The creative SME: a cautionary tale

This research was supported by the Arts and Humanities Research Council [grant Number AH/J005142/1].This research was supported by the Arts and Humanities Research Council [grant Number AH/J005142/1].The aim of this paper is to explore the debate about defining a small firm, or a small and medium-sized enterprise (SME), and examining the relevance of this concern to the creative industries and creative businesses. The first part of this paper navigates this formation, and the positioning of the idea of small business within economic and political thought. The second part explores how the concept of small business is operationalized as SMEs, and the challenges of classification and empirical definition. The final part reflects on the implications for the understanding and usage of the term ‘creative SME’.This research was supported by the Arts and Humanities Research Council [grant Number AH/J005142/1]

«Ridges on the floors of Hell»: traces ou palimpsestes dans le désert de The dead heart

The Dead Heart is American author Douglas Kennedy’s first novel. It was first translated into French in 1997 as Cul-de-sac . It was this translation that made Kennedy a household name in France and that gave The Dead Heart its identity as a roman noir. In the space of just 20 years the novel has been translated twice into French and adapted twice more, as a film and now as a graphic novel. Elsewhere, we have analyzed this trajectory from the perspective of retranslation and the ostensible differences between the two translation Skopoi, and the use of paratextual branding to target specific reading publics. Focusing on the graphic novel allows us here to go beyond the problematics of translation and to broaden the scope of our study of textual adaptation. It also allows us to reassess the originality of the source text

The rise of the quasi-public space and its consequences for cities and culture

This article argues that whilst appearing new, quasi-public spaces have emerged from a process of investment restructuring over the last 50 years. The profound change that is set in motion is a loss of control of public space and its cultural uses in cities. The tensions set up in this transformation are illustrated by the cultural fortunes of the largest such space in London, Granary Square; and, that of the City of London that has little, if any, public space

A Ca(V)2.1 N-terminal fragment relieves the dominant-negative inhibition by an Episodic ataxia 2 mutant

Episodic ataxia 2 (EA2) is an autosomal dominant disorder caused by mutations in the gene CACNA1A that encodes the pore-forming CaV2.1 calcium channel subunit. The majority of EA2 mutations reported so far are nonsense or deletion/insertion mutations predicted to form truncated proteins. Heterologous expression of wild-type CaV2.1, together with truncated constructs that mimic EA2 mutants, significantly suppressed wild-type calcium channel function, indicating that the truncated protein produces a dominant-negative effect (Jouvenceau et al., 2001; Page et al., 2004). A similar finding has been shown for CaV2.2 (Raghib et al., 2001). We show here that a highly conserved sequence in the cytoplasmic N-terminus is involved in this process, for both CaV2.1 and CaV2.2 channels. Additionally, we were able to interfere with the suppressive effect of an EA2 construct by mutating key N-terminal residues within it. We postulate that the N-terminus of the truncated channel plays an essential part in its interaction with the full-length CaV2.1, which prevents the correct folding of the wild-type channel. In agreement with this, we were able to disrupt the interaction between EA2 and the full length channel by co-expressing a free N-terminal peptide

Dominant-negative calcium channel suppression by truncated constructs involves a kinase implicated in the unfolded protein response

Expression of the calcium channel Ca(V)2.2 is markedly suppressed by coexpression with truncated constructs of Ca(V)2.2. Furthermore, a two-domain construct of Ca(V)2.1 mimicking an episodic ataxia-2 mutation strongly inhibited Ca(V)2.1 currents. We have now determined the specificity of this effect, identified a potential mechanism, and have shown that such constructs also inhibit endogenous calcium currents when transfected into neuronal cell lines. Suppression of calcium channel expression requires interaction between truncated and full-length channels, because there is inter-subfamily specificity. Although there is marked cross-suppression within the Ca(V)2 calcium channel family, there is no cross-suppression between Ca(V)2 and Ca(V)3 channels. The mechanism involves activation of a component of the unfolded protein response, the endoplasmic reticulum resident RNA-dependent kinase (PERK), because it is inhibited by expression of dominant-negative constructs of this kinase. Activation of PERK has been shown previously to cause translational arrest, which has the potential to result in a generalized effect on protein synthesis. In agreement with this, coexpression of the truncated domain I of Ca(V)2.2, together with full-length Ca(V)2.2, reduced the level not only of Ca(V)2.2 protein but also the coexpressed alpha2delta-2. Thapsigargin, which globally activates the unfolded protein response, very markedly suppressed Ca(V)2.2 currents and also reduced the expression level of both Ca(V)2.2 and alpha2delta-2 protein. We propose that voltage-gated calcium channels represent a class of difficult-to-fold transmembrane proteins, in this case misfolding is induced by interaction with a truncated cognate Ca(V) channel. This may represent a mechanism of pathology in episodic ataxia-2

Ablation of α_{2}δ-1 inhibits cell-surface trafficking of endogenous N-type calcium channels in the pain pathway in vivo

The auxiliary α_{2}δ calcium channel subunits play key roles in voltage-gated calcium channel function. Independent of this, α_{2}δ-1 has also been suggested to be important for synaptogenesis. Using an epitope-tagged knockin mouse strategy, we examined the effect of α_{2}δ-1 on Ca_{V}2.2 localization in the pain pathway in vivo, where Ca_{V}2.2 is important for nociceptive transmission and α_{2}δ-1 plays a critical role in neuropathic pain. We find Ca_{V}2.2 is preferentially expressed on the plasma membrane of calcitonin gene-related peptide-positive small nociceptors. This is paralleled by strong presynaptic expression of Ca_{V}2.2 in the superficial spinal cord dorsal horn. EM-immunogold localization shows Ca_{V}2.2 predominantly in active zones of glomerular primary afferent terminals. Genetic ablation of α_{2}δ-1 abolishes Ca_{V}2.2 cell-surface expression in dorsal root ganglion neurons and dramatically reduces dorsal horn expression. There was no effect of α2δ-1 knockout on other dorsal horn pre- and postsynaptic markers, indicating the primary afferent pathways are not otherwise affected by α_{2}δ-1 ablation

Proteolytic maturation of α 2 δ represents a checkpoint for activation and neuronal trafficking of latent calcium channels

The auxiliary α2δ subunits of voltage-gated calcium channels are extracellular membrane-associated proteins, which are post-translationally cleaved into disulfide-linked polypeptides α2 and δ. We now show, using α2δ constructs containing artificial cleavage sites, that this processing is an essential step permitting voltage-dependent activation of plasma membrane N-type (CaV2.2) calcium channels. Indeed, uncleaved α2δ inhibits native calcium currents in mammalian neurons. By inducing acute cell-surface proteolytic cleavage of α2δ, voltage-dependent activation of channels is promoted, independent from the trafficking role of α2δ. Uncleaved α2δ does not support trafficking of CaV2.2 channel complexes into neuronal processes, and inhibits Ca2+ entry into synaptic boutons, and we can reverse this by controlled intracellular proteolytic cleavage. We propose a model whereby uncleaved α2δ subunits maintain immature calcium channels in an inhibited state. Proteolytic processing of α2δ then permits voltage-dependent activation of the channels, acting as a checkpoint allowing trafficking only of mature calcium channel complexes into neuronal processes

Disruption of the Key Ca2+ Binding Site in the Selectivity Filter of Neuronal Voltage-Gated Calcium Channels Inhibits Channel Trafficking

Voltage-gated calcium channels are exquisitely Ca2+ selective, conferred primarily by four conserved pore-loop glutamate residues contributing to the selectivity filter. There has been little previous work directly measuring whether the trafficking of calcium channels requires their ability to bind Ca2+ in the selectivity filter or to conduct Ca2+. Here, we examine trafficking of neuronal CaV2.1 and 2.2 channels with mutations in their selectivity filter and find reduced trafficking to the cell surface in cell lines. Furthermore, in hippocampal neurons, there is reduced trafficking to the somatic plasma membrane, into neurites, and to presynaptic terminals. However, the CaV2.2 selectivity filter mutants are still influenced by auxiliary α2δ subunits and, albeit to a reduced extent, by β subunits, indicating the channels are not grossly misfolded. Our results indicate that Ca2+ binding in the pore of CaV2 channels may promote their correct trafficking, in combination with auxiliary subunits. Furthermore, physiological studies utilizing selectivity filter mutant CaV channels should be interpreted with caution

“…the point is to change it”: Critical realism and human geography

This paper picks up themes discussed in Cox’s (2013) ‘Notes on a brief encounter: critical realism, historical materialism and human geography’. I argue that perhaps the encounter was more complex than Cox allows. At core Cox underplays, or marginalises, the discussion of causality and dismisses the significance of ontology stressing instead epistemology. The paper makes a case for another reading of the debate, one that has continuing significance

Determinants of the voltage dependence of G protein modulation within calcium channel β subunits

CaVβ subunits of voltage-gated calcium channels contain two conserved domains, a src-homology-3 (SH3) domain and a guanylate kinase-like (GK) domain with an intervening HOOK domain. We have shown in a previous study that, although Gβγ-mediated inhibitory modulation of CaV2.2 channels did not require the interaction of a CaVβ subunit with the CaVα1 subunit, when such interaction was prevented by a mutation in the α1 subunit, G protein modulation could not be removed by a large depolarization and showed voltage-independent properties (Leroy et al., J Neurosci 25:6984–6996, 2005). In this study, we have investigated the ability of mutant and truncated CaVβ subunits to support voltage-dependent G protein modulation in order to determine the minimal domain of the CaVβ subunit that is required for this process. We have coexpressed the CaVβ subunit constructs with CaV2.2 and α2δ-2, studied modulation by the activation of the dopamine D2 receptor, and also examined basal tonic modulation. Our main finding is that the CaVβ subunit GK domains, from either β1b or β2, are sufficient to restore voltage dependence to G protein modulation. We also found that the removal of the variable HOOK region from β2a promotes tonic voltage-dependent G protein modulation. We propose that the absence of the HOOK region enhances Gβγ binding affinity, leading to greater tonic modulation by basal levels of Gβγ. This tonic modulation requires the presence of an SH3 domain, as tonic modulation is not supported by any of the CaVβ subunit GK domains alone