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Zhang N, Zhang H, Khan LA, Jafari G, Eun Y, Membreno E, Gobel V. The biosynthetic-secretory pathway, supplemented by recycling routes, determines epithelial membrane polarity. Sci Adv 2023; 9:eade4620. [PMID: 37379377 PMCID: PMC10306302 DOI: 10.1126/sciadv.ade4620] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 05/24/2023] [Indexed: 06/30/2023]
Abstract
In prevailing epithelial polarity models, membrane-based polarity cues (e.g., the partitioning-defective PARs) position apicobasal cellular membrane domains. Intracellular vesicular trafficking expands these domains by sorting polarized cargo toward them. How the polarity cues themselves are polarized in epithelia and how sorting confers long-range apicobasal directionality to vesicles is still unclear. Here, a systems-based approach using two-tiered C. elegans genomics-genetics screens identifies trafficking molecules that are not implicated in apical sorting yet polarize apical membrane and PAR complex components. Live tracking of polarized membrane biogenesis indicates that the biosynthetic-secretory pathway, linked to recycling routes, is asymmetrically oriented toward the apical domain during this domain's biosynthesis, and that this directionality is regulated upstream of PARs and independent of polarized target membrane domains. This alternative mode of membrane polarization could offer solutions to open questions in current models of epithelial polarity and polarized trafficking.
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Affiliation(s)
- Nan Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
- Key Laboratory of Zoonosis Research by the Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun 130062, China
| | - Hongjie Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
- Faculty of Health Sciences, University of Macau, Taipa, Macau, China
| | - Liakot A. Khan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
| | - Gholamali Jafari
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
| | - Yong Eun
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
- Department of Medicine, NYC Health & Hospitals/Harlem, Columbia University, New York, NY, USA
| | - Edward Membreno
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
| | - Verena Gobel
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
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Jafari G, Khan LA, Zhang H, Membreno E, Yan S, Dempsey G, Gobel V. Branched-chain actin dynamics polarizes vesicle trajectories and partitions apicobasal epithelial membrane domains. Sci Adv 2023; 9:eade4022. [PMID: 37379384 PMCID: PMC10306301 DOI: 10.1126/sciadv.ade4022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 05/24/2023] [Indexed: 06/30/2023]
Abstract
In prevailing epithelial polarity models, membrane- and junction-based polarity cues such as the partitioning-defective PARs specify the positions of apicobasal membrane domains. Recent findings indicate, however, that intracellular vesicular trafficking can determine the position of the apical domain, upstream of membrane-based polarity cues. These findings raise the question of how vesicular trafficking becomes polarized independent of apicobasal target membrane domains. Here, we show that the apical directionality of vesicle trajectories depends on actin dynamics during de novo polarized membrane biogenesis in the C. elegans intestine. We find that actin, powered by branched-chain actin modulators, determines the polarized distribution of apical membrane components, PARs, and itself. Using photomodulation, we demonstrate that F-actin travels through the cytoplasm and along the cortex toward the future apical domain. Our findings support an alternative polarity model where actin-directed trafficking asymmetrically inserts the nascent apical domain into the growing epithelial membrane to partition apicobasal membrane domains.
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Affiliation(s)
- Gholamali Jafari
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, MGHfC, Harvard Medical School, Boston, MA, USA
| | - Liakot A. Khan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, MGHfC, Harvard Medical School, Boston, MA, USA
| | - Hongjie Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, MGHfC, Harvard Medical School, Boston, MA, USA
- Faculty of Health Sciences, University of Macau, Taipa, Macau, China
| | - Edward Membreno
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, MGHfC, Harvard Medical School, Boston, MA, USA
| | - Siyang Yan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, MGHfC, Harvard Medical School, Boston, MA, USA
| | - Graham Dempsey
- Chemistry and Chemical Biology Department, Harvard University, Cambridge, MA, USA
| | - Verena Gobel
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, MGHfC, Harvard Medical School, Boston, MA, USA
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Khan LA, Jafari G, Zhang N, Membreno E, Yan S, Zhang H, Gobel V. A tensile trilayered cytoskeletal endotube drives capillary-like lumenogenesis. J Cell Biol 2019; 218:2403-2424. [PMID: 31239283 PMCID: PMC6605810 DOI: 10.1083/jcb.201811175] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Revised: 04/09/2019] [Accepted: 05/14/2019] [Indexed: 01/01/2023] Open
Abstract
Unicellular tubes are components of internal organs and capillaries. It is unclear how they meet the architectural challenge to extend a centered intracellular lumen of uniform diameter. In an RNAi-based Caenorhabditis elegans screen, we identified three intermediate filaments (IFs)-IFA-4, IFB-1, and IFC-2-as interactors of the lumenal membrane-actin linker ERM-1 in excretory-canal tubulogenesis. We find that IFs, generally thought to affect morphogenesis indirectly by maintaining tissue integrity, directly promote lumenogenesis in this capillary-like single-cell tube. We show that ERM-1, ACT-5/actin, and TBB-2/tubulin recruit membrane-forming endosomal and flux-promoting canalicular vesicles to the lumen, whereas IFs, themselves recruited to the lumen by ERM-1 and TBB-2, restrain lateral vesicle access. IFs thereby prevent cystogenesis, equilibrate the lumen diameter, and promote lumen forward extension. Genetic and imaging analyses suggest that IFB-1/IFA-4 and IFB-1/IFC-2 polymers form a perilumenal triple IF lattice, sandwiched between actin and helical tubulin. Our findings characterize a novel mechanism of capillary-like lumenogenesis, where a tensile trilayered cytoskeletal endotube transforms concentric into directional growth.
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Affiliation(s)
- Liakot A Khan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA
| | - Gholamali Jafari
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA
| | - Nan Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA
- Key Laboratory of Zoonosis Research, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Edward Membreno
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA
| | - Siyang Yan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA
| | - Hongjie Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA
- Faculty of Health Sciences, University of Macau, Taipa, Macau, China
| | - Verena Gobel
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA
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Zhang N, Wang X, Gobel V, Zhang X. The galectin LEC-5 is a novel binding partner for RAB-11. Biochem Biophys Res Commun 2018; 505:600-605. [PMID: 30274774 DOI: 10.1016/j.bbrc.2018.09.110] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 09/17/2018] [Indexed: 01/27/2023]
Abstract
RAB-11/Rab11 is an endosomal GTPase with conserved roles in directional trafficking and apical domain formation in polarized epithelial cells. From a yeast two-hybrid screen using full-length C. elegans RAB-11 as bait, we identified LEC-5 as a novel binding protein for RAB-11. LEC-5 is an ortholog of mammalian Galectin-9 which associates with glycosphingolipids and is implicated in apical cargo sorting. We further confirmed the interaction between RAB-11 and LEC-5 via GST-pull down, co-immunoprecipitation and bimolecular fluorescence complementation. In addition, we showed that LEC-5 binds to RAB-11 with its C-terminus. Our results indicate a novel role of RAB-11 in apical sorting via LEC-5. Such a role would extend RAB-11's function as a master regulator of apical trafficking and suggest it could translate apical sorting signals into apical vesicle directionality.
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Affiliation(s)
- Nan Zhang
- The First Bethune Hospital, Jilin University, Changchun, 130021, China; Key Laboratory of Zoonosis Research, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, 130062, China
| | - Xu Wang
- Key Laboratory of Zoonosis Research, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, 130062, China
| | - Verena Gobel
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, 02114, USA
| | - Xichen Zhang
- Key Laboratory of Zoonosis Research, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, 130062, China.
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Zhang N, Membreno E, Raj S, Zhang H, Khan LA, Gobel V. The C. elegans Excretory Canal as a Model for Intracellular Lumen Morphogenesis and In Vivo Polarized Membrane Biogenesis in a Single Cell: labeling by GFP-fusions, RNAi Interaction Screen and Imaging. J Vis Exp 2017. [PMID: 28994812 DOI: 10.3791/56101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The four C. elegans excretory canals are narrow tubes extended through the length of the animal from a single cell, with almost equally far extended intracellular endotubes that build and stabilize the lumen with a membrane and submembraneous cytoskeleton of apical character. The excretory cell expands its length approximately 2,000 times to generate these canals, making this model unique for the in vivo assessment of de novo polarized membrane biogenesis, intracellular lumen morphogenesis and unicellular tubulogenesis. The protocol presented here shows how to combine standard labeling, gain- and loss-of-function genetic or RNA interference (RNAi)-, and microscopic approaches to use this model to visually dissect and functionally analyze these processes on a molecular level. As an example of a labeling approach, the protocol outlines the generation of transgenic animals with fluorescent fusion proteins for live analysis of tubulogenesis. As an example of a genetic approach, it highlights key points of a visual RNAi-based interaction screen designed to modify a gain-of-function cystic canal phenotype. The specific methods described are how to: label and visualize the canals by expressing fluorescent proteins; construct a targeted RNAi library and strategize RNAi screening for the molecular analysis of canal morphogenesis; visually assess modifications of canal phenotypes; score them by dissecting fluorescence microscopy; characterize subcellular canal components at higher resolution by confocal microscopy; and quantify visual parameters. The approach is useful for the investigator who is interested in taking advantage of the C. elegans excretory canal for identifying and characterizing genes involved in the phylogenetically conserved processes of intracellular lumen and unicellular tube morphogenesis.
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Affiliation(s)
- Nan Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School; College of Life Sciences, Jilin University
| | - Edward Membreno
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School
| | - Susan Raj
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School
| | - Hongjie Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School; Faculty of Health Sciences, University of Macau
| | - Liakot A Khan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School;
| | - Verena Gobel
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School;
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Zhang N, Khan LA, Membreno E, Jafari G, Yan S, Zhang H, Gobel V. The C. elegans Intestine As a Model for Intercellular Lumen Morphogenesis and In Vivo Polarized Membrane Biogenesis at the Single-cell Level: Labeling by Antibody Staining, RNAi Loss-of-function Analysis and Imaging. J Vis Exp 2017:56100. [PMID: 28994799 PMCID: PMC5628585 DOI: 10.3791/56100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Multicellular tubes, fundamental units of all internal organs, are composed of polarized epithelial or endothelial cells, with apical membranes lining the lumen and basolateral membranes contacting each other and/or the extracellular matrix. How this distinctive membrane asymmetry is established and maintained during organ morphogenesis is still an unresolved question of cell biology. This protocol describes the C. elegans intestine as a model for the analysis of polarized membrane biogenesis during tube morphogenesis, with emphasis on apical membrane and lumen biogenesis. The C. elegans twenty-cell single-layered intestinal epithelium is arranged into a simple bilaterally symmetrical tube, permitting analysis on a single-cell level. Membrane polarization occurs concomitantly with polarized cell division and migration during early embryogenesis, but de novo polarized membrane biogenesis continues throughout larval growth, when cells no longer proliferate and move. The latter setting allows one to separate subcellular changes that simultaneously mediate these different polarizing processes, difficult to distinguish in most polarity models. Apical-, basolateral membrane-, junctional-, cytoskeletal- and endomembrane components can be labeled and tracked throughout development by GFP fusion proteins, or assessed by in situ antibody staining. Together with the organism's genetic versatility, the C. elegans intestine thus provides a unique in vivo model for the visual, developmental, and molecular genetic analysis of polarized membrane and tube biogenesis. The specific methods (all standard) described here include how to: label intestinal subcellular components by antibody staining; analyze genes involved in polarized membrane biogenesis by loss-of-function studies adapted to the typically essential tubulogenesis genes; assess polarity defects during different developmental stages; interpret phenotypes by epifluorescence, differential interference contrast (DIC) and confocal microscopy; quantify visual defects. This protocol can be adapted to analyze any of the often highly conserved molecules involved in epithelial polarity, membrane biogenesis, tube and lumen morphogenesis.
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Affiliation(s)
- Nan Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital, Harvard Medical School; College of Life Sciences, Jilin University
| | - Liakot A Khan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital, Harvard Medical School
| | - Edward Membreno
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital, Harvard Medical School
| | - Gholamali Jafari
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital, Harvard Medical School
| | - Siyang Yan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital, Harvard Medical School
| | - Hongjie Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital, Harvard Medical School; Faculty of Health Sciences, University of Macau;
| | - Verena Gobel
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital, Harvard Medical School;
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Zhang H, Abraham N, Khan LA, Gobel V. Erratum: Corrigendum: RNAi-based biosynthetic pathway screens to identify in vivo functions of non-nucleic acid–based metabolites such as lipids. Nat Protoc 2015; 10:939. [DOI: 10.1038/nprot0615-939a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Zhang H, Abraham N, Khan LA, Gobel V. RNAi-based biosynthetic pathway screens to identify in vivo functions of non-nucleic acid-based metabolites such as lipids. Nat Protoc 2015; 10:681-700. [PMID: 25837419 DOI: 10.1038/nprot.2015.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The field of metabolomics continues to catalog new compounds, but their functional analysis remains technically challenging, and roles beyond metabolism are largely unknown. Unbiased genetic/RNAi screens are powerful tools to identify the in vivo functions of protein-encoding genes, but not of nonproteinaceous compounds such as lipids. They can, however, identify the biosynthetic enzymes of these compounds-findings that are usually dismissed, as these typically synthesize multiple products. Here, we provide a method using follow-on biosynthetic pathway screens to identify the endpoint biosynthetic enzyme and thus the compound through which they act. The approach is based on the principle that all subsequently identified downstream biosynthetic enzymes contribute to the synthesis of at least this one end product. We describe how to systematically target lipid biosynthetic pathways; optimize targeting conditions; take advantage of pathway branchpoints; and validate results by genetic assays and biochemical analyses. This approach extends the power of unbiased genetic/RNAi screens to identify in vivo functions of non-nucleic acid-based metabolites beyond their metabolic roles. It will typically require several months to identify a metabolic end product by biosynthetic pathway screens, but this time will vary widely depending, among other factors, on the end product's location in the pathway, which determines the number of screens required for its identification.
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Affiliation(s)
- Hongjie Zhang
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Nessy Abraham
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Liakot A Khan
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Verena Gobel
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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Khan LA, Zhang H, Abraham N, Sun L, Fleming JT, Buechner M, Hall DH, Gobel V. Intracellular lumen extension requires ERM-1-dependent apical membrane expansion and AQP-8-mediated flux. Nat Cell Biol 2013; 15:143-56. [PMID: 23334498 PMCID: PMC4091717 DOI: 10.1038/ncb2656] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 11/16/2012] [Indexed: 01/29/2023]
Abstract
Many unicellular tubes such as capillaries form lumens intracellularly, a process that is not well understood. Here we show that the cortical membrane organizer ERM-1 is required to expand the intracellular apical/lumenal membrane and its actin undercoat during single-cell C.elegans excretory canal morphogenesis. We characterize AQP-8, identified in an ERM-1 overexpression (ERM-1[++]) suppressor screen, as a canalicular aquaporin that interacts with ERM-1 in lumen extension in a mercury-sensitive manner, implicating water-channel activity. AQP-8 is transiently recruited to the lumen by ERM-1, co-localizing in peri-lumenal cuffs interspaced along expanding canals. An ERM-1[++]-mediated increase in the number of lumen-associated canaliculi is reversed by AQP-8 depletion. We propose that the ERM-1-AQP-8 interaction propels lumen extension by translumenal flux, suggesting a direct morphogenetic effect of water-channel-regulated fluid pressure.
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Affiliation(s)
- Liakot A Khan
- Department of Pediatrics, Massachusetts General Hospital, Boston, 02114, USA
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Zhang H, Kim A, Abraham N, Khan LA, Hall DH, Fleming JT, Gobel V. Clathrin and AP-1 regulate apical polarity and lumen formation during C. elegans tubulogenesis. Development 2012; 139:2071-83. [PMID: 22535410 DOI: 10.1242/dev.077347] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Clathrin coats vesicles in all eukaryotic cells and has a well-defined role in endocytosis, moving molecules away from the plasma membrane. Its function on routes towards the plasma membrane was only recently appreciated and is thought to be limited to basolateral transport. Here, an unbiased RNAi-based tubulogenesis screen identifies a role of clathrin (CHC-1) and its AP-1 adaptor in apical polarity during de novo lumenal membrane biogenesis in the C. elegans intestine. We show that CHC-1/AP-1-mediated polarized transport intersects with a sphingolipid-dependent apical sorting process. Depleting each presumed trafficking component mislocalizes the same set of apical membrane molecules basolaterally, including the polarity regulator PAR-6, and generates ectopic lateral lumens. GFP::CHC-1 and BODIPY-ceramide vesicles associate perinuclearly and assemble asymmetrically at polarized plasma membrane domains in a co-dependent and AP-1-dependent manner. Based on these findings, we propose a trafficking pathway for apical membrane polarity and lumen morphogenesis that implies: (1) a clathrin/AP-1 function on an apically directed transport route; and (2) the convergence of this route with a sphingolipid-dependent apical trafficking path.
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Affiliation(s)
- Hongjie Zhang
- Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
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Affiliation(s)
- Mathew M Avram
- Department of Dermatology, Massachusetts General Hospital and Harvard Medical School, USA
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