Endocytosis of epidermal growth factor receptor regulated by Grb2-mediated recruitment of the Rab5 GTPase-activating protein RN-tre

The Grb2 adaptor protein is best known for its role in signaling to the small GTPase p21(ras), mediated through its interaction with the SOS guanine nucleotide exchange factor. Here, we demonstrate that Grb2 also signals to Rab5, a small GTPase that plays a key role in early endocytic trafficking. Grb2 functions through association with RN-tre, a GTPase-activating protein for Rab5. Grb2 and RN-tre associate both in vitro and in vivo, with interaction mediated by both SH3 domains of Grb2 and extended proline-rich sequences in RN-tre. Association between Grb2 and RN-tre is constitutive and occurs independently of Eps8, a previously identified binding partner of RN-tre. Epidermal growth factor (EGF) stimulates recruitment of RN-tre to the EGF receptor (EGFR) in a Grb2-dependent manner. Grb2 and the EGFR are internalized and co-localized in endocytic vesicles in response to EGF. Overexpression of RN-tre blocks the internalization of both proteins, consistent with its function as a negative regulator of Rab5 and endocytosis. Strikingly, RN-tre does not block EGF-induced internalization of a Grb2 mutant deficient in RN-tre binding. These results 1) suggest that the ability of RN-tre to inhibit internalization of the EGFR requires Grb2-mediated binding to the receptor and 2) identify Grb2 as a critical regulator of Rab5 and EGFR endocytosis.     

Medical ethnobotany of the Albanian Alps in Kosovo

Background

The boreal forest of Canada is home to several hundred thousands Aboriginal people who have been using medicinal plants in traditional health care systems for thousands of years. This knowledge, transmitted by oral tradition from generation to generation, has been eroding in recent decades due to rapid cultural change. Until now, published reviews about traditional uses of medicinal plants in boreal Canada have focused either on particular Aboriginal groups or on restricted regions. Here, we present a review of traditional uses of medicinal plants by the Aboriginal people of the entire Canadian boreal forest in order to provide comprehensive documentation, identify research gaps, and suggest perspectives for future research.

Methods

A review of the literature published in scientific journals, books, theses and reports.

Results

A total of 546 medicinal plant taxa used by the Aboriginal people of the Canadian boreal forest were reported in the reviewed literature. These plants were used to treat 28 disease and disorder categories, with the highest number of species being used for gastro-intestinal disorders, followed by musculoskeletal disorders. Herbs were the primary source of medicinal plants, followed by shrubs. The medicinal knowledge of Aboriginal peoples of the western Canadian boreal forest has been given considerably less attention by researchers. Canada is lacking comprehensive policy on harvesting, conservation and use of medicinal plants. This could be explained by the illusion of an infinite boreal forest, or by the fact that many boreal medicinal plant species are widely distributed.

Conclusion

To our knowledge, this review is the most comprehensive to date to reveal the rich traditional medicinal knowledge of Aboriginal peoples of the Canadian boreal forest. Future ethnobotanical research endeavours should focus on documenting the knowledge held by Aboriginal groups that have so far received less attention, particularly those of the western boreal forest. In addition, several critical issues need to be addressed regarding the legal, ethical and cultural aspects of the conservation of medicinal plant species and the protection of the associated traditional knowledge.     

Dimerization of the transmembrane domain of human tetherin in membrane mimetic environments

Tetherin/Bst-2 is a cell surface protein that can act as a restriction factor against a number of enveloped viruses, including HIV-1. It acts by tethering new virus particles to the host cell membrane, promoting their internalization and degradation. Tetherin is a type II membrane protein, with an N-terminal transmembrane domain, an extracellular coiled-coil domain, and a C-terminal GPI anchor. This double membrane anchor is important for anti-HIV activity, as is dimerization of the coiled-coil domain, but despite recent crystal structures of the coiled-coil ectodomains of human and mouse tetherin, the topology of tetherin with respect to host and viral membranes has yet to be determined. The tetherin transmembrane domain is also thought to mediate interactions with the HIV-1 encoded integral membrane protein Vpu, which is an antagonist of tetherin, through direct binding to the transmembrane region of Vpu. Using a combination of SDS-PAGE, size exclusion chromatography, and pyrene excimer fluorescence, we show that in the absence of the coiled-coil domain the transmembrane domain of human tetherin forms parallel homodimers in membrane mimetic environments. Transmembrane domain dimerization does not require disulfide bond formation and is favored in TFE, SDS micelles, and POPC liposomes. This observation has implications for functional models of tetherin, suggesting that both transmembrane domains in the dimeric molecule are inserted into the same lipid bilayer, rather than into opposing membranes.     

Expansion of tumor-associated Treg cells upon disruption of a CTLA-4-dependent feedback loop

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Protein kinase C delta stimulates apoptosis by initiating G1 phase cell cycle progression and S phase arrest

Overexpression of protein kinase C delta (PKCdelta) stimulates apoptosis in a wide variety of cell types through a mechanism that is incompletely understood. PKCdelta-deficient cells are impaired in their response to DNA damage-induced apoptosis, suggesting that PKCdelta is required to mount an appropriate apoptotic response under conditions of stress. The mechanism through which it does so remains elusive. In addition to effects on cell survival, PKCdelta elicits pleiotropic effects on cellular proliferation. We now provide the first evidence that the ability of PKCdelta to stimulate apoptosis is intimately linked to its ability to stimulate G(1) phase cell cycle progression. Using an adenoviral-based expression system to express PKCalpha,-delta, and -epsilon in epithelial cells, we demonstrate that a modest increase in PKCdelta activity selectively stimulates quiescent cells to initiate G(1) phase cell cycle progression. Rather than completing the cell cycle, PKCdelta-infected cells arrest in S phase, an event that triggers caspase-dependent apoptotic cell death. Apoptosis was preceded by the activation of cell cycle checkpoints, culminating in the phosphorylation of Chk-1 and p53. Strikingly, blockade of S phase entry using the phosphatidylinositol 3-kinase inhibitor LY294002 prevented checkpoint activation and apoptosis. In contrast, inhibitors of mitogen-activated protein kinase cascades failed to prevent apoptosis. These findings demonstrate that the biological effects of PKCdelta can be extended to include positive regulation of G(1) phase cell cycle progression. Importantly, they reveal the existence of a novel, cell cycle-dependent mechanism through which PKCdelta stimulates cell death.     

Chaenorhinum semispeluncarum sp. nov. and C. yildirimlii sp. nov. (Scrophulariaceae) from east Anatolia,Turkey

Chaenorhinum semispeluncarum H. Y?ld?r?m, Kit Tan, S. ?enol & A. Pirhan sp. nov. and C. yildirimlii Kit Tan, H. Y?ld?r?m, S. ?enol & A. Pirhan sp. nov. (Scrophulariaceae, C. sect. Microrrhinum) from east Anatolia are described and illustrated. They are both narrow endemics related to the rare C. cryptarum, also from east Anatolia. Chaenorhinum semispeluncarum occurs on calcareous marl rich in potassium nitrate at the entrance of wet caves in Malatya and differs from C. cryptarum by its erect habit, smaller corollas, shallowly ribbed and tuberculate, bicoloured seeds. Chaenorhinum yildirimlii from the neighbouring province of Erzincan was found on alluvial soil of stream banks and differs from C. semispeluncarum by its seed characters which are similar to those of C. cryptarum. Chaenorhinum yildirimlii differs from C. cryptarum, most conspicuously by the violet lower corolla lip spotted dark purple at the apex.     

Cost-Effectiveness of Empagliflozin and Metformin Combination Versus Standard Care as First-Line Therapy in Patients With Type 2 Diabetes Mellitus

ObjectiveSodium-glucose cotransporter 2 inhibitors have been shown to reduce cardiovascular events but are currently not used as the first-line therapy. This study was conducted to evaluate the cost-effectiveness of first-line empagliflozin plus metformin versus metformin monotherapy among Australians with type 2 diabetes mellitus (T2DM) and existing cardiovascular disease (CVD).MethodsA Markov model with 1-year cycles and a 5-year time horizon was constructed to simulate the occurrence of recurrent cardiovascular events among Australians aged 50 to 84 years with T2DM and CVD. Efficacy results were derived from the Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients-Removing Excess Glucose trial. Costs and utilities were drawn from published sources. The evaluation adopted both health care and societal perspectives, with the latter ascribing the Australian government’s “value of statistical life year” (A$213 000) to each year lived by a person. Future outcomes were discounted at 5% annually. Sensitivity analyses were conducted to enhance the robustness of conclusions.ResultsCompared with metformin monotherapy, first-line empagliflozin plus metformin reduced overall cardiovascular events by 0.82% and overall deaths by 7.72% over 5 years. There were 0.2 years of life saved per person and 0.16 quality-adjusted life years gained, at a net health care cost of A$4408. These equated to incremental cost-effectiveness ratios of A$22 076 per year of life saved and A$28 244 per quality-adjusted life year gained. The gains in the value of statistical life year equated to A$42 530 per person, meaning that from a societal perspective, the intervention was cost-saving.ConclusionFirst-line empagliflozin plus metformin may represent a cost-effective strategy for the management of T2DM and CVD in Australia.     

Burden of disease and productivity impact of Streptococcus suis infection in Thailand

BackgroundStreptoccocus suis (S.suis) infection is a neglected zoonosis disease in humans mainly affects men of working age. We estimated the health and economic burden of S.suis infection in Thailand in terms of years of life lost, quality-adjusted life years (QALYs) lost, and productivity-adjusted life years (PALYs) lost which is a novel measure that adjusts years of life lived for productivity loss attributable to disease.MethodsA decision-analytic Markov model was developed to simulate the impact of S. suis infection and its major complications: death, meningitis and infective endocarditis among Thai people in 2019 with starting age of 51 years. Transition probabilities, and inputs pertaining to costs, utilities and productivity impairment associated with long-term complications were derived from published sources. A lifetime time horizon with follow-up until death or age 100 years was adopted. The simulation was repeated assuming that the cohort had not been infected with S.suis. The differences between the two set of model outputs in years of life, QALYs, and PALYs lived reflected the impact of S.suis infection. An annual discount rate of 3% was applied to both costs and outcomes. One-way sensitivity analyses and Monte Carlo simulation modeling technique using 10,000 iterations were performed to assess the impact of uncertainty in the model.Key resultsThis cohort incurred 769 (95% uncertainty interval [UI]: 695 to 841) years of life lost (14% of predicted years of life lived if infection had not occurred), 826 (95% UI: 588 to 1,098) QALYs lost (21%) and 793 (95%UI: 717 to 867) PALYs (15%) lost. These equated to an average of 2.46 years of life, 2.64 QALYs and 2.54 PALYs lost per person. The loss in PALYs was associated with a loss of 346 (95% UI: 240 to 461) million Thai baht (US$11.3 million) in GDP, which equated to 1.1 million Thai baht (US$ 36,033) lost per person.ConclusionsS.suis infection imposes a significant economic burden both in terms of health and productivity. Further research to investigate the effectiveness of public health awareness programs and disease control interventions should be mandated to provide a clearer picture for decision making in public health strategies and resource allocations.