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Zhao H, Shi L, Li Z, Kong R, Jia L, Lu S, Wang JH, Dong MQ, Guo X, Li Z. Diamond controls epithelial polarity through the dynactin-dynein complex. Traffic 2023; 24:552-563. [PMID: 37642208 DOI: 10.1111/tra.12917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 07/10/2023] [Accepted: 08/21/2023] [Indexed: 08/31/2023]
Abstract
Epithelial polarity is critical for proper functions of epithelial tissues, tumorigenesis, and metastasis. The evolutionarily conserved transmembrane protein Crumbs (Crb) is a key regulator of epithelial polarity. Both Crb protein and its transcripts are apically localized in epithelial cells. However, it remains not fully understood how they are targeted to the apical domain. Here, using Drosophila ovarian follicular epithelia as a model, we show that epithelial polarity is lost and Crb protein is absent in the apical domain in follicular cells (FCs) in the absence of Diamond (Dind). Interestingly, Dind is found to associate with different components of the dynactin-dynein complex through co-IP-MS analysis. Dind stabilizes dynactin and depletion of dynactin results in almost identical defects as those observed in dind-defective FCs. Finally, both Dind and dynactin are also required for the apical localization of crb transcripts in FCs. Thus our data illustrate that Dind functions through dynactin/dynein-mediated transport of both Crb protein and its transcripts to the apical domain to control epithelial apico-basal (A/B) polarity.
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Affiliation(s)
- Hang Zhao
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Lin Shi
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Zhengran Li
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Ruiyan Kong
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Lemei Jia
- National Institute of Biological Sciences (NIBS), Beijing, China
| | - Shan Lu
- National Institute of Biological Sciences (NIBS), Beijing, China
| | - Jian-Hua Wang
- National Institute of Biological Sciences (NIBS), Beijing, China
| | - Meng-Qiu Dong
- National Institute of Biological Sciences (NIBS), Beijing, China
| | - Xuan Guo
- Life Science Institute, Jinzhou Medical University, Jinzhou, Liaoning, China
| | - Zhouhua Li
- College of Life Sciences, Capital Normal University, Beijing, China
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2
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Zulueta Díaz YDLM, Kure JL, Grosso RA, Andersen C, Pandzic E, Sengupta P, Wiseman PW, Arnspang EC. Quantitative image mean squared displacement (iMSD) analysis of the dynamics of Aquaporin 2 within the membrane of live cells. Biochim Biophys Acta Gen Subj 2023; 1867:130449. [PMID: 37748662 DOI: 10.1016/j.bbagen.2023.130449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 08/22/2023] [Accepted: 08/25/2023] [Indexed: 09/27/2023]
Abstract
Nanodomains are a biological membrane phenomenon which have a large impact on various cellular processes. They are often analysed by looking at the lateral dynamics of membrane lipids or proteins. The localization of the plasma membrane protein aquaporin-2 in nanodomains has so far been unknown. In this study, we use total internal reflection fluorescence microscopy to image Madin-Darby Canine Kidney (MDCK) cells expressing aquaporin-2 tagged with mEos 3.2. Then, image mean squared displacement (iMSD) approach was used to analyse the diffusion of aquaporin-2, revealing that aquaporin-2 is confined within membrane nanodomains. Using iMSD analysis, we found that the addition of the drug forskolin increases the diffusion of aquaporin-2 within the confined domains, which is in line with previous studies. Finally, we observed an increase in the size of the membrane domains and the extent of trapping of aquaporin-2 after stimulation with forskolin.
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Affiliation(s)
| | - Jakob Lavrsen Kure
- Department of Green Technology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Rubén Adrián Grosso
- Department of Green Technology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Camilla Andersen
- Department of Green Technology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Elvis Pandzic
- Mark Wainwright Analytical Centre, Lowy Cancer Research Centre C25, University of New South Wales, NSW, 2052, Australia
| | - Prabuddha Sengupta
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA; Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Paul W Wiseman
- Department of Chemistry, McGill University, Montreal, Québec, Canada; Department of Physics, McGill University, Montreal, Québec, Canada
| | - Eva C Arnspang
- Department of Green Technology, University of Southern Denmark, 5230 Odense M, Denmark; The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
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3
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Ebnet K, Gerke V. Rho and Rab Family Small GTPases in the Regulation of Membrane Polarity in Epithelial Cells. Front Cell Dev Biol 2022; 10:948013. [PMID: 35859901 PMCID: PMC9289151 DOI: 10.3389/fcell.2022.948013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 06/14/2022] [Indexed: 11/27/2022] Open
Abstract
Membrane polarity, defined as the asymmetric distribution of lipids and proteins in the plasma membrane, is a critical prerequisite for the development of multicellular tissues, such as epithelia and endothelia. Membrane polarity is regulated by polarized trafficking of membrane components to specific membrane domains and requires the presence of intramembrane diffusion barriers that prevent the intermixing of asymmetrically distributed membrane components. This intramembrane diffusion barrier is localized at the tight junctions (TJs) in these cells. Both the formation of cell-cell junctions and the polarized traffic of membrane proteins and lipids are regulated by Rho and Rab family small GTPases. In this review article, we will summarize the recent developments in the regulation of apico-basal membrane polarity by polarized membrane traffic and the formation of the intramembrane diffusion barrier in epithelial cells with a particular focus on the role of Rho and Rab family small GTPases.
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Affiliation(s)
- Klaus Ebnet
- Institute-Associated Research Group: Cell Adhesion and Cell Polarity, Institute of Medical Biochemistry, ZMBE, University of Münster, Münster, Germany
- Interdisciplinary Clinical Research Center (IZKF), University of Münster, Münster, Germany
- Cells-In-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
- *Correspondence: Klaus Ebnet, ; Volker Gerke,
| | - Volker Gerke
- Institute-Associated Research Group: Cell Adhesion and Cell Polarity, Institute of Medical Biochemistry, ZMBE, University of Münster, Münster, Germany
- Interdisciplinary Clinical Research Center (IZKF), University of Münster, Münster, Germany
- Cells-In-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
- *Correspondence: Klaus Ebnet, ; Volker Gerke,
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4
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Wang X, Li X, Wang J, Wang J, Hu C, Zeng J, Shi A, Lin L. SMGL-1/NBAS acts as a RAB-8 GEF to regulate unconventional protein secretion. J Cell Biol 2022; 221:213235. [PMID: 35604368 PMCID: PMC9129922 DOI: 10.1083/jcb.202111125] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 04/13/2022] [Accepted: 05/04/2022] [Indexed: 01/07/2023] Open
Abstract
Unconventional protein secretion (UPS) pathways are conserved across species. However, the underlying mechanisms that regulate Golgi-bypassing UPS of integral proteins remain elusive. In this study, we show that RAB-8 and SMGL-1/NBAS are required for the UPS of integral proteins in C. elegans intestine. SMGL-1 resides in the ER-Golgi intermediate compartment and adjacent RAB-8-positive structures, and NRZ complex component CZW-1/ZW10 is required for this residency. Notably, SMGL-1 acts as a guanine nucleotide exchange factor for RAB-8, ensuring UPS of integral proteins by driving the activation of RAB-8. Furthermore, we show that Pseudomonas aeruginosa infection elevated the expression of SMGL-1 and RAB-8. Loss of SMGL-1 or RAB-8 compromised resistance to environmental colchicine, arsenite, and pathogenic bacteria. These results suggest that the SMGL-1/RAB-8-mediated UPS could integrate environmental signals to serve as a host defense response. Together, by establishing the C. elegans intestine as a multicellular model, our findings provide insights into RAB-8-dependent Golgi-bypassing UPS, especially in the context of epithelia in vivo.
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Affiliation(s)
- Xianghong Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xinxin Li
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Junkai Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jiabin Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Can Hu
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jia Zeng
- Department of Biochemistry and Molecular Biology, Guizhou Medical University, Guiyang, Guizhou, China
| | - Anbing Shi
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China,Cell Architecture Research Center, Huazhong University of Science and Technology, Wuhan, Hubei, China,Correspondence to Anbing Shi:
| | - Long Lin
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China,Cell Architecture Research Center, Huazhong University of Science and Technology, Wuhan, Hubei, China,Long Lin:
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5
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Peterson RJ, Koval M. Above the Matrix: Functional Roles for Apically Localized Integrins. Front Cell Dev Biol 2021; 9:699407. [PMID: 34485286 PMCID: PMC8414885 DOI: 10.3389/fcell.2021.699407] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 07/23/2021] [Indexed: 12/14/2022] Open
Abstract
Integrins are transmembrane proteins that are most typically thought of as integrating adhesion to the extracellular matrix with intracellular signaling and cell regulation. Traditionally, integrins are found at basolateral and lateral cell surfaces where they facilitate binding to the ECM and intercellular adhesion through cytosolic binding partners that regulate organization of actin microfilaments. However, evidence is accumulating that integrins also are apically localized, either endogenously or due to an exogenous stimulus. Apically localized integrins have been shown to regulate several processes by interacting with proteins such as connexins, tight junction proteins, and polarity complex proteins. Integrins can also act as receptors to mediate endocytosis. Here we review these newly appreciated roles for integrins localized to the apical cell surface.
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Affiliation(s)
- Raven J Peterson
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA, United States
| | - Michael Koval
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA, United States.,Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
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6
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Tang BL. Defects in early secretory pathway transport machinery components and neurodevelopmental disorders. Rev Neurosci 2021; 32:851-869. [PMID: 33781010 DOI: 10.1515/revneuro-2021-0020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 03/12/2021] [Indexed: 12/23/2022]
Abstract
The early secretory pathway, provisionally comprising of vesicular traffic between the endoplasmic reticulum (ER) and the Golgi apparatus, occurs constitutively in mammalian cells. Critical for a constant supply of secretory and plasma membrane (PM) materials, the pathway is presumably essential for general cellular function and survival. Neurons exhibit a high intensity in membrane dynamics and protein/lipid trafficking, with differential and polarized trafficking towards the somatodendritic and axonal PM domains. Mutations in genes encoding early secretory pathway membrane trafficking machinery components are known to result in neurodevelopmental or neurological disorders with disease manifestation in early life. Here, such rare disorders associated with autosomal recessive mutations in coat proteins, membrane tethering complexes and membrane fusion machineries responsible for trafficking in the early secretory pathway are summarily discussed. These mutations affected genes encoding subunits of coat protein complex I and II, subunits of transport protein particle (TRAPP) complexes, members of the YIP1 domain family (YIPF) and a SNAP receptor (SNARE) family member. Why the ubiquitously present and constitutively acting early secretory pathway machinery components could specifically affect neurodevelopment is addressed, with the plausible underlying disease etiologies and neuropathological mechanisms resulting from these mutations explored.
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Affiliation(s)
- Bor Luen Tang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 8 Medical Drive, Singapore117597, Singapore
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7
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Su A, Fu Y, Meens J, Yang W, Meng F, Herrler G, Becher P. Infection of polarized bovine respiratory epithelial cells by bovine viral diarrhea virus (BVDV). Virulence 2021; 12:177-187. [PMID: 33300445 PMCID: PMC7801128 DOI: 10.1080/21505594.2020.1854539] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Bovine viral diarrhea virus (BVDV) is affecting cattle populations all over the world causing acute disease, immunosuppressive effects, respiratory diseases, gastrointestinal, and reproductive failure in cattle. The virus is taken up via the oronasal route and infection of epithelial and immune cells contributes to the dissemination of the virus throughout the body. However, it is not known how the virus gets across the barrier of epithelial cells encountered in the airways. Here, we analyzed the infection of polarized primary bovine airway epithelial cells (BAEC). Infection of BAEC by a non-cytopathogenic BVDV was possible via both the apical and the basolateral plasma membrane, but the infection was most efficient when the virus was applied to the basolateral plasma membrane. Irrespective of the site of infection, BVDV was efficiently released to the apical site, while only minor amounts of virus were detected in the basal medium. This indicates that the respiratory epithelium can release large amounts of BVDV to the environment and susceptible animals via respiratory fluids and aerosols, but BVDV cannot cross the airway epithelial cells to infect subepithelial cells and establish systemic infection. Further experiments showed that the receptor, bovine CD46, for BVDV is expressed predominantly on the apical membrane domain of the polarized epithelial cells. In a CD46 blocking experiment, the addition of an antibody directed against CD46 almost completely inhibited apical infection, whereas basolateral infection was not affected. While CD46 serves as a receptor for apical infection of BAEC by BVDV, the receptor for basolateral infection remains to be elucidated.
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Affiliation(s)
- Ang Su
- Department of Infectious Diseases, Institute of Virology, University of Veterinary Medicine Hannover, Foundation , Hannover, Germany
| | - Yuguang Fu
- State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences , Lanzhou, China
| | - Jochen Meens
- Institute of Microbiology, University of Veterinary Medicine Hannover, Foundation , Hannover, Germany
| | - Wei Yang
- Department of Infectious Diseases, Institute of Virology, University of Veterinary Medicine Hannover, Foundation , Hannover, Germany.,College of Veterinary Medicine, Northeast Agricultural University , Harbin, China
| | - Fandan Meng
- Department of Infectious Diseases, Institute of Virology, University of Veterinary Medicine Hannover, Foundation , Hannover, Germany.,State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences , Harbin, China
| | - Georg Herrler
- Department of Infectious Diseases, Institute of Virology, University of Veterinary Medicine Hannover, Foundation , Hannover, Germany
| | - Paul Becher
- Department of Infectious Diseases, Institute of Virology, University of Veterinary Medicine Hannover, Foundation , Hannover, Germany
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8
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Sogawa A, Takahashi I, Kyo M, Imaizumi-Anraku H, Tajima S, Nomura M. Requirements of Qa-SNARE LjSYP132s for Nodulation and Seed Development in Lotus japonicus. PLANT & CELL PHYSIOLOGY 2020; 61:1750-1759. [PMID: 32706881 DOI: 10.1093/pcp/pcaa099] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 07/16/2020] [Indexed: 06/11/2023]
Abstract
SNAREs (soluble N-ethyl maleimide-sensitive factor attachment protein receptors) mediate membrane fusion of vesicle transport in eukaryotic cells. LjSYP132s are the members of Qa-SNAREs in Lotus japonicus. Two isoforms, LjSYP132a and LjSYP132b, are generated by alternative splicing. Immunoblot analysis detected strong expression of LjSYP132s in infected root nodules and seeds by posttranscriptional modification. In either LjSYP132a or LjSYP132b silenced roots (RNAi-LjSYP132a, RNAi-LjSYP132b), the infection thread (IT) was not elongated, suggesting that both LjSYP132a and LjSYP132b have a role in IT progression. The results were consistent with the data of qRT-PCR showing that both genes were expressed at the early stage of infection. However, during the nodulation, only LjSYP132a was induced. LjSYP132s protein was observed in the Mesorhizobium loti-inoculated roots of mutants, nfr1, castor and pollux, suggesting that LjSYP132s can be induced without Nod factor signaling. Accumulation of LjSYP132s in the peribacteroid membrane suggests the function of not only IT formation but also nutrient transport. In contrast, qRT-PCR showed that LjSYP132b was expressed in the seeds. A stable transgenic plant of LjSYP132b, R132b, was produced by RNAi silencing. In the R132b plants, small pods with a few seeds and abnormal tip growth of the pollen tubes were observed, suggesting that LjSYP132b has a role in pollen tube growth and nutrient transport in the plasma membrane of seeds.
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Affiliation(s)
- Aoi Sogawa
- Faculty of Agriculture, Kagawa University, Miki, Kita, Kagawa, 761-0795 Japan
| | - Issei Takahashi
- Faculty of Agriculture, Kagawa University, Miki, Kita, Kagawa, 761-0795 Japan
| | - Masaharu Kyo
- Faculty of Agriculture, Kagawa University, Miki, Kita, Kagawa, 761-0795 Japan
| | - Haruko Imaizumi-Anraku
- Institute of Agrobiological Sciences, NARO, 3-1-3 Kannon-dai, Tsukuba, Ibaraki, 305-8604 Japan
| | - Shigeyuki Tajima
- Faculty of Agriculture, Kagawa University, Miki, Kita, Kagawa, 761-0795 Japan
| | - Mika Nomura
- Faculty of Agriculture, Kagawa University, Miki, Kita, Kagawa, 761-0795 Japan
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9
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Patil H, Hughes KR, Lemgruber L, Philip N, Dickens N, Starnes GL, Waters AP. Zygote morphogenesis but not the establishment of cell polarity in Plasmodium berghei is controlled by the small GTPase, RAB11A. PLoS Pathog 2020; 16:e1008091. [PMID: 32463831 PMCID: PMC7255598 DOI: 10.1371/journal.ppat.1008091] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 02/29/2020] [Indexed: 11/19/2022] Open
Abstract
Plasmodium species are apicomplexan parasites whose zoites are polarized cells with a marked apical organisation where the organelles associated with host cell invasion and colonization reside. Plasmodium gametes mate in the mosquito midgut to form the spherical and presumed apolar zygote that morphs during the following 24 hours into a polarized, elongated and motile zoite form, the ookinete. Endocytosis-mediated protein transport is generally necessary for the establishment and maintenance of polarity in epithelial cells and neurons, and the small GTPase RAB11A is an important regulator of protein transport via recycling endosomes. PbRAB11A is essential in blood stage asexual of Plasmodium. Therefore, a promoter swap strategy was employed to down-regulate PbRAB11A expression in gametocytes and zygotes of the rodent malaria parasite, Plasmodium berghei which demonstrated the essential role of RAB11A in ookinete development. The approach revealed that lack of PbRAB11A had no effect on gamete production and fertility rates however, the zygote to ookinete transition was almost totally inhibited and transmission through the mosquito was prevented. Lack of PbRAB11A did not prevent meiosis and mitosis, nor the establishment of polarity as indicated by the correct formation and positioning of the Inner Membrane Complex (IMC) and apical complex. However, morphological maturation was prevented and parasites remained spherical and immotile and furthermore, they were impaired in the secretion and distribution of microneme cargo. The data are consistent with the previously proposed model of RAB11A endosome mediated delivery of plasma membrane in Toxoplasma gondii if not its role in IMC formation and implicate it in microneme function.
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Affiliation(s)
- Harshal Patil
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Katie R. Hughes
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Leandro Lemgruber
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Nisha Philip
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Nicholas Dickens
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - G. Lucas Starnes
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Andrew. P. Waters
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, Scotland, United Kingdom
- * E-mail:
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10
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Duan Y, Guo Q, Zhang T, Meng Y, Sun D, Luo G, Liu Y. Cyclin-dependent kinase-mediated phosphorylation of the exocyst subunit Exo84 in late G 1 phase suppresses exocytic secretion and cell growth in yeast. J Biol Chem 2019; 294:11323-11332. [PMID: 31171719 DOI: 10.1074/jbc.ra119.008591] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2019] [Revised: 05/10/2019] [Indexed: 12/22/2022] Open
Abstract
In eukaryotic cells, the growth rate is strictly regulated for proper progression of the cell cycle. In the budding yeast Saccharomyces cerevisiae, it was previously shown that cell growth dramatically slows down when the cells start budding at the G1/S transition. However, the molecular mechanism for this G1/S-associated growth arrest is unclear. In this study, using exocytic secretion, cyclin-dependent kinase (CDK) assay, immunoprecipitation, and microscopy, we demonstrate that the exocyst subunit Exo84, which is known to be phosphorylated in mitosis, can also be phosphorylated directly by Cdk1 in the late G1 phase. Of note, we found that the Cdk1-mediated Exo84 phosphorylation impairs exocytic secretion in the late G1 phase. Using conditional cdc mutants and phosphodeficient and phosphomimetic exo84 mutants, we further observed that Cdk1-phosphoryated Exo84 inhibits the exocyst complex assembly, exocytic secretion, and cell growth, which may be important for proper execution of the G1/S-phase transition before commitment to a complete cell cycle. Our results suggest that the direct Cdk1-mediated regulation of the exocyst complex critically contributes to the coordination of cell growth and cell cycle progression.
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Affiliation(s)
- Yuran Duan
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang 110122, China
| | - Qingguo Guo
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang 110122, China
| | - Tianrui Zhang
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang 110122, China
| | - Yuan Meng
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang 110122, China
| | - Dong Sun
- Institute of Translational Medicine, China Medical University, Shenyang 110122, China
| | - Guangzuo Luo
- Institute of Translational Medicine, China Medical University, Shenyang 110122, China
| | - Ying Liu
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang 110122, China
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11
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Zhang T, Sun D, Luo G, Liu Y. Spatial and Translational Regulation of Exocyst Subunits by Cell Cycle in Budding Yeast. Med Sci Monit 2019; 25:4059-4067. [PMID: 31150370 PMCID: PMC6559343 DOI: 10.12659/msm.914194] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Previous studies have shown that exocyst complex is located at polarized growth sites at different cell cycle stages in budding yeast. But how cell cycle and the cyclin-dependent kinase, Cdk1, regulate the distribution of exocyst complex on the plasma membrane and the protein level of each exocyst subunit is not clear. MATERIAL AND METHODS Using budding yeast as a research material, regulation of cell cycle and Cdk1 on exocyst localization on the plasma membrane and on level of each exocyst subunit were examined by methods of cell biology and molecular biology. RESULTS Exocyst complex is located at growth sites on the plasma membrane in both budding and non-budding stages. Cdk1 activity is required for polarized distribution of exocyst complex in late G1, S and M phases, but not in cytokinesis stage. Cdk1 is not required for the assembly and localization of exocyst complex on plasma membrane. The protein level of Sec3 but not other exocyst subunits is regulated by the cell cycle. CONCLUSIONS Cdk1 activity is required for exocyst polarization before cytokinesis during the cell cycle progression, but not for its assembly and localization on the plasma membrane. Dynamic localization and protein level of the complex subunits are regulated by the cell cycle.
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Affiliation(s)
- Tianrui Zhang
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang, Liaoning, China (mainland)
| | - Dong Sun
- Institute of Translational Research, China Medical University, Shenyang, Liaoning, China (mainland)
| | - Guangzuo Luo
- Institute of Translational Research, China Medical University, Shenyang, Liaoning, China (mainland)
| | - Ying Liu
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang, Liaoning, China (mainland)
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12
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Arnspang EC, Login FH, Koffman JS, Sengupta P, Nejsum LN. AQP2 Plasma Membrane Diffusion Is Altered by the Degree of AQP2-S256 Phosphorylation. Int J Mol Sci 2016; 17:ijms17111804. [PMID: 27801846 PMCID: PMC5133805 DOI: 10.3390/ijms17111804] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 09/15/2016] [Accepted: 09/22/2016] [Indexed: 01/21/2023] Open
Abstract
Fine tuning of urine concentration occurs in the renal collecting duct in response to circulating levels of arginine vasopressin (AVP). AVP stimulates intracellular cAMP production, which mediates exocytosis of sub-apical vesicles containing the water channel aquaporin-2 (AQP2). Protein Kinase A (PKA) phosphorylates AQP2 on serine-256 (S256), which triggers plasma membrane accumulation of AQP2. This mediates insertion of AQP2 into the apical plasma membrane, increasing water permeability of the collecting duct. AQP2 is a homo-tetramer. When S256 on all four monomers is changed to the phosphomimic aspartic acid (S256D), AQP2-S256D localizes to the plasma membrane and internalization is decreased. In contrast, when S256 is mutated to alanine (S256A) to mimic non-phosphorylated AQP2, AQP2-S256A localizes to intracellular vesicles as well as the plasma membrane, with increased internalization from the plasma membrane. S256 phosphorylation is not necessary for exocytosis and dephosphorylation is not necessary for endocytosis, however, the degree of S256 phosphorylation is hypothesized to regulate the kinetics of AQP2 endocytosis and thus, retention time in the plasma membrane. Using k-space Image Correlation Spectroscopy (kICS), we determined how the number of phosphorylated to non-phosphorylated S256 monomers in the AQP2 tetramer affects diffusion speed of AQP2 in the plasma membrane. When all four monomers mimicked constitutive phosphorylation (AQP2-S256D), diffusion was faster than when all four were non-phosphorylated (AQP2-S256A). AQP2-WT diffused at a speed similar to that of AQP2-S256D. When an average of two or three monomers in the tetramer were constitutively phosphorylated, the average diffusion coefficients were not significantly different to that of AQP2-S256D. However, when only one monomer was phosphorylated, diffusion was slower and similar to AQP2-S256A. Thus, AQP2 with two to four phosphorylated monomers has faster plasma membrane kinetics, than the tetramer which contains just one or no phosphorylated monomers. This difference in diffusion rate may reflect behavior of AQP2 tetramers destined for either plasma membrane retention or endocytosis.
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Affiliation(s)
- Eva C Arnspang
- Department of Clinical Medicine, Aarhus University, DK-8000 Aarhus C, Denmark.
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Frédéric H Login
- Department of Clinical Medicine, Aarhus University, DK-8000 Aarhus C, Denmark.
| | - Jennifer S Koffman
- Department of Interdisciplinary Nanoscience Center, Aarhus University, DK-8000 Aarhus C, Denmark.
| | - Prabuddha Sengupta
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Lene N Nejsum
- Department of Clinical Medicine, Aarhus University, DK-8000 Aarhus C, Denmark.
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13
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Głogocka D, Przybyło M, Langner M. Molecular machines - a new dimension of biological sciences. Cell Mol Biol Lett 2015. [PMID: 26204406 DOI: 10.1515/cmble-2015-0014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Biological systems are characterized by directional and precisely controlled flow of matter and information along with the maintenance of their structural patterns. This is possible thanks to sequential transformations of information, energy and structure carried out by molecular machines. The new perception of biological systems, including their mechanical aspects, requires the implementation of tools and approaches previously developed for engineering sciences. In this review paper, a biological system is presented in a new perspective as an ensemble of coordinated molecular devices functioning in the limited space confined by the biological membrane. The working of a molecular machine is presented using the example of F0F1 ATPase, and the general conditions necessary for the coordination of a large number of functional units are described.
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14
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McLatchie LM, Fry CH. ATP release from freshly isolated guinea-pig bladder urothelial cells: a quantification and study of the mechanisms involved. BJU Int 2015; 115:987-93. [PMID: 25307747 DOI: 10.1111/bju.12954] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVES To quantify the amount of ATP released from freshly isolated bladder urothelial cells, study its control by intracellular and extracellular calcium and identify the pathways responsible for its release. MATERIALS AND METHODS Urothelial cells were isolated from male guinea-pig urinary bladders and stimulated to release ATP by imposition of drag forces by repeated pipetting. ATP was measured using a luciferin-luciferase assay and the effects of modifying internal and external calcium concentration and blockers of potential release pathways studied. RESULTS Freshly isolated guinea-pig urothelial cells released ATP at a mean (sem) rate of 1.9 (0.1) pmoles/mm(2) cell membrane, corresponding to about 700 pmoles/g of tissue, and about half [49 (6)%, n = 9) of the available cell ATP. This release was reduced to a mean (sem) of 0.46 (0.08) pmoles/mm(2) (160 pmoles/g) with 1.8 mm external calcium, and was increased about two-fold by increasing intracellular calcium. The release from umbrella cells was not significantly different from a mixed intermediate and basal cell population, suggesting that all three groups of cells release a similar amount of ATP per unit area. ATP release was reduced by ≈ 50% by agents that block pannexin and connexin hemichannels. It is suggested that the remainder may involve vesicular release. CONCLUSIONS A significant fraction of cellular ATP is released from isolated urothelial cells by imposing drag forces that cause minimal loss of cell viability. This release involves multiple release pathways, including hemichannels and vesicular release.
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Affiliation(s)
- Linda M McLatchie
- Department of Biochemistry and Physiology, FHMS, University of Surrey, Guildford, UK
| | - Christopher H Fry
- Department of Physiology and Pharmacology, University of Bristol, Bristol, UK
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15
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16
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Li X, Iida M, Tada M, Watari A, Kawahigashi Y, Kimura Y, Yamashita T, Ishii-Watabe A, Uno T, Fukasawa M, Kuniyasu H, Yagi K, Kondoh M. Development of an anti-claudin-3 and -4 bispecific monoclonal antibody for cancer diagnosis and therapy. J Pharmacol Exp Ther 2014; 351:206-13. [PMID: 25118216 DOI: 10.1124/jpet.114.216911] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Most malignant tumors are derived from epithelium, and claudin (CLDN)-3 and CLDN-4 are frequently overexpressed in such tumors. Although antibodies have potential in cancer diagnostics and therapy, development of antibodies against CLDNs has been difficult because the extracellular domains of CLDNs are too small and there is high homology among human, rat, and mouse sequences. Here, we created a monoclonal antibody that recognizes human CLDN-3 and CLDN-4 by immunizing rats with a plasmid vector encoding human CLDN-4. A hybridoma clone that produced a rat monoclonal antibody recognizing both CLDN-3 and -4 (clone 5A5) was obtained from a hybridoma screen by using CLDN-3- and -4-expressing cells; 5A5 did not bind to CLDN-1-, -2-, -5-, -6-, -7-, or -9-expressing cells. Fluorescence-conjugated 5A5 injected into xenograft mice bearing human cancer MKN74 or LoVo cells could visualize the tumor cells. The human-rat chimeric IgG1 monoclonal antibody (xi5A5) activated FcγRIIIa in the presence of CLDN-3- or -4-expressing cells, indicating that xi5A5 may exert antibody-dependent cellular cytotoxicity. Administration of xi5A5 attenuated tumor growth in xenograft mice bearing MKN74 or LoVo cells. These results suggest that 5A5 shows promise in the development of a diagnostic and therapeutic antibody for cancers.
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Affiliation(s)
- Xiangru Li
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Manami Iida
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Minoru Tada
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Akihiro Watari
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Yumi Kawahigashi
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Yuka Kimura
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Taku Yamashita
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Akiko Ishii-Watabe
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Tadayuki Uno
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Masayoshi Fukasawa
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Hiroki Kuniyasu
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Kiyohito Yagi
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
| | - Masuo Kondoh
- Laboratories of Bio-Functional Molecular Chemistry (X.L., M.I., A.W., Y.Ka., Y.Ki., K.Y., M.K.) and Analytical Chemistry (T.Y., T.U.), Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan; Division of Biological Chemistry and Biologicals, National Institutes of Health Sciences, Tokyo, Japan (M.T., A.I.-W.); Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan (M.F.); and Department of Molecular Pathology, Nara Medical University, Nara, Japan (H.K.)
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Luo G, Zhang J, Luca FC, Guo W. Mitotic phosphorylation of Exo84 disrupts exocyst assembly and arrests cell growth. ACTA ACUST UNITED AC 2013; 202:97-111. [PMID: 23836930 PMCID: PMC3704991 DOI: 10.1083/jcb.201211093] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mitotic phosphorylation of Exo84 disrupts the assembly of the exocyst complex, thereby inhibiting exocytosis of select secreted cargoes and cell surface expansion. The rate of eukaryotic cell growth is tightly controlled for proper progression through each cell cycle stage and is important for cell size homeostasis. It was previously shown that cell growth is inhibited during mitosis when cells are preparing for division. However, the mechanism for growth arrest at this stage is unknown. Here we demonstrate that exocytosis of a select group of cargoes was inhibited before the metaphase–anaphase transition in the budding yeast Saccharomyces cerevisiae. The cyclin-dependent kinase, Cdk1, when bound to the mitotic cyclin Clb2, directly phosphorylated Exo84, a component of the exocyst complex essential for exocytosis. Mitotic phosphorylation of Exo84 disrupted the assembly of the exocyst complex, thereby affecting exocytosis and cell surface expansion. Our study demonstrates the coordination between membrane trafficking and cell cycle progression and provides a molecular mechanism by which cell growth is controlled during the cell division cycle.
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Affiliation(s)
- Guangzuo Luo
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
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18
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Kuijpers M, Yu KL, Teuling E, Akhmanova A, Jaarsma D, Hoogenraad CC. The ALS8 protein VAPB interacts with the ER-Golgi recycling protein YIF1A and regulates membrane delivery into dendrites. EMBO J 2013; 32:2056-72. [PMID: 23736259 DOI: 10.1038/emboj.2013.131] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 05/07/2013] [Indexed: 02/06/2023] Open
Abstract
The vesicle-associated membrane protein (VAMP) associated protein B (VAPB) is an integral membrane protein localized to the endoplasmic reticulum (ER). The P56S mutation in VAPB has been linked to motor neuron degeneration in amyotrophic lateral sclerosis type 8 (ALS8) and forms ER-like inclusions in various model systems. However, the role of wild-type and mutant VAPB in neurons is poorly understood. Here, we identified Yip1-interacting factor homologue A (YIF1A) as a new VAPB binding partner and important component in the early secretory pathway. YIF1A interacts with VAPB via its transmembrane regions, recycles between the ER and Golgi and is mainly localized to the ER-Golgi intermediate compartments (ERGICs) in rat hippocampal neurons. VAPB strongly affects the distribution of YIF1A and is required for intracellular membrane trafficking into dendrites and normal dendritic morphology. When VAPB-P56S is present, YIF1A is recruited to the VAPB-P56S clusters and loses its ERGIC localization. These data suggest that both VAPB and YIF1A are important for ER-to-Golgi transport and that missorting of YIF1A may contribute to VAPB-associated motor neuron disease.
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Affiliation(s)
- Marijn Kuijpers
- Division of Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands
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19
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Abstract
In mammalian testes, the blood-testis barrier (BTB), created by specialized junctions between Sertoli cells near the basement membrane of the seminiferous epithelium, provides an indispensable immune-privileged microenvironment for spermatid development. However, the BTB must experience restructuring during the epithelial cycle to facilitate the transit of preleptotene spermatocytes upon the testosterone-induced new TJ fibrils forming behind these cells, which is intimately related to the extensive dynamics of junction protein complexes between Sertoli cells. As key regulators of protein traffic, Rab GTPases participate in delivery of proteins between distinct cellular sites and cross talk with proteins that constitute tight junction and adherens junction. Using primarily cultured Sertoli cells in vitro with an established tight junction permeability barrier that mimics the BTB in vivo, RAB13 was shown to decrease during the testosterone-induced TJ integrity enhancement, accompanied with an increment in protein kinase A (PKA) activity. Furthermore, knockdown of Rab13 was found to resemble the effect of testosterone on Sertoli cell TJ permeability by reinforcing filamentous actin and occludin distribution at the cell-cell interface and promoting the direct interaction between ZO-1 and occludin. Interestingly, the effects of testosterone and Rab13 knockdown on Sertoli cell epithelium were revealed to be antagonized by PKA activity inhibition. In summary, RAB13 serves as a regulatory component in the assembly and restructuring of the TJ fibrils between adjacent Sertoli cells.
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Affiliation(s)
- Wenhui Su
- Department of Biochemistry and Molecular Biology, Basic Medical College.
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20
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Effects of diet and development on the Drosophila lipidome. Mol Syst Biol 2013; 8:600. [PMID: 22864382 PMCID: PMC3421444 DOI: 10.1038/msb.2012.29] [Citation(s) in RCA: 186] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 06/25/2012] [Indexed: 12/12/2022] Open
Abstract
Cells produce tens of thousands of different lipid species, but the importance of this complexity in vivo is unclear. Analysis of individual tissues and cell types has revealed differences in abundance of individual lipid species, but there has been no comprehensive study comparing tissue lipidomes within a single developing organism. Here, we used quantitative shotgun profiling by high-resolution mass spectrometry to determine the absolute (molar) content of 250 species of 14 major lipid classes in 6 tissues of animals at 27 developmental stages raised on 4 different diets. Comparing these lipidomes revealed unexpected insights into lipid metabolism. Surprisingly, the fatty acids present in dietary lipids directly influence tissue phospholipid composition throughout the animal. Furthermore, Drosophila differentially regulates uptake, mobilization and tissue accumulation of specific sterols, and undergoes unsuspected shifts in fat metabolism during larval and pupal development. Finally, we observed striking differences between tissue lipidomes that are conserved between phyla. This study provides a comprehensive, quantitative and expandable resource for further pharmacological and genetic studies of metabolic disorders and molecular mechanisms underlying dietary response.
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Polarity protein complex Scribble/Lgl/Dlg and epithelial cell barriers. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 763:149-70. [PMID: 23397623 DOI: 10.1007/978-1-4614-4711-5_7] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The Scribble polarity complex or module is one of the three polarity modules that regulate cell polarity in multiple epithelia including blood-tissue barriers. This protein complex is composed of Scribble, Lethal giant larvae (Lgl) and Discs large (Dlg), which are well conserved across species from fruitflies and worms to mammals. Originally identified in Drosophila and C. elegans where the Scribble complex was found to work with the Par-based and Crumbs-based polarity modules to regulate apicobasal polarity and asymmetry in cells and tissues during embryogenesis, their mammalian homologs have all been identified in recent years. Components of the Scribble complex are known to regulate multiple cellular functions besides cell polarity, which include cell proliferation, assembly and maintenance of adherens junction (AJ) and tight junction (TJ), and they are also tumor suppressors. Herein, we provide an update on the Scribble polarity complex and how this protein complex modulates cell adhesion with some emphasis on its role in Sertoli cell blood-testis barrier (BTB) function. It should be noted that this is a rapidly developing field, in particular the role of this protein module in blood-tissue barriers, and this short chapter attempts to provide the information necessary for investigators studying reproductive biology and blood-tissue barriers to design future studies. We also include results of recent studies from flies and worms since this information will be helpful in planning experiments for future functional studies in the testis to understand how Scribble-based proteins regulate BTB dynamics and spermatogenesis.
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Abstract
Cell polarization is an evolutionarily conserved process that facilitates asymmetric distribution of organelles and proteins and that is modified dynamically during physiological processes such as cell division, migration, and morphogenesis. The plasticity with which cells change their behavior and phenotype in response to cell intrinsic and extrinsic cues is an essential feature of normal physiology. In disease states such as cancer, cells lose their ability to behave normally in response to physiological cues. A molecular understanding of mechanisms that alter the behavior of cancer cells is limited. Cell polarity proteins are a recognized class of molecules that can receive and interpret both intrinsic and extrinsic signals to modulate cell behavior. In this review, we discuss how cell polarity proteins regulate a diverse array of biological processes and how they can contribute to alterations in the behavior of cancer cells.
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Affiliation(s)
- Senthil K Muthuswamy
- Ontario Cancer Institute, Campbell Family Institute for Breast Cancer Research, University of Toronto, Toronto M5G 2M9, Canada.
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23
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Ren J, Guo W. ERK1/2 regulate exocytosis through direct phosphorylation of the exocyst component Exo70. Dev Cell 2012; 22:967-78. [PMID: 22595671 DOI: 10.1016/j.devcel.2012.03.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2011] [Revised: 01/23/2012] [Accepted: 03/14/2012] [Indexed: 11/30/2022]
Abstract
The exocyst is a multiprotein complex essential for exocytosis and plasma membrane remodeling. The assembly of the exocyst complex mediates the tethering of post-Golgi secretory vesicles to the plasma membrane prior to fusion. Elucidating the mechanisms regulating exocyst assembly is important for the understanding of exocytosis. Here we show that the exocyst component Exo70 is a direct substrate of the extracellular signal-regulated kinases 1/2 (ERK1/2). ERK1/2 phosphorylation enhances the binding of Exo70 to other exocyst components and promotes the assembly of the exocyst complex in response to epidermal growth factor (EGF) signaling. We further demonstrate that ERK1/2 regulates exocytosis, because blocking ERK1/2 signaling by a chemical inhibitor or the expression of an Exo70 mutant defective in ERK1/2 phosphorylation inhibited exocytosis. In tumor cells, blocking Exo70 phosphorylation inhibits matrix metalloproteinase secretion and invadopodia formation. ERK1/2 phosphorylation of Exo70 may thus coordinate exocytosis with other cellular events in response to growth factor signaling.
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Affiliation(s)
- Jinqi Ren
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
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Abstract
The polarized distribution of proteins and lipids at the surface membrane of epithelial cells results in the formation of an apical and a basolateral domain, which are separated by tight junctions. The generation and maintenance of epithelial polarity require elaborate mechanisms that guarantee correct sorting and vectorial delivery of cargo molecules. This dynamic process involves the interaction of sorting signals with sorting machineries and the formation of transport carriers. Here we review the recent advances in the field of polarized sorting in epithelial cells. We especially highlight the role of lipid rafts in apical sorting.
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25
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Mazzolini R, Dopeso H, Mateo-Lozano S, Chang W, Rodrigues P, Bazzocco S, Alazzouzi H, Landolfi S, Hernández-Losa J, Andretta E, Alhopuro P, Espín E, Armengol M, Tabernero J, Ramón y Cajal S, Kloor M, Gebert J, Mariadason JM, Schwartz S, Aaltonen LA, Mooseker MS, Arango D. Brush border myosin Ia has tumor suppressor activity in the intestine. Proc Natl Acad Sci U S A 2012; 109:1530-5. [PMID: 22307608 PMCID: PMC3277176 DOI: 10.1073/pnas.1108411109] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The loss of the epithelial architecture and cell polarity/differentiation is known to be important during the tumorigenic process. Here we demonstrate that the brush border protein Myosin Ia (MYO1A) is important for polarization and differentiation of colon cancer cells and is frequently inactivated in colorectal tumors by genetic and epigenetic mechanisms. MYO1A frame-shift mutations were observed in 32% (37 of 116) of the colorectal tumors with microsatellite instability analyzed, and evidence of promoter methylation was observed in a significant proportion of colon cancer cell lines and primary colorectal tumors. The loss of polarization/differentiation resulting from MYO1A inactivation is associated with higher tumor growth in soft agar and in a xenograft model. In addition, the progression of genetically and carcinogen-initiated intestinal tumors was significantly accelerated in Myo1a knockout mice compared with Myo1a wild-type animals. Moreover, MYO1A tumor expression was found to be an independent prognostic factor for colorectal cancer patients. Patients with low MYO1A tumor protein levels had significantly shorter disease-free and overall survival compared with patients with high tumoral MYO1A (logrank test P = 0.004 and P = 0.009, respectively). The median time-to-disease recurrence in patients with low MYO1A was 1 y, compared with >9 y in the group of patients with high MYO1A. These results identify MYO1A as a unique tumor-suppressor gene in colorectal cancer and demonstrate that the loss of structural brush border proteins involved in cell polarity are important for tumor development.
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Affiliation(s)
- Rocco Mazzolini
- Group of Molecular Oncology, and
- Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, 50018 Zaragoza, Spain
| | - Higinio Dopeso
- Group of Molecular Oncology, and
- Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, 50018 Zaragoza, Spain
| | - Silvia Mateo-Lozano
- Group of Molecular Oncology, and
- Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, 50018 Zaragoza, Spain
| | - Wakam Chang
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, 06520-8103 CT
| | - Paulo Rodrigues
- Group of Molecular Oncology, and
- Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, 50018 Zaragoza, Spain
| | | | | | | | | | - Elena Andretta
- Group of Molecular Oncology, and
- Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, 50018 Zaragoza, Spain
| | - Pia Alhopuro
- Department of Medical Genetics, Genome-Scale Biology Research Program, Biomedicum Helsinki, University of Helsinki, 00014 Helsinki, Finland
| | | | | | - Josep Tabernero
- Department of Medical Oncology, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain
| | | | - Matthias Kloor
- Department of Applied Tumor Biology, Institute of Pathology, University Hospital Heidelberg, 69120 Heidelberg, Germany; and
| | - Johannes Gebert
- Department of Applied Tumor Biology, Institute of Pathology, University Hospital Heidelberg, 69120 Heidelberg, Germany; and
| | - John M. Mariadason
- Ludwig Institute for Cancer Research, Melbourne Centre for Clinical Sciences, Austin Health, Heidelberg, Victoria 3084, Australia
| | - Simo Schwartz
- Group of Drug Delivery and Targeting, Centro de Investigaciones en Bioquímica y Biología Molecular-Nanomedicine, Vall d'Hebron University Hospital Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, 50018 Zaragoza, Spain
| | - Lauri A. Aaltonen
- Department of Medical Genetics, Genome-Scale Biology Research Program, Biomedicum Helsinki, University of Helsinki, 00014 Helsinki, Finland
| | - Mark S. Mooseker
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, 06520-8103 CT
| | - Diego Arango
- Group of Molecular Oncology, and
- Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, 50018 Zaragoza, Spain
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Ćurlin M, Kapuralin K, Muro AF, Baralle FE, Chowdhury K, Gajović S. Stam2 expression pattern during embryo development. Gene Expr Patterns 2012; 12:68-76. [DOI: 10.1016/j.gep.2011.11.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2011] [Revised: 11/19/2011] [Accepted: 11/21/2011] [Indexed: 10/14/2022]
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Fanning AS, Van Itallie CM, Anderson JM. Zonula occludens-1 and -2 regulate apical cell structure and the zonula adherens cytoskeleton in polarized epithelia. Mol Biol Cell 2011; 23:577-90. [PMID: 22190737 PMCID: PMC3279387 DOI: 10.1091/mbc.e11-09-0791] [Citation(s) in RCA: 178] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
ETOC: Our study reveals that ZO proteins in fully polarized cells regulate the assembly and contractility of the perijunctional actomyosin ring associated with the adherens junction. The structure and function of both adherens (AJ) and tight (TJ) junctions are dependent on the cortical actin cytoskeleton. The zonula occludens (ZO)-1 and -2 proteins have context-dependent interactions with both junction types and bind directly to F-actin and other cytoskeletal proteins, suggesting ZO-1 and -2 might regulate cytoskeletal activity at cell junctions. To address this hypothesis, we generated stable Madin-Darby canine kidney cell lines depleted of both ZO-1 and -2. Both paracellular permeability and the localization of TJ proteins are disrupted in ZO-1/-2–depleted cells. In addition, immunocytochemistry and electron microscopy revealed a significant expansion of the perijunctional actomyosin ring associated with the AJ. These structural changes are accompanied by a recruitment of 1-phosphomyosin light chain and Rho kinase 1, contraction of the actomyosin ring, and expansion of the apical domain. Despite these changes in the apical cytoskeleton, there are no detectable changes in cell polarity, localization of AJ proteins, or the organization of the basal and lateral actin cytoskeleton. We conclude that ZO proteins are required not only for TJ assembly but also for regulating the organization and functional activity of the apical cytoskeleton, particularly the perijunctional actomyosin ring, and we speculate that these activities are relevant both to cellular organization and epithelial morphogenesis.
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Affiliation(s)
- Alan S Fanning
- Department of Cell and Molecular Physiology and the Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7545, USA.
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Dolganiuc A. Role of lipid rafts in liver health and disease. World J Gastroenterol 2011; 17:2520-35. [PMID: 21633657 PMCID: PMC3103810 DOI: 10.3748/wjg.v17.i20.2520] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 02/24/2011] [Accepted: 03/03/2011] [Indexed: 02/06/2023] Open
Abstract
Liver diseases are an increasingly common cause of morbidity and mortality; new approaches for investigation of mechanisms of liver diseases and identification of therapeutic targets are emergent. Lipid rafts (LRs) are specialized domains of cellular membranes that are enriched in saturated lipids; they are small, mobile, and are key components of cellular architecture, protein partition to cellular membranes, and signaling events. LRs have been identified in the membranes of all liver cells, parenchymal and non-parenchymal; more importantly, LRs are active participants in multiple physiological and pathological conditions in individual types of liver cells. This article aims to review experimental-based evidence with regard to LRs in the liver, from the perspective of the liver as a whole organ composed of a multitude of cell types. We have gathered up-to-date information related to the role of LRs in individual types of liver cells, in liver health and diseases, and identified the possibilities of LR-dependent therapeutic targets in liver diseases.
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Chia PZC, Gleeson PA. The Regulation of Endosome-to-Golgi Retrograde Transport by Tethers and Scaffolds. Traffic 2011; 12:939-47. [DOI: 10.1111/j.1600-0854.2011.01185.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
IQGAP1, an effector of CDC42p GTPase, is a widely conserved, multifunctional protein that bundles F-actin through its N-terminus and binds microtubules through its C-terminus to modulate the cell architecture. It has emerged as a potential oncogene associated with diverse human cancers. Therefore, IQGAP1 has been heavily investigated; regardless, its precise cellular function remains unclear. Work from yeast suggests that IQGAP1 plays an important role in directed cell growth, which is a conserved feature crucial to morphogenesis, division axis, and body plan determination. New evidence suggests a conserved role for IQGAP1 in protein synthesis and membrane traffic, which may help to explain the diversity of its cellular functions. Membrane traffic mediates infections by intracellular pathogens and a range of degenerative human diseases arise from dysfunctions in intracellular traffic; thus, elucidating the mechanisms of cellular traffic will be important in order to understand the basis of a wide range of inherited and acquired human diseases. Recent evidence suggests that IQGAP1 plays its role in cell growth through regulating the conserved mTOR pathway. The mTOR signaling cascade has been implicated in membrane traffic and is activated in nearly all human cancers, but clinical response to the mTOR-specific inhibitor rapamycin has been disappointing. Thus, understanding the regulators of this pathway will be crucial in order to identify predictors of rapamycin sensitivity. In this review, I discuss emerging evidence that supports a potential role of IQGAP1 in regulating membrane traffic via regulating the mTOR pathway.
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Affiliation(s)
- Mahasin Osman
- Department of Molecular Pharmacology, Physiology and Biotechnology, Division of Biology and Medicine, Alpert School of Medicine, Brown University, Providence, RI, USA.
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31
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Wu H, Turner C, Gardner J, Temple B, Brennwald P. The Exo70 subunit of the exocyst is an effector for both Cdc42 and Rho3 function in polarized exocytosis. Mol Biol Cell 2010; 21:430-42. [PMID: 19955214 PMCID: PMC2814788 DOI: 10.1091/mbc.e09-06-0501] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Revised: 11/20/2009] [Accepted: 11/23/2009] [Indexed: 11/11/2022] Open
Abstract
The Rho3 and Cdc42 members of the Rho GTPase family are important regulators of exocytosis in yeast. However, the precise mechanism by which they regulate this process is controversial. Here, we present evidence that the Exo70 component of the exocyst complex is a direct effector of both Rho3 and Cdc42. We identify gain-of-function mutants in EXO70 that potently suppress mutants in RHO3 and CDC42 defective for exocytic function. We show that Exo70 has the biochemical properties expected of a direct effector for both Rho3 and Cdc42. Surprisingly, we find that C-terminal prenylation of these GTPases both promotes the interaction and influences the sites of binding within Exo70. Finally, we demonstrate that the phenotypes associated with novel loss-of-function mutants in EXO70, are entirely consistent with Exo70 as an effector for both Rho3 and Cdc42 function in secretion. These data suggest that interaction with the Exo70 component of the exocyst is a key event in spatial regulation of exocytosis by Rho GTPases.
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Affiliation(s)
- Hao Wu
- Departments of *Cell and Developmental Biology and
| | | | | | - Brenda Temple
- Biochemistry and Biophysics and R. L. Juliano Structural Bioinformatics Core, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7090
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Saunders M. Transplacental transport of nanomaterials. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2009; 1:671-84. [DOI: 10.1002/wnan.53] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Abstract
The formation of axons and dendrites and maintenance of the neuron's vastly expanded surface require the continuous addition of new membrane. This is achieved by membrane synthesis through the secretory pathway followed by regulated vesicle fusion with the plasma membrane, typically in the distal neurite. However, it is far from simple: multiple distinct membrane carriers are used to target specific membrane domains, dendrites seem to operate semi-autonomously from the rest of the neuron, and exocytosis for membrane expansion is different from that for release of synaptic vesicles. Current knowledge of this process and its implications for neuronal development, function and repair are reviewed.
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Gassama-Diagne A, Payrastre B. Phosphoinositide signaling pathways: promising role as builders of epithelial cell polarity. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 273:313-43. [PMID: 19215908 DOI: 10.1016/s1937-6448(08)01808-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Polarity is a prerequisite for proper development and function of epithelia in metazoa. The major feature of polarized epithelial cells is the presence of specialized domains with asymmetric distribution of macromolecular contents including proteins and lipids. The apical domain is involved in exchange with the organ lumen, and the basolateral membrane maintains contact with neighboring cells and the underlying extracellular matrix. The two domains are separated by tight junctions, which act as a diffusion barrier to prevent free mixing of domain-specific proteins and lipids. Extensive studies have shed light on the numerous protein families involved in cell polarization. However, many questions still remain regarding the molecular mechanisms of polarity regulation and in particular very little is known about the role of lipids in building polarity. In this chapter, essential determinants of epithelial polarity will be reviewed with a particular focus on metabolism and function of phosphoinositides.
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Affiliation(s)
- Ama Gassama-Diagne
- Unité Mixte INSERM U785/Université Paris XI, Centre Hépatobiliaire, Hôpital Paul Brousse, Villejuif, France
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35
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Protein kinase d regulates trafficking of dendritic membrane proteins in developing neurons. J Neurosci 2008; 28:9297-308. [PMID: 18784310 DOI: 10.1523/jneurosci.1879-08.2008] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
In non-neuronal cells, inactivation of protein kinase D (PKD) blocks fission of trans-Golgi network (TGN) transport carriers, inducing the appearance of long tubules filled with cargo. We now report on the function of PKD1 in neuronal protein trafficking. In cultured hippocampal pyramidal cells, the transferrin receptor (TfR) and the low-density receptor-related protein (LRP) are predominantly transported to dendrites and excluded from axons. Expression of kinase-inactive PKD1 or its depletion by RNA interference treatment dramatically and selectively alter the intracellular trafficking and membrane delivery of TfR- and LRP-containing vesicles, without inhibiting exit from the TGN or inducing Golgi tubulation. After PKD1 suppression, dendritic membrane proteins are mispackaged into carriers that transport VAMP2; these vesicles are distributed to both axons and dendrites, but are rapidly endocytosed from dendrites and preferentially delivered to the axonal membrane. A kinase-defective mutant of PKD1 lacking the ability to bind diacylglycerol and hence its Golgi localization does not cause missorting of TfR or LRP. These results suggest that in neurons PKD1 regulates TGN-derived sorting of dendritic proteins and hence has a role in neuronal polarity.
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Horne-Badovinac S, Bilder D. Dynein regulates epithelial polarity and the apical localization of stardust A mRNA. PLoS Genet 2008; 4:e8. [PMID: 18208331 PMCID: PMC2213700 DOI: 10.1371/journal.pgen.0040008] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Accepted: 11/27/2007] [Indexed: 11/19/2022] Open
Abstract
Intense investigation has identified an elaborate protein network controlling epithelial polarity. Although precise subcellular targeting of apical and basolateral determinants is required for epithelial architecture, little is known about how the individual determinant proteins become localized within the cell. Through a genetic screen for epithelial defects in the Drosophila follicle cells, we have found that the cytoplasmic Dynein motor is an essential regulator of apico–basal polarity. Our data suggest that Dynein acts through the cytoplasmic scaffolding protein Stardust (Sdt) to localize the transmembrane protein Crumbs, in part through the apical targeting of specific sdt mRNA isoforms. We have mapped the sdt mRNA localization signal to an alternatively spliced coding exon. Intriguingly, the presence or absence of this exon corresponds to a developmental switch in sdt mRNA localization in which apical transcripts are only found during early stages of epithelial development, while unlocalized transcripts predominate in mature epithelia. This work represents the first demonstration that Dynein is required for epithelial polarity and suggests that mRNA localization may have a functional role in the regulation of apico–basal organization. Moreover, we introduce a unique mechanism in which alternative splicing of a coding exon is used to control mRNA localization during development. Cells within epithelial sheets are highly polarized with distinct apical and basolateral membrane domains. This cellular organization is critical to both epithelial form and function, and a failure to maintain epithelial polarity is often linked to tumor progression. The protein network that establishes and maintains the two membrane domains relies on the precise subcellular localization of its molecular components, but little is known about how these proteins are targeted to their sites of action. We have shown that the localization of the apical determinant protein Stardust depends on the microtubule motor Dynein. While investigating the relationship between Dynein and Stardust, we also made two unexpected observations about stardust mRNA regulation. First, the mechanism by which Dynein localizes Stardust may depend, in part, on the apical targeting of the stardust mRNA. Second, some stardust mRNA is apically localized during early stages of epithelial development, but the selective removal of the apical localization signal leads to the sole production of uniformly localized transcripts in mature epithelial cells. Together, these results introduce roles for Dynein in apico–basal polarity regulation and raise important questions about the role of mRNA localization in the targeting of polarity determinant proteins and epithelial maturation.
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Affiliation(s)
- Sally Horne-Badovinac
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
| | - David Bilder
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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37
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Li Z, Wang L, Hays TS, Cai Y. Dynein-mediated apical localization of crumbs transcripts is required for Crumbs activity in epithelial polarity. ACTA ACUST UNITED AC 2008; 180:31-8. [PMID: 18195099 PMCID: PMC2213619 DOI: 10.1083/jcb.200707007] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Asymmetrical localization of transcripts coupled with localized translation constitutes an important mechanism widely deployed to regulate gene activity in a spatial manner. The conserved transmembrane protein Crumbs (Crb) is an important regulator of epithelial polarity. However, it remains unclear how Crb is targeted to the apical domain. Here, we show that the cytoplasmic dynein complex transports both Crb protein and transcripts to the apical domain of Drosophila melanogaster follicular cells (FCs). The crb 3′ untranslated region (UTR) is necessary and sufficient for the apical localization of its transcript and this apical transcript localization is crucial for crb function. In crb mutant FCs, Crb protein derived from transgenes lacking the 3′ UTR does not effectively localize to the apical domain and does not effectively restore normal epithelial polarity. We propose that dynein-mediated messenger RNA transport coupled with a localized translation mechanism is involved in localizing Crb to the apical domain to mediate epithelial apicobasal polarity and that this mechanism might be widely used to regulate cellular polarity.
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Affiliation(s)
- Zhouhua Li
- Temasek Lifesciences Laboratory, National University of Singapore, Singapore 117604
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38
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Influence of the M3-M4 intracellular domain upon nicotinic acetylcholine receptor assembly, targeting and function. Br J Pharmacol 2008; 153:1474-84. [PMID: 18204482 DOI: 10.1038/sj.bjp.0707676] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND AND PURPOSE The aim of this study was to investigate the influence of the intracellular domain of nicotinic acetylcholine receptor (nAChR) subunits upon receptor assembly, targeting and functional properties. EXPERIMENTAL APPROACH Because most nAChR subunits form functional receptors only as heteromeric complexes, it can be difficult to examine the influence of individual subunits or subunit domains in isolation. A series of subunit chimaeras was constructed which contain the intracellular loop region (located between the M3 and M4 transmembrane domains) from nAChR subunits alpha1-alpha10 or beta1-beta4. All of these chimaeras contain common extracellular and transmembrane domains (from the nAChR alpha7 subunit and the 5-hydroxytryptamine receptor 5-HT(3A) subunit, respectively), thereby facilitating both homomeric receptor assembly and detection with radiolabelled or fluorescent alpha-bungarotoxin. KEY RESULTS The nAChR M3-M4 intracellular loop domain had no significant effect upon levels of total subunit protein detected in transfected cells but had a significant influence upon levels of both cell surface and intracellular assembled receptors. Comparisons of functional properties revealed a significant influence of the intracellular loop domain upon both single-channel conductance and receptor desensitization. In addition, studies conducted in polarized epithelial cells demonstrate that the nAChR loop can influence receptor targeting, resulting in either polarized (apical) or non-polarized distribution. CONCLUSIONS AND IMPLICATIONS Evidence has been obtained which demonstrates that the large intracellular loop domain of nAChR subunits can exert a profound influence upon receptor assembly, targeting and ion channel properties.
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39
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Maier O, Hoekstra D, Baron W. Polarity Development in Oligodendrocytes: Sorting and Trafficking of Myelin Components. J Mol Neurosci 2008; 35:35-53. [DOI: 10.1007/s12031-007-9024-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2007] [Accepted: 11/13/2007] [Indexed: 12/15/2022]
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40
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Vagin O, Turdikulova S, Tokhtaeva E. Polarized membrane distribution of potassium-dependent ion pumps in epithelial cells: different roles of the N-glycans of their beta subunits. Cell Biochem Biophys 2007; 47:376-91. [PMID: 17652782 DOI: 10.1007/s12013-007-0033-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 10/23/2022]
Abstract
The Na,K-ATPases and the H,K-ATPases are two potassium-dependent homologous heterodimeric P2-type pumps that catalyze active transport of Na+ in exchange for K+ (Na,K-ATPase) or H+ in exchange for K+ (H,K-ATPase). The ubiquitous Na,K-ATPase maintains intracellular ion balance and membrane potential. The gastric H,K-ATPase is responsible for acid secretion by the parietal cell of the stomach. Both pumps consist of a catalytic alpha-subunit and a glycosylated beta-subunit that is obligatory for normal pump maturation and trafficking. Individual N-glycans linked to the beta-subunits of the Na,K-ATPase and H,K-ATPase are important for stable membrane integration of their respective alpha subunits, folding, stability, subunit assembly, and enzymatic activity of the pumps. They are also essential for the quality control of unassembled beta-subunits that results in either the exit of the subunits from the ER or their ER retention and subsequent degradation. Overall, the importance of N-glycans for the maturation and quality control of the H,K-ATPase is greater than that of the Na,K-ATPase. The roles of individual N-glycans of the beta-subunits in the post-ER trafficking, membrane targeting and plasma membrane retention of the Na,K-ATPase and H,K-ATPase are different. The Na,K-ATPase beta1-subunit is the major beta-subunit isoform in cells with lateral location of the pump. All three N-glycans of the Na,K-ATPase beta1-subunit are important for the lateral membrane retention of the pump due to glycan-mediated interaction between the beta1-subunits of the two neighboring cells in the cell monolayer and cytosolic linkage of the alpha-subunit to the cytoskeleton. This intercellular beta1-beta1 interaction is also important for formation of cell-cell contacts. In contrast, the N-glycans unique to the Na,K-ATPase beta2-subunit,which has up to eight N-glycosylation sites, contain apical sorting information. This is consistent with the apical location of the Na,K-ATPase in normal and malignant epithelial cells with high abundance of the beta2-subunit. Similarly, all seven N-glycans of the gastric H,K-ATPase beta-subunit determine apical sorting of this subunit.
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Affiliation(s)
- Olga Vagin
- Department of Physiology, School of Medicine, UCLA and Veterans Administration Greater Los Angeles Health Care System, VAGLAHS/West LA, Building 113, Room 324, 11301 Wilshire Blvd, Los Angeles, CA 90073, USA.
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41
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Abstract
The development of cancer is a multistep process in which the DNA of a single cell accumulates mutations in genes that control essential cellular processes. Loss of cell-cell adhesion and cell polarity is commonly observed in advanced tumours and correlates well with their invasion into adjacent tissues and the formation of metastases. Growing evidence indicates that loss of cell-cell adhesion and cell polarity may also be important in early stages of cancer. The strongest hints in this direction come from studies on tumour suppressor genes in the fruitfly Drosophila melanogaster, which have revealed their importance in the control of apical-basal cell polarity.
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Affiliation(s)
- Andreas Wodarz
- Department of Stem Cell Biology, DFG Research Center for Molecular Physiology of the Brain (CMPB), University of Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany.
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42
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Fasciotto BH, Kühn U, Cohn DV, Gorr SU. Secretory cargo composition affects polarized secretion in MDCK epithelial cells. Mol Cell Biochem 2007; 310:67-75. [PMID: 18049865 DOI: 10.1007/s11010-007-9666-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Accepted: 11/14/2007] [Indexed: 10/22/2022]
Abstract
Polarized epithelial cells secrete proteins at either the apical or basolateral cell surface. A number of non-epithelial secretory proteins also exhibit polarized secretion when they are expressed in polarized epithelial cells but it is difficult to predict where foreign proteins will be secreted in epithelial cells. The question is of interest since secretory epithelia are considered as target tissues for gene therapy protocols that aim to express therapeutic secretory proteins. In the parathyroid gland, parathyroid hormone is processed by furin and co-stored with chromogranin A in secretory granules. To test the secretion of these proteins in epithelial cells, they were expressed in MDCK cells. Chromogranin A and a secreted form of furin were secreted apically while parathyroid hormone was secreted 60% basolaterally. However, in the presence of chromogranin A, the secretion of parathyroid hormone was 65% apical, suggesting that chromogranin can act as a "sorting escort" (sorting chaperone) for parathyroid hormone. Conversely, apically secreted furin did not affect the sorting of parathyroid hormone. The apical secretion of chromogranin A was dependent on cholesterol, suggesting that this protein uses an established cellular sorting mechanism for apical secretion. However, this sorting does not involve the N-terminal membrane-binding domain of chromogranin A. These results suggest that foreign secretory proteins can be used as "sorting escorts" to direct secretory proteins to the apical secretory pathway without altering the primary structure of the secreted protein. Such a system may be of use in the targeted expression of secretory proteins from epithelial cells.
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Totong R, Achilleos A, Nance J. PAR-6 is required for junction formation but not apicobasal polarization in C. elegans embryonic epithelial cells. Development 2007; 134:1259-68. [PMID: 17314130 DOI: 10.1242/dev.02833] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Epithelial cells perform important roles in the formation and function of organs and the genesis of many solid tumors. A distinguishing feature of epithelial cells is their apicobasal polarity and the presence of apical junctions that link cells together. The interacting proteins Par-6 (a PDZ and CRIB domain protein) and aPKC (an atypical protein kinase C) localize apically in fly and mammalian epithelial cells and are important for apicobasal polarity and junction formation. Caenorhabditis elegans PAR-6 and PKC-3/aPKC also localize apically in epithelial cells, but a role for these proteins in polarizing epithelial cells or forming junctions has not been described. Here, we use a targeted protein degradation strategy to remove both maternal and zygotic PAR-6 from C. elegans embryos before epithelial cells are born. We find that PKC-3 does not localize asymmetrically in epithelial cells lacking PAR-6, apical junctions are fragmented, and epithelial cells lose adhesion with one another. Surprisingly, junction proteins still localize apically, indicating that PAR-6 and asymmetric PKC-3 are not needed for epithelial cells to polarize. Thus, whereas the role of PAR-6 in junction formation appears to be widely conserved, PAR-6-independent mechanisms can be used to polarize epithelial cells.
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Affiliation(s)
- Ronald Totong
- Skirball Institute of Biomolecular Medicine and NYU School of Medicine, 540 First Avenue, New York, NY 10016, USA
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44
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Mitra K, Frank J, Driessen A. Co- and post-translational translocation through the protein-conducting channel: analogous mechanisms at work? Nat Struct Mol Biol 2007; 13:957-64. [PMID: 17082791 DOI: 10.1038/nsmb1166] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many proteins are translocated across, or integrated into, membranes. Both functions are fulfilled by the 'translocon/translocase', which contains a membrane-embedded protein-conducting channel (PCC) and associated soluble factors that drive translocation and insertion reactions using nucleotide triphosphates as fuel. This perspective focuses on reinterpreting existing experimental data in light of a recently proposed PCC model comprising a front-to-front dimer of SecY or Sec61 heterotrimeric complexes. In this new framework, we propose (i) a revised model for SRP-SR-mediated docking of the ribosome-nascent polypeptide to the PCC; (ii) that the dynamic interplay between protein substrate, soluble factors and PCC controls the opening and closing of a transmembrane channel across, and/or a lateral gate into, the membrane; and (iii) that co- and post-translational translocation, involving the ribosome and SecA, respectively, not only converge at the PCC but also use analogous mechanisms for coordinating protein translocation.
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45
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Paladino S, Sarnataro D, Tivodar S, Zurzolo C. Oligomerization Is a Specific Requirement for Apical Sorting of Glycosyl-Phosphatidylinositol-Anchored Proteins but Not for Non-Raft-Associated Apical Proteins. Traffic 2006; 8:251-8. [PMID: 17233758 DOI: 10.1111/j.1600-0854.2006.00522.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Protein apical sorting in polarized epithelial cells is mediated by two different mechanisms, raft dependent and raft independent. In Madin-Darby canine kidney (MDCK) cells, an essential step for apical sorting of glycosyl-phosphatidylinositol (GPI)-anchored proteins (GPI-APs) is their coalescence into high-molecular-weight (HMW) oligomers. Here we show that this mechanism is also functional in Fischer rat thyroid cells, which possess a different sorting phenotype compared with MDCK cells. We demonstrate that, as in MDCK cells, both apical and basolateral GPI-APs associate with detergent-resistant microdomains, but that only the apical proteins are able to oligomerize into HMW complexes during their passage through the medial Golgi. We also show that oligomerization is a specific requirement for apical sorting of GPI-APs and is not used by transmembrane, non-raft-associated apical proteins.
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Affiliation(s)
- Simona Paladino
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli Federico II, Napoli 80131, Italy
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Wadskog I, Forsmark A, Rossi G, Konopka C, Öyen M, Goksör M, Ronne H, Brennwald P, Adler L. The yeast tumor suppressor homologue Sro7p is required for targeting of the sodium pumping ATPase to the cell surface. Mol Biol Cell 2006; 17:4988-5003. [PMID: 17005914 PMCID: PMC1679668 DOI: 10.1091/mbc.e05-08-0798] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The SRO7/SOP1 encoded tumor suppressor homologue of Saccharomyces cerevisiae is required for maintenance of ion homeostasis in cells exposed to NaCl stress. Here we show that the NaCl sensitivity of the sro7Delta mutant is due to defective sorting of Ena1p, the main sodium pump in yeast. On exposure of sro7Delta mutants to NaCl stress, Ena1p fails to be targeted to the cell surface, but is instead routed to the vacuole for degradation via the multivesicular endosome pathway. SRO7-deficient mutants accumulate post-Golgi vesicles at high salinity, in agreement with a previously described role for Sro7p in late exocytosis. However, Ena1p is not sorted into these post-Golgi vesicles, in contrast to what is observed for the vesicles that accumulate when exocytosis is blocked in sec6-4 mutants at high salinity. These observations imply that Sro7p has a previously unrecognized role for sorting of specific proteins into the exocytic pathway. Screening for multicopy suppressors identified RSN1, encoding a transmembrane protein of unknown function. Overexpression of RSN1 restores NaCl tolerance of sro7Delta mutants by retargeting Ena1p to the plasma membrane. We propose a model in which blocked exocytic sorting in sro7Delta mutants, gives rise to quality control-mediated routing of Ena1p to the vacuole.
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Affiliation(s)
- Ingrid Wadskog
- *Department of Cell and Molecular Biology, Microbiology, Göteborg University, SE-405 30 Göteborg, Sweden
| | - Annabelle Forsmark
- *Department of Cell and Molecular Biology, Microbiology, Göteborg University, SE-405 30 Göteborg, Sweden
| | - Guendalina Rossi
- Department of Cell and Developmental Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
| | - Catherine Konopka
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Mattias Öyen
- Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden
| | - Mattias Goksör
- Department of Physics, Göteborg University, SE-412 96 Göteborg, Sweden; and
| | - Hans Ronne
- Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden
- Department of Medical Biochemistry and Microbiology, Uppsala University, SE-751 23 Uppsala, Sweden
| | - Patrick Brennwald
- Department of Cell and Developmental Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
| | - Lennart Adler
- *Department of Cell and Molecular Biology, Microbiology, Göteborg University, SE-405 30 Göteborg, Sweden
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Kidd GJ, Yadav VK, Huang P, Brand SL, Low SH, Weimbs T, Trapp BD. A dual tyrosine-leucine motif mediates myelin protein P0 targeting in MDCK cells. Glia 2006; 54:135-45. [PMID: 16788992 DOI: 10.1002/glia.20366] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Differential targeting of myelin proteins to multiple, biochemically and functionally distinct Schwann cell plasma membrane domains is essential for myelin formation. In this study, we investigated whether the myelin protein P0 contains targeting signals using Madin-Darby canine kidney (MDCK) cells. By confocal microscopy, P0 was localized to MDCK cell basolateral membranes. C-terminal deletion resulted in apical accumulation, and stepwise deletions defined a 15-mer region that was required for basolateral targeting. Alanine substitutions within this region identified the YAML sequence as a functional tyrosine-based targeting signal, with the ML sequence serving as a secondary leucine-based signal. Replacement of the P0 ectodomain with green fluorescent protein altered the distribution of constructs lacking the YAML signal. Coexpression of the myelin-associated glycoprotein did not alter P0 distribution in MDCK cells. The results indicate that P0 contains a hierarchy of targeting signals, which may contribute to P0 localization in myelinating Schwann cells and the pathogenesis in human disease.
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Affiliation(s)
- Grahame J Kidd
- Department of Neurosciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
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Hodson CA, Ambrogi IG, Scott RO, Mohler PJ, Milgram SL. Polarized apical sorting of guanylyl cyclase C is specified by a cytosolic signal. Traffic 2006; 7:456-64. [PMID: 16536743 DOI: 10.1111/j.1600-0854.2006.00398.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Receptor guanylyl cyclases respond to ligand stimulation by increasing intracellular cGMP, thereby initiating a variety of cell-signaling pathways. Furthermore, these proteins are differentially localized at the apical and basolateral membranes of epithelial cells. We have identified a region of 11 amino acids in the cytosolic COOH terminus of guanylyl cyclase C (GCC) required for normal apical localization in Madin-Darby canine kidney (MDCK) cells. These amino acids share no significant sequence homology with previously identified cytosolic apical sorting determinants. However, these amino acids are highly conserved and are sufficient to confer apical polarity to the interleukin-2 receptor alpha-chain (Tac). Additionally, we find two molecular weight species of GCC in lysates prepared from MDCK cells over-expressing GCC but observe only the fully mature species on the cell surface. Using pulse-chase analysis in polarized MDCK cells, we followed the generation of this mature species over time finding it to be detectable only at the apical cell surface. These data support the hypothesis that selective apical sorting can be determined using short, cytosolic amino acid motifs and argue for the existence of apical sorting machinery comparable with the machinery identified for basolateral protein traffic.
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Affiliation(s)
- Caleb A Hodson
- Graduate Program in Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Grati M, Aggarwal N, Strehler EE, Wenthold RJ. Molecular determinants for differential membrane trafficking of PMCA1 and PMCA2 in mammalian hair cells. J Cell Sci 2006; 119:2995-3007. [PMID: 16803870 DOI: 10.1242/jcs.03030] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The plasma membrane Ca2+-ATPase-2 (PMCA2) is expressed in stereocilia of hair cells of the inner ear, whereas PMCA1 is expressed in the basolateral plasma membrane of hair cells. Both extrude excess Ca2+ from the cytosol. They are predicted to contain ten membrane-spanning segments, two large cytoplasmic loops as well as cytosolic N- and C-termini. Several isoform variants are generated for both PMCA1 and PMCA2 by alternative splicing, affecting their first cytosolic loop (A-site) and their C-terminal tail. To understand how these isoforms are differentially targeted in hair cells, we investigated their targeting regions and expression in hair cells. Our results show that a Leu-Ile motif in 'b'-tail splice variants promotes PMCA1b and PMCA2b basolateral sorting in hair cells. Moreover, apical targeting of PMCA2 depends on the size of the A-site-spliced insert, suggesting that the conformation of the cytoplasmic loop plays a role in apical targeting.
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Affiliation(s)
- M'hamed Grati
- Laboratory of Neurochemistry, National Institute on Deafness and other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
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Jakob V, Schreiner A, Tikkanen R, Starzinski-Powitz A. Targeting of transmembrane protein shrew-1 to adherens junctions is controlled by cytoplasmic sorting motifs. Mol Biol Cell 2006; 17:3397-408. [PMID: 16707570 PMCID: PMC1525240 DOI: 10.1091/mbc.e05-11-1034] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We recently identified transmembrane protein shrew-1 and showed that it is able to target to adherens junctions in polarized epithelial cells. This suggested shrew-1 possesses specific basolateral sorting motifs, which we analyzed by mutational analysis. Systematic mutation of amino acids in putative sorting signals in the cytoplasmic domain of shrew-1 revealed three tyrosines and a dileucine motif necessary for basolateral sorting. Substitution of these amino acids leads to apical localization of shrew-1. By applying tannic acid to either the apical or basolateral part of polarized epithelial cells, thereby blocking vesicle fusion with the plasma membrane, we obtained evidence that the apically localized mutants were primarily targeted to the basolateral membrane and were then redistributed to the apical domain. Further support for a postendocytic sorting mechanism of shrew-1 was obtained by demonstrating that mu1B, a subunit of the epithelial cell-specific adaptor complex AP-1B, interacts with shrew-1. In conclusion, our data provide evidence for a scenario where shrew-1 is primarily delivered to the basolateral membrane by a so far unknown mechanism. Once there, adaptor protein complex AP-1B is involved in retaining shrew-1 at the basolateral membrane by postendocytic sorting mechanisms.
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Affiliation(s)
- Viktor Jakob
- *Institute of Cell Biology and Neuroscience, Johann-Wolfgang Goethe University of Frankfurt, D-60323 Frankfurt am Main, Germany; and
| | - Alexander Schreiner
- *Institute of Cell Biology and Neuroscience, Johann-Wolfgang Goethe University of Frankfurt, D-60323 Frankfurt am Main, Germany; and
| | - Ritva Tikkanen
- Institute of Biochemistry II, University Clinic of Frankfurt, D-60590 Frankfurt am Main, Germany
| | - Anna Starzinski-Powitz
- *Institute of Cell Biology and Neuroscience, Johann-Wolfgang Goethe University of Frankfurt, D-60323 Frankfurt am Main, Germany; and
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