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El-Agamy SE, Guillaud L, Kono K, Wu Y, Terenzio M. FMRP Long-Range Transport and Degradation Are Mediated by Dynlrb1 in Sensory Neurons. Mol Cell Proteomics 2023; 22:100653. [PMID: 37739344 PMCID: PMC10625159 DOI: 10.1016/j.mcpro.2023.100653] [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: 02/10/2023] [Revised: 09/10/2023] [Accepted: 09/18/2023] [Indexed: 09/24/2023] Open
Abstract
The fragile X messenger ribonucleoprotein 1 (FMRP) is a multifunctional RNA-binding protein implicated in human neurodevelopmental and neurodegenerative disorders. FMRP mediates the localization and activity-dependent translation of its associated mRNAs through the formation of phase-separated condensates that are trafficked by microtubule-based motors in axons. Axonal transport and localized mRNA translation are critical processes for long-term neuronal survival and are closely linked to the pathogenesis of neurological diseases. FMRP dynein-mediated axonal trafficking is still largely unexplored but likely to constitute a key process underlying FMRP spatiotemporal translational regulation. Here, we show that dynein light chain roadblock 1 (Dynlrb1), a subunit of the dynein complex, is a critical regulator of FMRP function. In sensory axons, FMRP associates with endolysosomal organelles, likely through annexin A11, and is retrogradely trafficked by the dynein complex in a Dynlrb1-dependent manner. Moreover, Dynlrb1 silencing induced FMRP granule accumulation and repressed the translation of microtubule-associated protein 1b, one of its primary mRNA targets. Our findings suggest that Dynlrb1 regulates FMRP function through the control of its transport and targeted degradation.
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Affiliation(s)
- Sara Emad El-Agamy
- Molecular Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Kunigami-gun, Okinawa, Japan
| | - Laurent Guillaud
- Molecular Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Kunigami-gun, Okinawa, Japan
| | - Keiko Kono
- Membranology Unit, Okinawa Institute of Science and Technology Graduate University, Kunigami-gun, Okinawa, Japan
| | - Yibo Wu
- YCI Laboratory for Next-Generation Proteomics, RIKEN Center of Integrative Medical Sciences, Yokohama, Kanagawa, Japan; Chemical Biology Mass Spectrometry Platform (ChemBioMS), Faculty of Science, University of Geneva, Geneva, Switzerland
| | - Marco Terenzio
- Molecular Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Kunigami-gun, Okinawa, Japan.
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Rashid MA, Lin-Moshier Y, Gunaratne GS, Subramanian S, Marchant JS, Subramanian VS. Vitamin C transport in neurons and epithelia is regulated by secretory carrier-associated membrane protein-2 (SCAMP2). Int J Biol Macromol 2023; 230:123205. [PMID: 36632962 DOI: 10.1016/j.ijbiomac.2023.123205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 12/28/2022] [Accepted: 01/05/2023] [Indexed: 01/11/2023]
Abstract
The human sodium-dependent vitamin C transporter-1 (hSVCT1) is localized at the apical membrane domain of polarized intestinal and renal epithelial cells to mediate ascorbic acid (AA) uptake. Currently, little is known about the array of interacting proteins that aid hSVCT1 trafficking and functional expression at the cell surface. Here we used an affinity tagging ('One-STrEP') and proteomic approach to identify hSVCT1 interacting proteins, which resolved secretory carrier-associated membrane protein-2 (SCAMP2) as a novel accessary protein partner. SCAMP2 was validated as an accessory protein by co-immunoprecipitation with hSVCT1. Co-expression of hSVCT1 and SCAMP2 in HEK-293 cells revealed both proteins co-localized in intracellular structures and at the plasma membrane. Functionally, over-expression of SCAMP2 potentiated 14C-AA uptake, and reciprocally silencing endogenous SCAMP2 decreased 14C-AA uptake. Finally, knockdown of endogenous hSVCT1 or SCAMP2 impaired differentiation of human-induced pluripotent stem cells (hiPSCs) toward a neuronal fate. These results establish SCAMP2 as a novel hSVCT1 accessary protein partner that regulates AA uptake in absorptive epithelia and during neurogenesis.
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Affiliation(s)
- Mohammad A Rashid
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, WI 53226, United States
| | - Yaping Lin-Moshier
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, WI 53226, United States
| | - Gihan S Gunaratne
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, WI 53226, United States
| | - Sreya Subramanian
- Department of Medicine, University of California, Irvine, CA 92697, United States
| | - Jonathan S Marchant
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, WI 53226, United States
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Subramanian VS, Teafatiller T, Vidal J, Gunaratne GS, Rodriguez-Ortiz CJ, Kitazawa M, Marchant JS. Calsyntenin-3 interacts with the sodium-dependent vitamin C transporter-2 to regulate vitamin C uptake. Int J Biol Macromol 2021; 192:1178-1184. [PMID: 34673103 PMCID: PMC9842108 DOI: 10.1016/j.ijbiomac.2021.10.058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 10/07/2021] [Accepted: 10/08/2021] [Indexed: 01/19/2023]
Abstract
Ascorbic acid (AA) uptake in neurons occurs via a Na+-dependent carrier-mediated process mediated by the sodium-dependent vitamin C transporter-2 (SVCT2). Relatively little information is available concerning the network of interacting proteins that support human (h)SVCT2 trafficking and cell surface expression in neuronal cells. Here we identified the synaptogenic adhesion protein, calsyntenin-3 (CLSTN3) as an hSVCT2 interacting protein from yeast two-hybrid (Y2H) screening of a human adult brain cDNA library. This interaction was confirmed by co-immunoprecipitation, mammalian two-hybrid (M2H), and co-localization in human cell lines. Co-expression of hCLSTN3 with hSVCT2 in SH-SY5Y cells led to a marked increase in AA uptake. Reciprocally, siRNA targeting hCLSTN3 inhibited AA uptake. In the J20 mouse model of Alzheimer's disease (AD), mouse (m)SVCT2 and mCLSTN3 expression levels in hippocampus were decreased. Similarly, expression levels of hSVCT2 and hCLSTN3 were markedly decreased in hippocampal samples from AD patients. These findings establish CLSTN3 as a novel hSVCT2 interactor in neuronal cells with potential pathophysiological significance.
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Affiliation(s)
- Veedamali S. Subramanian
- Department of Medicine, University of California, Irvine, CA 92697, United States of America,Corresponding author. (V.S. Subramanian)
| | - Trevor Teafatiller
- Department of Medicine, University of California, Irvine, CA 92697, United States of America
| | - Janielle Vidal
- Department of Medicine, University of California, Irvine, CA 92697, United States of America,Department of Environmental and Occupational Health, University of California, Irvine, CA 92697, United States of America
| | - Gihan S. Gunaratne
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, United States of America
| | - Carlos J. Rodriguez-Ortiz
- Department of Medicine, University of California, Irvine, CA 92697, United States of America,Department of Environmental and Occupational Health, University of California, Irvine, CA 92697, United States of America
| | - Masashi Kitazawa
- Department of Medicine, University of California, Irvine, CA 92697, United States of America,Department of Environmental and Occupational Health, University of California, Irvine, CA 92697, United States of America
| | - Jonathan S. Marchant
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, United States of America
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Sabui S, Subramanian VS, Pham Q, Said HM. Identification of transmembrane protein 237 as a novel interactor with the intestinal riboflavin transporter-3 (RFVT-3): role in functionality and cell biology. Am J Physiol Cell Physiol 2019; 316:C805-C814. [PMID: 30892938 DOI: 10.1152/ajpcell.00029.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The apically localized riboflavin (RF) transporter-3 (RFVT-3) is involved in intestinal absorption of vitamin B2. Previous studies have characterized different physiological/biological aspects of the RFVT-3, but there is a lack of knowledge regarding possible existence of interacting partner(s) and consequence of interaction(s) on its function/cell biology. To address the latter, we performed yeast two-hybrid (Y2H) screening of a human colonic cDNA library and have identified transmembrane protein 237 (TMEM237) as a putative interactor with the human (h)RFVT-3; the interaction was further confirmed via "1-by-1" Y2H assay that involved appropriate positive and negative controls. TMEM237 was found to be highly expressed in human native intestine and in human intestinal epithelial cell lines; further, confocal images showed colocalization of the protein with hRFVT-3. The interaction between TMEM237 with hRFVT-3 in human intestinal epithelial HuTu-80 cells was established by coimmunoprecipitation. Expressing TMEM237 in HuTu-80 cells led to a significant induction in RF uptake, while its knockdown (with the use of gene-specific siRNA) led to a significant reduction in uptake. Transfecting TMEM237 into HuTu-80 cells also led to a marked enhancement in hRFVT-3 protein stability (reflected by an increase in the protein half-life). Interestingly, the level of expression of TMEM237 was found to be markedly reduced following treatment with TNF-α (a proinflammatory cytokine that inhibits intestinal RF uptake), while its expression was significantly upregulated following treatment with butyrate (an inducer of intestinal RF uptake). These findings identify TMEM237 as an interactor with the intestinal hRFVT-3 and show that the interaction has physiological/biological significance.
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Affiliation(s)
- Subrata Sabui
- Department of Physiology and Biophysics, School of Medicine, University of California , Irvine, California.,Department of Medicine, School of Medicine, University of California , Irvine, California.,Veterans Affairs Medical Center, Long Beach, California
| | - Veedamali S Subramanian
- Department of Physiology and Biophysics, School of Medicine, University of California , Irvine, California.,Department of Medicine, School of Medicine, University of California , Irvine, California.,Veterans Affairs Medical Center, Long Beach, California
| | - Quang Pham
- Department of Physiology and Biophysics, School of Medicine, University of California , Irvine, California
| | - Hamid M Said
- Department of Physiology and Biophysics, School of Medicine, University of California , Irvine, California.,Department of Medicine, School of Medicine, University of California , Irvine, California.,Veterans Affairs Medical Center, Long Beach, California
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Abstract
Nine compounds are classified as water-soluble vitamins, eight B vitamins and one vitamin C. The vitamins are mandatory for the function of numerous enzymes and lack of one or more of the vitamins may lead to severe medical conditions. All the vitamins are supplied by food in microgram to milligram quantities and in addition some of the vitamins are synthesized by the intestinal microbiota. In the gastrointestinal tract, the vitamins are liberated from binding proteins and for some of the vitamins modified prior to absorption. Due to their solubility in water, they all require specific carriers to be absorbed. Our current knowledge concerning each of the vitamins differs in depth and focus and is influenced by the prevalence of conditions and diseases related to lack of the individual vitamin. Because of that we have chosen to cover slightly different aspects for the individual vitamins. For each of the vitamins, we summarize the physiological role, the steps involved in the absorption, and the factors influencing the absorption. In addition, for some of the vitamins, the molecular base for absorption is described in details, while for others new aspects of relevance for human deficiency are included. © 2018 American Physiological Society. Compr Physiol 8:1291-1311, 2018.
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Affiliation(s)
- Hamid M Said
- University of California-School of Medicine, Irvine, California, USA.,VA Medical Center, Long Beach, California, USA
| | - Ebba Nexo
- Department of Clinical Medicine, Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
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6
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Islam MA, Sharif SR, Lee H, Seog DH, Moon IS. N-acetyl-D-glucosamine kinase interacts with dynein light-chain roadblock type 1 at Golgi outposts in neuronal dendritic branch points. Exp Mol Med 2015; 47:e177. [PMID: 26272270 PMCID: PMC4558486 DOI: 10.1038/emm.2015.48] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 03/23/2015] [Accepted: 04/10/2015] [Indexed: 11/09/2022] Open
Abstract
N-acetylglucosamine kinase (GlcNAc kinase or NAGK) is a ubiquitously expressed enzyme in mammalian cells. Recent studies have shown that NAGK has an essential structural, non-enzymatic role in the upregulation of dendritogenesis. In this study, we conducted yeast two-hybrid screening to search for NAGK-binding proteins and found a specific interaction between NAGK and dynein light-chain roadblock type 1 (DYNLRB1). Immunocytochemistry (ICC) on hippocampal neurons using antibodies against NAGK and DYNLRB1 or dynein heavy chain showed some colocalization, which was increased by treating the live cells with a crosslinker. A proximity ligation assay (PLA) of NAGK-dynein followed by tubulin ICC showed the localization of PLA signals on microtubule fibers at dendritic branch points. NAGK-dynein PLA combined with Golgi ICC showed the colocalization of PLA signals with somal Golgi facing the apical dendrite and with Golgi outposts in dendritic branch points and distensions. NAGK-Golgi PLA followed by tubulin or DYNLRB1 ICC showed that PLA signals colocalize with DYNLRB1 at dendritic branch points and at somal Golgi, indicating a tripartite interaction between NAGK, dynein and Golgi. Finally, the ectopic introduction of a small peptide derived from the C-terminal amino acids 74–96 of DYNLRB1 resulted in the stunting of hippocampal neuron dendrites in culture. Our data indicate that the NAGK-dynein-Golgi tripartite interaction at dendritic branch points functions to regulate dendritic growth and/or branching.
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Affiliation(s)
- Md Ariful Islam
- Department of Anatomy, Dongguk Medical Institute, College of Medicine Dongguk University, Gyeongju, Republic of Korea
| | - Syeda Ridita Sharif
- Department of Anatomy, Dongguk Medical Institute, College of Medicine Dongguk University, Gyeongju, Republic of Korea
| | - HyunSook Lee
- Neuroscience Section, Dongguk Medical Institute, College of Medicine Dongguk University, Gyeongju, Republic of Korea
| | - Dae-Hyun Seog
- Departments of Biochemistry, College of Medicine Inje University, Busan, Republic of Korea
| | - Il Soo Moon
- 1] Department of Anatomy, Dongguk Medical Institute, College of Medicine Dongguk University, Gyeongju, Republic of Korea [2] Neuroscience Section, Dongguk Medical Institute, College of Medicine Dongguk University, Gyeongju, Republic of Korea
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Subramanian VS, Nabokina SM, Said HM. Association of TM4SF4 with the human thiamine transporter-2 in intestinal epithelial cells. Dig Dis Sci 2014; 59:583-90. [PMID: 24282057 PMCID: PMC3943980 DOI: 10.1007/s10620-013-2952-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 11/12/2013] [Indexed: 01/19/2023]
Abstract
BACKGROUND The human thiamine transporter-2 (hTHTR-2) is involved in the intestinal absorption of thiamine. Recent studies with membrane transporters of other nutrients/substrates have shown that they have associated proteins that affect different aspects of their physiology and cell biology. Nothing is known about protein(s) that interact with hTHTR-2 in intestinal epithelial cells and influence its physiological function and/or its cell biology. AIMS The aim of this study was to identify protein partner(s) that interact with hTHTR-2 in human intestinal cells and determine the physiological/biological consequence of that interaction. METHODS The yeast split-ubiquitin two-hybrid approach was used to screen a human intestinal cDNA library. GST-pull-down and cellular co-localization approaches were used to confirm the interaction between hTHTR-2 and the associated protein(s). The effect of such an interaction on hTHTR-2 function was examined by (3)H-thiamine uptake assays. RESULTS Our screening results identified the human TransMembrane 4 SuperFamily 4 (TM4SF4) as a potential interactor with hTHTR-2. This interaction was confirmed by an in vitro GST-pull-down assay, and by live-cell confocal imaging of HuTu-80 cells co-expressing hTHTR-2-GFP and mCherry-TM4SF4 (the latter displayed a significant overlap of these two proteins in intracellular vesicles and at the cell membrane). Co-expression of hTHTR-2 with TM4SF4 in HuTu-80 cells led to a significant induction in thiamine uptake. In contrast, silencing TM4SF4 with gene-specific siRNA led to a significant decrease in thiamine uptake. CONCLUSIONS These results show for the first time that the accessory protein TM4SF4 interacts with hTHTR-2 and influences the physiological function of the thiamine transporter.
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Affiliation(s)
| | | | - Hamid M. Said
- To whom correspondence may be addressed: , Phone: 562-826-5811; Fax: 562-826-5018
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8
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Subramanian VS, Nabokina SM, Patton JR, Marchant JS, Moradi H, Said HM. Glyoxalate reductase/hydroxypyruvate reductase interacts with the sodium-dependent vitamin C transporter-1 to regulate cellular vitamin C homeostasis. Am J Physiol Gastrointest Liver Physiol 2013; 304:G1079-86. [PMID: 23599041 PMCID: PMC3680717 DOI: 10.1152/ajpgi.00090.2013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The human sodium-dependent vitamin C transporter 1 (hSVCT1) contributes to cellular uptake of ascorbic acid (AA). Although different aspects of hSVCT1 cell biology have been extensively studied, nothing is currently known about the broader hSVCT1 interactome that modulates its role in cellular physiology. Here, we identify the enzyme human glyoxalate reductase/hydroxypyruvate reductase (hGR/HPR) as an hSVCT1 associated protein by yeast two-hybrid (Y2H) screening of a human liver cDNA library. The interaction between hSVCT1 and hGR/HPR was further confirmed by in vitro GST pull-down assay, in vivo coimmunoprecipitation and mammalian two-hybrid firefly luciferase assays. This interaction had functional significance as coexpression of hGR/HPR with hSVCT1 led to an increase in AA uptake. Reciprocally, siRNA-mediated knockdown of endogenous hGR/HPR led to an inhibition of AA uptake. Given that oxalate is a degradation product of vitamin C and hGR/HPR acts to limit cellular oxalate levels, this association physically couples two independent regulators of cellular oxalate production. Furthermore, confocal imaging of human liver HepG2 cells coexpressing GFP-hSVCT1 and hGR/HPR-mCherry demonstrated that these two proteins colocalize within a subpopulation of intracellular organelles. This provides a possible molecular basis for organellar AA transport and regulation of local glyoxylate/glycolate concentration in the vicinity of organelle membranes.
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Affiliation(s)
- Veedamali S. Subramanian
- 1Departments of Medicine, Physiology and Biophysics, University of California, Irvine, California; ,2Department of Veterans Affairs Medical Center, Long Beach, California; and
| | - Svetlana M. Nabokina
- 1Departments of Medicine, Physiology and Biophysics, University of California, Irvine, California; ,2Department of Veterans Affairs Medical Center, Long Beach, California; and
| | - Joseph R. Patton
- 3Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota
| | - Jonathan S. Marchant
- 3Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota
| | - Hamid Moradi
- 1Departments of Medicine, Physiology and Biophysics, University of California, Irvine, California; ,2Department of Veterans Affairs Medical Center, Long Beach, California; and
| | - Hamid M. Said
- 1Departments of Medicine, Physiology and Biophysics, University of California, Irvine, California; ,2Department of Veterans Affairs Medical Center, Long Beach, California; and
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Requirement for protein kinase A in the phosphorylation of the TGFβ receptor-interacting protein km23-1 as a component of TGFβ downstream effects. Exp Cell Res 2013; 319:897-907. [PMID: 23333499 DOI: 10.1016/j.yexcr.2012.12.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Revised: 12/12/2012] [Accepted: 12/21/2012] [Indexed: 01/15/2023]
Abstract
km23-1 was previously identified as a TGFβ-receptor interacting protein that was phosphorylated on serines after TGFβ stimulation. In the current report, we examined the role of km23-1 phosphorylation in the downstream effects of TGFβ/protein kinase A (PKA) signaling. Using phosphorylation site prediction software, we found that km23-1 has two potential PKA consensus phosphorylation sites. In vitro kinase assays further demonstrated that PKA directly phosphorylates km23-1 on serine 73 (S73). Moreover, our results show that the PKA-specific inhibitor H89 diminishes phosphorylation of km23-1 on S73 after TGFβ stimulation. Taken together, our results demonstrate that TGFβ induction of PKA activity results in phosphorylation of km23-1 on S73. In order to assess the mechanisms underlying PKA phosphorylation of km23-1 on S73 (S73-km23-1) after TGFβ stimulation, immunoprecipitation (IP)/blot analyses were performed, which demonstrate that TGFβ regulates complex formation between the PKA regulatory subunit RIβ and km23-1 in vivo. In addition, an S73A mutant of km23-1 (S73A-km23-1), which could not be phosphorylated by PKA, inhibited TGFβ induction of the km23-1-dynein complex and transcriptional activation of the activin-responsive element (ARE). Furthermore, our results show that km23-1 is required for cAMP-responsive element (CRE) transcriptional activation by TGFβ, with S73-km23-1 being required for the CRE-dependent TGFβ stimulation of fibronectin (FN) transcription. Collectively, our results demonstrate for the first time that TGFβ/PKA phosphorylation of km23-1 on S73 is required for ARE- and CRE-mediated downstream events that include FN induction.
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Wei H, Xuling H, Yusong X. Molecular cloning of the Robl gene from Bombyx mori and studies of its developmental and physicochemical regulation. Mol Biol Rep 2012; 39:6439-47. [PMID: 22311012 DOI: 10.1007/s11033-012-1462-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 01/23/2012] [Indexed: 11/30/2022]
Abstract
Dynein light chains function as motor acceptor to recruit cargos, which play vital roles in many cellular processes such as intracellular transport and mitosis. In this study, we cloned and expressed the dynein light chain LC7 gene BmRobl in silkworm. The full-length cDNA of the dynein light chain LC7 gene BmRobl is 757 bp and encoded 97 aa polypeptide. Its molecular weight was ~11 kDa confirmed by western blotting. The tissue and stage expression profile of BmRobl drafted by real time PCR revealed that presence of BmRobl transcript was examined in all tissue but prominent expression level was found in brain, wing disc, ovary and testis. In metamorphosis wing disc, BmRobl reached to peak during the prepupae stage compared with the larval and pupal stages. This indicated BmRobl might involve in wing discs development during metamorphosis. Besides, in vitro wing discs 20E cultivation was performed and BmRobl expression profile was detected. The results demonstrated that the BmRobl gene was significantly up-regulated with increase of 20E concentration; the mRNA level peaked at 2 μg/ml of 20E. However, the BmRobl expression nearly has no change cultivated by 20 μg/ml 20E compared with 0.02 μg/ml 20E. These indicated that BmRobl expression might directly or indirectly induced by 20E, besides, high concentration 20E was far too inducible, suggesting that low concentrations of ecdysteroid induce cell proliferation, whereas high concentrations inhibit cell proliferation. Moreover, the transport role of BmRobl was clarified by UV challenge and vanadate cultivation. Both the real time PCR and western blotting results showed that the BmRobl gene was degraded with increase in the concentration of sodium vanadate combined with elongation in the time of UV challenge. Interestingly, compared with the single treatment group and non-treatment group, the group treated by both sodium vanadate and UV have severe degradation. This indicated that UV and vanadate might down-regulate BmRobl synergetically. It was further speculated that BmRobl may function as a positive regulator of the dynein complex during cellular transport.
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Affiliation(s)
- Hao Wei
- Institute of Sericulture & Apiculture, College of Animal Sciences, Zhejiang University, Hangzhou, People's Republic of China
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11
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Nabokina SM, Senthilkumar SR, Said HM. Tspan-1 interacts with the thiamine transporter-1 in human intestinal epithelial cells and modulates its stability. Am J Physiol Gastrointest Liver Physiol 2011; 301:G808-13. [PMID: 21836059 PMCID: PMC3220328 DOI: 10.1152/ajpgi.00269.2011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The human thiamine transporter-1 (hTHTR-1) contributes to intestinal thiamine uptake, and its function is regulated at both the transcriptional and posttranscriptional levels. Nothing, however, is known about the protein(s) that may interact with hTHTR-1 and affects its cell biology and physiology. We addressed this issue in the present investigation using a bacterial two-hybrid system to screen a human intestinal cDNA library with the complete coding sequence of hTHTR-1 as a bait. Our results showed that a member of the tetraspanin family of proteins, Tspan-1, interacts with hTHTR-1. Coimmunoprecipitation and glutathione S-transferase (GST)-pulldown assays confirmed the existence of such an interaction between hTspan-1 and hTHTR-1 in human intestinal epithelial Caco-2 cells. Furthermore, live cell confocal imaging demonstrated that hTspan-1 and hTHTR-1 colocalize in human intestinal epithelial HuTu-80 cells. The importance of the interaction between hTspan-1 and hTHTR-1 for cell biology of the thiamine transporter was examined in HuTu-80 cells stably expressing hTHTR-1. Coexpression of hTspan-1 in these cells led to a significant decrease in the rate of degradation of hTHTR-1 compared with cells expressing the hTHTR-1 alone; in fact the half-life of the hTHTR-1 protein was twice longer in the former cell type compared with the latter cell type (12 h vs. 6 h, respectively). This finding was also confirmed at the functional level when a significantly higher thiamine uptake was observed in cycloheximide-treated (6 h) cells expressing hTHTR-1 together with hTspan-1 compared with those expressing hTHTR-1 alone. These studies demonstrate for the first time that Tspan-1 is an interacting partner with hTHTR-1 and that this interaction affects hTHTR-1 stability.
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Affiliation(s)
- Svetlana M. Nabokina
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, California and Department of Veterans Affairs Medical Center, Long Beach, California
| | - Sundar Rajan Senthilkumar
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, California and Department of Veterans Affairs Medical Center, Long Beach, California
| | - Hamid M. Said
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, California and Department of Veterans Affairs Medical Center, Long Beach, California
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Abstract
Our knowledge of the mechanisms and regulation of intestinal absorption of water-soluble vitamins under normal physiological conditions, and of the factors/conditions that affect and interfere with theses processes has been significantly expanded in recent years as a result of the availability of a host of valuable molecular/cellular tools. Although structurally and functionally unrelated, the water-soluble vitamins share the feature of being essential for normal cellular functions, growth and development, and that their deficiency leads to a variety of clinical abnormalities that range from anaemia to growth retardation and neurological disorders. Humans cannot synthesize water-soluble vitamins (with the exception of some endogenous synthesis of niacin) and must obtain these micronutrients from exogenous sources. Thus body homoeostasis of these micronutrients depends on their normal absorption in the intestine. Interference with absorption, which occurs in a variety of conditions (e.g. congenital defects in the digestive or absorptive system, intestinal disease/resection, drug interaction and chronic alcohol use), leads to the development of deficiency (and sub-optimal status) and results in clinical abnormalities. It is well established now that intestinal absorption of the water-soluble vitamins ascorbate, biotin, folate, niacin, pantothenic acid, pyridoxine, riboflavin and thiamin is via specific carrier-mediated processes. These processes are regulated by a variety of factors and conditions, and the regulation involves transcriptional and/or post-transcriptional mechanisms. Also well recognized now is the fact that the large intestine possesses specific and efficient uptake systems to absorb a number of water-soluble vitamins that are synthesized by the normal microflora. This source may contribute to total body vitamin nutrition, and especially towards the cellular nutrition and health of the local colonocytes. The present review aims to outline our current understanding of the mechanisms involved in intestinal absorption of water-soluble vitamins, their regulation, the cell biology of the carriers involved and the factors that negatively affect these absorptive events.
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Affiliation(s)
- Hamid M Said
- School of Medicine, University of California-Irvine, Irvine, CA 92697, USA.
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Nabokina SM, Subramanian VS, Said HM. Association of PDZ-containing protein PDZD11 with the human sodium-dependent multivitamin transporter. Am J Physiol Gastrointest Liver Physiol 2011; 300:G561-7. [PMID: 21183659 PMCID: PMC3074986 DOI: 10.1152/ajpgi.00530.2010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Intestinal absorption of biotin is mediated via the sodium-dependent multivitamin transporter (SMVT). Studies from our laboratory and others have characterized different aspects of the human SMVT (hSMVT), but nothing is currently known about protein(s) that may interact with hSMVT and affect its physiology/biology. In this study, a PDZ-containing protein PDZD11 was identified as an interacting partner with hSMVT using yeast two-hybrid screen of a human intestinal cDNA library. The interaction between hSMVT and PDZD11 was confirmed by in vitro GST-pull-down assay and in vivo in a mammalian cell environment by a two-hybrid luciferase and coimmunoprecipitation assays. Furthermore, confocal imaging of live human intestinal epithelial HuTu-80 cells expressing hSMVT-GFP and DsRed-PDZD11 demonstrated colocalization of these two proteins. We also examined the functional consequence of the interaction between hSMVT and PDZD11 in HuTu-80 cells and observed significant induction in [(3)H]biotin uptake upon coexpression of hSMVT and PDZD11. In contrast, knocking down of PDZD11 with gene-specific small interfering RNA led to a significant decrease in biotin uptake; biotinylation assay showed this to be associated with a marked decrease in level of expression of hSMVT at the cell membrane. By truncation approach, we also demonstrated that the PDZ binding domain that is located in the COOH-terminal tail of hSMVT polypeptide is involved in the interaction with PDZD11. These results demonstrate for the first time that PDZD11 is an interacting partner with hSMVT in intestinal epithelial cells and that this interaction affects hSMVT function and cell biology.
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Affiliation(s)
- Svetlana M. Nabokina
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, and the Department of Veterans Affairs Medical Center, Long Beach, California
| | - Veedamali S. Subramanian
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, and the Department of Veterans Affairs Medical Center, Long Beach, California
| | - Hamid M. Said
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, and the Department of Veterans Affairs Medical Center, Long Beach, California
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Nyarko A, Barbar E. Light chain-dependent self-association of dynein intermediate chain. J Biol Chem 2011; 286:1556-66. [PMID: 20974845 PMCID: PMC3020764 DOI: 10.1074/jbc.m110.171686] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 10/15/2010] [Indexed: 11/06/2022] Open
Abstract
Dynein light chains are bivalent dimers that bind two copies of dynein intermediate chain IC to form a cargo attachment subcomplex. The interaction of light chain LC8 with the natively disordered N-terminal domain of IC induces helix formation at distant IC sites in or near a region predicted to form a coiled-coil. This fostered the hypothesis that LC8 binding promotes IC self-association to form a coiled-coil or other interchain helical structure. However, recent studies show that the predicted coiled-coil sequence partially overlaps the light chain LC7 recognition sequence on IC, raising questions about the apparently contradictory effects of LC8 and LC7. Here, we use NMR and fluorescence quenching to localize IC self-association to residues within the predicted coiled-coil that also correspond to helix 1 of the LC7 recognition sequence. LC8 binding promotes IC self-association of helix 1 from each of two IC chains, whereas LC7 binding reverses self-association by incorporating the same residues into two symmetrical, but distant, helices of the LC7-IC complex. Isothermal titration experiments confirm the distinction of LC8 enhancement of IC self-association and LC7 binding effects. When all three light chains are bound, IC self-association is shifted to another region. Such flexibility in association modes may function in maintaining a stable and versatile light chain-intermediate chain assembly under changing cellular conditions.
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Affiliation(s)
- Afua Nyarko
- From the Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331
| | - Elisar Barbar
- From the Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331
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Ghosal A, Said HM. Structure-function activity of the human sodium-dependent multivitamin transporter: role of His¹¹⁵ and His²⁵⁴. Am J Physiol Cell Physiol 2010; 300:C97-104. [PMID: 20962270 DOI: 10.1152/ajpcell.00398.2010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intestinal absorption of biotin occurs via a Na(+)-dependent carrier-mediated process that involves the sodium-dependent multivitamin transporter (SMVT; product of the Slc5a6 gene). The SMVT system is exclusively expressed at the apical membrane domain of the polarized intestinal epithelial cells. Whereas previous studies from our laboratory and others have characterized different physiological and biological aspects of SMVT, little is currently known about its structure-function activity relationship. Using site-directed mutagenesis approach, we examined the role of the positively charged histidine (His) residues of the human SMVT (hSMVT) in transporting the negatively charged biotin. Of the seven conserved (across species) His residues in the hSMVT polypeptide, only His¹¹⁵ and His²⁵⁴ were found to be important for the function of hSMVT as their mutation led to a significant reduction in carrier-mediated biotin uptake. This inhibition was mediated via a significant reduction in the maximal velocity (V(max)), but not the apparent Michaelis constant (K(m)), of the biotin uptake process and was not related to the charge of the His residue. The inhibition was also not due to changes in transcriptional or translational efficiency of the mutated hSMVT compared with wild-type carrier. However, surface biotinylation assay showed a significant reduction in the level of expression of the mutated hSMVT at the cell surface, a finding that was further confirmed by confocal imaging. Our results show important role for His¹¹⁵ and His²⁵⁴ residues in hSMVT function, which is most probably mediated via an effect on level of hSMVT expression at the cell membrane.
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Affiliation(s)
- Abhisek Ghosal
- Department of Medicine, University of California, Irvine, USA
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Hall J, Song Y, Karplus PA, Barbar E. The crystal structure of dynein intermediate chain-light chain roadblock complex gives new insights into dynein assembly. J Biol Chem 2010; 285:22566-75. [PMID: 20472935 DOI: 10.1074/jbc.m110.103861] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The roadblock/LC7 dynein light chain is a ubiquitous component of all dyneins and is essential for many diverse processes including proper axonal transport and dendrite growth. In addition, LC7 functions in non-dynein transcriptional activation of the transforming growth factor-beta complex. Crystal structures of Drosophila melanogaster LC7 in the apo form and in complex with a segment of the disordered N-terminal domain of dynein intermediate chain (IC) provide the first definitive identification of the IC sequence recognized by LC7. The site, confirmed by isothermal titration calorimetry studies, overlaps the IC sequence considered in the literature to be an IC self-association domain. The IC peptide binds as two amphipathic helices that lie along an extensive hydrophobic cleft on LC7 and ends with a polar side-chain interaction network that includes conserved residues from both proteins. The LC7 recognition sequence on IC and its interface with LC7 are well conserved and are, thus, likely representative of all IC x LC7 structures. Interestingly, the position of bound IC in the IC x LC7 complex mimics a helix that is integrated into the primary structure in distantly related LC7 homologs. The IC x LC7 structure further shows that the naturally occurring robl(Z) deletion mutation contains the majority of the IC binding site and suggests that promotion of IC binding by phosphorylation of LC7 is an indirect effect.
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Affiliation(s)
- Justin Hall
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, USA
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Subramanian VS, Marchant JS, Said HM. Molecular determinants dictating cell surface expression of the human sodium-dependent vitamin C transporter-2 in human liver cells. Am J Physiol Gastrointest Liver Physiol 2010; 298:G267-74. [PMID: 19926816 PMCID: PMC2822508 DOI: 10.1152/ajpgi.00435.2009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The human sodium-dependent vitamin C transporter-2 (hSVCT2) plays an important role in cellular accumulation of ascorbic acid in liver cells. However, little is known about the molecular determinants that direct hSVCT2 to the cell surface in hepatocytes. We addressed this issue using live cell imaging methods to resolve the distribution and trafficking of truncated or mutated hSVCT2 constructs in a cellular model of human hepatocytes, HepG2 cells. Whereas a full-length hSVCT2-yellow fluorescent protein (YFP) fusion protein was functionally expressed at the cell surface in HepG2 cells, serial truncation and mutation analysis demonstrated an essential role for both NH(2)- and COOH-terminal sequence(s) for cell surface expression and function. Video-rate confocal imaging showed evidence of dynamic hSVCT2-YFP containing intracellular trafficking vesicles, the motility of which was impaired following disruption of microtubules using nocodazole. However, in a HepG2 cell line stably expressing hSVCT2-YFP at the cell surface, plasma membrane levels of hSVCT2 were unaffected by inhibition of microtubule-associated motor proteins; rather, surface expression of hSVCT2-YFP was increased following treatment with myosin inhibitors. Together, these results show that 1) both NH(2)- and COOH-terminal sequences are essential for proper localization of hSVCT2, 2) cell surface delivery is dependent on intact microtubules, and 3) peripheral microfilaments regulate insertion and retrieval of hSVCT2 into the plasma membrane.
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Affiliation(s)
- Veedamali S. Subramanian
- Departments of 1Medicine, ,2Department of Physiology and Biophysics, University of California, Irvine, California; ,4Department of Veterans Affairs Medical Center, Long Beach, California
| | - Jonathan S. Marchant
- 3Department of Pharmacology, University of Minnesota Medical School, Minnesota; and
| | - Hamid M. Said
- Departments of 1Medicine, ,2Department of Physiology and Biophysics, University of California, Irvine, California; ,4Department of Veterans Affairs Medical Center, Long Beach, California
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