1
|
The insulin receptor endocytosis. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 194:79-107. [PMID: 36631202 DOI: 10.1016/bs.pmbts.2022.06.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Insulin signaling controls multiple aspects of animal physiology. At the cell surface, insulin binds and activates the insulin receptor (IR), a receptor tyrosine kinase. Insulin promotes a large conformational change of IR and stabilizes the active conformation. The insulin-activated IR triggers signaling cascades, thus controlling metabolism, growth, and proliferation. The activated IR undergoes internalization by clathrin- or caveolae-mediated endocytosis. The IR endocytosis plays important roles in insulin clearance from blood, and distribution and termination of the insulin signaling. Despite decades of extensive studies, the mechanism and regulation of IR endocytosis and its contribution to pathophysiology remain incompletely understood. Here we discuss recent findings that provide insights into the molecular mechanisms and regulatory pathways that mediate the IR endocytosis.
Collapse
|
2
|
Choi E, Kikuchi S, Gao H, Brodzik K, Nassour I, Yopp A, Singal AG, Zhu H, Yu H. Mitotic regulators and the SHP2-MAPK pathway promote IR endocytosis and feedback regulation of insulin signaling. Nat Commun 2019; 10:1473. [PMID: 30931927 PMCID: PMC6443781 DOI: 10.1038/s41467-019-09318-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 02/25/2019] [Indexed: 12/17/2022] Open
Abstract
Insulin controls glucose homeostasis and cell growth through bifurcated signaling pathways. Dysregulation of insulin signaling is linked to diabetes and cancer. The spindle checkpoint controls the fidelity of chromosome segregation during mitosis. Here, we show that insulin receptor substrate 1 and 2 (IRS1/2) cooperate with spindle checkpoint proteins to promote insulin receptor (IR) endocytosis through recruiting the clathrin adaptor complex AP2 to IR. A phosphorylation switch of IRS1/2 orchestrated by extracellular signal-regulated kinase 1 and 2 (ERK1/2) and Src homology phosphatase 2 (SHP2) ensures selective internalization of activated IR. SHP2 inhibition blocks this feedback regulation and growth-promoting IR signaling, prolongs insulin action on metabolism, and improves insulin sensitivity in mice. We propose that mitotic regulators and SHP2 promote feedback inhibition of IR, thereby limiting the duration of insulin signaling. Targeting this feedback inhibition can improve insulin sensitivity. The mechanisms promoting insulin resistance at the receptor level are poorly understood. Here, Choi et al. show that mitotic proteins and the SHP2-MAPK pathway regulate receptor endocytosis and insulin signaling feedback, identifying a potential role for SHP2 inhibitors to treat diabetes.
Collapse
Affiliation(s)
- Eunhee Choi
- Howard Hughes Medical Institute, Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX, 75390, USA
| | - Sotaro Kikuchi
- Howard Hughes Medical Institute, Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX, 75390, USA
| | - Haishan Gao
- Howard Hughes Medical Institute, Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX, 75390, USA
| | - Karolina Brodzik
- Howard Hughes Medical Institute, Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX, 75390, USA
| | - Ibrahim Nassour
- Children's Research Institute, Departments of Pediatrics and Internal Medicine, Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Adam Yopp
- Children's Research Institute, Departments of Pediatrics and Internal Medicine, Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Amit G Singal
- Children's Research Institute, Departments of Pediatrics and Internal Medicine, Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Hao Zhu
- Children's Research Institute, Departments of Pediatrics and Internal Medicine, Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Hongtao Yu
- Howard Hughes Medical Institute, Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX, 75390, USA.
| |
Collapse
|
3
|
Choi E, Yu H. Spindle Checkpoint Regulators in Insulin Signaling. Front Cell Dev Biol 2018; 6:161. [PMID: 30555826 PMCID: PMC6281718 DOI: 10.3389/fcell.2018.00161] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 11/08/2018] [Indexed: 12/17/2022] Open
Abstract
The spindle checkpoint ensures accurate chromosome segregation during mitosis and guards against aneuploidy. Insulin signaling governs metabolic homeostasis and cell growth, and its dysregulation leads to metabolic disorders, such as diabetes. These critical pathways have been extensively investigated, but a link between the two has not been established until recently. Our recent study reveals a critical role of spindle checkpoint regulators in insulin signaling and metabolic homeostasis through regulating endocytosis of the insulin receptor (IR). These findings have linked spindle checkpoint proteins to metabolic regulation, expanding the connection between cell division and metabolism. Here, we briefly review the unexpected roles of spindle checkpoint regulators in vesicle trafficking and insulin signaling.
Collapse
Affiliation(s)
- Eunhee Choi
- Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Hongtao Yu
- Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, United States
| |
Collapse
|
4
|
Kwon H, Jang D, Choi M, Lee J, Jeong K, Pak Y. Alternative translation initiation of Caveolin-2 desensitizes insulin signaling through dephosphorylation of insulin receptor by PTP1B and causes insulin resistance. Biochim Biophys Acta Mol Basis Dis 2018; 1864:2169-2182. [PMID: 29604334 DOI: 10.1016/j.bbadis.2018.03.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 03/08/2018] [Accepted: 03/26/2018] [Indexed: 12/30/2022]
Abstract
Insulin resistance, defined as attenuated sensitivity responding to insulin, impairs insulin action. Direct causes and molecular mechanisms of insulin resistance have thus far remained elusive. Here we show that alternative translation initiation (ATI) of Caveolin-2 (Cav-2) regulates insulin sensitivity. Cav-2β isoform yielded by ATI desensitizes insulin receptor (IR) via dephosphorylation by protein-tyrosine phosphatase 1B (PTP1B), and subsequent endocytosis and lysosomal degradation of IR, causing insulin resistance. Blockage of Cav-2 ATI protects against insulin resistance by preventing Cav-2β-PTP1B-directed IR desensitization, thereby normalizing insulin sensitivity and glucose uptake. Our findings show that Cav-2β is a negative regulator of IR signaling, and identify a mechanism causing insulin resistance through control of insulin sensitivity via Cav-2 ATI.
Collapse
Affiliation(s)
- Hayeong Kwon
- Division of Life Science, Graduate School of Applied Life Science (BK21 Plus Program), PMBBRC, Gyeongsang National University, Jinju 52828, Republic of Korea
| | - Donghwan Jang
- Division of Life Science, Graduate School of Applied Life Science (BK21 Plus Program), PMBBRC, Gyeongsang National University, Jinju 52828, Republic of Korea
| | - Moonjeong Choi
- Division of Life Science, Graduate School of Applied Life Science (BK21 Plus Program), PMBBRC, Gyeongsang National University, Jinju 52828, Republic of Korea
| | - Jaewoong Lee
- Division of Life Science, Graduate School of Applied Life Science (BK21 Plus Program), PMBBRC, Gyeongsang National University, Jinju 52828, Republic of Korea
| | - Kyuho Jeong
- Division of Life Science, Graduate School of Applied Life Science (BK21 Plus Program), PMBBRC, Gyeongsang National University, Jinju 52828, Republic of Korea
| | - Yunbae Pak
- Division of Life Science, Graduate School of Applied Life Science (BK21 Plus Program), PMBBRC, Gyeongsang National University, Jinju 52828, Republic of Korea.
| |
Collapse
|
5
|
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.
Collapse
Affiliation(s)
- Lai Kuan Goh
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | | |
Collapse
|
6
|
Huang HT, Leu JH, Huang PY, Chen LL. A putative cell surface receptor for white spot syndrome virus is a member of a transporter superfamily. PLoS One 2012; 7:e33216. [PMID: 22427993 PMCID: PMC3302809 DOI: 10.1371/journal.pone.0033216] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 02/05/2012] [Indexed: 01/07/2023] Open
Abstract
White spot syndrome virus (WSSV), a large enveloped DNA virus, can cause the most serious viral disease in shrimp and has a wide host range among crustaceans. In this study, we identified a surface protein, named glucose transporter 1 (Glut1), which could also interact with WSSV envelope protein, VP53A. Sequence analysis revealed that Glut1 is a member of a large superfamily of transporters and that it is most closely related to evolutionary branches of this superfamily, branches that function to transport this sugar. Tissue tropism analysis showed that Glut1 was constitutive and highly expressed in almost all organs. Glut1's localization in shrimp cells was further verified and so was its interaction with Penaeus monodon chitin-binding protein (PmCBP), which was itself identified to interact with an envelope protein complex formed by 11 WSSV envelope proteins. In vitro and in vivo neutralization experiments using synthetic peptide contained WSSV binding domain (WBD) showed that the WBD peptide could inhibit WSSV infection in primary cultured hemocytes and delay the mortality in shrimps challenged with WSSV. These findings have important implications for our understanding of WSSV entry.
Collapse
Affiliation(s)
- Huai-Ting Huang
- Institute of Marine Biology, National Taiwan Ocean University, Jhongjheng District, Keelung City, Taiwan, Republic of China
| | - Jiann-Horng Leu
- Institute of Marine Biology, National Taiwan Ocean University, Jhongjheng District, Keelung City, Taiwan, Republic of China
- Center of Excellence for Marine Bioenvironment and Biotechnology, National Taiwan Ocean University, Jhongjheng District, Keelung City, Taiwan, Republic of China
| | - Po-Yu Huang
- Institute of Marine Biology, National Taiwan Ocean University, Jhongjheng District, Keelung City, Taiwan, Republic of China
| | - Li-Li Chen
- Institute of Marine Biology, National Taiwan Ocean University, Jhongjheng District, Keelung City, Taiwan, Republic of China
- Center of Excellence for Marine Bioenvironment and Biotechnology, National Taiwan Ocean University, Jhongjheng District, Keelung City, Taiwan, Republic of China
- * E-mail:
| |
Collapse
|
7
|
LRAD3, a novel low-density lipoprotein receptor family member that modulates amyloid precursor protein trafficking. J Neurosci 2011; 31:10836-46. [PMID: 21795536 DOI: 10.1523/jneurosci.5065-10.2011] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
We have identified a novel low-density lipoprotein (LDL) receptor family member, termed LDL receptor class A domain containing 3 (LRAD3), which is expressed in neurons. The LRAD3 gene encodes an ∼50 kDa type I transmembrane receptor with an ectodomain containing three LDLa repeats, a transmembrane domain, and a cytoplasmic domain containing a conserved dileucine internalization motif and two polyproline motifs with potential to interact with WW-domain-containing proteins. Immunohistochemical analysis of mouse brain reveals LRAD3 expression in the cortex and hippocampus. In the mouse hippocampal-derived cell line HT22, LRAD3 partially colocalizes with amyloid precursor protein (APP) and interacts with APP as revealed by coimmunoprecipitation experiments. To identify the portion of APP that interacts with LRAD3, we used solid-phase binding assays that demonstrated that LRAD3 failed to bind to a soluble APP fragment (sAPPα) released after α-secretase cleavage. In contrast, C99, the β-secretase product that remains cell associated, coprecipitated with LRAD3, confirming that regions within this portion of APP are important for associating with LRAD3. The association of LRAD3 with APP increases the amyloidogenic pathway of APP processing, resulting in a decrease in sAPPα production and increased Aβ peptide production. Pulse-chase experiments confirm that LRAD3 expression significantly decreases the cellular half-life of mature APP. These results reveal that LRAD3 influences APP processing and raises the possibility that LRAD3 alters APP function in neurons, including its downstream signaling.
Collapse
|
8
|
Casas S, Casini P, Piquer S, Altirriba J, Soty M, Cadavez L, Gomis R, Novials A. BACE2 plays a role in the insulin receptor trafficking in pancreatic ß-cells. Am J Physiol Endocrinol Metab 2010; 299:E1087-95. [PMID: 20943756 DOI: 10.1152/ajpendo.00420.2010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
BACE1 (β-site amyloidogenic cleavage of precursor protein-cleaving enzyme 1) is a β-secretase protein that plays a central role in the production of the β-amyloid peptide in the brain and is thought to be involved in the Alzheimer's pathogenesis. In type 2 diabetes, amyloid deposition within the pancreatic islets is a pathophysiological hallmark, making crucial the study in the pancreas of BACE1 and its homologous BACE2 to understand the pathological mechanisms of this disease. The objectives of the present study were to characterize the localization of BACE proteins in human pancreas and determine their function. High levels of BACE enzymatic activity were detected in human pancreas. In normal human pancreas, BACE1 was observed in endocrine as well as in exocrine pancreas, whereas BACE2 expression was restricted to β-cells. Intracellular analysis using immunofluorescence showed colocalization of BACE1 with insulin and BACE2 with clathrin-coated vesicles of the plasma membrane in MIN6 cells. When BACE1 and -2 were pharmacologically inhibited, BACE1 localization was not altered, whereas BACE2 content in clathrin-coated vesicles was increased. Insulin internalization rate was reduced, insulin receptor β-subunit (IRβ) expression was decreased at the plasma membrane and increased in the Golgi apparatus, and a significant reduction in insulin gene expression was detected. Similar results were obtained after specific BACE2 silencing in MIN6 cells. All these data point to a role for BACE2 in the IRβ trafficking and insulin signaling. In conclusion, BACE2 is hereby presented as an important enzyme in β-cell function.
Collapse
Affiliation(s)
- Silvia Casas
- Hospital Clínic de Barcelona, Villarroel 170, 08036 Barcelona, Spain
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Robach JG, Lamb RA. Analysis of parainfluenza virus-5 hemagglutinin-neuraminidase protein mutants that are blocked in internalization and degradation. Virology 2010; 406:189-201. [PMID: 20684967 DOI: 10.1016/j.virol.2010.06.049] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Revised: 06/09/2010] [Accepted: 06/30/2010] [Indexed: 10/19/2022]
Abstract
The PIV-5 hemagglutinin-neuraminidase (HN) protein is a multifunctional protein with sialic acid binding, neuraminidase and fusion promotion activity. HN is internalized by clathrin-mediated endocytosis and degraded. HN lacks internalization signals in its cytoplasmic tail but a single glutamic acid present at residue 37 at the putative transmembrane/ectodomain boundary is critical. We rescued rPIV-5 with mutations E37D or E37K, which have been shown to impair or abolish HN internalization, respectively. These viruses exhibited growth properties similar to wild-type (wt) virus but are impaired for fitness in tissue culture. Biochemical analysis of HN activities showed differences between HN E37D and HN E37K in fusion promotion and incorporation of HN and F into virions. Furthermore, oligomeric analyses indicate that HN E37 mutants perturb the tetrameric organization of HN, probably by destabilizing the dimer-of-dimers interface.
Collapse
Affiliation(s)
- Jessica G Robach
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208-3500, USA
| | | |
Collapse
|
10
|
Hunter MG, McLemore M, Link DC, Loveland M, Copelan A, Avalos BR. Divergent pathways in COS-7 cells mediate defective internalization and intracellular routing of truncated G-CSFR forms in SCN/AML. PLoS One 2008; 3:e2452. [PMID: 18560579 PMCID: PMC2409964 DOI: 10.1371/journal.pone.0002452] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Accepted: 05/13/2008] [Indexed: 11/18/2022] Open
Abstract
Background Expression of truncated G-CSFR forms in patients with SCN/AML induces hyperproliferation and prolonged cell survival. Previously, we showed that ligand internalization is delayed and degradation of truncated G-CSFR forms is defective in patients with SCN/AML. Methodology/Principal Findings In this study, we investigated the potential roles of dileucine and tyrosine-based motifs within the cytoplasmic domain of the G-CSFR in modulating ligand/receptor internalization. Using standard binding assays with radiolabeled ligand and COS-7 cells, substitutions in the dileucine motif or deletion of tyrosine residues in the G-CSFR did not alter internalization. Attachment of the transferrin receptor YTRF internalization motif to a truncated G-CSFR form from a patient with SCN/AML corrected defective internalization, but not receptor degradation suggesting that receptor internalization and degradation occur independently via distinct domains and/or processes. Conclusions Our data suggest that distinct domains within the G-CSFR mediate separate processes for receptor internalization and degradation. Our findings using standard binding assays differ from recently published data utilizing flow cytometry.
Collapse
Affiliation(s)
- Melissa G. Hunter
- Pulmonary, Allergy, Critical Care and Sleep Medicine, The Ohio State University, Columbus, Ohio, United States of America
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, United States of America
| | - Morgan McLemore
- Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Daniel C. Link
- Division of Bone Marrow Transplantation and Stem Cell Biology, Washington University, St. Louis, Missouri, United States of America
| | - Megan Loveland
- Division of Hematology/Oncology, The Ohio State University, Columbus, Ohio, United States of America
| | - Alexander Copelan
- Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Belinda R. Avalos
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, United States of America
- Division of Hematology/Oncology, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
| |
Collapse
|
11
|
Wei SHY, Ming-Lum A, Liu Y, Wallach D, Ong CJ, Chung SW, Moore KW, Mui ALF. Proteasome-mediated proteolysis of the interleukin-10 receptor is important for signal downregulation. J Interferon Cytokine Res 2007; 26:281-90. [PMID: 16689656 DOI: 10.1089/jir.2006.26.281] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The cytokine interleukin-10 (IL-10) is an important regulator of immune cell function, proliferation, and survival. The IL-10 receptor (IL-10R) consists of two subunits, IL-10R1 and IL-10R2, both belonging to the class II cytokine receptor superfamily. Like other members of the cytokine receptor superfamily, IL-10R stimulation leads to activation of Jak family kinases and Stat transcription factors. To identify additional signal transduction pathways used by the IL-10R, we purified 92-kDa and 100-kDa proteins that coprecipitated with IL-10R1 from IL-10-stimulated cells. Both proteins were found to be related to the 97-kDa subunit of the regulatory component of the 26S proteasome. Subsequent studies confirmed that the IL-10R1 undergoes ligand- dependent internalization and proteasome-mediated degradation. An IL-10R1 cytoplasmic domain mutant deficient for internalization exhibited prolonged signaling through Jak1 and Stat3, reinforcing the importance of receptor internalization for signal termination.
Collapse
|
12
|
Foti M, Porcheron G, Fournier M, Maeder C, Carpentier JL. The neck of caveolae is a distinct plasma membrane subdomain that concentrates insulin receptors in 3T3-L1 adipocytes. Proc Natl Acad Sci U S A 2007; 104:1242-7. [PMID: 17227843 PMCID: PMC1783101 DOI: 10.1073/pnas.0610523104] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Indexed: 02/04/2023] Open
Abstract
Insulin receptors (IRs) segregate on plasma membrane microvilli, but in cells devoid of microvilli, such as adipocytes, the localization of IRs is a matter of controversy. In the present study, we examined the distribution of IRs in the plasma membrane of 3T3-L1 adipocytes. Quantitative electron microscopy indicates that IRs are predominantly associated with the neck, but not the bulb, of caveolae. Caveola necks represent distinct microdomains of the plasma membrane. Indeed, as shown by freeze-fracture analysis, intramembrane particles are concentrated as necklaces around the craters of caveolae. In addition, subcellular fractionation suggests that the neck and the bulb of caveolae present a different resistance to detergent solubility. Finally, cytoskeletal components, including actin, are highly enriched in the membrane area underlying the neck part of caveolae. IRs coimmunoprecipitate with cytoskeletal components, and disruption of the actin cytoskeleton alters IRs expression, localization, and signaling, thus supporting the notion that caveola necks are involved in intracellular signaling by IRs. Together, these results suggest that cytoskeletal proteins anchor IRs to microdomains in the caveola necks of 3T3-L1 adipocytes. By homology with IR localization in other cell types, we suggest that the necks of caveolae may represent the counterpart of microvillar domains in cells poor in microvilli such as adipocytes and that they play an important role as signaling platforms.
Collapse
Affiliation(s)
- Michelangelo Foti
- Department of Cellular Physiology and Metabolism, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland.
| | | | | | | | | |
Collapse
|
13
|
Shibuya A, Honda SI. Molecular and functional characteristics of the Fcα/μR, a novel Fc receptor for IgM and IgA. ACTA ACUST UNITED AC 2006; 28:377-82. [PMID: 17061088 DOI: 10.1007/s00281-006-0050-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Accepted: 09/27/2006] [Indexed: 10/24/2022]
Abstract
IgM is the first antibody to be produced in a humoral immune response and is a major isotope of natural antibodies and may play an important role in innate immunity. On the other hand, IgA is a secreted antibody at the mucosal membrane such as the gastrointestinal and respiratory tracts and protects from initial invasion of microbes. However, how these antibodies are involved in immunity has been poorly elucidated. We previously identified a novel Fc receptor for IgA and IgM, designated Fcalpha/mu receptor (Fcalpha/muR), whose gene is closely located at the polymeric immunoglobulin receptor (poly-IgR), also a receptor for IgA and IgM, in the Fc receptor gene cluster on the chromosome 1. In contrast to the the poly-IgR that is expressed on epithelial, but not hematopoietic, cells, Fcalpha/muR is constitutively expressed on the majority of B lymphocytes and macrophages in the spleen and at the center of the secondary lymphoid follicles. The Fcalpha/muR mediates endocytosis Staphylococcus aureus /anti-S. aureus IgM antibody immune complexes by B lymphocytes, for which the dileucine motif in the cytoplasmic tail of the mouse Fcalpha/muR is responsible. These results reveal a new mechanism in the primary stage of immune defense against microbes.
Collapse
Affiliation(s)
- Akira Shibuya
- Department of Immunology, Institute of Basic Medical Sciences, Graduate School of Comprehensive Human Sciences and Center for TARA, University of Tsukuba, 1-1-1 Tennodai, Tsukuba Science City, Ibaraki, 305-8575, Japan,
| | | |
Collapse
|
14
|
Chen Y, Wang X, Ben J, Yue S, Bai H, Guan X, Bai X, Jiang L, Ji Y, Fan L, Chen Q. The Di-Leucine Motif Contributes to Class A Scavenger Receptor-Mediated Internalization of Acetylated Lipoproteins. Arterioscler Thromb Vasc Biol 2006; 26:1317-22. [PMID: 16574888 DOI: 10.1161/01.atv.0000220171.50282.0c] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective—
The di-leucine motif exists in the intracellular domains of certain cell surface receptors, participating in the receptor-mediated endocytosis. The present study was aimed at determining the role of the di-leucine motif in class A scavenger receptor (SR-A)-mediated ligand endocytosis.
Methods and Results—
cDNA coding for a mutant (SR-A mutant N3132LM) with deletion of the di-leucine structure was transfected into Chinese hamster ovary (CHO) cells. Compared with wild-type SR-A–expressing cells, the cells expressing the SR-A mutant N3132LM showed a significant decrease in uptake but almost no change in binding of the SR-A ligand acetylated low-density lipoprotein (AcLDL). Western blot analysis revealed coimmunoprecipitation of SR-A mutant and clathrin from the lysates of the mutant but not wild-type CHO cells, suggesting that AcLDL-bound SR-A mutant N3132LM is associated with the clathrin-coated pit of cellular membrane. Removal of the first 27 amino acid residues from the SR-A N-terminus further reduced AcLDL uptake by the cells with the di-leucine motif mutation.
Conclusions—
The di-leucine motif of SR-A intracellular domain contributes to the SR-A–mediated cellular internalization of AcLDL. Di-leucine pair exists in the cytoplasmic domain of class A scavenger receptor. The cells expressing di-leucine mutants showed decreased uptake and unchanged binding of AcLDL. The di-leucine pair was not associated to coated pits. It suggests that di-leucine motif acts as a signal sequence to mediate SR-A into cell.
Collapse
Affiliation(s)
- Yaoyu Chen
- Institute of Reproductive Medicine, Nanjing Medical University, Nanjing, People's Republic of China
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Hunker CM, Kruk I, Hall J, Giambini H, Veisaga ML, Barbieri MA. Role of Rab5 in insulin receptor-mediated endocytosis and signaling. Arch Biochem Biophys 2006; 449:130-42. [PMID: 16554017 DOI: 10.1016/j.abb.2006.01.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Revised: 01/25/2006] [Accepted: 01/25/2006] [Indexed: 10/24/2022]
Abstract
Activated insulin receptors recruit various intracellular proteins leading to signal generation and endocytic trafficking. Although activated receptors are rapidly internalized into the endocytic compartment and subsequently degraded in lysosomes, the linkage between insulin receptor signaling and endocytosis is not well understood. This study utilizes both overexpression and depletion of Rab5 proteins to show that they play a critical role in both insulin-stimulated fluid phase and receptor-mediated endocytosis. Specifically, Rab5:WT and Rab5:Q79L (a GTP-hydrolysis defective mutant) enhance both types of endocytosis in response to insulin, while Rab5:S34N (a GTP-binding defective mutant) has the opposite effect. Morphological analysis indicates that both Rab5 and insulin receptor are found on early endosomes, but not at the plasma membrane. In addition, expression of Rab5:WT and Rab5:Q79L enhance both Erk1/2 and Akt activation without affecting JN- and p38-kinase activities, while the expression of Rab5:S34N blocks both Erk1/2 and Akt activation. Consistent with these observations, DNA synthesis is also altered by the expression of Rab5:S34N. Taken together, these results demonstrate that Rab5 is required for insulin receptor membrane trafficking and signaling.
Collapse
Affiliation(s)
- C M Hunker
- Department of Biological Sciences, Florida International University, University Park, Miami, FL 33199, USA
| | | | | | | | | | | |
Collapse
|
16
|
Hunker CM, Giambini H, Galvis A, Hall J, Kruk I, Veisaga ML, Barbieri MA. Rin1 regulates insulin receptor signal transduction pathways. Exp Cell Res 2006; 312:1106-18. [PMID: 16457816 DOI: 10.1016/j.yexcr.2005.12.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Revised: 12/21/2005] [Accepted: 12/21/2005] [Indexed: 10/25/2022]
Abstract
Rin1 is a multifunctional protein containing several domains, including Ras binding and Rab5 GEF domains. The role of Rin1 in insulin receptor internalization and signaling was examined by expressing Rin1 and deletion mutants in cells utilizing a retrovirus system. Here, we show that insulin-receptor-mediated endocystosis and fluid phase insulin-stimulated endocytosis are enhanced in cells expressing the Rin1:wild type and the Rin1:C deletion mutant, which contain both the Rab5-GEF and GTP-bound Ras binding domains. However, the Rin1:N deletion mutant, which contains both the SH2 and proline-rich domains, blocked insulin-stimulated receptor-mediated and insulin-stimulated fluid phase endocytosis. In addition, the expression of Rin1:delta (429-490), a natural occurring splice variant, also blocked both receptor-mediated and fluid phase endocystosis. Furthermore, association of the Rin1 SH2 domain with the insulin receptor was dependent on tyrosine phosphorylation of the insulin receptor. Morphological analysis indicates that Rin1 co-localizes with insulin receptor both at the cell surface and in endosomes upon insulin stimulation. Interestingly, the expression of Rin1:wild type and both deletion mutants blocks the activation of Erk1/2 and Akt1 kinase activities without affecting either JN or p38 kinase activities. DNA synthesis and Elk-1 activation are also altered by the expression of Rin1:wild type and the Rin1:C deletion mutant. In contrast, the expression of Rin1:delta stimulates both Erk1/2 and Akt1 activation, DNA synthesis and Elk-1 activation. These results demonstrate that Rin1 plays an important role in both insulin receptor membrane trafficking and signaling.
Collapse
Affiliation(s)
- C M Hunker
- Department of Biological Sciences, Florida International University, College of Arts and Sciences, 11200 S.W. 8th Street, Bldg. OE, Room 167, Miami, FL 33199, USA
| | | | | | | | | | | | | |
Collapse
|
17
|
Hunker CM, Galvis A, Kruk I, Giambini H, Veisaga ML, Barbieri MA. Rab5-activating protein 6, a novel endosomal protein with a role in endocytosis. Biochem Biophys Res Commun 2006; 340:967-75. [PMID: 16410077 DOI: 10.1016/j.bbrc.2005.12.099] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2005] [Accepted: 12/05/2005] [Indexed: 12/11/2022]
Abstract
Rab GTPases are regulators of membrane trafficking that cycle between active (GTP-bound) and inactive (GDP-bound) states. In this study, we report the identification of a new human Rab5 guanine nucleotide exchange factor (GEF), which we have named RAP6 (Rab5-activating protein 6). RAP6 contains a Rab5 GEF and a Ras GAP domain. We show that the Vps9 domain is sufficient for the interaction of RAP6 with GDP-bound Rab5 and that RAP6 stimulates Rab5 guanine nucleotide exchange. We also find that the Ras GAP domain of RAP6 shows GAP activity for Ras. Immunofluorescence experiments reveal that RAP6 is associated with plasma membrane and small intracellular vesicles that also contain Rab5. Additionally, the overexpression of RAP6 affects both fluid phase and receptor-mediated endocytosis. This study is the first to show that RAP6 is a novel regulator of endocytosis that exhibits GEF activity specific for Rab5 and GAP activity specific for Ras.
Collapse
Affiliation(s)
- C M Hunker
- Department of Biological Sciences, Florida International University, Miami, FL 33199, USA
| | | | | | | | | | | |
Collapse
|
18
|
Honda SI, Miyamoto A, Shibuya A. Fcα/μR, a novel Fc receptor for innate antibodies IgM and IgA. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.ics.2005.08.038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
19
|
Persaud-Sawin DA, McNamara JO, Rylova S, Vandongen A, Boustany RMN. A galactosylceramide binding domain is involved in trafficking of CLN3 from Golgi to rafts via recycling endosomes. Pediatr Res 2004; 56:449-63. [PMID: 15240864 DOI: 10.1203/01.pdr.0000136152.54638.95] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Juvenile neuronal ceroid lipofuscinosis (JNCL) is due to mutations in the CLN3 gene. We previously determined that CLN3 protein harbors a highly conserved motif, VYFAE, necessary for its impact on cell growth and apoptosis. Using molecular modeling we demonstrated that this motif is embedded in a stretch of amino acids that is homologous to and structurally compatible with a galactosylceramide (GalCer) binding domain. This domain is present in the V3 loop of the HIV-1 gp120 envelope protein, beta-amyloid protein, and the infectious form of prionic protein, and defines a binding site for lipid rafts. We determined the subcellular localization of CLN3 in different cell systems including human neurons, primary rat hippocampal neurons, normal human fibroblasts, and JNCL fibroblasts homozygous for the 1.02 kb deletion in genomic DNA. Wild-type CLN3 protein was present within Golgi, lipid rafts in the plasma membrane, and early recycling endosomes, but not late endosomes/lysosomes. Wild-type CLN3 internalized from the plasma membrane to the Golgi via Rab4- and Rab11-positive recycling endosomes. Wild-type CLN3 co-localized with GalCer in the Golgi and in lipid rafts at the plasma membrane in normal cells. Neither mutant CLN3 protein nor GalCer were found at the plasma membrane in JNCL fibroblasts. Mutant CLN3p was retained within the Golgi and partially mis-localized to lysosomes, failing to reach recycling endosomes, plasma membrane, or lipid rafts. These studies identify a novel CLN3 domain that may dictate localization and function of CLN3.
Collapse
|
20
|
Shin BC, McKnight RA, Devaskar SU. Glucose transporter GLUT8 translocation in neurons is not insulin responsive. J Neurosci Res 2004; 75:835-44. [PMID: 14994344 DOI: 10.1002/jnr.20054] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We examined the subcellular distribution of a novel glucose transporter isoform (GLUT8) in murine N2A neuroblastoma cells. Exogenous expression of GLUT8-green fluorescent protein (GFP) DNA constructs mimicked the endogenous GLUT8 localization to intracellular vesicles and minimally to the Giantin-positive Golgi. This distribution was unlike the distributions of endogenous GLUT1 and GLUT3 (predominant neuronal isoform), which were limited predominantly to the plasma membrane and minimal in the cytoplasm. Although GLUT4-GFP (insulin responsive isoform) was expressed transiently, no endogenous GLUT4 was detected in N2A cells. By employing stable transfectants that expressed GLUT8-GFP, the effect of insulin and insulin-like growth factor-I, potassium chloride (depolarized state), and 3% oxygen on translocation of GLUT8 to the plasma membrane of N2A cells was examined immunohistochemically and by subfractionation, followed by Western blot analysis. None of these agents translocated GLUT8 to the plasma membrane. However, when the internalization dileucine motif (L(12,13)) of GLUT8 was mutated to a dialanine motif (A(12,13)), GLUT8 colocalized with GLUT3 in the plasma membrane. We conclude that GLUT8 translocation to the N2A cellular plasma membrane is not observed secondary to the various stimuli investigated. Mutation of the N-terminal dileucine motif led to constitutive GLUT8 localization in the plasma membrane. The endogenous stimulus required for translocating neuronal GLUT8 is unknown. This stimulus, which is necessary for uncoupling the "cytoplasmic vesicular anchor" of GLUT8, would be crucial for its glucose-transporting function.
Collapse
Affiliation(s)
- Bo-Chul Shin
- Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1752, USA
| | | | | |
Collapse
|
21
|
Abstract
A variety of receptors have been analyzed in sufficient detail to identify sorting motifs. Initial studies focused on the identification of sequences in the cytoplasmic tails of the LDL and transferrin receptors that mediated their internalization. These motifs have since been found in the cytoplasmic domains of a wide variety of receptors and provide for numerous sorting functions. This review will outline the early studies on LDL and transferrin receptors and will then focus on two classes of signaling receptors, receptor tyrosine kinases (EGF and the insulin receptors) and heterotrimeric G-protein coupled receptors (beta2-adrenergic receptors). The identification of sorting motifs and proteins that bind these motifs will be discussed. Importantly, the studies identify a variety of potential targets for modulating the sorting and hence activity of these medically important receptors.
Collapse
MESH Headings
- Amino Acid Motifs
- Animals
- Endocytosis/physiology
- ErbB Receptors/metabolism
- ErbB Receptors/physiology
- Humans
- Protein Sorting Signals/physiology
- Receptor, Insulin/metabolism
- Receptor, Insulin/physiology
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, Adrenergic, beta-2/physiology
- Receptors, Cell Surface/metabolism
- Receptors, Cell Surface/physiology
- Receptors, LDL/metabolism
- Receptors, LDL/physiology
- Receptors, Transferrin/metabolism
- Receptors, Transferrin/physiology
- Signal Transduction
Collapse
Affiliation(s)
- Richard C Kurten
- Department Physiology and Biophysics, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72005, USA.
| |
Collapse
|
22
|
Soond SM, Terry JL, Colbert JD, Riches DWH. TRUSS, a novel tumor necrosis factor receptor 1 scaffolding protein that mediates activation of the transcription factor NF-kappaB. Mol Cell Biol 2003; 23:8334-44. [PMID: 14585990 PMCID: PMC262424 DOI: 10.1128/mcb.23.22.8334-8344.2003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2002] [Revised: 12/20/2002] [Accepted: 08/12/2003] [Indexed: 12/21/2022] Open
Abstract
We describe the cloning and characterization of tumor necrosis factor receptor (TNF-R)-associated ubiquitous scaffolding and signaling protein (TRUSS), a novel TNF-R1-interacting protein of 90.7 kDa. TRUSS mRNA was ubiquitously expressed in mouse tissues but was enriched in heart, liver, and testis. Co-immunoprecipitation experiments showed that TRUSS was constitutively associated with unligated TNF-R1 and that the complex was relatively insensitive to stimulation with TNF-alpha. Deletion mutagenesis of TNF-R1 indicated that TRUSS interacts with both the membrane-proximal region and the death domain of TNF-R1. In addition, the N-terminal region of TRUSS (residues 1 to 440) contains sequences that permit association with the cytoplasmic domain of TNF-R1. Transient overexpression of TRUSS activated NF-kappaB and increased NF-kappaB activation in response to ligation of TNF-R1. In contrast, a COOH-terminal-deletion mutant of TRUSS (TRUSS(1-723)) was found to inhibit NF-kappaB activation by TNF-alpha. Co-precipitation and co-immunoprecipitation assays revealed that TRUSS can interact with TRADD, TRAF2, and components of the IKK complex. These findings suggest that TRUSS may serve as a scaffolding protein that interacts with TNF-R1 signaling proteins and may link TNF-R1 to the activation of IKK.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Antigens, CD/chemistry
- Antigens, CD/genetics
- Antigens, CD/metabolism
- Binding Sites/genetics
- COS Cells
- Cell Line
- Cloning, Molecular
- Humans
- Male
- Mice
- Molecular Sequence Data
- NF-kappa B/metabolism
- NIH 3T3 Cells
- Proteins/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptor-Interacting Protein Serine-Threonine Kinases
- Receptors, Tumor Necrosis Factor/chemistry
- Receptors, Tumor Necrosis Factor/genetics
- Receptors, Tumor Necrosis Factor/metabolism
- Receptors, Tumor Necrosis Factor, Type I
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Sequence Deletion
- TNF Receptor-Associated Death Domain Protein
- TNF Receptor-Associated Factor 1
- TNF Receptor-Associated Factor 2
- Trans-Activators/chemistry
- Trans-Activators/genetics
- Trans-Activators/metabolism
- Transcriptional Activation/drug effects
- Transfection
- Tumor Necrosis Factor Receptor-Associated Peptides and Proteins
- Tumor Necrosis Factor-alpha/pharmacology
Collapse
Affiliation(s)
- Surinder M Soond
- Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Neustadt Room D405, Denver, CO 80206, USA
| | | | | | | |
Collapse
|
23
|
Boura-Halfon S, Voliovitch H, Feinstein R, Paz K, Zick Y. Extracellular matrix proteins modulate endocytosis of the insulin receptor. J Biol Chem 2003; 278:16397-404. [PMID: 12594209 DOI: 10.1074/jbc.m212385200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Internalization of the insulin receptor (IR) is a highly regulated multi-step process whose underlying molecular basis is not fully understood. Here we undertook to study the role of extracellular matrix (ECM) proteins in the modulation of IR internalization. Employing Chinese hamster ovary cells that overexpress IR (CHO-T cells), our results indicate that IR internalization proceeds unaffected even when Tyr phosphorylation of IR substrates, such as IRS-1, is impaired (e.g. in CHO-T cells overexpressing IRS-1 whose pleckstrin-homology domain has been deleted or in CHO-T cells that overexpress the PH/PTB domain of IRS-1). In contrast, IR internalization is affected by the context of the ECM proteins to which the cells adhere. Hence, IR internalization was inhibited 40-60% in CHO-T cells adherent onto galectin-8 (an ECM protein and an integrin ligand of the galectin family) when compared with cells adherent onto fibronectin, collagen, or laminin. Cells adherent to galectin-8 manifested a unique cytoskeletal organization, which involved formation of cortical actin and generation of F-actin microspikes that contrasted with the prominent stress-fibers formed when cells adhered to fibronectin. To better establish a role for actin filament organization in IR endocytosis, this process was assayed in CHO-T cells (adherent onto fibronectin), whose actin filaments were disrupted upon treatment with latrunculin B. Latrunculin B did not affect insulin-induced Tyr phosphorylation of IR or its ability to phosphorylate its substrates; still, a 30-50% reduction in the rate of IR internalization was observed in cells treated with latrunculin B. Treatment of cells with nocodazole, which disrupts formation of microtubules, did not affect IR internalization. These results indicate that proper actin, but not microtubular, organization is a critical requirement for IR internalization and suggest that integrin-mediated signaling pathways emitted upon cell adhesion to different extracellular matrices and the altered cytoskeletal organizations generated thereof affect the itinerary of the insulin receptor.
Collapse
Affiliation(s)
- Sigalit Boura-Halfon
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | | | | | | | | |
Collapse
|
24
|
Shackleton S, Hamer I, Foti M, Zumwald N, Maeder C, Carpentier JL. Role of two dileucine-like motifs in insulin receptor anchoring to microvilli. J Biol Chem 2002; 277:43631-7. [PMID: 12218050 DOI: 10.1074/jbc.m204036200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the absence of ligand, the insulin receptor is maintained on microvilli on the cell surface. A dileucine motif (LL(986-987)) is necessary but not sufficient for this anchoring, which also required the presence of additional sequence(s) downstream of position 1000. The aim of the present study was to identify this (these) additional sequence(s). First, exons 16 or 17 were fused to the extracellular and transmembrane domains of complement receptor 1 and stably expressed in Chinese hamster ovary cells. Results obtained indicate that exon 17 is sufficient for anchoring to microvilli. Second, analysis of insulin receptor mutants truncated within exon 17 demonstrated that whereas receptors truncated at position 1000 showed no preferential association with microvilli, receptors truncated at position 1012 displayed a level of association identical to that of the full-length insulin receptor. Third, mutation of a diisoleucine motif (II(1006-1007)) present within this 12-amino acid stretch abrogated the preferential association of the receptor with microvilli. These results indicate that the domain required for association of insulin receptor with microvilli is contained within the region encoded by exon 17 and that, within this sequence, two dileucine-like motifs (LL(986-987) and II(1006-1007)) play a crucial role.
Collapse
Affiliation(s)
- Sue Shackleton
- Department of Morphology, Faculty of Medicine, University of Geneva, Switzerland
| | | | | | | | | | | |
Collapse
|
25
|
Flint-Ashtamker G, Eisen-Lev R, Cohen J, Jun-shen Huang L, Neumann D. Amino acid residues 268-276 of the erythropoietin receptor contain an endocytosis motif and are required for erythropoietin-mediated proliferation. FEBS Lett 2002; 518:189-94. [PMID: 11997044 DOI: 10.1016/s0014-5793(02)02691-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Erythropoietin (EPO) promotes viability, proliferation and differentiation of mammalian erythroid progenitor cells via its specific cell surface receptor (EPO-R). We have previously shown that truncated EPO-Rs containing 267 amino acids or less were defective in internalization of (125)I-EPO, whereas internalization via a receptor derivative containing 276 amino acids was unaffected, thus directing focus to the nine amino acid residues FEGLFTTHK at positions 268-276 [Levin, Cohen, Supino, Yoshimura, Watowich, Neumann, FEBS Lett. 427 (1998) 164-170]. Here, a panel of EPO-R mutants was generated to determine the role of these residues in EPO endocytosis, down regulation of cell surface receptors and EPO-mediated signaling. While linking amino acid residues 268-276 to a truncated EPO-R (Delta+9 EPO-R) conferred both ligand uptake and ligand-independent down regulation of the respective receptor from the cell surface, Phe 272 was crucial for EPO endocytosis but not for ligand-independent down regulation. Additional receptor motifs probably play a role in EPO endocytosis and receptor down-regulation, as these processes were not adversely impaired in Delta268-276 EPO-R. A central role of residues 268-276, in particular Phe, was demonstrated by the inability of Delta268-276 and F268,272A EPO-Rs to support EPO-mediated signal transduction.
Collapse
Affiliation(s)
- Galit Flint-Ashtamker
- Department of Cell Biology and Histology, Sackler Faculty of Medicine Tel-Aviv University, 69978, Ramat Aviv, Israel
| | | | | | | | | |
Collapse
|
26
|
Czech MP, Van Renterghem B, Sleeman MW. Insulin Receptor Tyrosine Kinase. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
27
|
Kawakami K, Takeshita F, Puri RK. Identification of distinct roles for a dileucine and a tyrosine internalization motif in the interleukin (IL)-13 binding component IL-13 receptor alpha 2 chain. J Biol Chem 2001; 276:25114-20. [PMID: 11352909 DOI: 10.1074/jbc.m100936200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Interleukin (IL)-13 receptor alpha2 (IL-13Ralpha2) chain is an essential binding component for IL-13-mediated ligand binding. Recently, we have demonstrated that this receptor chain also plays an important role in the internalization of IL-13. To study the mechanism of IL-13 internalization, we generated mutated IL-13Ralpha2 chains that targeted trileucine residues (Leu(335), Leu(336), and Leu(337)) in the transmembrane domain and a tyrosine motif (Tyr(343)) in the intracellular domain and transfected these cDNAs in COS-7 cells. Cells that expressed a C-terminally truncated IL-13Ralpha2 chain (Delta335) did not bind IL-13, suggesting that the trileucine region modulates IL-13 binding. Truncation of IL-13Ralpha2 chain with a mutation in the trileucine region resulted in significantly decreased internalization compared with wild type IL-13Ralpha2 chain transfected cells. COS-7 cells transfected with tyrosine motif mutants exhibited a similar internalization level compared with wild type IL-13Ralpha2 chain transfected cells; however, dissociation of cell surface IL-13 was faster compared with wild type IL-13Ralpha2 transfectants. These results were further confirmed by determining the cytotoxicity of a chimeric protein composed of IL-13 and a mutated form of Pseudomonas exotoxin (IL13-PE38QQR) to cells that expressed IL-13Ralpha2 chain mutants. We further demonstrate that the IL-13Ralpha2 chain is not ubiquitinated and that internalization of IL-13Ralpha2 did not depend on ubiquitination. Together, our findings suggest that the dileucine motif in the trileucine region and tyrosine motif participate in IL-13Ralpha2 internalization in distinct manners.
Collapse
Affiliation(s)
- K Kawakami
- Laboratory of Molecular Tumor Biology, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA
| | | | | |
Collapse
|
28
|
Kawakami K, Taguchi J, Murata T, Puri RK. The interleukin-13 receptor alpha2 chain: an essential component for binding and internalization but not for interleukin-13-induced signal transduction through the STAT6 pathway. Blood 2001; 97:2673-9. [PMID: 11313257 DOI: 10.1182/blood.v97.9.2673] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The interleukin-13 receptor (IL-13R) complex is composed of 2 different chains, IL-13Ralpha1 (also known as IL-13Ralpha') and IL-13Ralpha2 (also known as IL-13Ralpha). For a functional IL-13 receptor, the IL-13Ralpha1 chain forms a productive complex with the primary IL-4 binding protein (IL-4Ralpha also known as IL-4Rbeta). However, the function of the IL-13Ralpha2 chain is not clear even though this chain binds IL-13 with high affinity. This study demonstrates that IL-13Ralpha2 can undergo internalization after binding to ligand without causing activation of its signaling pathways. These conclusions were drawn on the basis of (1) internalization of (125)I-IL-13 in Chinese hamster ovarian (CHO-K1) and T98G glioblastoma cells transiently transfected with the IL-13Ralpha2 chain; (2) a recombinant chimeric fusion protein comprising IL-13 and a mutated form of Pseudomonas exotoxin (termed IL13-PE38QQR or IL-13 toxin) is specifically cytotoxic to IL-13Ralpha2-transfected CHO-K1 cells in a gene dose-dependent manner, whereas cells transfected with vector alone were not sensitive; and (3) IL-13 did not cause activation of signal transduction and activation of transcription 6 (STAT6) in IL-13Ralpha2-transfected cells. IL-13 efficiently caused activation of STAT6 protein in cells transfected with the IL-13Ralpha1 and IL-4Ralpha chains, and IL-13Ralpha2 inhibited this activation. Taken together, these observations indicate that internalization of IL-13Ralpha2 is signal independent and that this property of IL-13Ralpha2 can be exploited for receptor-directed cancer therapy.
Collapse
Affiliation(s)
- K Kawakami
- Laboratory of Molecular Tumor Biology, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | | |
Collapse
|
29
|
Shibuya A, Sakamoto N, Shimizu Y, Shibuya K, Osawa M, Hiroyama T, Eyre HJ, Sutherland GR, Endo Y, Fujita T, Miyabayashi T, Sakano S, Tsuji T, Nakayama E, Phillips JH, Lanier LL, Nakauchi H. Fc alpha/mu receptor mediates endocytosis of IgM-coated microbes. Nat Immunol 2000; 1:441-6. [PMID: 11062505 DOI: 10.1038/80886] [Citation(s) in RCA: 283] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
IgM is the first antibody to be produced in a humoral immune response and plays an important role in the primary stages of immunity. Here we describe a mouse Fc receptor, designated Fc alpha/microR, and its human homolog, that bind both IgM and IgA with intermediate or high affinity. Fc alpha/microR is constitutively expressed on the majority of B lymphocytes and macrophages. Cross-linking Fc alpha/microR expressed on a pro-B cell line Ba/F3 transfectant with soluble IgM or IgM-coated microparticles induced internalization of the receptor. Fc alpha/microR also mediated primary B lymphocyte endocytosis of IgM-coated Staphylococcus aureus. Thus, Fc alpha/microR is involved in the primary stages of the immune response to microbes.
Collapse
Affiliation(s)
- A Shibuya
- Department of Immunology, Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki, Japan.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Abstract
Insulin (Ins) and various other hormones and growth factors have been shown to be rapidly internalized and translocated to the cell nucleus. This review summarizes the mechanisms that are involved in the translocation of Ins to the nucleus, and discusses its possible role in Ins action, based on observations by the authors and others. Ins is internalized to endosomes by both receptor-mediated and fluid-phase endocytosis, the latter occurring only at high Ins concentrations. The authors recently demonstrated the caveolae are the primary cell membrane locations responsible for initiating the signal transduction cascade induced by Ins. Once Ins is internalized, Ins dissociates from the Ins receptor in the endosome, and is translocated to the cytoplasm, where most Ins is degraded by Ins-degrading enzyme (IDE), although how the polypeptides cross the lipid bilayer is unknown. Some Ins escapes the degradation and binds to cytosolic Ins-binding proteins (CIBPs), in addition to IDE. IDE and some CIBPs are known to be binding proteins for other hormones or their receptors, and are involved in gene regulation, suggesting physiological relevance of CIBPs in the signaling of Ins and other hormones. Ins is eventually translocated through the nuclear pore to the nucleus, where Ins tightly associates with nuclear matrix. The role of Ins internalization and translocation to the nucleus is still controversial, although there is substantial evidence to support its role in cellular responses caused by Ins. Many studies indicate that nuclear translocation of various growth factors and hormones plays an important role in cell proliferation or DNA synthesis. It would be reasonable to suggest that Ins internalization, its association with CIBPs, and its translocation to the nucleus may be essential for the regulation of nuclear events by Ins.
Collapse
Affiliation(s)
- S Harada
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
| | | | | |
Collapse
|
31
|
Whitman SC, Daugherty A, Post SR. Regulation of acetylated low density lipoprotein uptake in macrophages by pertussis toxin-sensitive G proteins. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)32389-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
32
|
Fong LG, Le D. The processing of ligands by the class A scavenger receptor is dependent on signal information located in the cytoplasmic domain. J Biol Chem 1999; 274:36808-16. [PMID: 10593991 DOI: 10.1074/jbc.274.51.36808] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanisms that regulate the transport of the macrophage class A scavenger receptor during ligand uptake were investigated. Kinetic analysis of the changes in receptor phosphorylation demonstrated that serine phosphorylation increased during the internalization of acetyl-low density lipoproteins (LDL) by macrophages. The increase was maximal at about 2.5 min after the initiation of ligand uptake. Oxidized LDL also stimulated serine phosphorylation, but the relative increase was smaller and the time to maximum was shorter. Receptor mutants expressed in Chinese hamster ovary and COS cells showed that elimination of the potential phosphorylation site at Ser(21) increased acetyl-LDL metabolism, whereas inactivation of the site at Ser(49) reduced acetyl-LDL uptake. The increase in uptake by the Ser(21) mutant was due to an increase in surface receptor expression. In contrast, elimination of the site at Ser(49) did not affect receptor expression but slowed receptor internalization. To identify potential internalization signal sequences, beta-turn structure in the cytosolic domain was targeted for mutagenesis. Disruption of one region near Asp(25) inhibited receptor activity. The studies support a model whereby receptor internalization requires the presence of an internalization signal motif but that the rate of receptor internalization is governed by the pattern of receptor phosphorylation induced by the ligand.
Collapse
Affiliation(s)
- L G Fong
- Research Institute, Palo Alto Medical Foundation, Palo Alto, California 94301, USA.
| | | |
Collapse
|
33
|
Legendre V, Guimezanes A, Buferne M, Barad M, Schmitt-Verhulst AM, Boyer C. Antigen-induced TCR-CD3 down-modulation does not require CD3delta or CD3gamma cytoplasmic domains, necessary in response to anti-CD3 antibody. Int Immunol 1999; 11:1731-8. [PMID: 10545476 DOI: 10.1093/intimm/11.11.1731] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We studied cytotoxic T lymphocyte (CTL) clones expressing cytoplasmic domain-deleted CD3delta and CD3gamma chains. These cells retained efficient antigen-specific cytolysis. Because the cytoplasmic domains of native CD3delta and CD3gamma chains contain a dileucine-based and a tyrosine-based motif thought to be important for receptor endocytosis, we compared TCR-CD3 down-modulation on the CTL clones expressing or not these domains. We found that antigen-induced TCR-CD3 down-modulation was not dependent on either the CD3delta or CD3gamma cytoplasmic domains. This contrasts with phorbol ester- and anti-CD3 mAb (soluble or plastic-coated)-induced TCR-CD3 down-modulation, that are respectively dependent on CD3gamma and on either CD3delta or CD3gamma cytoplasmic domains, suggesting that differences may exist between the mechanisms of TCR-CD3 down-modulation in response to the three stimuli. TCR-CD3 down-modulation in response to antigen was demonstrated by confocal microscopy to be associated with TCRbeta chain internalization, whether CD3delta and CD3gamma were native or truncated. Inhibition by the protein tyrosine kinase inhibitor PP1 of TCR-CD3 down-modulation in response to antigen was also similar whether CD3delta and CD3gamma cytoplasmic domains were present or not. These properties of receptor down-modulation are discussed with respect to the requirements for TCR engagement on antigen-presenting cells.
Collapse
Affiliation(s)
- V Legendre
- Centre d'Immunologie INSERM-CNRS de Marseille-Luminy, Case 906, 13288 Marseilles, Cedex 9, France
| | | | | | | | | | | |
Collapse
|
34
|
Morinaka K, Koyama S, Nakashima S, Hinoi T, Okawa K, Iwamatsu A, Kikuchi A. Epsin binds to the EH domain of POB1 and regulates receptor-mediated endocytosis. Oncogene 1999; 18:5915-22. [PMID: 10557078 DOI: 10.1038/sj.onc.1202974] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
POB1 has been identified as a RalBP1-binding protein and has the Eps15 homology (EH) domain. The EH domain-containing proteins have been suggested to be involved in clathrin-dependent endocytosis. To clarify the function of POB1, we purified a protein which binds to the EH domain of POB1 from bovine brain cytosol and identified it as Epsin, which is known to bind to the EH domain of Eps15. Epsin has three Asn-Pro-Phe (NPF) motifs in the C-terminal region, which are known to form the core sequence for the binding to the EH domain. The EH domain of POB1 interacted directly with the region containing the NPF motifs of Epsin. Expression of Epsin in CHO-IR cells inhibited internalization of insulin although it affected neither insulin-binding nor autophosphorylation activities of the insulin receptor. Taken together with the observations that Epsin is involved in internalization of the receptors for epidermal growth factor and transferrin, these results suggest that Epsin is a binding partner of POB1 and their binding regulates receptor-mediated endocytosis.
Collapse
Affiliation(s)
- K Morinaka
- Department of Biochemistry, Hiroshima University School of Medicine, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan
| | | | | | | | | | | | | |
Collapse
|
35
|
Leser GP, Ector KJ, Ng DT, Shaughnessy MA, Lamb RA. The signal for clathrin-mediated endocytosis of the paramyxovirus SV5 HN protein resides at the transmembrane domain-ectodomain boundary region. Virology 1999; 262:79-92. [PMID: 10489343 DOI: 10.1006/viro.1999.9890] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The hemagglutinin-neuraminidase (HN) glycoprotein of the paramyxovirus SV5 is internalized from the cell surface via clathrin-coated pits. However, the cytoplasmic domain of SV5 HN does not contain a previously characterized internalization motif. A cell-surface-expressed chimeric protein (APK), consisting of the cytoplasmic tail, transmembrane (TM) domain, and 12 residues of the ectodomain of HN joined to the cytoplasmic protein pyruvate kinase is internalized, indicating that the N-terminal region of HN contains an internalization signal. Although SV5 HN is internalized at a rate similar to that of influenza virus hemagglutinin (HA) mutant Y543, which contains a degenerate tyrosine-based signal in its cytoplasmic tail, the elimination of the majority of the HN cytoplasmic tail, or substitution of the HN TM domain with leucine residues, did not affect the rate of HN internalization. The HN protein of the closely related virus, Newcastle disease virus (NDV), is not internalized from the cell surface. Working under the usual convention that the TM domain consists of the hydrophobic residues bounded by two charged residues, analysis of internalization of mutant and chimeric NDV HN molecules indicates that the first seven SV5 HN ectodomain residues are critical for internalization of HN. A glutamic acid residue (E37) that abuts this presumptive HN TM domain/ectodomain boundary is important for SV5 HN internalization.
Collapse
Affiliation(s)
- G P Leser
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500, USA
| | | | | | | | | |
Collapse
|
36
|
Tailor CS, Willett BJ, Kabat D. A putative cell surface receptor for anemia-inducing feline leukemia virus subgroup C is a member of a transporter superfamily. J Virol 1999; 73:6500-5. [PMID: 10400745 PMCID: PMC112732 DOI: 10.1128/jvi.73.8.6500-6505.1999] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Domestic cats infected with the horizontally transmitted feline leukemia virus subgroup A (FeLV-A) often produce mutants (termed FeLV-C) that bind to a distinct cell surface receptor and cause severe aplastic anemia in vivo and erythroblast destruction in bone marrow cultures. The major determinant for FeLV-C-induced anemia has been mapped to a small region of the surface envelope glycoprotein that is responsible for its receptor binding specificity. Thus, erythroblast destruction may directly or indirectly result from FeLV-C binding to its receptor. To address these issues, we functionally cloned a putative cell surface receptor for FeLV-C (FLVCR) by using a human T-lymphocyte cDNA library in a retroviral vector. Expression of the 2.0-kbp FLVCR cDNA in naturally resistant Swiss mouse fibroblasts and Chinese hamster ovary cells caused substantial susceptibility to FeLV-C but no change in susceptibilities to FeLV-B and other retroviruses. The predicted FLVCR protein contains 555 amino acids and 12 hydrophobic potential membrane-spanning sequences. Database searches indicated that FLVCR is a member of the major-facilitator superfamily of transporters and implied that it may transport an organic anion. RNA blot analyses showed that FLVCR mRNA is expressed in multiple hematopoietic lineages rather than specifically in erythroblasts. These results suggest that the targeted destruction of erythroblasts by FeLV-C may derive from their greater sensitivity to this virus rather than from a preferential susceptibility to infection.
Collapse
Affiliation(s)
- C S Tailor
- Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland, Oregon 97201-3098, USA.
| | | | | |
Collapse
|
37
|
Sasaoka T, Wada T, Ishihara H, Takata Y, Haruta T, Usui I, Ishiki M, Kobayashi M. Synergistic role of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase cascade in the regulation of insulin receptor trafficking. Endocrinology 1999; 140:3826-34. [PMID: 10433244 DOI: 10.1210/endo.140.8.6904] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To examine the molecular mechanism of insulin receptor trafficking, we investigated the intracellular signaling molecules that regulate this process in Rat1 fibroblasts overexpressing insulin receptors. Cellular localization of insulin receptors was assessed by confocal laser microscopy with indirect immunofluorescence staining. Insulin receptors were visualized diffusely in the basal state. Insulin treatment induced the change of insulin receptor localization to perinuclear compartment. This insulin-induced insulin receptor trafficking was not affected by treatment of the cells with PI3-kinase inhibitor (wortmannin), whereas treatment with MEK [mitogen-activated protein (MAP) kinase-Erk kinase] inhibitor (PD98059) partly inhibited the process in a dose-dependent manner. Interestingly, treatment with both wortmannin and PD98059 almost completely inhibited insulin receptor trafficking. The functional importance of PI3-kinase and MAP kinase in the trafficking process was directly assessed by using single cell microinjection analysis. Microinjection of p85-SH2 and/or catalytically inactive MAP kinase ([K71A]Erk1) GST fusion protein gave the same results as treatment with wortmannin and PD98059. Furthermore, to determine the crucial step for the requirement of PI3-kinase and MAP kinase pathways, the effect of wortmannin and PD98059 on insulin receptor endocytosis was studied. Insulin internalization from the plasma membrane and subsequent insulin degradation were not affected by treatment with wortmannin and PD98059. In contrast, insulin receptor down-regulation from the cell surface and insulin receptor degradation, after prolonged incubation with insulin, were markedly impaired by the treatment. These results suggest that PI3-kinase and MAP kinase pathways synergistically regulate insulin receptor trafficking at a step subsequent to the receptor internalization.
Collapse
Affiliation(s)
- T Sasaoka
- First Department of Medicine, Toyama Medical & Pharmaceutical University, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
38
|
Supino-Rosin L, Yoshimura A, Altaratz H, Neumann D. A cytosolic domain of the erythropoietin receptor contributes to endoplasmic reticulum-associated degradation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 263:410-9. [PMID: 10406949 DOI: 10.1046/j.1432-1327.1999.00516.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The erythropoietin receptor (EPO-R) is the cellular target for erythropoietin (EPO), the primary hormone that mediates the proliferation of immature erythroblasts and their differentiation into mature erythrocytes. Unusual features of the EPO-R are its short half-life (t(1/2) 1-2 h), its degradation via multiple pathways and the fact that less than 1% of total cellular EPO-R molecules are found on the cell surface. The contribution of EPO-R structural determinants to the regulation of its intracellular metabolism is still unclear. The epidermal growth factor receptor (EGF-R), unlike the EPO-R, is efficiently transported to the cell surface and displays a much longer metabolic half-life. To determine which EPO-R cytosolic domains are involved in intracellular degradation, we studied chimeric receptor molecules constructed of EGF-R extracellular and transmembrane parts, linked to the full length or truncated cytosolic part of the EPO-R. The chimeras were expressed in transiently transfected COS 7 cells and stably expressed in Ba/F3 cells. Our experiments indicate that the cytosolic part of the EPO-R contains determinants that mark it for rapid degradation, in association with the endoplasmic reticulum (ER). This degradation was insensitive to brefeldin A and was inhibited by specific proteasomal inhibitors. A truncated EGF-R/EPO-R chimera containing only 50 amino acids of the EPO-R membrane-proximal cytosolic part was also rapidly degraded suggesting that these 50 amino acids are involved in receptor degradation.
Collapse
Affiliation(s)
- L Supino-Rosin
- Department of Cell Biology and Histology, Sackler Faculty of Medicine, Tel-Aviv University, Israel Institute of Life Science, Kurume University, Japan
| | | | | | | |
Collapse
|
39
|
Brideau AD, del Rio T, Wolffe EJ, Enquist LW. Intracellular trafficking and localization of the pseudorabies virus Us9 type II envelope protein to host and viral membranes. J Virol 1999; 73:4372-84. [PMID: 10196335 PMCID: PMC104218 DOI: 10.1128/jvi.73.5.4372-4384.1999] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Us9 protein is a phosphorylated membrane protein present in the lipid envelope of pseudorabies virus (PRV) particles in a unique tail-anchored type II membrane topology. In this report, we demonstrate that the steady-state residence of the Us9 protein is in a cellular compartment in or near the trans-Golgi network (TGN). Through internalization assays with an enhanced green fluorescent protein epitope-tagged Us9 protein, we demonstrate that the maintenance of Us9 to the TGN region is a dynamic process involving retrieval of molecules from the cell surface. Deletion analysis of the cytoplasmic tail reveals that an acidic cluster containing putative phosphorylation sites is necessary for the recycling of Us9 from the plasma membrane. The absence of this cluster results in the relocalization of Us9 to the plasma membrane due to a defect in endocytosis. The acidic motif, however, does not contain signals needed to direct the incorporation of Us9 into viral envelopes. In this study, we also investigate the role of a dileucine endocytosis signal in the Us9 cytoplasmic tail in the recycling and retention of Us9 to the TGN region. Site-directed mutagenesis of the dileucine motif results in an increase in Us9 plasma membrane staining and a partial internalization defect.
Collapse
Affiliation(s)
- A D Brideau
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| | | | | | | |
Collapse
|
40
|
Tailor CS, Nouri A, Lee CG, Kozak C, Kabat D. Cloning and characterization of a cell surface receptor for xenotropic and polytropic murine leukemia viruses. Proc Natl Acad Sci U S A 1999; 96:927-32. [PMID: 9927670 PMCID: PMC15327 DOI: 10.1073/pnas.96.3.927] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/1998] [Accepted: 11/17/1998] [Indexed: 11/18/2022] Open
Abstract
Xenotropic and polytropic murine leukemia viruses (X-MLVs and P-MLVs) cross-interfere to various extents in non-mouse species and in wild Asian mice, suggesting that they might use a common receptor for infection. Consistent with this hypothesis, the susceptibility of some wild mice to X-MLVs has been mapped to the P-MLV receptor locus at the distal end of mouse chromosome 1. In this study, we report the isolation and characterization of a cDNA for the human X-MLV cell surface receptor (X-receptor) by using a human T lymphocyte cDNA library in a retroviral vector. The predicted X-receptor contains 696 amino acids with multiple hydrophobic potential membrane-spanning sequences and with weak homologies to the yeast proteins SYG1, of unknown function, and PHO81, which has been implicated in a system that regulates transport of inorganic phosphate. Expression of the X-receptor in Chinese hamster ovary cells, which are substantially resistant to P-MLVs and to X-MLVs, made them susceptible to both of these virus groups. The mouse homologue of the X-receptor was mapped by hybridization to the distal end of chromosome 1 at the same position as the P-MLV receptor gene Rmc1. These results strongly support the hypothesis that a common gene encodes the receptors for X-MLVs and P-MLVs, with the human X-receptor preferentially mediating X-MLV infections and the homologous protein of inbred mice mediating only P-MLV infections. We propose that X-MLVs and P-MLVs comprise a single family of retroviruses that have coevolved in response to diversification in X-receptor genes of the host.
Collapse
Affiliation(s)
- C S Tailor
- Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland, OR 97201-3098, USA.
| | | | | | | | | |
Collapse
|
41
|
Brown MC, Curtis MS, Turner CE. Paxillin LD motifs may define a new family of protein recognition domains. NATURE STRUCTURAL BIOLOGY 1998; 5:677-8. [PMID: 9699628 DOI: 10.1038/1370] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- M C Brown
- Department of Anatomy and Cell Biology, College of Medicine, State University of New York Health Science Center at Syracuse, 13210, USA.
| | | | | |
Collapse
|
42
|
Al-Hasani H, Hinck CS, Cushman SW. Endocytosis of the glucose transporter GLUT4 is mediated by the GTPase dynamin. J Biol Chem 1998; 273:17504-10. [PMID: 9651341 DOI: 10.1074/jbc.273.28.17504] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
To study the role of the GTPase dynamin in GLUT4 intracellular recycling, we have overexpressed dynamin-1 wild type and a GTPase-negative mutant (K44A) in primary rat adipose cells. Transfection was accomplished by electroporation using an hemagglutinin (HA)-tagged GLUT4 as a reporter protein. In cells expressing HA-GLUT4 alone, insulin results in an approximately 7-fold increase in cell surface anti-HA antibody binding. Studies with wortmannin indicate that the kinetics of HA-GLUT4-trafficking parallel those of the native GLUT4 and in addition, that newly synthesized HA-GLUT4 goes to the plasma membrane before being sorted into the insulin-responsive compartments. Short term (4 h) coexpression of dynamin-K44A and HA-GLUT4 increases the amount of cell surface HA-GLUT4 in both the basal and insulin-stimulated states. Under conditions of maximal expression of dynamin-K44A (24 h), most or all of the intracellular HA-GLUT4 appears to be present on the cell surface in the basal state, and insulin has no further effect. Measurements of the kinetics of HA-GLUT4 endocytosis show that dynamin-K44A blocks internalization of the glucose transporters. In contrast, expression of dynamin wild type decreases the amount of cell surface HA-GLUT4 in both the basal and insulin-stimulated states. These data demonstrate that the endocytosis of GLUT4 is largely mediated by processes which require dynamin.
Collapse
Affiliation(s)
- H Al-Hasani
- Experimental Diabetes, Metabolism, and Nutrition Section, Diabetes Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA.
| | | | | |
Collapse
|
43
|
Ceresa BP, Kao AW, Santeler SR, Pessin JE. Inhibition of clathrin-mediated endocytosis selectively attenuates specific insulin receptor signal transduction pathways. Mol Cell Biol 1998; 18:3862-70. [PMID: 9632770 PMCID: PMC108970 DOI: 10.1128/mcb.18.7.3862] [Citation(s) in RCA: 187] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/1997] [Accepted: 04/06/1998] [Indexed: 02/07/2023] Open
Abstract
To examine the role of clathrin-dependent insulin receptor internalization in insulin-stimulated signal transduction events, we expressed a dominant-interfering mutant of dynamin (K44A/dynamin) by using a recombinant adenovirus in the H4IIE hepatoma and 3T3L1 adipocyte cell lines. Expression of K44A/dynamin inhibited endocytosis of the insulin receptor as determined by both cell surface radioligand binding and trypsin protection analysis. The inhibition of the insulin receptor endocytosis had no effect on either the extent of insulin receptor autophosphorylation or insulin receptor substrate 1 (IRS1) tyrosine phosphorylation. In contrast, expression of K44A/dynamin partially inhibited insulin-stimulated Shc tyrosine phosphorylation and activation of the mitogen-activated protein kinases ERK1 and -2. Although there was an approximately 50% decrease in the insulin-stimulated activation of the phosphatidylinositol 3-kinase associated with IRS1, insulin-stimulated Akt kinase phosphorylation and activation were unaffected. The expression of K44A/dynamin increased the basal rate of amino acid transport, which was additive with the effect of insulin but had no effect on the basal or insulin-stimulated DNA synthesis. In 3T3L1 adipocytes, expression of K44A/dynamin increased the basal rate of glucose uptake, glycogen synthesis, and lipogenesis without any significant effect on insulin stimulation. Together, these data demonstrate that the acute actions of insulin are largely independent of insulin receptor endocytosis and are initiated by activation of the plasma membrane-localized insulin receptor.
Collapse
Affiliation(s)
- B P Ceresa
- Department of Physiology and Biophysics, The University of Iowa, Iowa City, Iowa 52242-1109, USA
| | | | | | | |
Collapse
|
44
|
Levin I, Cohen J, Supino-Rosin L, Yoshimura A, Watowich SS, Neumann D. Identification of a cytoplasmic motif in the erythropoietin receptor required for receptor internalization. FEBS Lett 1998; 427:164-70. [PMID: 9607304 DOI: 10.1016/s0014-5793(98)00414-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Erythropoietin (EPO) promotes the viability, proliferation and differentiation of mammalian erythroid progenitor cells via its specific cell surface receptor. The EPO receptor (EPO-R) is a member of the cytokine receptor superfamily and is comprised of one identified subunit which homodimerizes upon ligand binding. To study the role of the intracellular domain of the EPO-R in the endocytosis of EPO, we compared the rate and extent of 125I-EPO endocytosis by wild type (wt) EPO-R and five cytoplasmically truncated EPO-Rs: 1-251 EPO-R, 1-257 EPO-R, 1-267 EPO-R, 1-276 EPO-R and 1-306 EPO-R which contain 4, 10, 20, 29 or 59 amino acids of the cytoplasmic domain, respectively. We also studied an EPO-R mutant (PB) which lacks amino acid residues 281-300 of the cytoplasmic domain. The experiments were conducted in COS 7 cells transfected with the EPO-R cDNAs and in Ba/F3 cells stably expressing the wt EPO-R, 1-251 or 1-257 EPO-R. Cells expressing wt EPO-R, PB EPO-R (delta281-300), 1-276 EPO-R or 1-306 EPO-R internalized approximately 50% of 125I-EPO bound to the cell surface, while cells expressing 1-251, 1-257 or 1-267 EPO-R internalized only 25% of the bound 125I-EPO. The steady-state expression levels of these latter receptors on the cell surface were typically 2-5-fold higher than wt EPO-R. Our data indicate that amino acid residues 267-276 (FEGLFTTHK) of the EPO-R cytoplasmic domain may have a role in receptor internalization. Metabolic labeling experiments suggest that in transiently transfected COS 7 cells most of the wt EPO-R and 1-257 EPO-Rs do not exit the ER and may be degraded there. The half-life of both receptors was essentially similar and was in the range of 1 h. In Ba/F3 cells the mature Golgi processed 1-257 EPO-R was more stable than the corresponding form of the wt EPO-R, possibly contributing to its higher cell surface expression.
Collapse
Affiliation(s)
- I Levin
- Department of Cell Biology and Histology, Sackler Faculty of Medicine, Tel-Aviv University, Ramat Aviv, Israel
| | | | | | | | | | | |
Collapse
|
45
|
Reaves BJ, Banting G, Luzio JP. Lumenal and transmembrane domains play a role in sorting type I membrane proteins on endocytic pathways. Mol Biol Cell 1998; 9:1107-22. [PMID: 9571243 PMCID: PMC25333 DOI: 10.1091/mbc.9.5.1107] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/1998] [Accepted: 02/27/1998] [Indexed: 02/07/2023] Open
Abstract
Previous studies have shown that when the cytosolic domains of the type I membrane proteins TGN38 and lysosomal glycoprotein 120 (lgp120) are added to a variety of reporter molecules, the resultant chimeric molecules are localized to the trans-Golgi network (TGN) and to lysosomes, respectively. In the present study we expressed chimeric constructs of rat TGN38 and rat lgp120 in HeLa cells. We found that targeting information in the cytosolic domain of TGN38 could be overridden by the presence of the lumenal and transmembrane domains of lgp120. In contrast, the presence of the transmembrane and cytosolic domains of TGN38 was sufficient to deliver the lumenal domain of lgp120 to the trans-Golgi network. On the basis of steady-state localization of the various chimeras and antibody uptake experiments, we propose that there is a hierarchy of targeting information in each molecule contributing to sorting within the endocytic pathway. The lumenal and cytosolic domains of lgp120 contribute to sorting and delivery to lysosomes, whereas the transmembrane and cytosolic domains of TGN38 contribute to sorting and delivery to the trans-Golgi network.
Collapse
Affiliation(s)
- B J Reaves
- Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QR, United Kingdom
| | | | | |
Collapse
|
46
|
Maggi D, Andraghetti G, Carpentier JL, Cordera R. Cys860 in the extracellular domain of insulin receptor beta-subunit is critical for internalization and signal transduction. Endocrinology 1998; 139:496-504. [PMID: 9449617 DOI: 10.1210/endo.139.2.5744] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The C860S mutation (IRC860S) in the extracellular domain of the insulin receptor beta-subunit has previously been shown to result in an inhibition of insulin receptor internalization. The present work aims at further dissecting the consequences of this mutation not only on insulin receptor internalization, but also on the signaling of the receptor. Following transfection of Chinese hamster ovary (CHO) cells with insulin receptors with the C860S mutation (CHO-IRC860S) and quantitative electron microscopic analysis of [125I]insulin localization in these cells, the inhibition of receptor internalization appears to be due to an inhibition of the lateral translocation of the receptor from microvilli to nonvillous domains of the cell surface. At 37 C, insulin-stimulated insulin receptor substrate-1 (IRS-1) phosphorylation is inhibited by 50% in CHO-IRC860S, whereas Shc phosphorylation remains unaffected. The inhibition of IRS-1 phosphorylation is still present when experiments are conducted at 4 C, a temperature at which insulin receptor internalization is prevented, suggesting that the defect in IRS-1 phosphorylation is not due to the reduced internalization of the receptor. In terms of biological effects, the mutation has negative consequences on insulin-stimulated c-fos expression and DNA synthesis as well as on glycogen synthase activity. Eventually, the events observed are specific for Cys860, as individual substitution of the two more proximal Cys residues (795 and 872) to Ser is not accompanied by any change in either insulin-induced insulin receptor internalization or IRS-1 phosphorylation. Thus, the present analysis of CHO-IRC860S 1) reveals that insulin receptor surface redistribution is not solely dependent on receptor autophosphorylation, 2) emphasizes that IRS-1 phosphorylation is not dependent on receptor internalization and can be triggered from microvilli, and 3) stresses divergent aspects between two of the major signaling pathways of the insulin receptor.
Collapse
Affiliation(s)
- D Maggi
- Department of Endocrinology and Metabolism, University of Genova, Italy
| | | | | | | |
Collapse
|