Dynasore

Dynasore is a noncompetitive inhibitor of GTPases with the IC50 value of 15 μM[1] [2].
GTPases (singular GTPase) are hydrolase enzymes that play an important role in GTP binding and hydrolyzing. GTPases involve in many processes, like, transduction signal, protein biosynthesis, translocation proteins through membranes, and transporting vesicles within the cell. It has been reported that dynasore could inhibit the GTPase activity of dynamin1, dynamin2 and Drp1 [3] [4].
Dynasore is a potent GTPases inhibitor and functions on the sites of dynamin1, dynamin2 or Drp1. When tested with HL-1 cells, treated cells with dynasore blocked the endocytic process via inhibiting the activity of dynamin [1].  Using genetically encoded pH-sensitive fluorescent probe synaptopHluorin to study the role of dynasore in the synapses expressing spH, and the results showed that dyansore treatment resulted in the normal stimulus-triggered increase in fluorescence intensity via reducing the GTPase activity of dynamin which in turn blocked the synaptic endocytosis[4]. Dynasore worked as inhibitor of dynamin GTPase activity which blocks dynamin-dependent endocytosis not only in cells, but also including neurons [3].
References:
[1].Zheng, J., et al., Chymase mediates injury and mitochondrial damage in cardiomyocytes during acute ischemia/reperfusion in the dog. PLoS One, 2014. 9(4): p. e94732.
[2].McCluskey, A., et al., Building a better dynasore: the dyngo compounds potently inhibit dynamin and endocytosis. Traffic, 2013. 14(12): p. 1272-89.
[3].Kirchhausen, T., E. Macia, and H.E. Pelish, Use of dynasore, the small molecule inhibitor of dynamin, in the regulation of endocytosis. Methods Enzymol, 2008. 438: p. 77-93.
[4].Newton, A.J., T. Kirchhausen, and V.N. Murthy, Inhibition of dynamin completely blocks compensatory synaptic vesicle endocytosis. Proc Natl Acad Sci U S A, 2006. 103(47): p. 17955-60.

Dynasore Improves Motor Function Recovery via Inhibition of Neuronal Apoptosis and Astrocytic Proliferation after Spinal Cord Injury in Rats.[Pubmed:27822712]

Mol Neurobiol. 2017 Nov;54(9):7471-7482.

Spinal cord injury (SCI) is a common and devastating central nervous system insult which lacks efficient treatment. Our previous experimental findings indicated that dynamin-related protein 1 (Drp1) mediates mitochondrial fission during SCI, and inhibition of Drp1 plays a significant protective effect after SCI in rats. Dynasore inhibits GTPase activity at both the plasma membrane (dynamin 1, 2) and the mitochondria membrane (Drp1). The aim of the present study was to investigate the beneficial effects of Dynasore on SCI and its underlying mechanism in a rat model. Sprague-Dawley rats were randomly assigned to sham, SCI, and 1, 10, and 30 mg Dynasore groups. The rat model of SCI was established using an established Allen's model. Dynasore was administered via intraperitoneal injection immediately. Results of motor functional test indicated that Dynasore ameliorated the motor dysfunction greatly at 3, 7, and 10 days after SCI in rats (P < 0.05). Results of western blot showed that Dynasore has remarkably reduced the expressions of Drp1, dynamin 1, and dynamin 2 and, moreover, decreased the Bax, cytochrome C, and active Caspase-3 expressions, but increased the expressions of Bcl-2 at 3 days after SCI (P < 0.05). Notably, the upregulation of proliferating cell nuclear antigen (PCNA) and glial fibrillary acidic protein (GAFP) are inhibited by Dynasore at 3 days after SCI (P < 0.05). Results of immunofluorescent double labeling showed that there were less apoptotic neurons and proliferative astrocytes in the Dynasore groups compared with SCI group (P < 0.05). Finally, histological assessment via Nissl staining demonstrated that the Dynasore groups exhibited a significantly greater number of surviving neurons compared with the SCI group (P < 0.05). This neuroprotective effect was dose-dependent (P < 0.05). To our knowledge, this is the first study to indicate that Dynasore significantly enhances motor function which may be by inhibiting the activation of neuronal mitochondrial apoptotic pathway and astrocytic proliferation in rats after SCI.

Dynasore blocks evoked release while augmenting spontaneous synaptic transmission from primary visceral afferents.[Pubmed:28358887]

PLoS One. 2017 Mar 30;12(3):e0174915.

The recycling of vesicle membrane fused during exocytosis is essential to maintaining neurotransmission. The GTPase dynamin is involved in pinching off membrane to complete endocytosis and can be inhibited by Dynasore resulting in activity-dependent depletion of release-competent synaptic vesicles. In rat brainstem slices, we examined the effects of Dynasore on three different modes of glutamate release-spontaneous, evoked, and asynchronous release-at solitary tract (ST) inputs to neurons in the nucleus of the solitary tract (NTS). Intermittent bursts of stimuli to the ST interspersed with pauses in stimulation allowed examination of these three modes in each neuron continuously. Application of 100 muM Dynasore rapidly increased the spontaneous EPSC (sEPSC) frequency which was followed by inhibition of both ST-evoked EPSCs (ST-EPSC) as well as asynchronous EPSCs. The onset of ST-EPSC failures was not accompanied by amplitude reduction-a pattern more consistent with conduction block than reduced probability of vesicle release. Neither result suggested that Dynasore interrupted endocytosis. The Dynasore response profile resembled intense presynaptic TRPV1 activation. The TRPV1 antagonist capsazepine failed to prevent Dynasore increases in sEPSC frequency but did prevent the block of the ST-EPSC. In contrast, the TRPV1 antagonist JNJ 17203212 prevented both actions of Dynasore in neurons with TRPV1-expressing ST inputs. In a neuron lacking TRPV1-expressing ST inputs, however, Dynasore promptly increased sEPSC rate followed by block of ST-evoked EPSCs. Together our results suggest that Dynasore actions on ST-NTS transmission are TRPV1-independent and changes in glutamatergic transmission are not consistent with changes in vesicle recycling and endocytosis.

Dynasore impairs VEGFR2 signalling in an endocytosis-independent manner.[Pubmed:28327657]

Sci Rep. 2017 Mar 22;7:45035.

VEGFR2 is a critical angiogenic receptor playing a key role in vascular homeostasis. Upon activation by VEGF, VEGFR2 becomes endocytosed. Internalisation of VEGFR2 is facilitated, in part, through clathrin mediated endocytosis (CME), the role of which in VEGFR2 function is debated. Here, we confirm the contribution of CME in VEGFR2 uptake. However, curiously, we find that different approaches of inhibition of CME exert contradictory effects on VEGF signalling; knockdown of clathrin, or of dynamin, or overexpression of dynamin K44A, do not affect VEGF-induced phosphorylation of ERK1/2, while Dynasore causes strong inhibition. We resolve this discrepancy by showing that although Dynasore inhibits CME of VEGFR2, its inhibitory action in ERK1/2 phosphorylation is not related to attenuation of VEGFR2 endocytosis; it is rather due to an off-target effect of the drug. Dynasore inhibits VEGF-induced calcium release, a signalling event that lies upstream of ERK1/2, which implies that this effect could be responsible, at least in part, for the inhibitory action of the drug on VEGF-to-ERK1/2 signalling. These results raise caution that although Dynasore is specific in inhibiting clathrin- and dynamin-mediated endocytosis, it may also exert off-target effects on signalling molecules, hence influencing the interpretation of the role of endocytosis in signalling.

The dynamin inhibitor dynasore inhibits bone resorption by rapidly disrupting actin rings of osteoclasts.[Pubmed:26063501]

J Bone Miner Metab. 2016 Jul;34(4):395-405.

The cytoskeletal organization of osteoclasts is required for bone resorption. Binding of dynamin with guanosine triphosphate (GTP) was previously suggested to be required for the organization of the actin cytoskeleton. However, the role of the GTPase activity of dynamin in the organization of the actin cytoskeleton as well as in the bone-resorbing activity of osteoclasts remains unclear. This study investigated the effects of Dynasore, an inhibitor of the GTPase activity of dynamin, on the bone-resorbing activity of and actin ring formation in mouse osteoclasts in vitro and in vivo. Dynasore inhibited the formation of resorption pits in osteoclast cultures by suppressing actin ring formation and rapidly disrupting actin rings in osteoclasts. A time-lapse image analysis showed that Dynasore shrank actin rings in osteoclasts within 30 min. The intraperitoneal administration of Dynasore inhibited receptor activator of nuclear factor kappaB ligand (RANKL)-induced trabecular bone loss in mouse femurs. These in vitro and in vivo results suggest that the GTPase activity of dynamin is critical for the bone-resorbing activity of osteoclasts and that Dynasore is a seed for the development of novel anti-resorbing agents.