxins secreted as monomers by some Gram-positive and Gram-negative bacteria that contribute to their pathogenicity. These toxins bind to either cholesterol or human CD59, leading to massive structural changes, toxin oligomerization, formation of very large pores, and ultimately cell death, making these proteins promising targets for inhibition. Myricetin, and its related flavonoids, have been previously identified as a candidate small molecule inhibitor of specific CDCs such as listeriolysin O (LLO) and suilysin (SLY), interfering with their oligomerization. In this work, molecular docking was performed to assess the interaction of myricetin with other CDCs whose crystal structures are already known. Results indicated that although myricetin bound to the hitherto identified cavity in domain 4 (D4), much more efficient and stable binding was obtained in sites along the interfacial regions of domains 1 – 3 (D1 – D3). This was common among the tested CDCs, which was primarily due to much more extensive stabilizing intermolecular interactions, as indicated by post-docking analysis. Specifically, myricetin bound to (1) the interface of the three domains in anthrolysin O (ALO), perfringolysin O (PFO), pneumolysin (PLY), SLY, and vaginolysin (VLY), (2) at/near the D1/D3 interface in LLO and streptolysin O (SLO), and (3) along the D2/D3 interface in intermedilysin (ILY). These findings provide theoretical basis on the possibility of using myricetin and its related compounds as a broad-spectrum inhibitor of CDCs to potentially address the diseases associated with these pathogens.</p>

Roles for the adhension molecule Contactin2 in the development and function of neural circuits in zebrafish

Neuronal migration and axon guidance are critical developmental processes that are essential for establishing functional neural circuits underlying complex cognitive and motor functions. Precise neuronal migration and axon guidance are dependent upon cell-cell and cell-substrate interactions, which are mediated by several membrane-associated molecules. The relatively concise segmental organization of the hindbrain and the simple scaffold of axon tracts in the zebrafish brain provides an ideal model to study how different molecules collaborate to guide migrating neurons and growing axons to their final location. In this thesis, I examine the roles of membrane molecules during neuron migration and axon guidance in zebrafish. In Chapter 3, I show the generation of Contactin2 (Cntn2) null mutant using CRISPR/Cas9 and characterize cntn2 mutant. I demonstrate a role for cntn2 in facial branchiomotor (FBM) neuron migration and fasciculation of medial longitudinal fascicle (MLF) axons. In addition, using touch-evoked escape response and swimming assays, I show sensorimotor deficits in cntn2 mutants. Collectively, these data demonstrate distinct developmental roles for zebrafish cntn2 in neuronal migration and axon fasciculation, and in the function of sensorimotor circuits. In Chapter 4, I examine pairwise genetic interactions between several PCP and non-PCP genes for FBM neuron migration. I show that vangl2 is rather unique in exhibiting genetic interactions with several PCP and non-PCP genes. These data suggest that vangl2 might be playing a central role in regulating the function of many PCP and non-PCP genes for FBM neuron migration. In Chapter 6, I describe a novel genetic approach which utilizes the human CD59 receptor (hCD59) and the bacterial toxin intermedilysin (ILY) for rapid cell ablation in zebrafish.