A Role for Glutamate Transporters in the Regulation of Insulin Secretion

In the brain, glutamate is an extracellular transmitter that mediates cell-to-cell communication. Prior to synaptic release it is pumped into vesicles by vesicular glutamate transporters (VGLUTs). To inactivate glutamate receptor responses after release, glutamate is taken up into glial cells or neurons by excitatory amino acid transporters (EAATs). In the pancreatic islets of Langerhans, glutamate is proposed to act as an intracellular messenger, regulating insulin secretion from beta-cells, but the mechanisms involved are unknown. By immunogold cytochemistry we show that insulin containing secretory granules express VGLUT3. Despite the fact that they have a VGLUT, the levels of glutamate in these granules are low, indicating the presence of a protein that can transport glutamate out of the granules. Surprisingly, in beta-cells the glutamate transporter EAAT2 is located, not in the plasma membrane as it is in brain cells, but exclusively in insulin-containing secretory granules, together with VGLUT3. In EAAT2 knock out mice, the content of glutamate in secretory granules is higher than in wild type mice. These data imply a glutamate cycle in which glutamate is carried into the granules by VGLUT3 and carried out by EAAT2. Perturbing this cycle by knocking down EAAT2 expression with a small interfering RNA, or by over-expressing EAAT2 or a VGLUT in insulin granules, significantly reduced the rate of granule exocytosis. Simulations of granule energetics suggest that VGLUT3 and EAAT2 may regulate the pH and membrane potential of the granules and thereby regulate insulin secretion. These data suggest that insulin secretion from beta-cells is modulated by the flux of glutamate through the secretory granules

Fixing it for PFA Scotland: building union influence out of a transnational project to tackle match-fixing in football

This article deploys frameworks from the fields of trade union theory and professional football governance theory to gain an understanding of the tactics deployed by the Professional Footballers’ Association, Scotland (PFAS) for collectively representing the interests of its members. The article explores how the union used the advantages gained through participation in a counter match-fixing project managed by FIFPro to establish itself as a member of an array of committees, task groups and panels so that it might become the collective ‘voice’ of players at the institutional level in football. The article commences with a review of the industrial relations landscape of professional football and the ‘peculiarities’ of the labour market that have produced equally unique trade union strategies that seek to individualise rather than collectivise wage bargaining. The implications of such a strategy are felt in the lack of appropriate contemporary theories of trade union power that might act as explanatory frameworks to aid an understanding of the tactics deployed by PFAS. The article proposes a return to a political institutional model of trade union power popularised by Sidney and Beatrice Webb in the late nineteenth-century. An analysis of interview data collected from a small cohort of expert informants shows that PFAS has taken advantage of a new body in Scottish professional football, the integrity forum, to establish itself as a credible and trustworthy voice of players within broader governing structures, while acknowledging that its sphere of influence remains constrained within a system dominated by more established institutions

Converging towards American dominance? Developments and structures of the consultancy fields in Western Europe

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