Heterotrimeric guanine-nucleotide-binding regulatory proteins (G proteins) transduce signals from a wide variety of cell-surface receptors to generate physiological responses. Protein-tyrosine kinases are another group of critical cellular signal transducers and their malfunction often leads to cancer. Although activation of G-protein-coupled receptors can elicit rapid stimulation of cellular protein-tyrosine phosphorylation, the mechanism used by G proteins to activate protein-tyrosine kinases is unclear. Here we show that the purified alpha-subunit of the G(q) class of G proteins (G[alpha]q) directly stimulates the activity of a purified non-receptor kinase, Bruton's tyrosine kinase (Btk), whereas purified alpha-subunits from G(il), G(O) or G(z) proteins do not. G(alpha)q can also activate Btk in vivo. Furthermore, in Btk-deficient cells, stimulation of another kinase, a p38 MAP kinase, by Gq-coupled receptors is blocked. Our results demonstrate that certain protein-tyrosine kinases can be direct effectors of G proteins.
The structural organisation of pancreatic β-cells in the islets of Langerhans is relatively unknown. Here, using three-dimensional (3D) two-photon, 3D confocal and 3D block-face serial electron microscopy, we demonstrate a consistent in situ polarisation of β-cells and define three distinct cell surface domains. An apical domain located at the vascular apogee of β-cells, defined by the location of PAR-3 (also known as PARD3) and ZO-1 (also known as TJP1), delineates an extracellular space into which adjacent β-cells project their primary cilia. A separate lateral domain, is enriched in scribble and Dlg, and colocalises with E-cadherin and GLUT2 (also known as SLC2A2). Finally, a distinct basal domain, where the β-cells contact the islet vasculature, is enriched in synaptic scaffold proteins such as liprin. This 3D analysis of β-cells within intact islets, and the definition of distinct domains, provides new insights into understanding β-cell structure and function.
Heterotrimeric guanine-nucleotide-binding proteins (G proteins) are signal transducers that relay messages from many receptors on the cell surface to modulate various cellular processes. The direct downstream effectors of G proteins consist of the signalling molecules that are activated by their physical interactions with a G alpha or Gbetagamma subunit. Effectors that interact directly with G alpha12 G proteins have yet to be identified. Here we show that G alpha12 binds directly to, and stimulates the activity of, Bruton's tyrosine kinase (Btk) and a Ras GTPase-activating protein, Gap1m, in vitro and in vivo. G alpha12 interacts with a conserved domain, composed of the pleckstrin-homology domain and the adjacent Btk motif, that is present in both Btk and Gap1m. Our results are, to our knowledge, the first to identify direct effectors for G alpha12 and to show that there is a direct link between heterotrimeric and monomeric G proteins.
Background In the past, many data collection systems were in operation for different HIV/AIDS projects in China. We describe the creation of a unified, web-based national HIV/AIDS information system designed to streamline data collection and facilitate data use.Methods Integration of separate HIV/AIDS data systems was carried out in three phases. Phase 1, from January 2006 to December 2007, involved creating a set of unified data collection forms that took into account existing program needs and the reporting requirements of various international organizations. Phase 2, from January to October 2007, involved creating a web-based platform to host the integrated HIV/AIDS data collection system. Phase 3, from November to December 2007, involved pilot testing the new, integrated system prior to nationwide application.Results Eight web-based data collection subsystems based on one platform began operation on 1 January 2008. These eight subsystems cover: (i) HIV/AIDS case reporting; (ii) HIV testing and counselling; (iii) antiretroviral treatment (ART) for adults; (iv) ART for children; (v) behavioural interventions for high-risk groups; (vi) methadone maintenance treatment; (vii) sentinel and behavioural surveillance; and (viii) local county background information. The system provides real-time data to monitor HIV testing, prevention and treatment programs across the country.Conclusion China’s new unified, web-based HIV/AIDS information system has improved the efficiency of data collection, reporting, analysis and use, as well as data quality and security. It is a powerful tool to support policy making, program evaluation and implementation of the national HIV/AIDS program and, thus, may serve a model for other countries.
Propofol infusion syndrome (PRIS) is an uncommon life-threatening complication observed most often in patients receiving high-dose propofol. High-dose propofol treatment with a prolonged duration can damage the immune system. However, the associated molecular mechanisms remain unclear. An increasing number of clinical and experimental observations have demonstrated that tissue-resident macrophages play a critical role in immune regulation during anaesthesia and procedural sedation. Since the inflammatory response is essential for mediating propofol-induced cell death and proinflammatory reactions, we hypothesised that propofol overdose induces macrophage pyroptosis through inflammasomes. Using primary cultured bone marrow-derived macrophages, murine macrophage cell lines (RAW264.7, RAW-asc and J774) and a mouse model, we investigated the role of NLRP3 inflammasome activation and secondary pyroptosis in propofol-induced cell death. We found that high-dose propofol strongly cleaved caspase-1 but not caspase-11 and biosynthesis of downstream interleukin (IL)-1β and IL-18. Inhibition of caspase-1 activity blocks IL-1β production. Moreover, NLRP3 deletion moderately suppressed cleaved caspase-1 as well as the proportion of pyroptosis, while levels of AIM2 were increased, triggering a compensatory pathway to pyroptosis in NLRP3 -/- macrophages. Here, we show that propofol-induced mitochondrial reactive oxygen species (ROS) can trigger NLRP3 inflammasome activation. Furthermore, apoptosis-associated speck-like protein (ASC) was found to mediate NLRP3 and AIM2 signalling and contribute to propofol-induced macrophage pyroptosis. In addition, our work shows that propofol-induced apoptotic initiator caspase (caspase-9) subsequently cleaved effector caspases (caspase-3 and 7), indicating that both apoptotic and pyroptotic cellular death pathways are activated after propofol exposure. Our studies suggest, for the first time, that propofol-induced pyroptosis might be restricted to macrophage through an NLRP3/ASC/caspase-1 pathway, which provides potential targets for limiting adverse reactions during propofol application. These findings demonstrate that propofol overdose can trigger cell death through caspase-1 activation and offer new insights into the use of anaesthetic drugs.
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