http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:10254 We report the development of a homology model for the GTP binding domain of human dynamin I based on the corresponding crystal structure of Dictyostelium discoidum dynamin A. Virtual screening identified 2-[(2-biphenyl-2-yl-1,3-dioxo-2,3-dihydro-1H-isoindole-5-carbonyl)amino]-4-chlorobenzoic acid (1) as a ~ 170 μM potent inhibitor. Homology modeling- and focused library-led synthesis resulted in development of a series of active compounds (the “pthaladyns”) with 4-chloro-2-(2-(4-(hydroxymethyl)phenyl)-1,3-dioxoisoindoline-5-carboxamido)benzoic acid (29), a 4.58 ± 0.06 μM dynamin I GTPase inhibitor. Pthaladyn-29 displays borderline selectivity for dynamin I relative to dynamin II (~5−10 fold). Only pthaladyn-23 (dynamin I IC₅₀ 17.4 ± 5.8 μM) was an effective inhibitor of dynamin I mediated synaptic vesicle endocytosis in brain synaptosomes with an IC50 of 12.9 ± 5.9 μM. This compound was also competitive with respect to Mg²⁺·GTP. Thus the pthaladyns are the first GTP competitive inhibitors of dynamin I and II GTPase and may be effective new tools for the study of neuronal endocytosis. 2012-03-13T05:00:03.478Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:2267 Dynamin I is a GTPase enzyme required for endocytosis and is an excellent target for the design of potential endocytosis inhibitors. Screening of a library of tyrphostins, in our laboratory, against the GTPase activity of dynamin I gave rise to a μM potent lead, 2-cyano-3-(3,4-dihydroxyphenyl)thioacrylamide (1, IC₅₀ 70 μM). Our initial investigations suggested that only the dimeric form of 1 displayed dynamin I GTPase inhibitory activity. Subsequent synthetic iterations were based on dimeric analogues and afforded a number of small molecules, low μM potent, inhibitors of dynamin I GTPase, in particular, symmetrical analogues with a minimum of two free phenolic -OHs: catechol-acrylamide (9) (IC₅₀ = 5.1 ± 0.6 μM), its 3,4,5-trihydroxy congener (10) (IC₅₀ = 1.7 ± 0.2 μM), and the corresponding 3-methyl ether (11) (IC₅₀ = 9 ± 3 μM). Increasing the length of the central alkyl spacer from ethyl to propyl (22-24) afforded essentially identical activity with IC₅₀'s of 1.7 ± 0.2, 1.7 ± 0.2, and 5 ± 1 μM, respectively. No decrease in activity was noted until the introduction of a hexyl spacer. Our studies highlight the requirement for two free amido NHs with neither the mono-N-methyl (86) nor the bis-N-methyl (87) analogues inhibiting dynamin I GTPase. A similar effect was noted for the removal of the nitrile moieties. However, modest potency was observed with the corresponding ester analogues of 9-11: ethyl ester (90), propyl ester (91), and butyl ester (92), with IC₅₀'s of 42 ± 3, 38 ± 2, and 61 ± 2 μM, respectively. Our studies reveal the most potent and promising dynamin I GTPase inhibitor in this series as (22), which is also known as BisT. 2010-04-27T06:19:23.766Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3266 We examined a number of ligands with the view of inhibiting the GTPase activity of dynamin. Dynamin contains a pleckstrin homology (PH) domain that interacts with lipids. We report a series of simple lipid-like molecules that display moderate inhibitory activity. Inhibitory activity is linked to chain length and quaternarization of the terminal amine. A change in the counterion, Cl versus Br or I, had little effect on potency. However, introduction of a hydrophobic collar proximal to the charged site was beneficial to dynamin GTPase inhibitory action. The most potent compound was myristoyl trimethyl ammonium bromide (MTMAB, IC₅₀ 3.15 μM). Dynamin 1 GTPase contains a pleckstrin homology (PH) domain that interacts with lipids. We report a series of simple lipid-like molecules that display moderate inhibitory activity. Inhibitory activity is linked to chain length and quaternarization of the terminal amine. A change in the counterion, Cl versus Br or I, had little effect on potency. However, introduction of a hydrophobic collar proximal to the charged site was beneficial to dynamin GTPase inhibitory action. 2010-04-27T05:23:59.415Z ]]>