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Bagalkot T, Sorkin A. Amphetamine Induces Sex-Dependent Loss of the Striatal Dopamine Transporter in Sensitized Mice. eNeuro 2024; 11:ENEURO.0491-23.2023. [PMID: 38164591 PMCID: PMC10849026 DOI: 10.1523/eneuro.0491-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 12/10/2023] [Accepted: 12/12/2023] [Indexed: 01/03/2024] Open
Abstract
Dopamine transporter (DAT) controls dopamine signaling in the brain through the reuptake of synaptically released dopamine. DAT is a target of abused psychostimulants such as amphetamine (Amph). Acute Amph administration induces transient DAT endocytosis, which, among other Amph effects on dopaminergic neurons, elevates extracellular dopamine. However, the effects of repeated Amph abuse, leading to behavioral sensitization and drug addiction, on DAT are unknown. Hence, we developed a 14 d Amph-sensitization protocol in knock-in mice expressing HA-epitope-tagged DAT (HA-DAT) and investigated the effects of Amph challenge on sensitized HA-DAT animals. The Amph challenge resulted in the highest locomotor activity on Day 14 in both sexes, which was sustained for 1 h in male but not female mice. Strikingly, significant (by 30-60%) loss of the HA-DAT protein in the striatum was caused by the Amph challenge of sensitized males but not females. Amph also reduced V max of dopamine transport in the striatal synaptosomes of males without changing K m values. Consistently, immunofluorescence microscopy revealed a significant increase of HA-DAT colocalization with the endosomal protein VPS35 only in Amph-challenged males. Amph-induced loss of striatal HA-DAT in sensitized mice was blocked by chloroquine, vacuolin-1, and inhibitor of Rho-associated kinases ROCK1/2, indicative of the involvement of endocytic trafficking in the DAT protein loss. Interestingly, an apparent degradation of HA-DAT protein was observed in the nucleus accumbens and not in the dorsal striatum. We propose that Amph challenge in sensitized mice triggers Rho-mediated endocytosis and post-endocytic trafficking of DAT in a brain-region-specific and sex-dependent manner.
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Affiliation(s)
- Tarique Bagalkot
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh 15261, Pennsylvania
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh 15261, Pennsylvania
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2
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Pinilla-Macua I, Sorkin A. Cbl and Cbl-b independently regulate EGFR through distinct receptor interaction modes. Mol Biol Cell 2023; 34:ar134. [PMID: 37903221 PMCID: PMC10848940 DOI: 10.1091/mbc.e23-02-0058] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 09/22/2023] [Accepted: 10/11/2023] [Indexed: 11/01/2023] Open
Abstract
Highly homologous E3 ubiquitin ligases, Cbl and Cbl-b, mediate ubiquitination of EGF receptor (EGFR), leading to its endocytosis and lysosomal degradation. Cbl and Cbl-b, are thought to function in a redundant manner by binding directly to phosphorylated Y1045 (pY1045) of EGFR and indirectly via the Grb2 adaptor. Unexpectedly, we found that inducible expression of Cbl or Cbl-b mutants lacking the E3 ligase activity but fully capable of EGFR binding does not significantly affect EGFR ubiquitination and endocytosis in human oral squamous cell carcinoma (HSC3) cells which endogenously express Cbl-b at a relatively high level. Each endogenous Cbl species remained associated with ligand-activated EGFR in the presence of an overexpressed counterpart species or its mutant, although Cbl-b overexpression partially decreased Cbl association with EGFR. Binding to pY1045 was the preferential mode for Cbl-b:EGFR interaction, whereas Cbl relied mainly on the Grb2-dependent mechanism. Overexpression of the E3-dead mutant of Cbl-b slowed down EGF-induced degradation of active EGFR, while this mutant and a similar mutant of Cbl did not significantly affect MAPK/ERK1/2 activity. EGF-guided chemotaxis migration of HSC3 cells was diminished by overexpression of the E3-dead Cbl-b mutant but was not significantly affected by the E3-dead Cbl mutant. By contrast, the inhibitory effect of the same Cbl mutant on the migration of OSC-19 cells expressing low Cbl-b levels was substantially stronger than that of the Cbl-b mutant. Altogether, our data demonstrate that Cbl and Cbl-b may operate independently through different modes of EGFR binding to jointly control receptor ubiquitination, endocytic trafficking, and signaling.
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Affiliation(s)
- Itziar Pinilla-Macua
- Department of Cell Biology, University of Pittsburgh, School of Medicine, Pittsburgh, PA, 15261
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh, School of Medicine, Pittsburgh, PA, 15261
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3
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Chen J, Tsur AM, Nadler R, Beit Ner E, Sorkin A, Radomislensky I, Peleg K, Ben Avi R, Shushan G, Glassberg E, Benov A. Ten-year reduction in thoracic injury-related mortality among Israel Defense Forces soldiers. BMJ Mil Health 2023; 169:510-516. [PMID: 34930818 DOI: 10.1136/bmjmilitary-2021-001986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 12/06/2021] [Indexed: 11/04/2022]
Abstract
INTRODUCTION This study aims to describe injury patterns, prehospital interventions and mortality rates of combat-related thoracic injuries during the past decade among Israel Defense Forces (IDF) soldiers before and after implementation of the 2012 IDF-Military Corps 'My Brother's Keeper' plan which included the publication of clinical practice guidelines (CPGs) for thoracic injuries, emphasis on adequate torso protection, introduction of modern life-saving procedures and encouragement of rapid evacuation. METHODS The IDF prehospital trauma registry was reviewed to identify all patients who sustained thoracic injuries from January 2006 to December 2017. IDF soldiers who were injured, died of wounds or killed in action (KIA) were included. These were cross-referenced with the Israel National Trauma Registry. The periods before and after the plan were compared. RESULTS 458 (12.3%) of 3733 IDF soldiers wounded on the battlefield sustained combat-related thoracic injuries. The overall mortality was 44.3% before the CPG and 17.3% after (p<0.001). Most were KIA: 97% (95 of 98) died by 30 June 2012, and 83% (20 of 24) after (p<0.001). Casualties treated with needle thoracostomy before and after CPG were 6.3% and 18.3%, respectively (p=0.002). More tube thoracostomies were performed after June 2012 (16.1% vs 5.4%, p=0.001). Evacuation was faster after June 2012 (119.4 min vs 560.8 min, p<0.001), but the rates of casualties evacuated within 60 min were similar (21.1% vs 25%, p=0.617). CONCLUSIONS Among military casualties with thoracic injuries, the rate of life-saving interventions increased, evacuation time decreased and mortality dropped following the implementation of My Brother's Keeper plan.
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Affiliation(s)
- Jacob Chen
- Medical Corps, Surgeon General's Headquarters, Israel Defense Forces, Ramat Gan, Israel
- Hospital Management, Meir Medical Center, Kefar Saba, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - A M Tsur
- Medical Corps, Surgeon General's Headquarters, Israel Defense Forces, Ramat Gan, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Department of Medicine B, Zabludowicz Center for Autoimmune Diseases Israel, Chaim Sheba Medical Center, Tel Hashomer, Ramat Gan, Israel
| | - R Nadler
- Medical Corps, Surgeon General's Headquarters, Israel Defense Forces, Ramat Gan, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- General Surgery B, Sheba Medical Center, Ramat Gan, Israel
| | - E Beit Ner
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Orthopedic, Shamir Medical Center, Zerifin, Israel
| | - A Sorkin
- Medical Corps, Surgeon General's Headquarters, Israel Defense Forces, Ramat Gan, Israel
| | - I Radomislensky
- Medical Corps, Surgeon General's Headquarters, Israel Defense Forces, Ramat Gan, Israel
- Gertner Institute for Health Policy and Epidemiology, Tel HaShomer, Israel
| | - K Peleg
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Gertner Institute for Health Policy and Epidemiology, Tel HaShomer, Israel
| | - R Ben Avi
- Cardiovascular Department and Research Center, Poriya Medical Center, Tiberias, Israel
| | - G Shushan
- Ground Forces Technology Unit, Tel Hashomer, Israel Defense Forces, Ramat Gan, Israel
| | - E Glassberg
- Medical Corps, Surgeon General's Headquarters, Israel Defense Forces, Ramat Gan, Israel
- The Azrieli Faculty of Medicine, Bar Ilan University, Safed, Israel
| | - A Benov
- Medical Corps, Surgeon General's Headquarters, Israel Defense Forces, Ramat Gan, Israel
- The Azrieli Faculty of Medicine, Bar Ilan University, Safed, Israel
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Small C, Cheng MH, Belay SS, Bulloch SL, Zimmerman B, Sorkin A, Block ER. The Alkylamine Stimulant 1,3-Dimethylamylamine Exhibits Substrate-Like Regulation of Dopamine Transporter Function and Localization. J Pharmacol Exp Ther 2023:JPET-AR-2022-001573. [PMID: 37348963 PMCID: PMC10353075 DOI: 10.1124/jpet.122.001573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 02/16/2023] [Accepted: 05/04/2023] [Indexed: 06/24/2023] Open
Abstract
The alkylamine stimulant 1,3-dimethylamylamine (DMAA) is used non-medically as an appetite suppressant and exercise performance enhancer despite adverse cardiovascular effects that have limited its legal status. There is scant research describing the mechanism of action of DMAA, making it difficult to gauge risks or therapeutic potential. An important molecular target of structurally related phenethylamines, such as amphetamine, for regulating mood, cognition, movement, and the development of substance use disorder is the dopamine transporter, which limits the range and magnitude of dopamine signaling via re-uptake from the extracellular space. The present studies were therefore initiated to characterize the effects of DMAA on dopamine transporter function. Specifically, we tested the hypothesis that DMAA exhibits substrate-like effects on dopamine transporter function and trafficking. In transport assays in human embryonic kidney cells, DMAA inhibited dopamine uptake by the human dopamine transporter in a competitive manner. Docking analysis and molecular dynamics simulations supported these findings, revealing that DMAA binds to the S1 substrate binding site and induces a conformational change from outward-facing open to outward-facing closed states, similar to the known substrates. Further supporting substrate-like effects of DMAA, the drug stimulated dopamine transporter endocytosis in a heterologous expression system via cocaine- and protein kinase A-sensitive mechanisms, mirroring findings with amphetamine. Together, these data indicate that DMAA elicits neurological effects by binding to and regulating function of the dopamine transporter. Furthermore, pharmacologic distinctions from amphetamine reveal structural determinants for regulating transporter conformation and add mechanistic insight for the regulation of dopamine transporter endocytosis. Significance Statement The alkylamine stimulant 1,3-dimethylamylamine (DMAA) is used as an appetite suppressant and exercise performance enhancer and is structurally similar to amphetamine, but there is scant research describing its mechanism of action. Characterizing the effects of DMAA on dopamine transporter function supports evaluation of potential risks and therapeutic potential, while also revealing mechanistic details of dynamic transporter-substrate interactions.
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5
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Bagalkot T, Sorkin A. Endocytic down-regulation of the striatal dopamine transporter by amphetamine in sensitized mice in sex-dependent manner. bioRxiv 2023:2023.05.17.541165. [PMID: 37293021 PMCID: PMC10245703 DOI: 10.1101/2023.05.17.541165] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Dopamine transporter (DAT) controls dopamine signaling in the brain through the reuptake of synaptically released dopamine. DAT is a target of abused psychostimulants such as amphetamine (Amph). Acute Amph is proposed to cause transient DAT endocytosis which among other Amph effects on dopaminergic neurons elevates extracellular dopamine. However, the effects of repeated Amph abuse, leading to behavioral sensitization and drug addiction, on DAT traffic are unknown. Hence, we developed a 14-day Amph-sensitization protocol in knock-in mice expressing HA-epitope tagged DAT (HA-DAT) and investigated effects of Amph challenge on HA-DAT in sensitized animals. Amph challenge resulted in the highest locomotor activity on day 14 in both sexes, which was however sustained for 1 hour in male but not female mice. Strikingly, significant (by 30-60%) reduction in the amount of the HA-DAT protein in striatum was observed in response to Amph challenge of sensitized males but not females. Amph reduced Vmax of dopamine transport in striatal synaptosomes of males without changing Km values. Consistently, immunofluorescence microscopy revealed a significant increase of HA-DAT co-localization with the endosomal protein VPS35 only in males. Amph-induced HA-DAT down-regulation in the striatum of sensitized mice was blocked by chloroquine, vacuolin-1 (inhibitor of PIKfive kinase), and inhibitor of Rho-associated kinases (ROCK1/2), indicative of the involvement of endocytic trafficking in DAT down-regulation. Interestingly, HA-DAT protein down-regulation was observed in nucleus accumbens and not in dorsal striatum. We propose that Amph challenge in sensitized mice leads to ROCK-dependent endocytosis and post-endocytic traffic of DAT in a brain-region-specific and sex-dependent manner.
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6
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Perez Verdaguer M, Zhang T, Surve S, Paulo JA, Wallace C, Watkins SC, Gygi SP, Sorkin A. Time-resolved proximity labeling of protein networks associated with ligand-activated EGFR. Cell Rep 2022; 39:110950. [PMID: 35705039 PMCID: PMC9248364 DOI: 10.1016/j.celrep.2022.110950] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 04/13/2022] [Accepted: 05/22/2022] [Indexed: 11/26/2022] Open
Abstract
Ligand binding to the EGF receptor (EGFR) triggers multiple signal-transduction processes and promotes endocytosis of the receptor. The mechanisms of EGFR endocytosis and its cross-talk with signaling are poorly understood. Here, we combine peroxidase-catalyzed proximity labeling, isobaric peptide tagging, and quantitative mass spectrometry to define the dynamics of the proximity proteome of ligand-activated EGFR. Using this approach, we identify a network of signaling proteins, which remain associated with the receptor during its internalization and trafficking through the endosomal system. We show that Trk-fused gene (TFG), a protein known to function at the endoplasmic reticulum exit sites, is enriched in the proximity proteome of EGFR in early/sorting endosomes and localized in these endosomes and demonstrate that TFG regulates endosomal sorting of EGFR. This study provides a comprehensive resource of time-dependent nanoscale environment of EGFR, thus opening avenues to discovering new regulatory mechanisms of signaling and intracellular trafficking of receptor tyrosine kinases. Perez Verdaguer et al. use time-resolved APEX labeling of the proximity proteome of EGFR upon ligand activation to provide comprehensive information about the dynamics of the EGFR-associated protein networks involved in receptor endocytosis and signaling.
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Affiliation(s)
- Mireia Perez Verdaguer
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Tian Zhang
- Department of Cell Biology, Harvard University Medical School, Boston, MA, USA
| | - Sachin Surve
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Joao A Paulo
- Department of Cell Biology, Harvard University Medical School, Boston, MA, USA
| | - Callen Wallace
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard University Medical School, Boston, MA, USA.
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
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Surve S, Sorkin A. CRISPR/Cas9 Gene Editing of HeLa Cells to Tag Proteins with mNeonGreen. Bio Protoc 2022; 12:e4415. [PMID: 35813028 PMCID: PMC9183963 DOI: 10.21769/bioprotoc.4415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 04/05/2022] [Accepted: 04/08/2022] [Indexed: 12/29/2022] Open
Abstract
Subcellular localization dynamics of proteins involved in signal transduction processes is crucial in determining the signaling outcome. However, there is very limited information about the localization of endogenous signaling proteins in living cells. For example, biochemical mechanisms underlying the signaling pathway from epidermal growth factor (EGF) receptor (EGFR) to RAS-RAF and ERK1/2/MAPK are well understood, whereas the operational domains of this pathway in the cell remain poorly characterized. Tagging of endogenous components of signaling pathways with fluorescent proteins allows more accurate characterization of their intracellular dynamics at their native expression levels controlled by endogenous regulatory mechanisms, thus avoiding possible tainting effects of overexpression and mistargeting. In this study, we describe methodological approaches to label components of the EGFR-RAS-MAPK pathway, such as Grb2, KRAS, and NRAS, with the fluorescent protein mNeonGreen (mNG) using CRISPR/Cas9 gene-editing, as well as generation of homozygous single-cell clones of the edited target protein.
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Affiliation(s)
- Sachin Surve
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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8
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Surve S, Watkins SC, Sorkin A. EGFR-RAS-MAPK signaling is confined to the plasma membrane and associated endorecycling protrusions. J Cell Biol 2021; 220:212639. [PMID: 34515735 PMCID: PMC8563293 DOI: 10.1083/jcb.202107103] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 08/21/2021] [Accepted: 08/24/2021] [Indexed: 12/16/2022] Open
Abstract
The subcellular localization of RAS GTPases defines the operational compartment of the EGFR-ERK1/2 signaling pathway within cells. Hence, we used live-cell imaging to demonstrate that endogenous KRAS and NRAS tagged with mNeonGreen are predominantly localized to the plasma membrane. NRAS was also present in the Golgi apparatus and a tubular, plasma-membrane derived endorecycling compartment, enriched in recycling endosome markers (TERC). In EGF-stimulated cells, there was essentially no colocalization of either mNeonGreen-KRAS or mNeonGreen-NRAS with endosomal EGFR, which, by contrast, remained associated with endogenous Grb2-mNeonGreen, a receptor adaptor upstream of RAS. ERK1/2 activity was diminished by blocking cell surface EGFR with cetuximab, even after most ligand-bound, Grb2-associated EGFRs were internalized. Endogenous mCherry-tagged RAF1, an effector of RAS, was recruited to the plasma membrane, with subsequent accumulation in mNG-NRAS–containing TERCs. We propose that a small pool of surface EGFRs sustain signaling within the RAS-ERK1/2 pathway and that RAS activation persists in TERCs, whereas endosomal EGFR does not significantly contribute to ERK1/2 activity.
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Affiliation(s)
- Sachin Surve
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
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Mourad M, Jacob T, Sadovsky E, Bejerano S, Simone GSD, Bagalkot TR, Zucker J, Yin MT, Chang JY, Liu L, Debelenko L, Shawber CJ, Firestein M, Ouyang Y, Gyamfi-Bannerman C, Penn A, Sorkin A, Wapner R, Sadovsky Y. Placental response to maternal SARS-CoV-2 infection. Sci Rep 2021; 11:14390. [PMID: 34257394 PMCID: PMC8277865 DOI: 10.1038/s41598-021-93931-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 06/29/2021] [Indexed: 02/07/2023] Open
Abstract
The coronavirus disease 2019 (COVID-19) pandemic affected people at all ages. Whereas pregnant women seemed to have a worse course of disease than age-matched non-pregnant women, the risk of feto-placental infection is low. Using a cohort of 66 COVID-19-positive women in late pregnancy, we correlated clinical parameters with disease severity, placental histopathology, and the expression of viral entry and Interferon-induced transmembrane (IFITM) antiviral transcripts. All newborns were negative for SARS-CoV-2. None of the demographic parameters or placental histopathological characteristics were associated with disease severity. The fetal-maternal transfer ratio for IgG against the N or S viral proteins was commonly less than one, as recently reported. We found that the expression level of placental ACE2, but not TMPRSS2 or Furin, was higher in women with severe COVID-19. Placental expression of IFITM1 and IFITM3, which have been implicated in antiviral response, was higher in participants with severe disease. We also showed that IFITM3 protein expression, which localized to early and late endosomes, was enhanced in severe COVID-19. Our data suggest an association between disease severity and placental SARS-CoV-2 processing and antiviral pathways, implying a role for these proteins in placental response to SARS-CoV-2.
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Affiliation(s)
- Mirella Mourad
- Department of Obstetrics, Gynecology and Reproductive Science, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Taylor Jacob
- Department of Obstetrics, Gynecology and Reproductive Science, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Elena Sadovsky
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Avenue, Pittsburgh, PA, 15213, USA
| | - Shai Bejerano
- Department of Obstetrics, Gynecology and Reproductive Science, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Glicella Salazar-De Simone
- Department of Obstetrics, Gynecology and Reproductive Science, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | | | - Jason Zucker
- Department of Medicine, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Michael T Yin
- Department of Medicine, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Jennifer Y Chang
- Department of Medicine, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Lihong Liu
- Department of Medicine, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Larisa Debelenko
- Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Carrie J Shawber
- Department of Obstetrics, Gynecology and Reproductive Science, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
- Department of Surgery, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Morgan Firestein
- Department of Psychiatry, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Yingshi Ouyang
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Avenue, Pittsburgh, PA, 15213, USA
| | - Cynthia Gyamfi-Bannerman
- Department of Obstetrics, Gynecology and Reproductive Science, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Anna Penn
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Ronald Wapner
- Department of Obstetrics, Gynecology and Reproductive Science, College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Yoel Sadovsky
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Avenue, Pittsburgh, PA, 15213, USA.
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
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10
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Perez Verdaguer M, Zhang T, Paulo JA, Gygi S, Watkins SC, Sakurai H, Sorkin A. Mechanism of p38 MAPK-induced EGFR endocytosis and its crosstalk with ligand-induced pathways. J Cell Biol 2021; 220:212181. [PMID: 34032851 PMCID: PMC8155814 DOI: 10.1083/jcb.202102005] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/21/2021] [Accepted: 04/27/2021] [Indexed: 11/22/2022] Open
Abstract
Ligand binding triggers clathrin-mediated and, at high ligand concentrations, clathrin-independent endocytosis of EGFR. Clathrin-mediated endocytosis (CME) of EGFR is also induced by stimuli activating p38 MAPK. Mechanisms of both ligand- and p38-induced endocytosis are not fully understood, and how these pathways intermingle when concurrently activated remains unknown. Here we dissect the mechanisms of p38-induced endocytosis using a pH-sensitive model of endogenous EGFR, which is extracellularly tagged with a fluorogen-activating protein, and propose a unifying model of the crosstalk between multiple EGFR endocytosis pathways. We found that a new locus of p38-dependent phosphorylation in EGFR is essential for the receptor dileucine motif interaction with the σ2 subunit of clathrin adaptor AP2 and concomitant receptor internalization. p38-dependent endocytosis of EGFR induced by cytokines was additive to CME induced by picomolar EGF concentrations but constrained to internalizing ligand-free EGFRs due to Grb2 recruitment by ligand-activated EGFRs. Nanomolar EGF concentrations rerouted EGFR from CME to clathrin-independent endocytosis, primarily by diminishing p38-dependent endocytosis.
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Affiliation(s)
| | - Tian Zhang
- Department of Cell Biology, Harvard University Medical School, Boston, MA
| | - Joao A Paulo
- Department of Cell Biology, Harvard University Medical School, Boston, MA
| | - Steven Gygi
- Department of Cell Biology, Harvard University Medical School, Boston, MA
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Hiroaki Sakurai
- Department of Cancer Cell Biology, Faculty of Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
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11
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Abstract
Intricate relationships between endocytosis and cellular signaling, first recognized nearly 40 years ago through the study of tyrosine kinase growth factor receptors, are now known to exist for multiple receptor classes and to affect myriad physiological and developmental processes. This review summarizes our present understanding of how endocytosis orchestrates cellular signaling networks, with an emphasis on mechanistic underpinnings and focusing on two receptor classes-tyrosine kinase and G protein-coupled receptors-that have been investigated in particular detail. Together, these examples provide a useful survey of the current consensus, uncertainties, and controversies in this rapidly advancing area of cell biology.
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Affiliation(s)
- Mark von Zastrow
- Department of Psychiatry, University of California, San Francisco, California 94143, USA;
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA;
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12
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Sorkina T, Cheng MH, Bagalkot TR, Wallace C, Watkins SC, Bahar I, Sorkin A. Direct coupling of oligomerization and oligomerization-driven endocytosis of the dopamine transporter to its conformational mechanics and activity. J Biol Chem 2021; 296:100430. [PMID: 33610553 PMCID: PMC8010718 DOI: 10.1016/j.jbc.2021.100430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 02/08/2021] [Accepted: 02/16/2021] [Indexed: 12/15/2022] Open
Abstract
Dopamine transporter (DAT) mediates the reuptake of synaptically released dopamine, and thus controls the duration and intensity of dopamine neurotransmission. Mammalian DAT has been observed to form oligomers, although the mechanisms of oligomerization and its role in DAT activity and trafficking remain largely unknown. We discovered a series of small molecule compounds that stabilize trimers and induce high-order oligomers of DAT and concomitantly promote its clathrin-independent endocytosis. Using a combination of chemical cross-linking, fluorescence resonance energy transfer microscopy, antibody-uptake endocytosis assay, live-cell lattice light sheet microscopy, ligand binding and substrate transport kinetics analyses, and molecular modeling and simulations, we investigated molecular basis of DAT oligomerization and endocytosis induced by these compounds. Our study showed that small molecule–induced DAT oligomerization and endocytosis are favored by the inward-facing DAT conformation and involve interactions of four hydrophobic residues at the interface between transmembrane (TM) helices TM4 and TM9. Surprisingly, a corresponding quadruple DAT mutant displays altered dopamine transport kinetics and increased cocaine-analog binding. The latter is shown to originate from an increased preference for outward-facing conformation and inward-to-outward transition. Taken together, our results demonstrate a direct coupling between conformational dynamics of DAT, functional activity of the transporter, and its oligomerization leading to endocytosis. The high specificity of such coupling for DAT makes the TM4-9 hub a new target for pharmacological modulation of DAT activity and subcellular localization.
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Affiliation(s)
- Tatiana Sorkina
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Mary Hongying Cheng
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Tarique R Bagalkot
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Callen Wallace
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Simon C Watkins
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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13
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Ouyang Y, Mouillet JF, Sorkin A, Sadovsky Y. Trophoblastic extracellular vesicles and viruses: Friends or foes? Am J Reprod Immunol 2021; 85:e13345. [PMID: 32939907 PMCID: PMC7880881 DOI: 10.1111/aji.13345] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 09/02/2020] [Accepted: 09/03/2020] [Indexed: 12/21/2022] Open
Abstract
Cells produce cytoplasmic vesicles to facilitate the processing and transport of RNAs, proteins, and other signaling molecules among intracellular organelles. Moreover, most cells release a range of extracellular vesicles (EVs) that mediate intercellular communication in both physiological and pathological settings. In addition to a better understanding of their biological functions, the diagnostic and therapeutic prospects of EVs, particularly the nano-sized small EVs (sEVs, exosomes), are currently being rigorously pursued. While EVs and viruses such as retroviruses might have evolved independently, they share a number of similar characteristics, including biogenesis pathways, size distribution, cargo, and cell-targeting mechanisms. The interplay of EVs with viruses has profound effects on viral replication and infectivity. Our research indicates that sEVs, produced by primary human trophoblasts, can endow other non-placental cell types with antiviral response. Better insights into the interaction of EVs with viruses may illuminate new ways to attenuate viral infections during pregnancy, and perhaps develop new antiviral therapeutics to protect the feto-placental unit during critical times of human development.
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Affiliation(s)
- Yingshi Ouyang
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Jean-Francois Mouillet
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Yoel Sadovsky
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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14
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Bagalkot TR, Block ER, Bucchin K, Balcita-Pedicino JJ, Calderon M, Sesack SR, Sorkin A. Dopamine Transporter Localization in Medial Forebrain Bundle Axons Indicates Its Long-Range Transport Primarily by Membrane Diffusion with a Limited Contribution of Vesicular Traffic on Retromer-Positive Compartments. J Neurosci 2021; 41:234-250. [PMID: 33234607 PMCID: PMC7810657 DOI: 10.1523/jneurosci.0744-20.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 11/05/2020] [Accepted: 11/13/2020] [Indexed: 12/18/2022] Open
Abstract
Dopamine transporter (DAT) controls dopamine neurotransmission by clearing synaptically released dopamine. However, trafficking itineraries of DAT, which determine its cell-surface concentration near synapses, are poorly characterized. It is especially unknown how DAT is transported between spatially distant midbrain somatodendritic and striatal axonal compartments. To examine this "long-range" trafficking, the localization and membrane diffusion of HA-epitope tagged DAT in the medial forebrain bundle (MFB) of a knock-in mouse (both sexes) were analyzed using confocal, super-resolution and EM in intact brain and acute brain slices. HA-DAT was abundant in the plasma membrane of MFB axons, similar to the striatum, although the intracellular fraction of HA-DAT in MFB was more substantial. Intracellular HA-DAT colocalized with VPS35, a subunit of the retromer complex mediating recycling from endosomes, in a subset of axons. Late endosomes, lysosomes, and endoplasmic reticulum were abundant in the soma but minimally present in MFB axons, suggesting that biosynthesis and lysosomal degradation of DAT are confined to soma. Together, the data suggest that membrane diffusion is the main mode of long-range DAT transport through MFB, although the contribution of vesicular traffic can be significant in a population of MFB axons. Based on HA-DAT diffusion rates, plasma membrane DAT in MFB axons turns over with a halftime of ∼20 d, which explains the extremely slow turnover of DAT protein in the brain. Unexpectedly, the mean diameter of DAT-labeled MFB axons was observed to be twice larger than reported for striatum. The implications of this finding for dopamine neuron physiology are discussed.SIGNIFICANCE STATEMENT The dopamine transporter (DAT) is a key regulator of dopamine neurotransmission and a target of abused psychostimulants. In the present study, we examined, for the first time, mechanisms of the long-range traffic of DAT in intact brain and acute brain slices from the knock-in mouse expressing epitope-tagged DAT. Using a combination of confocal, super-resolution and EM, we defined DAT localization and its membrane diffusion parameters in medial forebrain bundle axonal tracts connecting midbrain somatodendritic and striatal axonal compartments of dopaminergic neurons. In contrast to the widely accepted model of long-range axonal transport, our studies suggest that DAT traffics between midbrain and striatum, mainly by lateral diffusion in the plasma membrane with only a limited contribution of vesicular transport in recycling endosomes.
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Affiliation(s)
- Tarique R Bagalkot
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Ethan R Block
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
- Chatham University, Pittsburgh, Pennsylvania 15232
| | - Kristen Bucchin
- Department of Neuroscience, Dietrich School of Arts and Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Judith Joyce Balcita-Pedicino
- Department of Neuroscience, Dietrich School of Arts and Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Michael Calderon
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Susan R Sesack
- Department of Neuroscience, Dietrich School of Arts and Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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15
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Li H, Pinilla-Macua I, Ouyang Y, Sadovsky E, Kajiwara K, Sorkin A, Sadovsky Y. Internalization of trophoblastic small extracellular vesicles and detection of their miRNA cargo in P-bodies. J Extracell Vesicles 2020; 9:1812261. [PMID: 32944196 PMCID: PMC7480505 DOI: 10.1080/20013078.2020.1812261] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Pregnancy is a unique situation, in which placenta-derived small extracellular vesicles (sEVs) may communicate with maternal and foetal tissues. While relevant to homoeostatic and pathological functions, the mechanisms underlying sEV entry and cargo handling in target cells remain largely unknown. Using fluorescently or luminescently labelled sEVs, derived from primary human placental trophoblasts or from a placental cell line, we interrogated the endocytic pathways used by these sEVs to enter relevant target cells, including the neighbouring primary placental fibroblasts and human uterine microvascular endothelial cells. We found that trophoblastic sEVs can enter target cells, where they retain biological activity. Importantly, using a broad series of pharmacological inhibitors and siRNA-dependent silencing approaches, we showed that trophoblastic sEVs enter target cells using macropinocytosis and clathrin-mediated endocytosis pathways, but not caveolin-dependent endocytosis. Tracking their intracellular course, we localized the sEVs to early endosomes, late endosomes, and lysosomes. Finally, we used coimmunoprecipitation to demonstrate the association of the sEV microRNA (miRNA) with the P-body proteins AGO2 and GW182. Together, our data systematically detail endocytic pathways used by placental sEVs to enter relevant fibroblastic and endothelial target cells, and provide support for “endocytic escape” of sEV miRNA to P-bodies, a key site for cytoplasmic RNA regulation.
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Affiliation(s)
- Hui Li
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Reproductive Department of Xiangya Hospital, Central South University, Changsha, Hunan, China.,The Third Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Itziar Pinilla-Macua
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Yingshi Ouyang
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Elena Sadovsky
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Kazuhiro Kajiwara
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Yoel Sadovsky
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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16
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Estadella I, Pedrós-Gámez O, Colomer-Molera M, Bosch M, Sorkin A, Felipe A. Endocytosis: A Turnover Mechanism Controlling Ion Channel Function. Cells 2020; 9:E1833. [PMID: 32759790 PMCID: PMC7463639 DOI: 10.3390/cells9081833] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/30/2020] [Accepted: 08/02/2020] [Indexed: 01/08/2023] Open
Abstract
Ion channels (IChs) are transmembrane proteins that selectively drive ions across membranes. The function of IChs partially relies on their abundance and proper location in the cell, fine-tuned by the delicate balance between secretory, endocytic, and degradative pathways. The disruption of this balance is associated with several diseases, such as Liddle's and long QT syndromes. Because of the vital role of these proteins in human health and disease, knowledge of ICh turnover is essential. Clathrin-dependent and -independent mechanisms have been the primary mechanisms identified with ICh endocytosis and degradation. Several molecular determinants recognized by the cellular internalization machinery have been discovered. Moreover, specific conditions can trigger the endocytosis of many IChs, such as the activation of certain receptors, hypokalemia, and some drugs. Ligand-dependent receptor activation primarily results in the posttranslational modification of IChs and the recruitment of important mediators, such as β-arrestins and ubiquitin ligases. However, endocytosis is not a final fate. Once internalized into endosomes, IChs are either sorted to lysosomes for degradation or recycled back to the plasma membrane. Rab proteins are crucial participants during these turnover steps. In this review, we describe the major ICh endocytic pathways, the signaling inputs triggering ICh internalization, and the key mediators of this essential cellular process.
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Affiliation(s)
- Irene Estadella
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
| | - Oriol Pedrós-Gámez
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
| | - Magalí Colomer-Molera
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
| | - Manel Bosch
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
- Centres Científics i Tecnològics de la Universitat de Barcelona (CCiTUB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA;
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
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17
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Sadovsky Y, Ouyang Y, Powell JS, Li H, Mouillet JF, Morelli AE, Sorkin A, Margolis L. Placental small extracellular vesicles: Current questions and investigative opportunities. Placenta 2020; 102:34-38. [PMID: 33218576 DOI: 10.1016/j.placenta.2020.03.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 02/19/2020] [Accepted: 03/02/2020] [Indexed: 12/12/2022]
Abstract
The discovery of regulated trafficking of extracellular vesicles (EVs) has added a new dimension to our understanding of local and distant communication among cells and tissues. Notwithstanding the expanded landscape of EV subtypes, the majority of research in the field centers on small and large EVs that are commonly termed exosomes, microvesicles and apoptotic cell-derived vesicles. In the context of pregnancy, EV-based communication has a special role in the crosstalk among the placenta, maternal and fetal compartments, with most studies focusing on trophoblastic EVs and their effect on other placental cell types, endothelial cells, and distant tissues. Many unanswered questions in the field of EV biology center on the mechanisms of vesicle biogenesis, loading of cargo molecules, EV release and trafficking, the interaction of EVs with target cells and the endocytic pathways underlying their uptake, and the intracellular processing of EVs inside target cells. These questions are directly relevant to EV-based placental-maternal-fetal communication and have unique implications in the context of interaction between two organisms. Despite rapid progress in the field, the number of speculative, unsubstantiated assumptions about placental EVs is concerning. Here we attempt to delineate existing knowledge in the field, focusing primarily on placental small EVs (exosomes). We define central questions that require investigative attention in order to advance the field.
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Affiliation(s)
- Yoel Sadovsky
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, USA; Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, USA.
| | - Yingshi Ouyang
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Juliana S Powell
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Hui Li
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, USA; Reproductive Department of Xiangya Hospital, Central South University, Changsha, Hunan, China; The Third Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Jean-Francois Mouillet
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Adrian E Morelli
- Thomas E. Starzl Transplantation Institute, Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA; Department of Immunology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Leonid Margolis
- Section for Intercellular Interactions, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA
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18
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Verdaguer MP, Larsen MB, Bruchez MP, Watkins SC, Sorkin A. Analysis of EGF Receptor Endocytosis Using Fluorogen Activating Protein Tagged Receptor. Bio Protoc 2019; 9:e3463. [PMID: 33654955 DOI: 10.21769/bioprotoc.3463] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 11/22/2019] [Accepted: 12/22/2019] [Indexed: 12/26/2022] Open
Abstract
Functional activities of many transmembrane proteins are controlled by their endocytosis. One of the most studied experimental models is the epidermal growth factor (EGF) receptor (EGFR). However, endocytic trafficking of EGFR has been predominantly analyzed using labeled EGF, whereas quantitative analyses of the endocytosis of the receptor itself have been sparse. The fluorescence microscopy methods described here are designed to directly quantify EGFR internalization in living cells without labeled EGFR ligands or antibodies. These methods utilize an engineered EGFR chimera in which the fluorogen activating protein (FAP) is fused to the receptor extracellular domain (FAP-EGFR). Binding of malachite green (MG) based dyes to FAP results in a strong far-red fluorescence of MG, thus efficiently labeling FAP-EGFR. In particular, binding of the cell impermeant MG-Bis-SA dye to FAP produces the pH-sensitive dual-excitation fluorescence, which allows differentiation of the cell-surface and internalized pools of FAP-EGFR. Two modifications of the methodology are described: 1) single-cell three-dimensional confocal imaging; and 2) high-throughput assay in multi-well plates. These methodologies can be adopted to study endocytosis of any other transmembrane protein extracellularly tagged with FAP.
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Affiliation(s)
- Mireia Perez Verdaguer
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Mads B Larsen
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Marcel P Bruchez
- Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, United States.,Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, United States.,Department of Chemistry, Carnegie Mellon University, Pittsburgh, United States.,Sharp Edge Laboratories, Pittsburgh, United States
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
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19
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Cheng MH, Ponzoni L, Sorkina T, Lee JY, Zhang S, Sorkin A, Bahar I. Trimerization of dopamine transporter triggered by AIM-100 binding: Molecular mechanism and effect of mutations. Neuropharmacology 2019; 161:107676. [PMID: 31228486 DOI: 10.1016/j.neuropharm.2019.107676] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 06/17/2019] [Accepted: 06/18/2019] [Indexed: 10/26/2022]
Abstract
Recent work demonstrated the propensity of dopamine transporters (DATs) to form trimers or higher oligomers, enhanced upon binding a furopyrimidine, AIM-100. AIM-100 binding promotes DAT endocytosis and thereby moderates dopaminergic transmission. Despite the neurobiological significance of these events, the molecular mechanisms that underlie the stabilization of DAT trimer and the key interactions that modulate the trimerization of DAT, and not serotonin transporter SERT, remain unclear. In the present study, we determined three structural models, termed trimer-W238, -C306 and -Y303, for possible trimerization of DATs . To this aim, we used structural data resolved for DAT and its structural homologs that share the LeuT fold, advanced computational modeling and simulations, site-directed mutagenesis experiments and live-cell imaging assays. The models are in accord with the versatility of LeuT fold to stabilize dimeric or higher order constructs. Selected residues show a high propensity to occupy interfacial regions. Among them, D231-W238 in the extracellular loop EL2, including the intersubunit salt-bridge forming pair D231/D232-R237 (not present in SERT) (in trimer-W238), the loop EL3 (trimers-C306 and -Y303), and W497 on the intracellularly exposed IL5 loop (trimer-C306) and its spatial neighbors (e.g. K525) near the C-terminus are computationally predicted and experimentally confirmed to play important roles in enabling the correct folding and/or oligomerization of DATs in the presence of AIM-100. The study suggests the possibility of controlling the effective transport of dopamine by altering the oligomerization state of DAT upon small molecule binding, as a possible intervention strategy to modulate dopaminergic signaling. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- Mary Hongying Cheng
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Luca Ponzoni
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Tatiana Sorkina
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ji Young Lee
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - She Zhang
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
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20
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Larsen MB, Perez Verdaguer M, Schmidt BF, Bruchez MP, Watkins SC, Sorkin A. Generation of endogenous pH-sensitive EGF receptor and its application in high-throughput screening for proteins involved in clathrin-mediated endocytosis. eLife 2019; 8:46135. [PMID: 31066673 PMCID: PMC6533059 DOI: 10.7554/elife.46135] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 05/07/2019] [Indexed: 12/15/2022] Open
Abstract
Previously we used gene-editing to label endogenous EGF receptor (EGFR) with GFP and demonstrate that picomolar concentrations of EGFR ligand drive signaling and endocytosis of EGFR in tumors in vivo (Pinilla-Macua et al., 2017). We now use gene-editing to insert a fluorogen activating protein (FAP) in the EGFR extracellular domain. Binding of the tandem dye pair MG-Bis-SA to FAP-EGFR provides a ratiometric pH-sensitive model with dual fluorescence excitation and a single far-red emission. The excitation ratio of fluorescence intensities was demonstrated to faithfully report the fraction of FAP-EGFR located in acidic endosomal/lysosomal compartments. Coupling native FAP-EGFR expression with the high method sensitivity has allowed development of a high-throughput assay to measure the rates of clathrin-mediated FAP-EGFR endocytosis stimulated with physiological EGF concentrations. The assay was utilized to screen a phosphatase siRNA library. These studies highlight the utility of endogenous pH-sensitive FAP-receptor chimeras in high-throughput analysis of endocytosis.
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Affiliation(s)
- Mads Breum Larsen
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, United States
| | - Mireia Perez Verdaguer
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, United States
| | - Brigitte F Schmidt
- Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, United States
| | - Marcel P Bruchez
- Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, United States.,Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, United States.,Department of Chemistry, Carnegie Mellon University, Pittsburgh, United States.,Sharp Edge Laboratories, Pittsburgh, United States
| | - Simon C Watkins
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, United States
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, United States
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21
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Surve SV, Myers PJ, Clayton SA, Watkins SC, Lazzara MJ, Sorkin A. Localization dynamics of endogenous fluorescently labeled RAF1 in EGF-stimulated cells. Mol Biol Cell 2019; 30:506-523. [PMID: 30586319 PMCID: PMC6594441 DOI: 10.1091/mbc.e18-08-0512] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Activation of the epidermal growth factor (EGF) receptor (EGFR) at the cell surface initiates signaling through the RAS-RAF-MAPK/ERK1/2 pathway and receptor endocytosis. Whether this signaling continues from endosomes remains unclear, because RAS is predominantly located on the plasma membrane, and the localization of endogenous RAF kinases, downstream effectors of RAS, is not defined. To examine RAF localization, we labeled endogenous RAF1 with mVenus using gene editing. From 10 to 15% of RAF1-mVenus (<2000 molecules/cell), which was initially entirely cytosolic, transiently translocated to the plasma membrane after EGF stimulation. Following an early burst of translocation, the membrane-associated RAF1-mVenus was undetectable by microscopy or subcellular fractionation, and this pool was estimated to be <200 molecules per cell. In contrast, persistent EGF-dependent translocation of RAF1-mVenus to the plasma membrane was driven by the RAF inhibitor sorafenib, which increases the affinity of Ras-GTP:RAF1 interactions. RAF1-mVenus was not found in EGFR-containing endosomes under any conditions. Computational modeling of RAF1 dynamics revealed that RAF1 membrane abundance is controlled most prominently by association and dissociation rates from RAS-GTP and by RAS-GTP concentration. The model further suggested that the relatively protracted activation of the RAF-MEK1/2-ERK1/2 module, in comparison with RAF1 membrane localization, may involve multiple rounds of cytosolic RAF1 rebinding to active RAS at the membrane.
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Affiliation(s)
- Sachin V Surve
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Paul J Myers
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22904
| | - Samantha A Clayton
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22904
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Matthew J Lazzara
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22904.,Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22904
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
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22
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Sorkina T, Ma S, Larsen MB, Watkins SC, Sorkin A. Small molecule induced oligomerization, clustering and clathrin-independent endocytosis of the dopamine transporter. eLife 2018; 7:32293. [PMID: 29630493 PMCID: PMC5896956 DOI: 10.7554/elife.32293] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 03/22/2018] [Indexed: 12/14/2022] Open
Abstract
Clathrin-independent endocytosis (CIE) mediates internalization of many transmembrane proteins but the mechanisms of cargo recruitment during CIE are poorly understood. We found that the cell-permeable furopyrimidine AIM-100 promotes dramatic oligomerization, clustering and CIE of human and mouse dopamine transporters (DAT), but not of their close homologues, norepinephrine and serotonin transporters. All effects of AIM-100 on DAT and the occupancy of substrate binding sites in the transporter were mutually exclusive, suggesting that AIM-100 may act by binding to DAT. Surprisingly, AIM-100-induced DAT endocytosis was independent of dynamin, cholesterol-rich microdomains and actin cytoskeleton, implying that a novel endocytic mechanism is involved. AIM-100 stimulated trafficking of internalized DAT was also unusual: DAT accumulated in early endosomes without significant recycling or degradation. We propose that AIM-100 augments DAT oligomerization through an allosteric mechanism associated with the DAT conformational state, and that oligomerization-triggered clustering leads to a coat-independent endocytosis and subsequent endosomal retention of DAT.
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Affiliation(s)
- Tatiana Sorkina
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Shiqi Ma
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Mads Breum Larsen
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
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23
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Martínez-Mármol R, Styrczewska K, Pérez-Verdaguer M, Vallejo-Gracia A, Comes N, Sorkin A, Felipe A. PKC Activation Induces Ubiquitination-Dependent KV1.3 Endocytosis Mediated by Nedd4-2 Ubiquitin Ligase. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.1713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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24
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25
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Pinilla-Macua I, Grassart A, Duvvuri U, Watkins SC, Sorkin A. EGF receptor signaling, phosphorylation, ubiquitylation and endocytosis in tumors in vivo. eLife 2017; 6. [PMID: 29268862 PMCID: PMC5741375 DOI: 10.7554/elife.31993] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 11/14/2017] [Indexed: 12/11/2022] Open
Abstract
Despite a well-established role for the epidermal growth factor receptor (EGFR) in tumorigenesis, EGFR activities and endocytosis in tumors in vivo have not been studied. We labeled endogenous EGFR with GFP by genome-editing of human oral squamous cell carcinoma cells, which were used to examine EGFR-GFP behavior in mouse tumor xenografts in vivo. Intravital multiphoton imaging, confocal imaging of cryosections and biochemical analysis revealed that localization and trafficking patterns, as well as levels of phosphorylation and ubiquitylation of EGFR in tumors in vivo closely resemble patterns and levels observed in the same cells treated with 20–200 pM EGF in vitro. Consistent with the prediction of low ligand concentrations in tumors, EGFR endocytosis was kinase-dependent and blocked by inhibitors of clathrin-mediated internalization; and EGFR activity was insensitive to Cbl overexpression. Collectively, our data suggest that a small pool of active EGFRs is sufficient to drive tumorigenesis by signaling primarily through the Ras-MAPK pathway.
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Affiliation(s)
- Itziar Pinilla-Macua
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Alexandre Grassart
- Department of Molecular Microbial Pathogenesis, Institute Pasteur, Paris, France
| | - Umamaheswar Duvvuri
- Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, United States
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26
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Martínez-Mármol R, Styrczewska K, Pérez-Verdaguer M, Vallejo-Gracia A, Comes N, Sorkin A, Felipe A. Ubiquitination mediates Kv1.3 endocytosis as a mechanism for protein kinase C-dependent modulation. Sci Rep 2017; 7:42395. [PMID: 28186199 PMCID: PMC5301257 DOI: 10.1038/srep42395] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 01/09/2017] [Indexed: 12/29/2022] Open
Abstract
The voltage-dependent potassium channel Kv1.3 plays essential physiological functions in the immune system. Kv1.3, regulating the membrane potential, facilitates downstream Ca2+ -dependent pathways and becomes concentrated in specific membrane microdomains that serve as signaling platforms. Increased and/or delocalized expression of the channel is observed at the onset of several autoimmune diseases. In this work, we show that adenosine (ADO), which is a potent endogenous modulator, stimulates PKC, thereby causing immunosuppression. PKC activation triggers down-regulation of Kv1.3 by inducing a clathrin-mediated endocytic event that targets the channel to lysosomal-degradative compartments. Therefore, the abundance of Kv1.3 at the cell surface decreases, which is clearly compatible with an effective anti-inflammatory response. This mechanism requires ubiquitination of Kv1.3, catalyzed by the E3 ubiquitin-ligase Nedd4-2. Postsynaptic density protein 95 (PSD-95), a member of the MAGUK family, recruits Kv1.3 into lipid-raft microdomains and protects the channel against ubiquitination and endocytosis. Therefore, the Kv1.3/PSD-95 association fine-tunes the anti-inflammatory response in leukocytes. Because Kv1.3 is a promising multi-therapeutic target against human pathologies, our results have physiological relevance. In addition, this work elucidates the ADO-dependent PKC-mediated molecular mechanism that triggers immunomodulation by targeting Kv1.3 in leukocytes.
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Affiliation(s)
- Ramón Martínez-Mármol
- Molecular Physiology laboratory, Departament de Bioquímica i Biomedicna Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain.,Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Katarzyna Styrczewska
- Molecular Physiology laboratory, Departament de Bioquímica i Biomedicna Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Mireia Pérez-Verdaguer
- Molecular Physiology laboratory, Departament de Bioquímica i Biomedicna Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Albert Vallejo-Gracia
- Molecular Physiology laboratory, Departament de Bioquímica i Biomedicna Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Núria Comes
- Molecular Physiology laboratory, Departament de Bioquímica i Biomedicna Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain.,Laboratory of Neurophysiology, Universitat de Barcelona and Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Antonio Felipe
- Molecular Physiology laboratory, Departament de Bioquímica i Biomedicna Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain
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27
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Styrczewska K, Martínez-Mármol R, Comes N, Estadella I, Pérez-Verdaguer M, Pujadas L, Soriano E, Sorkin A, Felipe A. ERK1/2 Mediates EGF-Dependent Kv1.3 Endocytosis. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.1374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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28
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Kaya C, Cheng MH, Block ER, Sorkin A, Faeder JR, Bahar I. Effect of Spatial Complexity on Dopaminergic Signaling Revealed from Multiscale Simulations. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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29
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Kaya C, Block ER, Sorkin A, Faeder JR, Bahar I. Multi-Scale Spatial Simulations Reveal the Effect of Dopamine Transporter Localization on Dopamine Neurotransmission. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.3385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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30
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Martínez-Mármol R, Comes N, Styrczewska K, Pérez-Verdaguer M, Vicente R, Pujadas L, Soriano E, Sorkin A, Felipe A. Unconventional EGF-induced ERK1/2-mediated Kv1.3 endocytosis. Cell Mol Life Sci 2015; 73:1515-28. [PMID: 26542799 DOI: 10.1007/s00018-015-2082-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 10/14/2015] [Accepted: 10/26/2015] [Indexed: 12/13/2022]
Abstract
The potassium channel Kv1.3 plays roles in immunity, neuronal development and sensory discrimination. Regulation of Kv1.3 by kinase signaling has been studied. In this context, EGF binds to specific receptors (EGFR) and triggers tyrosine kinase-dependent signaling, which down-regulates Kv1.3 currents. We show that Kv1.3 undergoes EGF-dependent endocytosis. This EGF-mediated mechanism is relevant because is involved in adult neural stem cell fate determination. We demonstrated that changes in Kv1.3 subcellular distribution upon EGFR activation were due to Kv1.3 clathrin-dependent endocytosis, which targets the Kv1.3 channels to the lysosomal degradative pathway. Interestingly, our results further revealed that relevant tyrosines and other interacting motifs, such as PDZ and SH3 domains, were not involved in the EGF-dependent Kv1.3 internalization. However, a new, and yet undescribed mechanism, of ERK1/2-mediated threonine phosphorylation is crucial for the EGF-mediated Kv1.3 endocytosis. Our results demonstrate that EGF triggers the down-regulation of Kv1.3 activity and its expression at the cell surface, which is important for the development and migration of adult neural progenitors.
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Affiliation(s)
- Ramón Martínez-Mármol
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Barcelona, Spain.,Departament de Biologia Celular, Universitat de Barcelona, Barcelona, Spain
| | - Núria Comes
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Barcelona, Spain
| | - Katarzyna Styrczewska
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Barcelona, Spain
| | - Mireia Pérez-Verdaguer
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Barcelona, Spain
| | - Rubén Vicente
- Laboratory of Molecular Physiology and Channelopathies, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain
| | - Lluís Pujadas
- Departament de Biologia Celular, Universitat de Barcelona, Barcelona, Spain
| | - Eduardo Soriano
- Departament de Biologia Celular, Universitat de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), ISCIII, Madrid, Spain.,Vall d´Hebron Institute of Research (VHIR) and Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Barcelona, Spain. .,Departament de Bioquímica i Biologia Molecular, Universitat de Barcelona, Avda. Diagonal 643, 08028, Barcelona, Spain.
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31
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Fortian A, Dionne LK, Hong SH, Kim W, Gygi SP, Watkins SC, Sorkin A. Endocytosis of Ubiquitylation-Deficient EGFR Mutants via Clathrin-Coated Pits is Mediated by Ubiquitylation. Traffic 2015; 16:1137-54. [PMID: 26251007 DOI: 10.1111/tra.12314] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 08/03/2015] [Accepted: 08/03/2015] [Indexed: 12/11/2022]
Abstract
Signaling by epidermal growth factor receptor (EGFR) is controlled by endocytosis. However, mechanisms of EGFR endocytosis remain poorly understood. Here, we found that the EGFR mutant lacking known ubiquitylation, acetylation and clathrin adaptor AP-2-binding sites (21KRΔAP2) was internalized at relatively high rates via the clathrin-dependent pathway in human duodenal adenocarcinoma HuTu-80 cells. RNA interference analysis revealed that this residual internalization is strongly inhibited by depletion of Grb2 and the E2 ubiquitin-conjugating enzyme UbcH5b/c, and partially affected by depletion of the E3 ubiquitin ligase Cbl and ubiquitin-binding adaptors, indicating that an ubiquitylation process is involved. Several new ubiquitin conjugation sites were identified by mass spectrometry in the 21KRΔAP2 mutant, suggesting that cryptic ubiquitylation may mediate endocytosis of this mutant. Total internal reflection fluorescence microscopy imaging of HuTu-80 cells transfected with labeled ubiquitin adaptor epsin1 demonstrated that the ubiquitylation-deficient EGFR mutant was endocytosed through a limited population of epsin-enriched clathrin-coated pits (CCPs), although with a prolonged CCP lifetime. Native EGFR was recruited with the same efficiency into CCPs containing either AP-2 or epsin1 that were tagged with fluorescent proteins by genome editing of MDA-MD-231 cells. We propose that two redundant mechanisms, ubiquitylation and interaction with AP-2, contribute to EGFR endocytosis via CCPs in a stochastic fashion.
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Affiliation(s)
- Arola Fortian
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA,, USA
| | - Lai K Dionne
- Department of Pharmacology, University of Colorado Anschutz Medical Center, Aurora, CO,, USA
| | - Sun H Hong
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA,, USA
| | - Woong Kim
- Department of Cell Biology, University of Harvard School of Medicine, Boston, MA,, USA
| | - Steven P Gygi
- Department of Cell Biology, University of Harvard School of Medicine, Boston, MA,, USA
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA,, USA
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA,, USA
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32
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Abstract
Endocytosis and postendocytic sorting of epidermal growth factor (EGF) receptor (EGFR) are the major regulators of EGFR signaling. EGFR endocytosis and ubiquitin-dependent lysosomal targeting are also considered to be the prototypic experimental system for studying the molecular mechanisms of stimulus-induced and constitutive endocytic trafficking. Therefore, elucidation of the mechanisms of EGFR endocytosis and its regulation of the signaling network is essential not only for better understanding of the EGFR biology but also for defining general regulatory principles in the endocytosis system. Comprehensive analysis of these mechanisms requires quantitative and physiologically relevant methodological approaches for measuring the rates of EGFR internalization, degradation, and recycling. Basic experimental protocols described in this chapter cover a combination of single-cell microscopy and biochemical methods that are used to follow EGF-induced endocytosis of EGFR in real time, measure the kinetic rate parameters of EGFR internalization and recycling, and analyze EGF-dependent ubiquitination and degradation of EGFR.
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Affiliation(s)
- Itziar Pinilla-Macua
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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33
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Tomas A, Vaughan SO, Burgoyne T, Sorkin A, Hartley JA, Hochhauser D, Futter CE. WASH and Tsg101/ALIX-dependent diversion of stress-internalized EGFR from the canonical endocytic pathway. Nat Commun 2015; 6:7324. [PMID: 26066081 PMCID: PMC4490399 DOI: 10.1038/ncomms8324] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 04/27/2015] [Indexed: 12/14/2022] Open
Abstract
Stress exposure triggers ligand-independent EGF receptor (EGFR) endocytosis, but its post-endocytic fate and role in regulating signalling are unclear. We show that the p38 MAP kinase-dependent, EGFR tyrosine kinase (TK)-independent EGFR internalization induced by ultraviolet light C (UVC) or the cancer therapeutic cisplatin, is followed by diversion from the canonical endocytic pathway. Instead of lysosomal degradation or plasma membrane recycling, EGFR accumulates in a subset of LBPA-rich perinuclear multivesicular bodies (MVBs) distinct from those carrying EGF-stimulated EGFR. Stress-internalized EGFR co-segregates with exogenously expressed pre-melanosomal markers OA1 and fibrillar PMEL, following early endosomal sorting by the actin polymerization-promoting WASH complex. Stress-internalized EGFR is retained intracellularly by continued p38 activity in a mechanism involving ubiquitin-independent, ESCRT/ALIX-dependent incorporation onto intraluminal vesicles (ILVs) of MVBs. In contrast to the internalization-independent EGF-stimulated activation, UVC/cisplatin-triggered EGFR activation depends on EGFR internalization and intracellular retention. EGFR signalling from this MVB subpopulation delays apoptosis and might contribute to chemoresistance.
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Affiliation(s)
- Alejandra Tomas
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
- Present address: Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Hammersmith Campus, Du Cane Road, London W12 0NN, UK
| | - Simon O. Vaughan
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Thomas Burgoyne
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
| | - John A. Hartley
- Cancer Research UK Drug-DNA Interactions Research Group, UCL Cancer Institute, Paul O'Gorman Building, University College London, 72 Huntley Street, London WC1E 6BT, UK
| | - Daniel Hochhauser
- Cancer Research UK Drug-DNA Interactions Research Group, UCL Cancer Institute, Paul O'Gorman Building, University College London, 72 Huntley Street, London WC1E 6BT, UK
| | - Clare E. Futter
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
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34
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Cheng MH, Block E, Hu F, Cobanoglu MC, Sorkin A, Bahar I. Insights into the Modulation of Dopamine Transporter Function by Amphetamine, Orphenadrine, and Cocaine Binding. Front Neurol 2015; 6:134. [PMID: 26106364 PMCID: PMC4460958 DOI: 10.3389/fneur.2015.00134] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 05/26/2015] [Indexed: 12/29/2022] Open
Abstract
Human dopamine (DA) transporter (hDAT) regulates dopaminergic signaling in the central nervous system by maintaining the synaptic concentration of DA at physiological levels, upon reuptake of DA into presynaptic terminals. DA translocation involves the co-transport of two sodium ions and the channeling of a chloride ion, and it is achieved via alternating access between outward-facing (OF) and inward-facing states of DAT. hDAT is a target for addictive drugs, such as cocaine, amphetamine (AMPH), and therapeutic antidepressants. Our recent quantitative systems pharmacology study suggested that orphenadrine (ORPH), an anticholinergic agent and anti-Parkinson drug, might be repurposable as a DAT drug. Previous studies have shown that DAT-substrates like AMPH or -blockers like cocaine modulate the function of DAT in different ways. However, the molecular mechanisms of modulation remained elusive due to the lack of structural data on DAT. The newly resolved DAT structure from Drosophila melanogaster opens the way to a deeper understanding of the mechanism and time evolution of DAT–drug/ligand interactions. Using a combination of homology modeling, docking analysis, molecular dynamics simulations, and molecular biology experiments, we performed a comparative study of the binding properties of DA, AMPH, ORPH, and cocaine and their modulation of hDAT function. Simulations demonstrate that binding DA or AMPH drives a structural transition toward a functional form predisposed to translocate the ligand. In contrast, ORPH appears to inhibit DAT function by arresting it in the OF open conformation. The analysis shows that cocaine and ORPH competitively bind DAT, with the binding pose and affinity dependent on the conformational state of DAT. Further assays show that the effect of ORPH on DAT uptake and endocytosis is comparable to that of cocaine.
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Affiliation(s)
- Mary Hongying Cheng
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
| | - Ethan Block
- Department of Cell Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
| | - Feizhuo Hu
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA ; Department of Pharmacology and Pharmaceutical Sciences, School of Medicine, Tsinghua University , Beijing , China
| | - Murat Can Cobanoglu
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
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35
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Nagashima T, Inoue N, Yumoto N, Saeki Y, Magi S, Volinsky N, Sorkin A, Kholodenko BN, Okada-Hatakeyama M. Feedforward regulation of mRNA stability by prolonged extracellular signal-regulated kinase activity. FEBS J 2015; 282:613-29. [PMID: 25491268 PMCID: PMC4334673 DOI: 10.1111/febs.13172] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 12/03/2014] [Accepted: 12/05/2014] [Indexed: 01/08/2023]
Abstract
Extracellular signal-regulated kinase (ERK) plays a central role in signal transduction networks and cell fate decisions. Sustained ERK activation induces cell differentiation, whereas transient ERK results in the proliferation of several types of cells. Sustained ERK activity stabilizes the proteins of early-response gene products. However, the effect of ERK activity duration on mRNA stability is unknown. We analyzed the quantitative relationship between the duration of four ERK activity kinetics and the mRNA expression profile in growth factor-treated cells. Time-course transcriptome analysis revealed that the cells with prolonged ERK activity generally showed sustained mRNA expression of late response genes but not early or mid genes. Selected late response genes decayed more rapidly in the presence of a specific ERK inhibitor than a general transcription inhibitor and the decay rate was not related to the number of AU-rich elements. Our results suggest that sustained ERK activity plays an important role in the lifespan of the mRNA encoded by late response genes, in addition to the previously demonstrated role in protein stabilization of early-response genes, including transcription factors regulating the transcription of mid and late genes. This double-positive regulation of ligand-induced genes, also termed feedforward regulation, is critical in cell fate decisions.
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Affiliation(s)
- Takeshi Nagashima
- Laboratory for Integrated Cellular Systems, RIKEN Center for Integrative Medical Sciences (IMS), Tsurumi-ku, Yokohama, Kanagawa, Japan
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Affiliation(s)
- Sandra L Schmid
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas 75390
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Marino Zerial
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
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Saunders MJ, Block E, Sorkin A, Waggoner AS, Bruchez MP. A bifunctional converter: fluorescein quenching scFv/fluorogen activating protein for photostability and improved signal to noise in fluorescence experiments. Bioconjug Chem 2014; 25:1556-64. [PMID: 25072845 PMCID: PMC4140548 DOI: 10.1021/bc500273n] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
![]()
Monoclonal antibodies are one of
the most useful and ubiquitous
affinity reagents used in the biological sciences. Immunostaining
of fixed and live cells for microscopy or cytometry measurements frequently
employs fluorescently labeled antibodies, in particular fluorescein-labeled
antibodies. This dye emits light at a wavelength overlapping with
cellular autofluorescence, making it difficult to measure antibody
binding to proteins of relatively low copy number or in cells of high
green autofluorescence. A number of high affinity fluorescein binding
antibodies and antibody domains have been developed that quench the
dye’s fluorescence. Using a fluorescein-binding recombinant
antibody domain genetically fused to a fluorogen activating protein
(FAP), we demonstrate a molecular converter capable of binding and
quenching fluorescein, while binding and activating a fluorogenic
triarylmethane dye. This reagent converts fluorescein conjugates to
far-red fluorescent probes, where cellular autofluorescence is low,
improving signal-to-background of cell-based antibody binding measurements
by ∼7-fold. Microscopy experiments show colocalization of both
fluorescein and MG fluorescence. This dual affinity fluorescein-quenching-FAP
can also be used to convert fluorescein to the red fluorescing MG
fluorogen on biological molecules other than antibodies.
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Affiliation(s)
- Matthew J Saunders
- Molecular Biosensor and Imaging Center, §Department of Biological Sciences, ∥Department of Chemistry, Carnegie-Mellon University , Pittsburgh, Pennsylvania 15213, United States
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Fortian A, Sorkin A. Live-cell fluorescence imaging reveals high stoichiometry of Grb2 binding to the EGF receptor sustained during endocytosis. J Cell Sci 2013; 127:432-44. [PMID: 24259669 DOI: 10.1242/jcs.137786] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Activation of epidermal growth factor (EGF) receptor (EGFR) leads to its interaction with Grb2, a dual-function adapter mediating both signaling through Ras and receptor endocytosis. We used time-lapse three-dimensional imaging by spinning disk confocal microscopy to analyze trafficking of EGFR and Grb2 in living HeLa cells stimulated with low, physiological concentrations of EGFR ligands. Endogenous Grb2 was replaced in these cells by Grb2 fused to yellow fluorescent protein (YFP). After transient residence in the plasma membrane, Rhodamine-conjugated EGF (EGF-Rh) and Grb2-YFP were rapidly internalized and accumulated in endosomes. Quantitative image analysis revealed that on average two Grb2-YFP molecules were colocalized with one EGF-Rh in cells stimulated with 2 ng/ml EGF-Rh, and the excess of Grb2-YFP over EGF-Rh was even higher when a receptor-saturating concentration of EGF-Rh was used. Therefore, we hypothesize that a single EGFR molecule can be simultaneously associated with functionally distinct Grb2 interaction partners during and after endocytosis. Continuous presence of Grb2-YFP in endosomes was also observed when EGFR was activated by transforming growth factor-α and amphiregulin, suggesting that endosomal EGFRs remain ligand occupied and signaling competent, despite the fact that these growth factors are thought to dissociate from the receptor at acidic pH. The prolonged localization and activity of EGFR-Grb2 complexes in endosomes correlated with the sustained activation of extracellular stimulus-regulated kinase 1/2, suggesting that endosomal EGFRs contribute significantly to this signaling pathway. We propose that endosomal EGFRs function to extend signaling in time and space to compensate for rapid downregulation of surface EGFRs in cells with low receptor expression levels.
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Affiliation(s)
- Arola Fortian
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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39
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Rao A, Sorkin A, Zahniser NR. Mice expressing markedly reduced striatal dopamine transporters exhibit increased locomotor activity, dopamine uptake turnover rate, and cocaine responsiveness. Synapse 2013; 67:668-77. [PMID: 23564231 DOI: 10.1002/syn.21671] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 03/23/2013] [Indexed: 02/06/2023]
Abstract
Variations in the expression levels of the dopamine transporter (DAT) can influence responsiveness to psychostimulant drugs like cocaine. To better understand this relationship, we studied a new DAT-low expresser (DAT-LE) mouse model and performed behavioral and biochemical studies with it. Immunoblotting and [(3) H]WIN 35,428 binding analyses revealed that these mice express ∼35% of wildtype (WT) mouse striatal DAT levels. Compared to WT mice, DAT-LE mice were hyperactive in a novel open-field environment. Despite their higher basal locomotor activity, cocaine (10 or 20 mg/kg, i.p.) induced greater locomotor activation in DAT-LE mice than in WT mice. The maximal velocity (Vmax ) of DAT-mediated [(3) H]DA uptake into striatal synaptosomes was reduced by 46% in DAT-LE mice, as compared to WT. Overall, considering the reduced number of DAT binding sites (Bmax ) along with the reduced Vmax in DAT-LE mice, a 2-fold increase in DA uptake turnover rate (Vmax /Bmax ) was found, relative to WT mice. This suggests that neuroadaptive changes have occurred in the DAT-LE mice that would help to compensate for their low DAT numbers. Interestingly, these changes do not include a reduction in tyrosine hydroxylase levels, as was previously reported in DAT knockout homozygous and heterozygous animals. Further, these changes are not sufficient to prevent elevated novelty- and cocaine-induced locomotor activity. Hence, these mice represent a unique model for studying changes of in vivo DAT function and regulation that result from markedly reduced levels of DAT expression.
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Affiliation(s)
- Anjali Rao
- Department of Pharmacology, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado, 80045, USA.
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40
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Rogstad SM, Sorkina T, Sorkin A, Wu CC. Improved precision of proteomic measurements in immunoprecipitation based purifications using relative quantitation. Anal Chem 2013; 85:4301-6. [PMID: 23517085 PMCID: PMC3995537 DOI: 10.1021/ac4002222] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mass spectrometry coupled immunoprecipitation (MS-IP) studies are useful in identifying and quantitating potential binding partners of a target protein. However, they are often conducted without appropriate loading controls. Western blots are often used to analyze loading controls, yet there are limitations to their usefulness as analytical tools. One remedy for this is the use of selected reaction monitoring (SRM), where the areas under the curve (AUCs) of peptides from a protein of interest can be normalized to those from the constant regions of the immunoglobulins used for the IP. Using this normalization method, significant changes in relative peptide abundance were observed between samples when there appeared to be an unequal load based on immunoglobulin peptide abundance.
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Affiliation(s)
- Sarah M. Rogstad
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
- Pharmacology Training Program, School of Medicine, University of Colorado–Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Tatiana Sorkina
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
| | - Alexander Sorkin
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
| | - Christine C. Wu
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
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41
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Abstract
Endocytosis is the major regulator of signaling from receptor tyrosine kinases (RTKs). The canonical model of RTK endocytosis involves rapid internalization of an RTK activated by ligand binding at the cell surface and subsequent sorting of internalized ligand-RTK complexes to lysosomes for degradation. Activation of the intrinsic tyrosine kinase activity of RTKs results in autophosphorylation, which is mechanistically coupled to the recruitment of adaptor proteins and conjugation of ubiquitin to RTKs. Ubiquitination serves to mediate interactions of RTKs with sorting machineries both at the cell surface and on endosomes. The pathways and kinetics of RTK endocytic trafficking, molecular mechanisms underlying sorting processes, and examples of deviations from the standard trafficking itinerary in the RTK family are discussed in this work.
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Affiliation(s)
- Lai Kuan Goh
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Sorkina T, Caltagarone J, Sorkin A. Flotillins regulate membrane mobility of the dopamine transporter but are not required for its protein kinase C dependent endocytosis. Traffic 2013; 14:709-24. [PMID: 23418867 DOI: 10.1111/tra.12059] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 02/13/2013] [Accepted: 02/18/2013] [Indexed: 12/15/2022]
Abstract
Flotillins were proposed to mediate clathrin-independent endocytosis, and recently, flotillin-1 was implicated in the protein kinase C (PKC)-triggered endocytosis of the dopamine transporter (DAT). Since endocytosis of DAT was previously shown to be clathrin-mediated, we re-examined the role of clathrin coat proteins and flotillin in DAT endocytosis using DAT tagged with the hemagglutinin epitope (HA) in the extracellular loop and a quantitative HA antibody uptake assay. Depletion of flotillin-1, flotillin-2 or both flotillins together by small interfering RNAs (siRNAs) did not inhibit PKC-dependent internalization and degradation of HA-DAT. In contrast, siRNAs to clathrin heavy chain and μ2 subunit of clathrin adaptor complex AP-2 as well as a dynamin inhibitor Dyngo-4A significantly decreased PKC-dependent endocytosis of HA-DAT. Similarly, endocytosis and degradation of DAT that is not epitope-tagged were highly sensitive to the clathrin siRNAs and dynamin inhibition but were not affected by flotillin knockdown. Very little co-localization of DAT with flotillins was observed in cells ectopically expressing DAT and in cultured mouse dopaminergic neurons. Depletion of flotillins increased diffusion rates of HA-DAT in the plasma membrane, suggesting that flotillin-organized microdomains may regulate the lateral mobility of DAT. We propose that clathrin-mediated endocytosis is the major pathway of PKC-dependent internalization of DAT, and that flotillins may modulate functional association of DAT with plasma membrane rafts rather than mediate DAT endocytosis.
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Affiliation(s)
- Tatiana Sorkina
- Department of Cell Biology, University of Pittsburgh, School of Medicine, Pittsburgh, PA, USA
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Galperin E, Abdelmoti L, Sorkin A. Shoc2 is targeted to late endosomes and required for Erk1/2 activation in EGF-stimulated cells. PLoS One 2012; 7:e36469. [PMID: 22606262 PMCID: PMC3351432 DOI: 10.1371/journal.pone.0036469] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2011] [Accepted: 04/05/2012] [Indexed: 12/21/2022] Open
Abstract
Shoc2 is the putative scaffold protein that interacts with RAS and RAF, and positively regulates signaling to extracellular signal-regulated protein kinases 1 and 2 (ERK1/2). To elucidate the mechanism by which Shoc2 regulates ERK1/2 activation by the epidermal growth factor (EGF) receptor (EGFR), we studied subcellular localization of Shoc2. Upon EGFR activation, endogenous Shoc2 and red fluorescent protein tagged Shoc2 were translocated from the cytosol to a subset of late endosomes containing Rab7. The endosomal recruitment of Shoc2 was blocked by overexpression of a GDP-bound H-RAS (N17S) mutant and RNAi knockdown of clathrin, suggesting the requirement of RAS activity and clathrin-dependent endocytosis. RNAi depletion of Shoc2 strongly inhibited activation of ERK1/2 by low, physiological EGF concentrations, which was rescued by expression of wild-type recombinant Shoc2. In contrast, the Shoc2 (S2G) mutant, that is myristoylated and found in patients with the Noonan-like syndrome, did not rescue ERK1/2 activation in Shoc2-depleted cells. Shoc2 (S2G) was not located in late endosomes but was present on the plasma membrane and early endosomes. These data suggest that targeting of Shoc2 to late endosomes may facilitate EGFR-induced ERK activation under physiological conditions of cell stimulation by EGF, and therefore, may be involved in the spatiotemporal regulation of signaling through the RAS-RAF module.
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Affiliation(s)
- Emilia Galperin
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, Kentucky, United States of America.
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44
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Rao A, Richards TL, Simmons D, Zahniser NR, Sorkin A. Epitope-tagged dopamine transporter knock-in mice reveal rapid endocytic trafficking and filopodia targeting of the transporter in dopaminergic axons. FASEB J 2012; 26:1921-33. [PMID: 22267337 DOI: 10.1096/fj.11-196113] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The plasma membrane dopamine (DA) transporter (DAT) is essential for reuptake of extracellular DA. DAT function in heterologous cells is regulated by subcellular targeting, endocytosis, and intracellular trafficking, but the mechanisms regulating neuronal DAT remain poorly understood. Hence, we generated a knock-in mouse expressing a hemagglutinin (HA)-epitope-tagged DAT to study endogenous transporter trafficking. Introduction of the HA tag into the second extracellular loop of mouse DAT did not perturb its expression level, distribution pattern, or substrate uptake kinetics. Live-cell fluorescence microscopy imaging using fluorescently labeled HA-specific antibody and a quantitative HA-antibody endocytosis assay demonstrated that in axons HA-DAT was primarily located in the plasma membrane and internalized mostly in growth cones and varicosities, where synaptic vesicle markers were also concentrated. Formation of varicosities was frequently preceded or accompanied by highly dynamic filopodia-like membrane protrusions. Remarkably, HA-DAT often concentrated at the tips of these filopodia. This pool of HA-DATs exhibited low lateral membrane mobility. Thus, DAT-containing filopodia may be involved in synaptogenesis in developing DA neurons. Treatment of neurons with amphetamine increased mobility of filopodial HA-DAT and accelerated HA-DAT endocytosis in axons, suggesting that chronic amphetamine may interfere with DA synapse development. Interestingly, phorbol esters did not accelerate endocytosis of axonal DAT.
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Affiliation(s)
- Anjali Rao
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, S368 Biomedical Science Tower South, 3500 Terrace St., Pittsburgh, PA 15261, USA
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Eden ER, Huang F, Sorkin A, Futter CE. The role of EGF receptor ubiquitination in regulating its intracellular traffic. Traffic 2011; 13:329-37. [PMID: 22017370 DOI: 10.1111/j.1600-0854.2011.01305.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2011] [Revised: 10/19/2011] [Accepted: 10/19/2011] [Indexed: 12/21/2022]
Abstract
Progression of activated EGF receptor (EGFR) through the endocytic pathway regulates EGFR signaling. Here we show that a non-ubiquitinated EGFR mutant, unable to bind the endosomal-sorting complex required for transport (ESCRT) component, Hrs, is not efficiently targeted onto intraluminal vesicles (ILVs) of multivesicular endosomes/bodies (MVBs). Moreover, ubiquitination and ESCRT engagement of activated EGFR are required for EGF-stimulated ILV formation. Non-ubiquitinated EGFRs enter clathrin-coated tubules emanating from MVBs and show enhanced recycling to the plasma membrane, compared to wild-type EGFR.
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Affiliation(s)
- Emily R Eden
- UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK
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46
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Duex JE, Comeau L, Sorkin A, Purow B, Kefas B. Usp18 regulates epidermal growth factor (EGF) receptor expression and cancer cell survival via microRNA-7. J Biol Chem 2011; 286:25377-86. [PMID: 21592959 DOI: 10.1074/jbc.m111.222760] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Epidermal growth factor receptor (EGFR) is involved in development and progression of many human cancers. We have previously demonstrated that the ubiquitin-specific peptidase Usp18 (Ubp43) is a potent regulator of EGFR protein expression. Here we report that the 3'-untranslated region (3'-UTR) of the EGFR message modulates RNA translation following cell treatment with Usp18 siRNA, suggesting microRNA as a possible mediator. Given earlier evidence of EGFR regulation by the microRNA miR-7, we assessed whether miR-7 mediates Usp18 siRNA effects. We found that Usp18 depletion elevates miR-7 levels in several cancer cell lines because of a transcriptional activation and/or mRNA stabilization of miR-7 host genes and that miR-7 acts downstream of Usp18 to regulate EGFR mRNA translation via the 3'-UTR. Also, depletion of Usp18 led to a decrease in protein levels of other known oncogenic targets of miR-7, reduced cell proliferation and soft agar colony formation, and increased apoptosis. Notably, all of these phenotypes were reversed by a specific inhibitor of miR-7. Thus, our findings support a model in which Usp18 inhibition promotes up-regulation of miR-7, which in turn inhibits EGFR expression and the tumorigenic activity of cancer cells.
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Affiliation(s)
- Jason E Duex
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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Duex JE, Kefas B, Purow B, Sorkin A. Abstract 4691: Inhibition of ubiquitin specific protease Usp18 reduces cancer cell proliferation by down regulating multiple proto-oncogenes including EGFR. Cancer Res 2011. [DOI: 10.1158/1538-7445.am2011-4691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
A greater understanding of the mechanisms by which specific oncogenic proteins are regulated is critical to developing improved targeted therapies. To identify novel regulators of oncogenic cell surface receptors we screened for enzymes whose inhibition promoted down-regulation of these receptors. One of these screens involved exposing cancer cells to an RNAi library targeting deubiquitinase enzymes and subsequently analyzing the cell-surface levels of the proto-oncogene, epidermal growth factor receptor (EGFR) in squamous cell carcinoma cells. This screen ultimately led to the discovery that depletion of the ubiquitin specific protease Usp18 from numerous cancer cell lines dramatically reduced protein and activity levels of EGFR, by as much as 90%. Furthermore, the activity of Usp18 was critical to its ability to control EGFR protein levels. Interestingly, this study also determined that Usp18 does not directly target EGFR proteins but instead controls EGFR protein synthesis. The work to be presented here shows that Usp18 executes this function by regulating the levels of microRNA-7 (miR-7). Acute depletion (72h) of Usp18 from several cancer cell lines, including squamous cell carcinoma (SCC2) and glioma (T98; U87), leads to an increase (up to 2-fold) in miR-7. Since miR-7 has previously been shown to be inhibitory to EGFR mRNA translation we hypothesized that miR-7 functions intermediary to Usp18 regulation of EGFR. This idea was confirmed when we observed that addition of a miR-7 specific inhibitor to Usp18 siRNA experiments completely reversed EGFR down-regulation. These findings illuminate for the first time the Usp18/miR-7/EGFR pathway in cancer cells. We have also found that Usp18 depletion promotes down-regulation of the proto-oncogene cyclin D1. Thus, acute depletion of Usp18 in numerous cancer cell lines leads to the down-regulation of multiple proto-oncogenes. To determine if chronic Usp18 inhibition also promotes down-regulation of EGFR and cyclin D1 we generated clonal SCC2 and U87 cells which express inducible Usp18 shRNA via lentiviral integration. Long term Usp18 depletion (5-15 days) also promotes proto-oncogene down-regulation. Furthermore, we observed a >50% reduction in cellular proliferation, matching observations made with acute depletion. We also hypothesized that since miR-7 regulates EGFR mRNA translation at the 3’ UTR the mutational status of EGFR would not counter the capabilities of Usp18 inhibition. Indeed, depletion of Usp18 from cancer cell lines encoding mutated EGFR also leads to dramatic down-regulation of the receptor (e.g., 75% in EGFR-T790M expressing H1975 cells). Thus, Usp18 inhibition may represent a unique therapeutic opportunity, even in tumors which express a heterogenic population of EGFR.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4691. doi:10.1158/1538-7445.AM2011-4691
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Affiliation(s)
- Jason E. Duex
- 1University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Benjamin Kefas
- 2University of Virginia Neuro-Oncology Center, Charlottesville, VA
| | - Benjamin Purow
- 2University of Virginia Neuro-Oncology Center, Charlottesville, VA
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48
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Vina-Vilaseca A, Bender-Sigel J, Sorkina T, Closs EI, Sorkin A. Protein kinase C-dependent ubiquitination and clathrin-mediated endocytosis of the cationic amino acid transporter CAT-1. J Biol Chem 2011; 286:8697-8706. [PMID: 21212261 DOI: 10.1074/jbc.m110.186858] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cationic amino acid transporter 1 (CAT-1) is responsible for the bulk of the uptake of cationic amino acids in most mammalian cells. Activation of protein kinase C (PKC) leads to down-regulation of the cell surface CAT-1. To examine the mechanisms of PKC-induced down-regulation of CAT-1, a functional mutant of CAT-1 (CAT-1-HA-GFP) was generated in which a hemagglutinin antigen (HA) epitope tag was introduced into the second extracellular loop and GFP was attached to the carboxyl terminus. CAT-1-HA-GFP was stably expressed in porcine aorthic endothelial and human epithelial kidney (HEK) 293 cells. Using the HA antibody internalization assay we have demonstrated that PKC-dependent endocytosis was strongly inhibited by siRNA depletion of clathrin heavy chain, indicating that CAT-1-HA-GFP internalization requires clathrin-coated pits. Internalized CAT-1-HA-GFP was accumulated in early, recycling, and late endosomes. PKC activation also resulted in ubiquitination of CAT-1. CAT-1 ubiquitination and endocytosis in phorbol ester-stimulated porcine aorthic endothelial and HEK293 cells were inhibited by siRNA knockdown of NEDD4-2 and NEDD4-1 E3 ubiquitin ligases, respectively. In contrast, ubiquitination and endocytosis of the dopamine transporter was dependent on NEDD4-2 in all cell types tested. Altogether, our data suggest that ubiquitination mediated by NEDD4-2 or NEDD4-1 leading to clathrin-mediated endocytosis is the common mode of regulation of various transporter proteins by PKC.
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Affiliation(s)
- Arnau Vina-Vilaseca
- From the Department of Pharmacology, Anschutz Medical Center, University of Colorado Denver, Aurora, Colorado 80010
| | - Julia Bender-Sigel
- the Department of Pharmacology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz 55101, Germany
| | - Tatiana Sorkina
- the Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, and
| | - Ellen Ildicho Closs
- the Department of Pharmacology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz 55101, Germany
| | - Alexander Sorkin
- From the Department of Pharmacology, Anschutz Medical Center, University of Colorado Denver, Aurora, Colorado 80010,; the Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, and.
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Goh LK, Huang F, Kim W, Gygi S, Sorkin A. Multiple mechanisms collectively regulate clathrin-mediated endocytosis of the epidermal growth factor receptor. ACTA ACUST UNITED AC 2010; 189:871-83. [PMID: 20513767 PMCID: PMC2878939 DOI: 10.1083/jcb.201001008] [Citation(s) in RCA: 191] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Four independent mechanisms for uptake of activated EGFR are identified by a combination of receptor mutagenesis and RNA interference approaches. Endocytosis of the epidermal growth factor receptor (EGFR) is important for the regulation of EGFR signaling. However, EGFR endocytosis mechanisms are poorly understood, which precludes development of approaches to specifically inhibit EGFR endocytosis and analyze its impact on signaling. Using a combination of receptor mutagenesis and RNA interference, we demonstrate that clathrin-dependent internalization of activated EGFR is regulated by four mechanisms, which function in a redundant and cooperative fashion. These mechanisms involve ubiquitination of the receptor kinase domain, the clathrin adaptor complex AP-2, the Grb2 adaptor protein, and three C-terminal lysine residues (K1155, K1158, and K1164), which are acetylated, a novel posttranslational modification for the EGFR. Based on these findings, the first internalization-defective EGFR mutant with functional kinase and normal tyrosine phosphorylation was generated. Analysis of the signaling kinetics of this mutant revealed that EGFR internalization is required for the sustained activation of protein kinase B/AKT but not for the activation of mitogen-activated protein kinase.
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Affiliation(s)
- Lai Kuan Goh
- Department of Pharmacology, School of Medicine, University of Colorado Denver, Aurora, CO 80045, USA
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Abstract
Binding of epidermal growth factor (EGF) to the EGF receptor (EGFR) initiates signal transduction, ultimately leading to altered gene expression. Ligand-activated EGFR is also rapidly internalized and then targeted to lysosomes for degradation or recycled back to the plasma membrane. Endocytosis is a major regulator of EGFR signaling. Therefore, elucidation of the mechanisms of EGFR endocytosis is essential for a better understanding of EGFR biology. In order to achieve a comprehensive analysis of these mechanisms, reliable methods for measuring the rates of EGFR protein turnover and the rate parameters for individual steps of EGFR endocytic trafficking must be employed. The protocols in this unit describe methodologies to measure the rates of EGFR synthesis and degradation, to monitor EGF-induced down-regulation of surface EGFR, to measure the kinetic rate parameters of internalization, recycling, and degradation of radiolabeled EGF, and to perform radioiodination of EGF by the chloramine T method.
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Affiliation(s)
- Alexander Sorkin
- Department of Pharmacology, University of Colorado Denver Medical School, Aurora, Colorado, USA
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