Covalent post-translational modification of proteins by ubiquitin and ubiquitin-like factors has emerged as a general mechanism to regulate myriad intra-cellular processes. The addition and removal of ubiquitin or ubiquitin-like proteins from factors has recently been demonstrated as a key mechanism to modulate DNA damage response (DDR) pathways. It is thus, timely to evaluate the potential for ubiquitin pathway enzymes as DDR drug targets for therapeutic intervention. The synthetic lethal approach provides exciting opportunities for the development of targeted therapies to treat cancer: most tumours have lost critical DDR pathways, and thus rely more heavily on the remaining pathways, while normal tissues are still equipped with all DDR pathways. Here, we review key deubiquitylating enzymes (DUBs) involved in DDR pathways, and describe how targeting DUBs may lead to selective therapies to treat cancer patients.

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BACKGROUND AND PURPOSENaV1.8 ion channels have been highlighted as important molecular targets for the design of low MW blockers for the treatment of chronic pain. Here, we describe the effects of PF-01247324, a new generation, selective, orally bioavailable Nav1.8 channel blocker of novel chemotype. EXPERIMENTAL APPROACHThe inhibition of Nav1.8 channels by PF-01247324 was studied using in vitro patch-clamp electrophysiology and the oral bioavailability and antinociceptive effects demonstrated using in vivo rodent models of inflammatory and neuropathic pain. KEY RESULTSPF-01247324 inhibited native tetrodotoxin-resistant (TTX-R) currents in human dorsal root ganglion (DRG) neurons (IC50: 331 nM) and in recombinantly expressed h Nav1.8 channels (IC50: 196 nM), with 50-fold selectivity over recombinantly expressed TTX-R hNav1.5 channels (IC50: ∼10 μM) and 65-100-fold selectivity over TTX-sensitive (TTX-S) channels (IC50: ∼10-18 μM). Native TTX-R currents in small-diameter rodent DRG neurons were inhibited with an IC50 448 nM, and the block of both human recombinant Nav1.8 channels and TTX-R from rat DRG neurons was both frequency and state dependent. In vitro current clamp showed that PF-01247324 reduced excitability in both rat and human DRG neurons and also altered the waveform of the action potential. In vivo experiments n rodents demonstrated efficacy in both inflammatory and neuropathic pain models. CONCLUSIONS AND IMPLICATIONSUsing PF-01247324, we have confirmed a role for Nav1.8 channels in both inflammatory and neuropathic pain. We have also demonstrated a key role for Nav1.8 channels in action potential upstroke and repetitive firing of rat and human DRG neurons.

1 Two-electrode voltage-clamp electrophysiology has been used to study the actions of two amyloid peptides (Ab 1-42 , Ab 1-40 ) on a7, a4b2 and a3b4 recombinant human neuronal nicotinic acetylcholine receptors (nicotinic AChRs), heterologously expressed in Xenopus laevis oocytes. 2 The application of Ab 1-42 or Ab (1 pM-100 nM) for 5 s does not directly activate expressed human a7, a4b2 or a3b4 nicotinic AChRs. 3 Ab 1-42 and Ab 1-40 are antagonists of a7 nicotinic AChRs. For example, 10 nM Ab 1-42 and Ab 1-40 both reduced the peak amplitude of currents recorded (3 mM ACh) to 4875 and 45710% (respectively) of control currents recorded in the absence of peptide. In both the cases the effect is sustained throughout a 30 min peptide application and is poorly reversible. 4 Ab 1-42 and Ab 1-40 (10 nM) enhance currents recorded in response to ACh (3 mM) from oocytes expressing a4b2 nicotinic AChRs by 195740 and 195741% respectively. This effect is transient, reaching a peak after 3 min and returning to control values after a 24 min application of 10 nM Ab 1-42 . We observe an enhancement of 157722% of control ACh-evoked current amplitude in response to 100 nM Ab 1-42 recorded from oocytes expressing a4b2 nicotinic AChRs. 5 Ab 1-42 and Ab 1-40 (10 nM) were without antagonist actions on the responses of a3b4 nicotinic AChRs to ACh (1 nM-3 mM).

1 In this study we describe the potent antagonist activity of a novel metabotropic glutamate (mGlu) receptor antagonist (RS)-cx-cyclopropyl-4-phosphonophenylglycine ((RS)-CPPG) which exhibits selectivity for mGlu receptors (group II and III) negatively coupled to adenylyl cyclase in the adult rat cortex. 4 In the rat cerebral cortex, (RS)-CPPG is the most potent antagonist of group II/III mGlu receptors yet described (with 20 fold selectivity for group III mGlu receptors), having negligible activity at group I mGlu receptors.