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Vear A, Gaspari T, Thompson P, Chai SY. Is There an Interplay Between the Functional Domains of IRAP? Front Cell Dev Biol 2020; 8:585237. [PMID: 33134302 PMCID: PMC7550531 DOI: 10.3389/fcell.2020.585237] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 09/08/2020] [Indexed: 01/16/2023] Open
Abstract
As a member of the M1 family of aminopeptidases, insulin regulated aminopeptidase (IRAP) is characterized by distinct binding motifs at the active site in the C-terminal domain that mediate the catalysis of peptide substrates. However, what makes IRAP unique in this family of enzymes is that it also possesses trafficking motifs at the N-terminal domain which regulate the movement of IRAP within different intracellular compartments. Research on the role of IRAP has focused predominantly on the C-terminus catalytic domain in different physiological and pathophysiological states ranging from pregnancy to memory loss. Many of these studies have utilized IRAP inhibitors, that bind competitively to the active site of IRAP, to explore the functional significance of its catalytic activity. However, it is unknown whether these inhibitors are able to access intracellular sites where IRAP is predominantly located in a basal state as the enzyme may need to be at the cell surface for the inhibitors to mediate their effects. This property of IRAP has often been overlooked. Interestingly, in some pathophysiological states, the distribution of IRAP is altered. This, together with the fact that IRAP possesses trafficking motifs, suggest the localization of IRAP may play an important role in defining its physiological or pathological functions and provide insights into the interplay between the two functional domains of the protein.
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Affiliation(s)
- Anika Vear
- Department of Physiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Tracey Gaspari
- Department of Pharmacology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Philip Thompson
- Department of Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Siew Yeen Chai
- Department of Physiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
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Building GLUT4 Vesicles: CHC22 Clathrin's Human Touch. Trends Cell Biol 2020; 30:705-719. [PMID: 32620516 DOI: 10.1016/j.tcb.2020.05.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 05/24/2020] [Accepted: 05/27/2020] [Indexed: 12/18/2022]
Abstract
Insulin stimulates glucose transport by triggering regulated delivery of intracellular vesicles containing the GLUT4 glucose transporter to the plasma membrane. This process is defective in diseases such as type 2 diabetes (T2DM). While studies in rodent cells have been invaluable in understanding GLUT4 traffic, evolutionary plasticity must be considered when extrapolating these findings to humans. Recent work has identified species-specific distinctions in GLUT4 traffic, notably the participation of a novel clathrin isoform, CHC22, in humans but not rodents. Here, we discuss GLUT4 sorting in different species and how studies of CHC22 have identified new routes for GLUT4 trafficking. We further consider how different sorting-protein complexes relate to these routes and discuss other implications of these pathways in cell biology and disease.
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Nikolaou A, Stijlemans B, Laoui D, Schouppe E, Tran HTT, Tourwé D, Chai SY, Vanderheyden PML, Van Ginderachter JA. Presence and regulation of insulin-regulated aminopeptidase in mouse macrophages. J Renin Angiotensin Aldosterone Syst 2014; 15:466-79. [DOI: 10.1177/1470320313507621] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- Alexandros Nikolaou
- Molecular and Biochemical Pharmacology, Vrije Universiteit Brussel, Belgium
- Cellular and Molecular Immunology Unit, Vrije Universiteit Brussel, Belgium
| | - Benoit Stijlemans
- Myeloid Cell Immunology Laboratory, VIB, Belgium
- Cellular and Molecular Immunology Unit, Vrije Universiteit Brussel, Belgium
| | - Damya Laoui
- Myeloid Cell Immunology Laboratory, VIB, Belgium
- Cellular and Molecular Immunology Unit, Vrije Universiteit Brussel, Belgium
| | - Elio Schouppe
- Myeloid Cell Immunology Laboratory, VIB, Belgium
- Cellular and Molecular Immunology Unit, Vrije Universiteit Brussel, Belgium
| | - Huyen TT Tran
- Myeloid Cell Immunology Laboratory, VIB, Belgium
- Cellular and Molecular Immunology Unit, Vrije Universiteit Brussel, Belgium
| | - Dirk Tourwé
- Laboratory of Organic Chemistry, Vrije Universiteit Brussel, Belgium
| | - Siew Y Chai
- Department of Physiology, Monash University, Australia
| | | | - Jo A Van Ginderachter
- Myeloid Cell Immunology Laboratory, VIB, Belgium
- Cellular and Molecular Immunology Unit, Vrije Universiteit Brussel, Belgium
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Roberts CK, Hevener AL, Barnard RJ. Metabolic syndrome and insulin resistance: underlying causes and modification by exercise training. Compr Physiol 2013; 3:1-58. [PMID: 23720280 DOI: 10.1002/cphy.c110062] [Citation(s) in RCA: 266] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Metabolic syndrome (MS) is a collection of cardiometabolic risk factors that includes obesity, insulin resistance, hypertension, and dyslipidemia. Although there has been significant debate regarding the criteria and concept of the syndrome, this clustering of risk factors is unequivocally linked to an increased risk of developing type 2 diabetes and cardiovascular disease. Regardless of the true definition, based on current population estimates, nearly 100 million have MS. It is often characterized by insulin resistance, which some have suggested is a major underpinning link between physical inactivity and MS. The purpose of this review is to: (i) provide an overview of the history, causes and clinical aspects of MS, (ii) review the molecular mechanisms of insulin action and the causes of insulin resistance, and (iii) discuss the epidemiological and intervention data on the effects of exercise on MS and insulin sensitivity.
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Affiliation(s)
- Christian K Roberts
- Exercise and Metabolic Disease Research Laboratory, Translational Sciences Section, School of Nursing, University of California at Los Angeles, Los Angeles, California, USA.
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Nikolaou A, Eynde IVD, Tourwé D, Vauquelin G, Tóth G, Mallareddy JR, Poglitsch M, Van Ginderachter JA, Vanderheyden PM. [3H]IVDE77, a novel radioligand with high affinity and selectivity for the insulin-regulated aminopeptidase. Eur J Pharmacol 2013; 702:93-102. [DOI: 10.1016/j.ejphar.2013.01.026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 01/14/2013] [Accepted: 01/16/2013] [Indexed: 10/27/2022]
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Abstract
To enhance glucose uptake into muscle and fat cells, insulin stimulates the translocation of GLUT4 glucose transporters from intracellular membranes to the cell surface. This response requires the intersection of insulin signaling and vesicle trafficking pathways, and it is compromised in the setting of overnutrition to cause insulin resistance. Insulin signals through AS160/Tbc1D4 and Tbc1D1 to modulate Rab GTPases and through the Rho GTPase TC10α to act on other targets. In unstimulated cells, GLUT4 is incorporated into specialized storage vesicles containing IRAP, LRP1, sortilin, and VAMP2, which are sequestered by TUG, Ubc9, and other proteins. Insulin mobilizes these vesicles directly to the plasma membrane, and it modulates the trafficking itinerary so that cargo recycles from endosomes during ongoing insulin exposure. Knowledge of how signaling and trafficking pathways are coordinated will be essential to understanding the pathogenesis of diabetes and the metabolic syndrome and may also inform a wide range of other physiologies.
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Affiliation(s)
- Jonathan S Bogan
- Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520-8020, USA.
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Saveanu L, van Endert P. The role of insulin-regulated aminopeptidase in MHC class I antigen presentation. Front Immunol 2012; 3:57. [PMID: 22566938 PMCID: PMC3342382 DOI: 10.3389/fimmu.2012.00057] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 03/03/2012] [Indexed: 01/08/2023] Open
Abstract
Production of MHC-I ligands from antigenic proteins generally requires multiple proteolytic events. While the proteolytic steps required for antigen processing in the endogenous pathway are clearly established, persisting gaps of knowledge regarding putative cross-presentation compartments have made it difficult to map the precise proteolytic events required for generation of cross-presented antigens. It is only in the past decade that the importance of aminoterminal trimming as the final step in the endogenous presentation pathway has been recognized and that the corresponding enzymes have been described. This review focuses on the aminoterminal trimming of exogenous cross-presented peptides, with particular emphasis on the identification of insulin responsive aminopeptidase (IRAP) as the principal trimming aminopeptidase in endosomes and phagosomes.
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Affiliation(s)
- Loredana Saveanu
- Institut National de la Santé et de le Recherche Médicale Paris, France
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Rubin BR, Bogan JS. Intracellular retention and insulin-stimulated mobilization of GLUT4 glucose transporters. VITAMINS AND HORMONES 2009; 80:155-92. [PMID: 19251038 DOI: 10.1016/s0083-6729(08)00607-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
GLUT4 glucose transporters are expressed nearly exclusively in adipose and muscle cells, where they cycle to and from the plasma membrane. In cells not stimulated with insulin, GLUT4 is targeted to specialized GLUT4 storage vesicles (GSVs), which sequester it away from the cell surface. Insulin acts within minutes to mobilize these vesicles, translocating GLUT4 to the plasma membrane to enhance glucose uptake. The mechanisms controlling GSV sequestration and mobilization are poorly understood. An insulin-regulated aminopeptidase that cotraffics with GLUT4, IRAP, is required for basal GSV retention and insulin-stimulated mobilization. TUG and Ubc9 bind GLUT4, and likely retain GSVs within unstimulated cells. These proteins may be components of a retention receptor, which sequesters GLUT4 and IRAP away from recycling vesicles. Insulin may then act on this protein complex to liberate GLUT4 and IRAP, discharging GSVs into a recycling pathway for fusion at the cell surface. How GSVs are anchored intracellularly, and how insulin mobilizes these vesicles, are the important topics for ongoing research. Regulation of GLUT4 trafficking is tissue-specific, perhaps in part because the formation of GSVs requires cell type-specific expression of sortilin. Proteins controlling GSV retention and mobilization can then be more widely expressed. Indeed, GLUT4 likely participates in a general mechanism by which the cell surface delivery of various membrane proteins can be controlled by extracellular stimuli. Finally, it is not known if defects in the formation or intracellular retention of GSVs contribute to human insulin resistance, or play a role in the pathogenesis of type 2 diabetes.
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Affiliation(s)
- Bradley R Rubin
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT 06520-8020, USA
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Watson RT, Hou JC, Pessin JE. Recycling of IRAP from the plasma membrane back to the insulin-responsive compartment requires the Q-SNARE syntaxin 6 but not the GGA clathrin adaptors. J Cell Sci 2008; 121:1243-51. [PMID: 18388312 DOI: 10.1242/jcs.017517] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Insulin recruits two transmembrane proteins, GLUT4 and IRAP, to the plasma membrane of muscle cells and adipocytes. The subcellular trafficking and localization of GLUT4, and to a lesser extent IRAP, have been intensely studied, yet the molecular mechanisms responsible for their insulin-responsive compartmentalization remain unknown. Herein we have investigated the endocytosis and recycling of IRAP from the cell surface back to the insulin-responsive compartment (IRC). Our results show that a key dileucine motif at position 76,77 (LL76,77), although required for the initial biosynthetic entry of IRAP into the IRC, is dispensable for entry into the IRC via the endosomal system. Indeed, we found that an AA76,77 mutant of IRAP is fully capable of undergoing endocytosis and is correctly routed back to the IRC. To verify that the AA76,77 mutant enters the bona fide IRC, we show that the internalized IRAP-AA76,77 construct is sequestered in an IRC that is insensitive to brefeldin A yet sensitive to a dominant-interfering mutant of AS160 (AS160-4P). In addition, we show that the GGA clathrin adaptors are not required for the re-entry of IRAP from the cell surface back into the IRC, whereas the Q-SNARE syntaxin 6 is required for this process.
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Affiliation(s)
- Robert T Watson
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
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Williams D, Pessin JE. Mapping of R-SNARE function at distinct intracellular GLUT4 trafficking steps in adipocytes. ACTA ACUST UNITED AC 2008; 180:375-87. [PMID: 18227281 PMCID: PMC2213575 DOI: 10.1083/jcb.200709108] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The functional trafficking steps used by soluble NSF attachment protein receptor (SNARE) proteins have been difficult to establish because of substantial overlap in subcellular localization and because in vitro SNARE-dependent binding and fusion reactions can be promiscuous. Therefore, to functionally identify the site of action of the vesicle-associated membrane protein (VAMP) family of R-SNAREs, we have taken advantage of the temporal requirements of adipocyte biosynthetic sorting of a dual-tagged GLUT4 reporter (myc-GLUT4-GFP) coupled with small interfering RNA gene silencing. Using this approach, we confirm the requirement of VAMP2 and VAMP7 for insulin and osmotic shock trafficking from the vesicle storage sites, respectively, and fusion with the plasma membrane. Moreover, we identify a requirement for VAMP4 for the initial biosynthetic entry of GLUT4 from the Golgi apparatus into the insulin-responsive vesicle compartment, VAMP8, for plasma membrane endocytosis and VAMP2 for sorting to the specialized insulin-responsive compartment after plasma membrane endocytosis.
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Affiliation(s)
- Dumaine Williams
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
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Abstract
Few physiological parameters are more tightly and acutely regulated in humans than blood glucose concentration. The major cellular mechanism that diminishes blood glucose when carbohydrates are ingested is insulin-stimulated glucose transport into skeletal muscle. Skeletal muscle both stores glucose as glycogen and oxidizes it to produce energy following the transport step. The principal glucose transporter protein that mediates this uptake is GLUT4, which plays a key role in regulating whole body glucose homeostasis. This review focuses on recent advances on the biology of GLUT4.
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Affiliation(s)
- Shaohui Huang
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
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Procino G, Caces DB, Valenti G, Pessin JE. Adipocytes support cAMP-dependent translocation of aquaporin-2 from intracellular sites distinct from the insulin-responsive GLUT4 storage compartment. Am J Physiol Renal Physiol 2005; 290:F985-94. [PMID: 16303856 DOI: 10.1152/ajprenal.00369.2005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Aquaporin-2 (AQP2), when expressed in fully differentiated 3T3-L1 adipocytes, displays cAMP-dependent plasma membrane translocation in a manner similar to its behavior in renal epithelial cells. The translocation of AQP2 required phosphorylation at serine 256, as the expression of AQP2/S256D was constitutively plasma membrane localized, whereas AQP2/S256A was refractory to forskolin stimulation. Unlike GLUT4, this property is not inhibited by depolymerization of cortical actin. In addition, coexpression with the dominant negative form of TC10 (TC10/T31N) or inhibition of phosphatidylinositol 3-kinase did not abrogate the cAMP-mediated response. Under basal conditions, AQP2 is localized in both the perinuclear region and in punctate vesicles scattered within the periphery of the cell. Two- and three-dimensional confocal immunofluorescence microscopy demonstrated that the adipocyte AQP2 cAMP-responsive compartment was distinct from the GLUT4 insulin-responsive compartment. Consistent with this conclusion, insulin was an effective stimulator of GLUT4 translocation but had no effect on AQP2. Conversely, forskolin induced AQP2 translocation but not GLUT4. Colocalization studies with the early endosomal marker EEA1 and transferrin receptor suggested that the AQP2 compartment is mostly distinct from endosomal vesicles. Interestingly, however, the peripheral AQP2 vesicles significantly overlapped vesicle-associated membrane protein-2, underscoring the role of the latter in hormone-regulated exocytosis. To acquire insulin responsiveness following biosynthesis, GLUT4 undergoes a slow sorting step that requires 6-9 h. In contrast, AQP2 rapidly acquires forskolin responsiveness (3 h following biosynthesis) and directly enters the cAMP-regulated compartment without transiting the plasma membrane. Together, these data demonstrate that adipocytes display two different intracellular sorting mechanisms that direct distinct hormone-sensitive partitioning of GLUT4 and AQP2.
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Affiliation(s)
- Giuseppe Procino
- Dept. of Pharmacological Sciences, Stony Brook Univ., Stony Brook, NY 11794-8651, USA
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