scholarly journals v-SNARE cellubrevin is required for basolateral sorting of AP-1B–dependent cargo in polarized epithelial cells

2007 ◽  
Vol 177 (3) ◽  
pp. 477-488 ◽  
Author(s):  
Ian C. Fields ◽  
Elina Shteyn ◽  
Marc Pypaert ◽  
Véronique Proux-Gillardeaux ◽  
Richard S. Kang ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Low Density Lipoprotein ◽  
Basolateral Membrane ◽  
Density Lipoprotein ◽  
Recycling Endosomes ◽  
Transport Vesicles ◽  
Density Lipoprotein Receptor ◽  
Target Membrane ◽  
Syntaxin 4 ◽  
Basolateral Plasma Membrane

The epithelial cell–specific adaptor complex AP-1B is crucial for correct delivery of many transmembrane proteins from recycling endosomes to the basolateral plasma membrane. Subsequently, membrane fusion is dependent on the formation of complexes between SNARE proteins located at the target membrane and on transport vesicles. Although the t-SNARE syntaxin 4 has been localized to the basolateral membrane, the v-SNARE operative in the AP-1B pathway remained unknown. We show that the ubiquitously expressed v-SNARE cellubrevin localizes to the basolateral membrane and to recycling endosomes, where it colocalizes with AP-1B. Furthermore, we demonstrate that cellubrevin coimmunoprecipitates preferentially with syntaxin 4, implicating this v-SNARE in basolateral fusion events. Cleavage of cellubrevin with tetanus neurotoxin (TeNT) results in scattering of AP-1B localization and missorting of AP-1B–dependent cargos, such as transferrin receptor and a truncated low-density lipoprotein receptor, LDLR-CT27. These data suggest that cellubrevin and AP-1B cooperate in basolateral membrane trafficking.

scholarly journals Distribution and Function of Ap-1 Clathrin Adaptor Complexes in Polarized Epithelial Cells

2001 ◽  
Vol 152 (3) ◽  
pp. 595-606 ◽  
Author(s):  
Heike Fölsch ◽  
Marc Pypaert ◽  
Peter Schu ◽  
Ira Mellman
Keyword(s):  
Membrane Proteins ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Apical Surface ◽  
Recycling Endosomes ◽  
Density Lipoprotein Receptor ◽  
Basolateral Plasma Membrane ◽  
Clathrin Adaptor ◽  
And Function ◽  
Golgi Network

Expression of the epithelial cell–specific heterotetrameric adaptor complex AP-1B is required for the polarized distribution of many membrane proteins to the basolateral surface of LLC-PK1 kidney cells. AP-1B is distinguished from the ubiquitously expressed AP-1A by exchange of its single 50-kD μ subunit, μ1A, being replaced by the closely related μ1B. Here we show that this substitution is sufficient to couple basolateral plasma membrane proteins, such as a low-density lipoprotein receptor (LDLR), to the AP-1B complex and to clathrin. The interaction between LDLR and AP-1B is likely to occur in the trans-Golgi network (TGN), as was suggested by the localization of functional, epitope-tagged μ1 by immunofluorescence and immunoelectron microscopy. Tagged AP-1A and AP-1B complexes were found in the perinuclear region close to the Golgi complex and recycling endosomes, often in clathrin-coated buds and vesicles. Yet, AP-1A and AP-1B localized to different subdomains of the TGN, with only AP-1A colocalizing with furin, a membrane protein that uses AP-1 to recycle between the TGN and endosomes. We conclude that AP-1B functions by interacting with its cargo molecules and clathrin in the TGN, where it acts to sort basolateral proteins from proteins destined for the apical surface and from those selected by AP-1A for transport to endosomes and lysosomes.

The functions of Reelin in membrane trafficking and cytoskeletal dynamics: implications for neuronal migration, polarization and differentiation

2017 ◽  
Vol 474 (18) ◽  
pp. 3137-3165 ◽  
Author(s):  
Jessica Santana ◽  
María-Paz Marzolo
Keyword(s):  
Membrane Trafficking ◽  
Neuronal Migration ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Signaling Cascade ◽  
Low Density ◽  
Lipoprotein Receptor ◽  
Density Lipoprotein Receptor ◽  
Reelin Signaling

Reelin is a large extracellular matrix protein with relevant roles in mammalian central nervous system including neurogenesis, neuronal polarization and migration during development; and synaptic plasticity with its implications in learning and memory, in the adult. Dysfunctions in reelin signaling are associated with brain lamination defects such as lissencephaly, but also with neuropsychiatric diseases like autism, schizophrenia and depression as well with neurodegeneration. Reelin signaling involves a core pathway that activates upon reelin binding to its receptors, particularly ApoER2 (apolipoprotein E receptor 2)/LRP8 (low-density lipoprotein receptor-related protein 8) and very low-density lipoprotein receptor, followed by Src/Fyn-mediated phosphorylation of the adaptor protein Dab1 (Disabled-1). Phosphorylated Dab1 (pDab1) is a hub in the signaling cascade, from which several other downstream pathways diverge reflecting the different roles of reelin. Many of these pathways affect the dynamics of the actin and microtubular cytoskeleton, as well as membrane trafficking through the regulation of the activity of small GTPases, including the Rho and Rap families and molecules involved in cell polarity. The complexity of reelin functions is reflected by the fact that, even now, the precise mode of action of this signaling cascade in vivo at the cellular and molecular levels remains unclear. This review addresses and discusses in detail the participation of reelin in the processes underlying neurogenesis, neuronal migration in the cerebral cortex and the hippocampus; and the polarization, differentiation and maturation processes that neurons experiment in order to be functional in the adult brain. In vivo and in vitro evidence is presented in order to facilitate a better understanding of this fascinating system.

scholarly journals Clathrin and clathrin adaptor AP-1 control apical trafficking of megalin in the biosynthetic and recycling routes

2019 ◽  
Vol 30 (14) ◽  
pp. 1716-1728 ◽  
Author(s):  
Diego Gravotta ◽  
Andres Perez Bay ◽  
Caspar T. H. Jonker ◽  
Patrick J. Zager ◽  
Ignacio Benedicto ◽  
...  
Keyword(s):  
Mdck Cells ◽  
Transmembrane Protein ◽  
Low Density Lipoprotein ◽  
Basolateral Membrane ◽  
Density Lipoprotein ◽  
Apical Surface ◽  
Density Lipoprotein Receptor ◽  
Clathrin Adaptor ◽  
Apical Sorting ◽  
Apical Localization

Megalin (gp330, LRP-2) is a protein structurally related to the low-density lipoprotein receptor family that displays a large luminal domain with multiligand binding properties. Megalin localizes to the apical surface of multiple epithelia, where it participates in endocytosis of a variety of ligands performing roles important for development or homeostasis. We recently described the apical recycling pathway of megalin in Madin–Darby canine kidney (MDCK) cells and found that it is a long-lived, fast recycling receptor with a recycling turnover of 15 min and a half-life of 4.8 h. Previous work implicated clathrin and clathrin adaptors in the polarized trafficking of fast recycling basolateral receptors. Hence, here we study the role of clathrin and clathrin adaptors in megalin’s apical localization and trafficking. Targeted silencing of clathrin or the γ1 subunit of clathrin adaptor AP-1 by RNA interference in MDCK cells disrupted apical localization of megalin, causing its redistribution to the basolateral membrane. In contrast, silencing of the γ2 subunit of AP-1 had no effect on megalin polarity. Trafficking assays we developed using FM4-HA-miniMegalin-GFP, a reversible conditional endoplasmic reticulum–retained chimera, revealed that clathrin and AP-1 silencing disrupted apical sorting of megalin in both biosynthetic and recycling routes. Our experiments demonstrate that clathrin and AP-1 control the sorting of an apical transmembrane protein.

scholarly journals BLOS1 mediates kinesin switch during endosomal recycling of LDL receptor

2020 ◽  
Author(s):  
Chang Zhang ◽  
Chanjuan Hao ◽  
Guanghou Shui ◽  
Wei Li
Keyword(s):  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Cholesterol Homeostasis ◽  
Whole Body ◽  
Cellular Mechanisms ◽  
Anterograde Transport ◽  
Recycling Endosomes ◽  
Endosomal Recycling ◽  
Density Lipoprotein Receptor

AbstractLow-density lipoprotein receptor (LDLR) in hepatocytes plays a key role in normal clearance of circulating LDL and in whole body cholesterol homeostasis. The trafficking of LDLR is highly regulated in clathrin-dependent endocytosis, endosomal recycling and lysosomal degradation. Current studies have been focusing on its endocytosis and degradation. However, the detailed molecular and cellular mechanisms underlying its endosomal recycling are largely unknown. We found that BLOS1, a shared subunit of BLOC-1 and BORC, is involved in LDLR endosomal recycling. Loss of BLOS1 leads to less membrane LDLR and impairs LDL clearance from plasma in hepatocyte-specific BLOS1 knockout mice. BLOS1 interacts with kinesin-3, and that BLOS1 acts as a new adaptor for kinesin-2 to coordinate kinesin-3 and kinesin-2 during the long-range transport of recycling endosomes (REs) to plasma membrane along microtubule tracks to overcome hurdles at microtubule intersections. These findings provide new insights into RE’s anterograde transport and the pathogenesis of dyslipidemia.

scholarly journals Polarized Traffic of LRP1 Involves AP1B and SNX17 Operating on Y-dependent Sorting Motifs in Different Pathways

2009 ◽  
Vol 20 (1) ◽  
pp. 481-497 ◽  
Author(s):  
Maribel Donoso ◽  
Jorge Cancino ◽  
Jiyeon Lee ◽  
Peter van Kerkhof ◽  
Claudio Retamal ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Low Density Lipoprotein ◽  
Basolateral Membrane ◽  
Density Lipoprotein ◽  
Recycling Endosome ◽  
Sorting Nexin ◽  
Sorting Signals ◽  
Density Lipoprotein Receptor ◽  
Npxy Motif ◽  
Lipoprotein Receptor Related Protein

Low-density lipoprotein receptor–related protein 1 (LRP1) is an endocytic recycling receptor with two cytoplasmic tyrosine-based basolateral sorting signals. Here we show that during biosynthetic trafficking LRP1 uses AP1B adaptor complex to move from a post-TGN recycling endosome (RE) to the basolateral membrane. Then it recycles basolaterally from the basolateral sorting endosome (BSE) involving recognition by sorting nexin 17 (SNX17). In the biosynthetic pathway, Y29 but not N26 from a proximal NPXY directs LRP1 basolateral sorting from the TGN. A N26A mutant revealed that this NPXY motif recognized by SNX17 is required for the receptor's exit from BSE. An endocytic Y63ATL66 motif also functions in basolateral recycling, in concert with an additional endocytic motif (LL86,87), by preventing LRP1 entry into the transcytotic apical pathway. All this sorting information operates similarly in hippocampal neurons to mediate LRP1 somatodendritic distribution regardless of the absence of AP1B in neurons. LRP1 basolateral distribution results then from spatially and temporally segregation steps mediated by recognition of distinct tyrosine-based motifs. We also demonstrate a novel function of SNX17 in basolateral/somatodendritic recycling from a different compartment than AP1B endosomes.

The hepatitis C virus and its hepatic environment: a toxic but finely tuned partnership

2009 ◽  
Vol 423 (3) ◽  
pp. 303-314 ◽  
Author(s):  
Marie Perrault ◽  
Eve-Isabelle Pécheur
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Low Density Lipoprotein ◽  
Basolateral Membrane ◽  
Scavenger Receptor ◽  
Density Lipoprotein ◽  
Target Cells ◽  
Enveloped Virus ◽  
Sequence Of Events ◽  
Density Lipoprotein Receptor

Twenty years after its discovery, HCV (hepatitis C virus) still infects 170 million people worldwide and cannot be properly treated due to the lack of efficient medication. Its life cycle must be better understood to develop targeted pharmacological arsenals. HCV is an enveloped virus bearing two surface glycoproteins, E1 and E2. It only infects humans through blood transmission, and hepatocytes are its only target cells. Hepatic trabeculae are formed by hepatocyte rows surrounded by sinusoid capillaries, irrigating hepatic cells. Hepatocytes are polarized and have basolateral and apical poles, separated by tight junctions in contact with blood and bile respectively. In blood, HCV remains in contact with lipoproteins. It then navigates through hepatic microenvironment and extracellular matrix, composed of glycosaminoglycans and proteins. HCV then encounters the hepatocyte basolateral membrane, where it interacts with its entry factors: the low-density lipoprotein receptor, CD81 tetraspanin, and the high-density lipoprotein (scavenger) receptor SR-BI (scavenger receptor BI). How these molecules interact with HCV remains unclear; however, a tentative sequence of events has been proposed. Two essential factors of HCV entry are the tight junction proteins claudin-1 and occludin. Cell polarity therefore seems to be a key for HCV entry. This raises several exciting questions on the HCV internalization pathway. Clathrin-dependent endocytosis is probably the route of HCV transport to intracellular compartments, and the ultimate step of its entry is fusion, which probably takes place within endosomes. The mechanisms of HCV membrane fusion are still unclear, notably the nature of the fusion proteins is unknown and the contribution of HCV-associated lipoproteins to this event is currently under investigation.

scholarly journals BLOS1 mediates kinesin switch during endosomal recycling of LDL receptor

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Chang Zhang ◽  
Chanjuan Hao ◽  
Guanghou Shui ◽  
Wei Li
Keyword(s):  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Cholesterol Homeostasis ◽  
Whole Body ◽  
Cellular Mechanisms ◽  
Anterograde Transport ◽  
Recycling Endosomes ◽  
Endosomal Recycling ◽  
Density Lipoprotein Receptor

Low-density lipoprotein receptor (LDLR) in hepatocytes plays a key role in plasma clearance of circulating LDL and in whole body cholesterol homeostasis. The trafficking of LDLR is highly regulated in clathrin-dependent endocytosis, endosomal recycling and lysosomal degradation. Current studies focus on its endocytosis and degradation. However, the detailed molecular and cellular mechanisms underlying its endosomal recycling are largely unknown. We found that BLOS1, a shared subunit of BLOC-1 and BORC, is involved in LDLR endosomal recycling. Loss of BLOS1 leads to less membrane LDLR and impairs LDL clearance from plasma in hepatocyte-specific BLOS1 knockout mice. BLOS1 interacts with kinesin-3 motor KIF13A, and BLOS1 acts as a new adaptor for kinesin-2 motor KIF3 to coordinate kinesin-3 and kinesin-2 during the long-range transport of recycling endosomes (REs) to plasma membrane along microtubule tracks to overcome hurdles at microtubule intersections. This provides new insights into RE’s anterograde transport and the pathogenesis of dyslipidemia.

The Role of the Low-Density Lipoprotein Receptor-Related Protein (LRP) in the Plasma Clearance and Liver Uptake of Recombinant Single-chain Urokinase-type Plasminogen Activator in Rats

1997 ◽  
Vol 77 (04) ◽  
pp. 710-717 ◽  
Author(s):  
Marieke E van der Kaaden ◽  
Dingeman C Rijken ◽  
J Kar Kruijt ◽  
Theo J C van Berkel ◽  
Johan Kuiper
Keyword(s):  
Plasminogen Activator ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Single Chain ◽  
Liver Uptake ◽  
Type Plasminogen Activator ◽  
Parenchymal Liver ◽  
Urokinase Type Plasminogen Activator ◽  
Density Lipoprotein Receptor

SummaryUrokinase-type plasminogen activator (u-PA) is used as a thrombolytic agent in the treatment of acute myocardial infarction. In vitro, recombinant single-chain u-PA (rscu-PA) expressed in E.coli is recognized by the Low-Density Lipoprotein Receptor-related Protein (LRP) on rat parenchymal liver cells. In this study we investigated the role of LRP in the liver uptake and plasma clearance of rscu-PA in rats. A preinjection of the LRP inhibitor GST-RAP reduced the maximal liver uptake of 125I-rscu-PA at 5 min after injection from 50 to 30% of the injected dose and decreased the clearance of rscu-PA from 2.37 ml/min to 1.58 ml/min. Parenchymal, Kupffer and endothelial cells were responsible for 40, 50 and 10% of the liver uptake, respectively. The reduction in liver uptake of rscu-PA by the preinjection of GST-RAP was caused by a 91 % and 62% reduction in the uptake by parenchymal and Kupffer cells, respectively. In order to investigate the part of rscu-PA that accounted for the interaction with LRP, experiments were performed with a mutant of rscu-PA lacking residues 11-135 (= deltal25- rscu-PA). Deletion of residues 11-135 resulted in a 80% reduction in liver uptake and a 2.4 times slower clearance (0.97 ml/min). The parenchymal, Kupffer and endothelial cells were responsible for respectively 60, 33 and 7% of the liver uptake of 125I-deltal25-rscu-PA. Preinjection of GST-RAP completely reduced the liver uptake of delta 125-rscu-PA and reduced its clearance to 0.79 ml/min. Treatment of isolated Kupffer cells with PI-PLC reduced the binding of rscu-PA by 40%, suggesting the involvement of the urokinase-type Plasminogen Activator Receptor (u-PAR) in the recognition of rscu-PA. Our results demonstrate that in vivo LRP is responsible for more than 90% of the parenchymal liver cell mediated uptake of rscu-PA and for 60% of the Kupffer cell interaction. It is also suggested that u-PAR is involved in the Kupffer cell recognition of rscu-PA.

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