Regulation of Progranulin Expression in Human Microglia and Proteolysis of Progranulin by Matrix Metalloproteinase-12 (MMP-12)

Background: The essential role of progranulin (PGRN) as a neurotrophic factor has been demonstrated by the discovery that haploinsufficiency due to GRN gene mutations causes frontotemporal lobar dementia. In addition to neurons, microglia in vivo express PGRN, but little is known about the regulation of PGRN expression by microglia. Goal: In the current study, we examined the regulation of expression and function of PGRN, its proteolytic enzyme macrophage elastase (MMP-12), as well as the inhibitor of PGRN proteolysis, secretory leukocyte protease inhibitor (SLPI), in human CNS cells. Methods: Cultures of primary human microglia and astrocytes were stimulated with the TLR ligands (LPS or poly IC), Th1 cytokines (IL-1/IFNc), or Th2 cytokines (IL-4, IL-13). Results were analyzed by Q-PCR, immunoblotting or ELISA. The roles of MMP-12 and SLPI in PGRN cleavage were also examined. Results: Unstimulated microglia produced nanogram levels of PGRN, and PGRN release from microglia was suppressed by the TLR ligands or IL-1/IFNc, but increased by IL-4 or IL-13. Unexpectedly, while astrocytes stimulated with proinflammatory factors released large amounts of SLPI, none were detected in microglial cultures. We also identified MMP-12 as a PGRN proteolytic enzyme, and SLPI as an inhibitor of MMP-12-induced PGRN proteolysis. Experiments employing PGRN siRNA demonstrated that microglial PGRN was involved in the cytokine and chemokine production following TLR3/4 activation

Molecular blueprint of allosteric binding sites in a homologue of the agonist-binding domain of the alpha 7 nicotinic acetylcholine receptor

The α7 nicotinic acetylcholine receptor (nAChR) belongs to the family of pentameric ligand-gated ion channels and is involved in fast synaptic signaling. In this study, we take advantage of a recently identified chimera of the extracellular domain of the native α7 nicotinic acetylcholine receptor and acetylcholine binding protein, termed α7-AChBP. This chimeric receptor was used to conduct an innovative fragment-library screening in combination with X-ray crystallography to identify allosteric binding sites. One allosteric site is surface-exposed and is located near the N-terminal α-helix of the extracellular domain. Ligand binding at this site causes a conformational change of the α-helix as the fragment wedges between the α-helix and a loop homologous to the main immunogenic region of the muscle α1 subunit. A second site is located in the vestibule of the receptor, in a preexisting intrasubunit pocket opposite the agonist binding site and corresponds to a previously identified site involved in positive allosteric modulation of the bacterial homolog ELIC. A third site is located at a pocket right below the agonist binding site. Using electrophysiological recordings on the human α7 nAChR we demonstrate that the identified fragments, which bind at these sites, can modulate receptor activation. This work presents a structural framework for different allosteric binding sites in the α7 nAChR and paves the way for future development of novel allosteric modulators with therapeutic potential.status: publishe

Molecular blueprint of allosteric binding sites in a homologue of the agonist-binding domain of the α7 nicotinic acetylcholine receptor

In this study we take advantage of a recently described chimera of the α7 nicotinic acetylcholine receptor (nAChR) and acetylcholine binding protein (AChBP), termed α7-AChBP. To date, more than 70 crystal structures have been determined for AChBP in complex with ligands that occupy the orthosteric binding site. Here, we use an innovative screening strategy to discover molecular fragments that occupy allosteric binding sites. In combination with X-ray crystallography we determine a molecular blueprint of three different allosteric sites in α7-AChBP. Using electrophysiological recordings on the human α7 nAChR we demonstrate that each of the three sites is involved in allosteric modulation of the receptor. Our study contributes to understanding the sites of allosteric binding in ion channels

Hybrid Governance: The case of household solid waste management in Sweden

Governance is hybrid to the extent that it involves several types of stakeholders, jurisdictional domains, and organisational forms. This paper analyses governance of household solid waste management in Sweden from a hybridity perspective, with the City of Helsingborg as example. The empirical material on which the paper is based consists of interviews with politicians, civil servants and management of the municipal waste management company; and of documents of various kinds, from board meeting minutes to formal municipal plans to website pages. Waste governance in Sweden, it is shown, includes conflicting legislation, entanglement of urban infrastructure and planning, and long planning and investment horizons. The latter has resulted in significant innovations over the last twenty years. But the study also shows how organisational forms and the composition of tasks, as well as networks and jurisdiction, change over time, in turn causing tensions in governance processes and relationships