Providing medical care to members of the military and their families remains a societal duty carried out not only by military physicians but also, and in large part, by civilian providers. As many ...military families are geographically dispersed, it is probable that all physicians at some point in their training or careers will care for this unique patient population. Understanding the military culture can help physicians provide the best care possible to our military families, and inclusion of military cultural competency curricula in all medical schools is a first step in advancing this understanding. The authors review the knowledge, skills, and attitudes that all health professionals should acquire to be able to care for those who serve and offer recommendations for developing these among all students and trainees.
The secretion of Wnt signaling proteins is dependent upon the transmembrane sorting receptor, Wntless (Wls), which recycles between the trans-Golgi network and the cell surface. Loss of Wls results ...in impairment of Wnt secretion and defects in development and homeostasis in Drosophila, Caenorhabditis elegans, and the mouse. The sorting signals for the internalization and trafficking of Wls have not been defined. Here, we demonstrate that Wls internalization requires clathrin and dynamin I, components of the clathrin-mediated endocytosis pathway. Moreover, we have identified a conserved YXXφ endocytosis motif in the third intracellular loop of the multipass membrane protein Wls. Mutation of the tyrosine-based motif YEGL to AEGL (Y425A) resulted in the accumulation of human mutant Wls on the cell surface of transfected HeLa cells. The cell surface accumulation of WlsAEGL was rescued by the insertion of a classical YXXφ motif in the cytoplasmic tail. Significantly, a Drosophila WlsAEGL mutant displayed a wing notch phenotype, with reduced Wnt secretion and signaling. These findings demonstrate that YXXφ endocytosis motifs can occur in the intracellular loops of multipass membrane proteins and, moreover, provide direct evidence that the trafficking of Wls is required for efficient secretion of Wnt signaling proteins.
Background: The secretion of Wnt molecules is dependent on the multipass membrane-sorting receptor, Wntless.
Results: A tyrosine-based internalization motif has been identified in an intracellular loop of Wntless.
Conclusion: Endocytosis of Wntless is required for efficient secretion of Wnt signaling molecules.
Significance: Defining the sorting signals and intracellular trafficking of Wntless is crucial to appreciate the regulation of Wnt secretion and development processes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Retrograde transport between endosomes and the trans‐Golgi network (TGN) is essential for the recycling of membrane proteins which are involved in a range of biological processes. A variety of ...machinery components have been identified at the TGN which regulate endosome‐to‐TGN transport, including small G proteins, SNAREs, tethering factors and scaffold molecules. The challenge is to understand how these regulatory components orchestrate not only the specific docking and fusion of retrograde membrane carriers with the TGN, but also maintain the integrity of this highly dynamic compartment to ensure efficient delivery and export of cargo. Here we review recent advances in defining the form and function of tethers and scaffolds in the regulation of the retrograde transport pathways.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Four mammalian golgins are specifically targeted to the trans‐Golgi network (TGN) membranes via their C‐terminal GRIP domains. The TGN golgins, p230/golgin‐245 and golgin‐97, are recruited via the ...GTPase Arl1, whereas the TGN golgin GCC185 is recruited independently of Arl1. Here we show that GCC185 is localized to a region of the TGN distinct from Arl1 and plays an essential role in maintaining the organization of the Golgi apparatus. Using both small interfering RNA (siRNA) and microRNA (miRNA), we show that depletion of GCC185 in HeLa cells frequently resulted in fragmentation of the Golgi apparatus. Golgi apparatus fragments were dispersed throughout the cytoplasm and contained both cis and trans markers. Trafficking of anterograde and retrograde cargo was analysed over an extended period following GCC185 depletion. Early effects of GCC185 depletion included a perturbation in the distribution of the mannose‐6‐phosphate receptor and a block in shiga toxin trafficking to the Golgi apparatus, which occurred in parallel with the fragmentation of the Golgi ribbon. Internalized shiga toxin accumulated in Rab11‐positive endosomes, indicating GCC185 is essential for transport between the recycling endosome and the TGN. In contrast, the plasma membrane–TGN recycling protein TGN38 was efficiently transported into GCC185‐depleted Golgi apparatus fragments throughout a 96‐h period, and anterograde transport of E‐cadherin was functional until a late stage of GCC185 depletion. This study demonstrated (i) a more effective long‐term depletion of GCC185 using miRNA than siRNA and (ii) a dual role for the GCC185 golgin in the regulation of endosome‐to‐TGN membrane transport and in the organization of the Golgi apparatus.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Membrane tethering Chia, Pei Zhi Cheryl; Gleeson, Paul A
F1000 prime reports,
2014, Volume:
6
Journal Article
Peer reviewed
Open access
Membrane trafficking depends on transport vesicles and carriers docking and fusing with the target organelle for the delivery of cargo. Membrane tethers and small guanosine triphosphatases (GTPases) ...mediate the docking of transport vesicles/carriers to enhance the efficiency of the subsequent SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-mediated fusion event with the target membrane bilayer. Different classes of membrane tethers and their specific intracellular location throughout the endomembrane system are now well defined. Recent biochemical and structural studies have led to a deeper understanding of the mechanism by which membrane tethers mediate docking of membrane carriers as well as an appreciation of the role of tethers in coordinating the correct SNARE complex and in regulating the organization of membrane compartments. This review will summarize the properties and roles of membrane tethers of both secretory and endocytic systems.
BACE1 cleavage of the amyloid precursor protein (APP) is the initial step in the formation of the amyloidogenic Aβ peptide. This article reports that cell surface BACE1 is internalised by the ...AP2/clathrin‐dependent pathway and traffics to early endosomes then recycling endosomes. In contrast, internalised wild‐type APP traffics to late endosomes/lysosomes. A BACE/TGN38 chimera that recycles via the TGN is more efficient in Aβ production than wild‐type BACE1 indicating that the recycling itinerary of BACE1 influences Aβ biogenesis.
β‐Secretase (BACE1) cleavage of the amyloid precursor protein (APP) represents the initial step in the formation of the Alzheimer's disease associated amyloidogenic Aβ peptide. Substantive evidence indicates that APP processing by BACE1 is dependent on intracellular sorting of this enzyme. Nonetheless, knowledge of the intracellular trafficking pathway of internalised BACE1 remains in doubt. Here we show that cell surface BACE1 is rapidly internalised by the AP2/clathrin dependent pathway in transfected cells and traffics to early endosomes and Rab11‐positive, juxtanuclear recycling endosomes, with very little transported to the TGN as has been previously suggested. Moreover, BACE1 is predominantly localised to the early and recycling endosome compartments in different cell types, including neuronal cells. In contrast, the majority of internalised wild‐type APP traffics to late endosomes/lysosomes. To explore the relevance of the itinerary of BACE1 on APP processing, we generated a BACE1 chimera containing the cytoplasmic tail of TGN38 (BACE/TGN38), which cycles between the cell surface and TGN in an AP2‐dependent manner. Wild‐type BACE1 is less efficient in Aβ production than the BACE/TGN38 chimera, highlighting the relevance of the itinerary of BACE1 on APP processing. Overall the data suggests that internalised BACE1 and APP diverge at early endosomes and that Aβ biogenesis is regulated in part by the recycling itinerary of BACE1.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Rab30 is a poorly characterized small GTPase. Here we show that Rab30 is localised primarily to the TGN and recycling endosomes in a range of cell types, including primary neurons; minor levels of ...Rab30 were also detected throughout the Golgi stack and early endosomes. Silencing of Rab30 resulted in the dispersal of both early and recycling endosomes and TGN compartments in HeLa cells. By analyzing cargo trafficking in Rab30-silenced and Rab30-overexpressing HeLa cells, we demonstrate that Rab30 plays a role in retrograde trafficking of TGN38 from endosomes to the Golgi, but has no apparent role in the endocytic recycling of the transferrin receptor to the plasma membrane. Five interactive partners with Rab30 were identified by pull-down and MS analysis using GFP-tagged Rab30 mutant, Rab30(Q68L). Two of the interactive partners identified were Arf1 and Arf4, known regulators of endosome to TGN retrograde transport. Knockdown of Arf1 and Arf4 results in GFP-Rab30 decorated tubules arising from the recycling endosomes, suggesting association of Rab30 with tubular carriers. Overall our data demonstrates a role for Rab30 in regulating retrograde transport to the TGN and maintenance of endosomal-TGN organization.
•Rab30 localised primarily to TGN and recycling endosomes.•Rab30 plays a major role in the spatial organization of the TGN and recycling endosomes.•Deficiency of Rab30 results in a perturbation in endosome-TGN retrograde transport.•Interactive partners of Rab30 include Arf1 and Arf4.•Findings highlight the interconnected network between the TGN and endosomal system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The retrograde membrane transport pathways from endosomes to the
trans
-Golgi network (TGN) are now recognized as critical intracellular pathways to recycle and shuttle a selective subgroup of ...membrane proteins, including sorting receptors, membrane-bound enzymes, transporters, as well as providing an avenue for the intracellular transport of various bacterial toxins. Multiple pathways from endosomes to the TGN have now been defined which differ between the cargo transported and the machinery used. Here, we review advances in these pathways and the requirement for TGN organization, and also discuss the development of unbiased analytical approaches to quantitatively track cargo that use these endosome-to-TGN pathways.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, VSZLJ, ZAGLJ
Dendritic cell (DC)-targeted vaccination is a new mode of antigen delivery that relies on the use of monoclonal antibodies (mAb) to target antigen to specific DC subsets. The neonatal Fc receptor ...(FcRn) is a non-classical Fc receptor that binds to immunoglobulin G (IgG) in acidified endosomes and controls its intracellular transport and recycling. FcRn is known to participate in the antigen presentation of immune complexes, however its contribution to DC-targeted vaccination has not previously been examined. Here we have investigated the role of FcRn in antigen presentation using antigen conjugated to IgG mAb which target specific DC receptors, including DEC205 and Clec9A expressed by the conventional DC 1 (cDC1) subset. We show that FcRn is expressed at high levels by cDC1, both at steady-state and following activation and plays a significant role in MHC I cross-presentation and MHC II presentation of antigens that are targeted to cDC1 via mAb specific for DEC205. This effect of FcRn is intrinsic to cDC1 and FcRn impacts the efficacy of anti-DEC205-mediated vaccination against B cell lymphoma. In contrast, FcRn does not impact presentation of antigens targeted to Clec9A and does not regulate presentation of cell-associated antigen. These data highlight a new and unique role of FcRn in controlling the immunogenicity of anti-DEC205-based vaccination, with consequences for exploiting this pathway to improve DC-targeted vaccine outcomes.
The expression of the Ikaros transcription factor family member, Helios, has been shown to be associated with T‐cell tolerance in both the thymus and the periphery. To better understand the ...importance of Helios in tolerance pathways, we have examined the expression of Helios in TCR‐transgenic T cells specific for the gastric H+/K+ ATPase, the autoantigen target in autoimmune gastritis. Analysis of H+/K+ ATPase‐specific T cells in mice with different patterns of H+/K+ ATPase expression revealed that, in addition to the expression of Helios in CD4+Foxp3+ regulatory T (Treg) cells, Helios is expressed by a large proportion of CD4+Foxp3− T cells in both the thymus and the paragastric lymph node (PgLN), which drains the stomach. In the thymus, Helios was expressed by H+/K+ ATPase‐specific thymocytes that were undergoing negative selection. In the periphery, Helios was expressed in H+/K+ ATPase‐specific CD4+ T cells following H+/K+ ATPase presentation and was more highly expressed when T‐cell activation occurred in the absence of inflammation. Analysis of purified H+/K+ ATPase‐specific CD4+Foxp3−Helios+ T cells demonstrated that they were functionally anergic. These results demonstrate that Helios is expressed by thymic and peripheral T cells that are being driven to tolerance in response to a genuine autoantigen.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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