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Kulesza T, Typiak M, Rachubik P, Rogacka D, Audzeyenka I, Saleem MA, Piwkowska A. Pit 1 transporter (SLC20A1) as a key factor in the NPP1-mediated inhibition of insulin signaling in human podocytes. J Cell Physiol 2023; 238:1921-1936. [PMID: 37269459 DOI: 10.1002/jcp.31051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 05/12/2023] [Accepted: 05/16/2023] [Indexed: 06/05/2023]
Abstract
Podocytes are crucially involved in blood filtration in the glomerulus. Their proper function relies on efficient insulin responsiveness. The insulin resistance of podocytes, defined as a reduction of cell sensitivity to this hormone, is the earliest pathomechanism of microalbuminuria that is observed in metabolic syndrome and diabetic nephropathy. In many tissues, this alteration is mediated by the phosphate homeostasis-controlling enzyme nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1). By binding to the insulin receptor (IR), NPP1 inhibits downstream cellular signaling. Our previous research found that hyperglycemic conditions affect another protein that is involved in phosphate balance, type III sodium-dependent phosphate transporter 1 (Pit 1). In the present study, we evaluated the insulin resistance of podocytes after 24 h of incubation under hyperinsulinemic conditions. Thereafter, insulin signaling was inhibited. The formation of NPP1/IR complexes was observed at that time. A novel finding in the present study was our observation of an interaction between NPP1 and Pit 1 after the 24 h stimulation of podocytes with insulin. After downregulation of the SLC20A1 gene, which encodes Pit 1, we established insulin resistance in podocytes that were cultured under native conditions, manifested as a lack of intracellular insulin signaling and the inhibition of glucose uptake via the glucose transporter type 4. These findings suggest that Pit 1 might be a major factor that participates in the NPP1-mediated inhibition of insulin signaling.
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Affiliation(s)
- Tomasz Kulesza
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Gdansk, Poland
| | - Marlena Typiak
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Gdansk, Poland
- Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, Gdansk, Poland
| | - Patrycja Rachubik
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Gdansk, Poland
| | - Dorota Rogacka
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Gdansk, Poland
- Department of Molecular Biotechnology, Faculty of Chemistry, University of Gdansk, Gdansk, Poland
| | - Irena Audzeyenka
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Gdansk, Poland
- Department of Molecular Biotechnology, Faculty of Chemistry, University of Gdansk, Gdansk, Poland
| | | | - Agnieszka Piwkowska
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Gdansk, Poland
- Department of Molecular Biotechnology, Faculty of Chemistry, University of Gdansk, Gdansk, Poland
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2
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Abstract
The global prevalences of obesity and type 2 diabetes mellitus have reached epidemic status, presenting a heavy burden on society. It is therefore essential to find novel mechanisms and targets that could be utilized in potential treatment strategies and, as such, intracellular membrane trafficking has re-emerged as a regulatory tool for controlling metabolic homeostasis. Membrane trafficking is an essential physiological process that is responsible for the sorting and distribution of signalling receptors, membrane transporters and hormones or other ligands between different intracellular compartments and the plasma membrane. Dysregulation of intracellular transport is associated with many human diseases, including cancer, neurodegeneration, immune deficiencies and metabolic diseases, such as type 2 diabetes mellitus and its associated complications. This Review focuses on the latest advances on the role of endosomal membrane trafficking in metabolic physiology and pathology in vivo, highlighting the importance of this research field in targeting metabolic diseases.
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Affiliation(s)
- Jerome Gilleron
- Université Côte d'Azur, Institut National de la Santé et de la Recherche Médicale (Inserm), UMR1065 C3M, Team Cellular and Molecular Pathophysiology of Obesity, Nice, France.
| | - Anja Zeigerer
- Institute for Diabetes and Cancer, Helmholtz Center Munich, Neuherberg, Germany.
- German Center for Diabetes Research (DZD), Neuherberg, Germany.
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3
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Heng J, Lv P, Zhang Y, Cheng X, Wang L, Ma D, Liu F. Rab5c-mediated endocytic trafficking regulates hematopoietic stem and progenitor cell development via Notch and AKT signaling. PLoS Biol 2020; 18:e3000696. [PMID: 32275659 PMCID: PMC7176290 DOI: 10.1371/journal.pbio.3000696] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 04/22/2020] [Accepted: 03/24/2020] [Indexed: 12/12/2022] Open
Abstract
It is well known that various developmental signals play diverse roles in hematopoietic stem and progenitor cell (HSPC) production; however, how these signaling pathways are orchestrated remains incompletely understood. Here, we report that Rab5c is essential for HSPC specification by endocytic trafficking of Notch and AKT signaling in zebrafish embryos. Rab5c deficiency leads to defects in HSPC production. Mechanistically, Rab5c regulates hemogenic endothelium (HE) specification by endocytic trafficking of Notch ligands and receptor. We further show that the interaction between Rab5c and Appl1 in the endosome is required for the survival of HE in the ventral wall of the dorsal aorta through AKT signaling. Interestingly, Rab5c overactivation can also lead to defects in HSPC production, which is attributed to excessive endolysosomal trafficking inducing Notch signaling defect. Taken together, our findings establish a previously unrecognized role of Rab5c-mediated endocytic trafficking in HSPC development and provide new insights into how spatiotemporal signals are orchestrated to accurately execute cell fate transition. Cell-autonomous Notch signaling regulated by the membrane trafficking protein Rab5c plays an instructive role in hematopoietic stem and progenitor cell specification, while the AKT signaling seems to provide a permissive signal to maintain hemogenic endothelium survival.
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Affiliation(s)
- Jian Heng
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Peng Lv
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yifan Zhang
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xinjie Cheng
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Lu Wang
- State Key Laboratory of Experimental Hematology, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, China
| | - Dongyuan Ma
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
| | - Feng Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- * E-mail:
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4
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Ahmed MU, Velkov T, Zhou QT, Fulcher AJ, Callaghan J, Zhou F, Chan K, Azad MAK, Li J. Intracellular localization of polymyxins in human alveolar epithelial cells. J Antimicrob Chemother 2020; 74:48-57. [PMID: 30357331 DOI: 10.1093/jac/dky409] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 09/06/2018] [Indexed: 01/05/2023] Open
Abstract
Background Current inhaled polymyxin therapy is empirical and often large doses are administered, which can lead to pulmonary adverse effects. There is a dearth of information on the mechanisms of polymyxin-induced lung toxicity and their intracellular localization in lung epithelial cells. Objectives To investigate the intracellular localization of polymyxins in human lung epithelial A549 cells. Methods A549 cells were treated with polymyxin B and intracellular organelles (early and late endosomes, endoplasmic reticulum, mitochondria, lysosomes and autophagosomes), ubiquitin protein and polymyxin B were visualized using immunostaining and confocal microscopy. Fluorescence intensities of the organelles and polymyxin B were quantified and correlated for co-localization using ImageJ and Imaris platforms. Results Polymyxin B co-localized with early endosomes, lysosomes and ubiquitin at 24 h. Significantly increased lysosomal activity and the autophagic protein LC3A were observed after 0.5 and 1.0 mM polymyxin B treatment at 24 h. Polymyxin B also significantly co-localized with mitochondria (Pearson's R = 0.45) and led to the alteration of mitochondrial morphology from filamentous to fragmented form (n = 3, P < 0.001). These results are in line with the polymyxin-induced activation of the mitochondrial apoptotic pathway observed in A549 cells. Conclusions Accumulation of polymyxins on mitochondria probably caused mitochondrial toxicity, resulting in increased oxidative stress and cell death. The formation of autophagosomes and lysosomes was likely a cellular response to the polymyxin-induced stress and played a defensive role by disassembling dysfunctional organelles and proteins. Our study provides new mechanistic information on polymyxin-induced lung toxicity, which is vital for optimizing inhaled polymyxins in the clinic.
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Affiliation(s)
- Maizbha U Ahmed
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia.,Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
| | - Tony Velkov
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Qi Tony Zhou
- Department of Industrial and Physical Pharmacy, College of Pharmacy, Purdue University, West Lafayette, IN, USA
| | - Alex J Fulcher
- Monash Micro Imaging, Monash University, Victoria, Australia
| | - Judy Callaghan
- Monash Micro Imaging, Monash University, Victoria, Australia
| | - Fanfan Zhou
- School of Pharmacy, The University of Sydney, Camperdown, NSW, Australia
| | - Kim Chan
- School of Pharmacy, The University of Sydney, Camperdown, NSW, Australia
| | - Mohammad A K Azad
- Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
| | - Jian Li
- Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
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5
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Chen Y, Huang L, Qi X, Chen C. Insulin Receptor Trafficking: Consequences for Insulin Sensitivity and Diabetes. Int J Mol Sci 2019; 20:ijms20205007. [PMID: 31658625 PMCID: PMC6834171 DOI: 10.3390/ijms20205007] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/04/2019] [Accepted: 10/08/2019] [Indexed: 12/12/2022] Open
Abstract
Insulin receptor (INSR) has been extensively studied in the area of cell proliferation and energy metabolism. Impaired INSR activities lead to insulin resistance, the key factor in the pathology of metabolic disorders including type 2 diabetes mellitus (T2DM). The mainstream opinion is that insulin resistance begins at a post-receptor level. The role of INSR activities and trafficking in insulin resistance pathogenesis has been largely ignored. Ligand-activated INSR is internalized and trafficked to early endosome (EE), where INSR is dephosphorylated and sorted. INSR can be subsequently conducted to lysosome for degradation or recycled back to the plasma membrane. The metabolic fate of INSR in cellular events implies the profound influence of INSR on insulin signaling pathways. Disruption of INSR-coupled activities has been identified in a wide range of insulin resistance-related diseases such as T2DM. Accumulating evidence suggests that alterations in INSR trafficking may lead to severe insulin resistance. However, there is very little understanding of how altered INSR activities undermine complex signaling pathways to the development of insulin resistance and T2DM. Here, we focus this review on summarizing previous findings on the molecular pathways of INSR trafficking in normal and diseased states. Through this review, we provide insights into the mechanistic role of INSR intracellular processes and activities in the development of insulin resistance and diabetes.
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Affiliation(s)
- Yang Chen
- School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia.
| | - Lili Huang
- School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia.
| | - Xinzhou Qi
- School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia.
| | - Chen Chen
- School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia.
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6
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Mani M, Thao DT, Kim BC, Lee UH, Kim DJ, Jang SH, Back SH, Lee BJ, Cho WJ, Han IS, Park JW. DRG2 knockdown induces Golgi fragmentation via GSK3β phosphorylation and microtubule stabilization. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:1463-1474. [PMID: 31199931 DOI: 10.1016/j.bbamcr.2019.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Revised: 05/19/2019] [Accepted: 06/04/2019] [Indexed: 01/01/2023]
Abstract
The perinuclear stacks of the Golgi apparatus maintained by dynamic microtubules are essential for cell migration. Activation of Akt (protein kinase B, PKB) negatively regulates glycogen synthase kinase 3β (GSK3β)-mediated tau phosphorylation, which enhances tau binding to microtubules and microtubule stability. In this study, experiments were performed on developmentally regulated GTP-binding protein 2 (DRG2)-stably knockdown HeLa cells to determine whether knockdown of DRG2 in HeLa cells treated with epidermal growth factor (EGF) affects microtubule dynamics, perinuclear Golgi stacking, and cell migration. Here, we show that DRG2 plays a key role in regulating microtubule stability, perinuclear Golgi stack formation, and cell migration. DRG2 knockdown prolonged the EGF receptor (EGFR) localization in endosome, enhanced Akt activity and inhibitory phosphorylation of GSK3β. Tau, a target of GSK3β, was hypo-phosphorylated in DRG2-knockdown cells and showed greater association with microtubules, resulting in microtubule stabilization. DRG2-knockdown cells showed defects in microtubule growth and microtubule organizing centers (MTOC), Golgi fragmentation, and loss of directional cell migration. These results reveal a previously unappreciated role for DRG2 in the regulation of perinuclear Golgi stacking and cell migration via its effects on GSK3β phosphorylation, and microtubule stability.
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Affiliation(s)
- Muralidharan Mani
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - Dang Thi Thao
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - Beom Chang Kim
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - Unn Hwa Lee
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - Dong Jun Kim
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - Soo Hwa Jang
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - Sung Hoon Back
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - Byung Ju Lee
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - Wha Ja Cho
- Metainflammation Research Center, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - In-Seob Han
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea.
| | - Jeong Woo Park
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, Republic of Korea.
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7
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Agrawal S, Łuc M, Ziółkowski P, Agrawal AK, Pielka E, Walaszek K, Zduniak K, Woźniak M. Insulin-induced enhancement of MCF-7 breast cancer cell response to 5-fluorouracil and cyclophosphamide. Tumour Biol 2017. [PMID: 28631569 DOI: 10.1177/1010428317702901] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The study was designed to evaluate the potential use of insulin for cancer-specific treatment. Insulin-induced sensitivity of MCF-7 breast cancer cells to chemotherapeutic agents 5-fluorouracil and cyclophosphamide was evaluated. To investigate and establish the possible mechanisms of this phenomenon, we assessed cell proliferation, induction of apoptosis, activation of apoptotic and autophagic pathways, expression of glucose transporters 1 and 3, formation of reactive oxygen species, and wound-healing assay. Additionally, we reviewed the literature regarding theuse of insulin in cancer-specific treatment. We found that insulin increases the cytotoxic effect of 5-fluorouracil and cyclophosphamide in vitro up to two-fold. The effect was linked to enhancement of apoptosis, activation of apoptotic and autophagic pathways, and overexpression of glucose transporters 1 and 3 as well as inhibition of cell proliferation and motility. We propose a model for insulin-induced sensitization process. Insulin acts as a sensitizer of cancer cells to cytotoxic therapy through various mechanisms opening a possibility for metronomic insulin-based treatments.
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Affiliation(s)
- Siddarth Agrawal
- 1 Department of Pathology, Wroclaw Medical University, Wroclaw, Poland
| | - Mateusz Łuc
- 1 Department of Pathology, Wroclaw Medical University, Wroclaw, Poland
| | - Piotr Ziółkowski
- 1 Department of Pathology, Wroclaw Medical University, Wroclaw, Poland
| | - Anil Kumar Agrawal
- 2 Department of General and Oncological Surgery, Wroclaw Medical University, Wroclaw, Poland
| | - Ewa Pielka
- 1 Department of Pathology, Wroclaw Medical University, Wroclaw, Poland
| | - Kinga Walaszek
- 1 Department of Pathology, Wroclaw Medical University, Wroclaw, Poland
| | - Krzysztof Zduniak
- 1 Department of Pathology, Wroclaw Medical University, Wroclaw, Poland
| | - Marta Woźniak
- 1 Department of Pathology, Wroclaw Medical University, Wroclaw, Poland
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8
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Roux A, Loranger A, Lavoie JN, Marceau N. Keratin 8/18 regulation of insulin receptor signaling and trafficking in hepatocytes through a concerted phosphoinositide-dependent Akt and Rab5 modulation. FASEB J 2017; 31:3555-3573. [PMID: 28442548 DOI: 10.1096/fj.201700036r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 04/11/2017] [Indexed: 01/30/2023]
Abstract
Keratins (Ks) are epithelial cell intermediate filament (IF) proteins that are expressed as pairs in a differentiation-regulated manner. Hepatocyte IFs are made only of K8/K18 pairs, which means that a K8 loss in K8-null mice leads to degradation of K18. Functionally, there is accumulating evidence that IFs contribute to signaling platforms. Here, we investigate the role of K8/K18 IFs in the regulation of insulin receptor (IR) signaling and trafficking in hepatocytes. We find that the IR substrate 1 (IRS1)/PI3K/Akt signaling cascade-downstream of IR-displays prolonged activation in K8-null compared with wild-type hepatocytes. Assessment of the Akt/mammalian target of rapamycin complex 1-mediated feedback loop to IRS1/PI3K, in the absence or presence of drug inhibitors, further supports a preferential K8/K18 IF intervention at the surface membrane. In K8-null hepatocytes, IR trafficking vesicles that are labeled by Rab5/EEA1/phosphatidylinositol 3-phosphate accumulate at a juxtanuclear region via a microtubule-dependent process. Moreover, interference with phosphatidylinositol 4,5-biphosphate signaling aggravates IR/Rab5 accumulation. Overall, results uncover K8/K18 IF regulation of IR signaling via a concerted modulation of phosphatidylinositol 4,5-biphosphate-dependent IRS1/PI3K/Akt signaling and Rab5/phosphatidylinositol 3-phosphate/microtubule trafficking in hepatocytes.-Roux, A., Loranger, A., Lavoie, J. N., Marceau, N. Keratin 8/18 regulation of insulin receptor signaling and trafficking in hepatocytes through a concerted phosphoinositide-dependent Akt and Rab5 modulation.
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Affiliation(s)
- Alexandra Roux
- Centre de Recherche Sur le Cancer de l'Université Laval, Québec City, Quebec, Canada.,Centre de Recherche du Centre Hospitalier Universitaire de Québec-Université Laval, L'Hôtel-Dieu de Québec, Québec City, Quebec, Canada
| | - Anne Loranger
- Centre de Recherche Sur le Cancer de l'Université Laval, Québec City, Quebec, Canada.,Centre de Recherche du Centre Hospitalier Universitaire de Québec-Université Laval, L'Hôtel-Dieu de Québec, Québec City, Quebec, Canada
| | - Josée N Lavoie
- Centre de Recherche Sur le Cancer de l'Université Laval, Québec City, Quebec, Canada.,Centre de Recherche du Centre Hospitalier Universitaire de Québec-Université Laval, L'Hôtel-Dieu de Québec, Québec City, Quebec, Canada
| | - Normand Marceau
- Centre de Recherche Sur le Cancer de l'Université Laval, Québec City, Quebec, Canada; .,Centre de Recherche du Centre Hospitalier Universitaire de Québec-Université Laval, L'Hôtel-Dieu de Québec, Québec City, Quebec, Canada
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9
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Basagiannis D, Christoforidis S. Constitutive Endocytosis of VEGFR2 Protects the Receptor against Shedding. J Biol Chem 2016; 291:16892-903. [PMID: 27298320 DOI: 10.1074/jbc.m116.730309] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Indexed: 12/19/2022] Open
Abstract
VEGFR2 plays a fundamental role in blood vessel formation and in life threatening diseases, such as cancer angiogenesis and cardiovascular disorders. Although inactive growth factor receptors are mainly localized at the plasma membrane, VEGFR2 undergoes constitutive endocytosis (in the absence of ligand) and recycling. Intriguingly, the significance of these futile transport cycles of VEGFR2 remains unclear. Here we found that, unexpectedly, the function of constitutive endocytosis of VEGFR2 is to protect the receptor against plasma membrane cleavage (shedding), thereby preserving the functional state of the receptor until the time of activation by VEGF. Inhibition of constitutive endocytosis of VEGFR2, by interference with the function of clathrin, dynamin, or Rab5, increases dramatically the cleavage/shedding of VEGFR2. Shedding of VEGFR2 produces an N-terminal soluble fragment (100 kDa, s100), which is released in the extracellular space, and a residual C-terminal part (130 kDa, p130) that remains integrated at the plasma membrane. The released soluble fragment (s100) co-immunoprecipitates with VEGF, in line with the topology of the VEGF-binding domain at the N terminus of VEGFR2. Increased shedding of VEGFR2 (via inhibition of constitutive endocytosis) results in reduced response to VEGF, consistently with the loss of the VEGF-binding domain from the membrane remnant of VEGFR2. These data suggest that constitutive internalization of VEGFR2 protects the receptor against shedding and provides evidence for an unprecedented mechanism via which endocytosis can regulate the fate and activity of growth factor receptors.
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Affiliation(s)
- Dimitris Basagiannis
- From the Institute of Molecular Biology and Biotechnology-Biomedical Research, Foundation for Research and Technology, 45110 Ioannina and the Department of Medicine, Laboratory of Biological Chemistry, School of Health Sciences, University of Ioannina, 45110 Ioannina, Greece
| | - Savvas Christoforidis
- From the Institute of Molecular Biology and Biotechnology-Biomedical Research, Foundation for Research and Technology, 45110 Ioannina and the Department of Medicine, Laboratory of Biological Chemistry, School of Health Sciences, University of Ioannina, 45110 Ioannina, Greece
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10
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Nemazanyy I, Montagnac G, Russell RC, Morzyglod L, Burnol AF, Guan KL, Pende M, Panasyuk G. Class III PI3K regulates organismal glucose homeostasis by providing negative feedback on hepatic insulin signalling. Nat Commun 2015; 6:8283. [PMID: 26387534 PMCID: PMC4579570 DOI: 10.1038/ncomms9283] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 08/07/2015] [Indexed: 11/09/2022] Open
Abstract
Defective hepatic insulin receptor (IR) signalling is a pathogenic manifestation of metabolic disorders including obesity and diabetes. The endo/lysosomal trafficking system may coordinate insulin action and nutrient homeostasis by endocytosis of IR and the autophagic control of intracellular nutrient levels. Here we show that class III PI3K--a master regulator of endocytosis, endosomal sorting and autophagy--provides negative feedback on hepatic insulin signalling. The ultraviolet radiation resistance-associated gene protein (UVRAG)-associated class III PI3K complex interacts with IR and is stimulated by insulin treatment. Acute and chronic depletion of hepatic Vps15, the regulatory subunit of class III PI3K, increases insulin sensitivity and Akt signalling, an effect that requires functional IR. This is reflected by FoxO1-dependent transcriptional defects and blunted gluconeogenesis in Vps15 mutant cells. On depletion of Vps15, the metabolic syndrome in genetic and diet-induced models of insulin resistance and diabetes is alleviated. Thus, feedback regulation of IR trafficking and function by class III PI3K may be a therapeutic target in metabolic conditions of insulin resistance.
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Affiliation(s)
- Ivan Nemazanyy
- Institut Necker-Enfants Malades (INEM), Cedex 14, 75993 Paris, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), Cedex 14, U1151, 75993 Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France
| | - Guillaume Montagnac
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1170, Gustave Roussy Institute, 94805 Villejuif, France
| | - Ryan C Russell
- Department of Pharmacology, University of California at San Diego, La Jolla, California 92093, USA.,Moores Cancer Center, University of California at San Diego, La Jolla, California 92093, USA
| | - Lucille Morzyglod
- Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1016, Institut Cochin, 75014 Paris, France.,Centre national de la recherche scientifique (CNRS), UMR8104, 75014 Paris, France
| | - Anne-Françoise Burnol
- Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1016, Institut Cochin, 75014 Paris, France.,Centre national de la recherche scientifique (CNRS), UMR8104, 75014 Paris, France
| | - Kun-Liang Guan
- Department of Pharmacology, University of California at San Diego, La Jolla, California 92093, USA.,Moores Cancer Center, University of California at San Diego, La Jolla, California 92093, USA
| | - Mario Pende
- Institut Necker-Enfants Malades (INEM), Cedex 14, 75993 Paris, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), Cedex 14, U1151, 75993 Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France
| | - Ganna Panasyuk
- Institut Necker-Enfants Malades (INEM), Cedex 14, 75993 Paris, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), Cedex 14, U1151, 75993 Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France
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11
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Desbuquois B, Authier F. [Involvement of the endosomal compartment in cellular insulin signaling]. Biol Aujourdhui 2014; 208:137-150. [PMID: 25190573 DOI: 10.1051/jbio/2014016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Indexed: 06/03/2023]
Abstract
The insulin receptor and insulin signaling proteins downstream the receptor reside in different subcellular compartments and undergo redistribution within the cell upon insulin activation. Endocytosis of the insulin-receptor complex, by mediating ligand degradation and receptor dephosphorylation, is generally viewed as a mechanism which attenuates or arrests insulin signal transduction. However, several observations suggest that insulin receptor endocytosis and/or recruitement of insulin signaling proteins to endosomes are also involved in a positive regulation of insulin signaling: (1) upon internalization, the insulin receptor remains transiently phosphorylated and activated; (2) in insulin-stimulated cells or tissues, signaling proteins of the PI3K/Akt and Ras/Raf/Mek/Erk pathways are recruited to endosomes or other intracellular compartments, in which they undergo phosphorylation and/or activation; and (3) depletion or overexpression of proteins involved in the regulation of membrane trafficking and endocytosis interfere with insulin signaling. These observations support a spatial and temporal regulation of insulin signal transduction and reinforce the concept that, as for other membrane signaling receptors, endocytosis and signaling are functionally linked.
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Affiliation(s)
- Bernard Desbuquois
- Inserm U1016 et CNRS UMR 8104, Institut Cochin, et Université Paris Descartes, 24 rue du Faubourg Saint Jacques, 75014 Paris, France
| | - François Authier
- Service Information Scientifique et Technique (IST) de l'Inserm, Délégation Régionale Inserm Paris V, 2 rue d'Alésia, 75014 Paris, France
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12
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Stokes L. Rab5 regulates internalisation of P2X4 receptors and potentiation by ivermectin. Purinergic Signal 2012; 9:113-21. [PMID: 23086000 DOI: 10.1007/s11302-012-9336-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Accepted: 10/08/2012] [Indexed: 01/21/2023] Open
Abstract
The P2X4 receptor is an ATP-gated ion channel expressed in neurons, endothelia and immune cells. Plasma membrane expression of P2X4 is regulated by dynamin-dependent endocytosis, and this study identifies a Rab5-dependent pathway of receptor internalisation. Expression of Rab5 constructs altered the distribution of P2X4 in HEK-293 cells, and both constitutive internalisation and agonist-induced desensitisation of P2X4 were increased by co-expression of wild-type Rab5 or constitutively active Rab5 (Q79L). Expression of inactive dynamin K44A and Rab5 S34N constructs abolished agonist-induced desensitisation, suggesting internalisation as the underlying mechanism. Blocking P2X4 internalisation in this way also abolished potentiation of ATP-induced currents by the allosteric modulator ivermectin. This suggests that the dynamin-Rab5 internalisation pathway is essential for the ivermectin potentiation effect. In agreement with this hypothesis, the co-expression of wild-type dynamin, wild-type Rab5 or active Rab5 (Q79L) could increase the potentiation of the ATP-induced P2X4 response by ivermectin. These findings highlight Rab5 GTPase as a key regulator of P2X4 receptor cell surface expression and internalisation.
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Affiliation(s)
- Leanne Stokes
- Department of Biomedical Science, University of Sheffield, Sheffield, UK.
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13
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Mechanisms of transcellular transport of wheat germ agglutinin-functionalized polymeric nanoparticles in Caco-2 cells. Biomaterials 2012; 33:6769-82. [DOI: 10.1016/j.biomaterials.2012.05.066] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2012] [Accepted: 05/28/2012] [Indexed: 12/15/2022]
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14
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Gulappa T, Clouser CL, Menon KMJ. The role of Rab5a GTPase in endocytosis and post-endocytic trafficking of the hCG-human luteinizing hormone receptor complex. Cell Mol Life Sci 2011; 68:2785-95. [PMID: 21104291 PMCID: PMC4479136 DOI: 10.1007/s00018-010-0594-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 10/29/2010] [Accepted: 11/05/2010] [Indexed: 01/25/2023]
Abstract
This study examined the role of Rab5a GTPase in regulating hCG-induced internalization and trafficking of the hCG-LH receptor complex in transfected 293T cells. Coexpression of wild-type Rab5a (WT) or constitutively active Rab5a (Q79L) with LHR significantly increased hCG-induced LHR internalization. Conversely, coexpression of dominant negative Rab5a (S34N) with LHR reduced internalization. Confocal microscopy showed LHR colocalizing with Rab5a (WT) and Rab5a (Q79L) in punctuate structures. Coexpression of Rab5a (WT) and Rab5a (Q79L) with LHR significantly increased colocalization of LHR in early endosomes. Conversely, dominant negative Rab5a (S34N) decreased this colocalization. While Rab5a stimulated internalization of LHR, it significantly decreased LHR recycling to the cell surface and increased degradation. Dominant negative Rab5a (S34N) increased LHR recycling and decreased degradation. These results suggest that Rab5a plays a role in LHR trafficking by facilitating internalization and fusion to early endosomes, increasing the degradation of internalized receptor resulting in a reduction in LHR recycling.
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Affiliation(s)
- Thippeswamy Gulappa
- Departments of Obstetrics and Gynecology and Biological Chemistry, University of Michigan Medical School, University of Michigan, 6428 Medical Science I, 1301 Catherine Street, Ann Arbor, MI 48109-0617, USA
| | - Christine L. Clouser
- Departments of Obstetrics and Gynecology and Biological Chemistry, University of Michigan Medical School, University of Michigan, 6428 Medical Science I, 1301 Catherine Street, Ann Arbor, MI 48109-0617, USA
| | - K. M. J. Menon
- Departments of Obstetrics and Gynecology and Biological Chemistry, University of Michigan Medical School, University of Michigan, 6428 Medical Science I, 1301 Catherine Street, Ann Arbor, MI 48109-0617, USA
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15
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Katsarou K, Lavdas AΑ, Tsitoura P, Serti E, Markoulatos P, Mavromara P, Georgopoulou U. Endocytosis of hepatitis C virus non-enveloped capsid-like particles induces MAPK-ERK1/2 signaling events. Cell Mol Life Sci 2010; 67:2491-506. [PMID: 20358251 PMCID: PMC11115770 DOI: 10.1007/s00018-010-0351-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Revised: 03/08/2010] [Accepted: 03/11/2010] [Indexed: 12/12/2022]
Abstract
Although HCV is an enveloped virus, naked nucleocapsids have been reported in the serum of infected patients. The HCV core particle serves as a protective capsid shell for the viral genome and recombinant in vitro assembled HCV core particles induce strong specific immunity. We investigated the post-binding mechanism of recombinant core particle uptake and its intracellular fate. In hepatic cells, these particles are internalized, most likely in a clathrin-dependent pathway, reaching early to late endosomes and finally lysosomes. The endocytic acidic milieu is implicated in trafficking process. Using specific phosphoantibodies, signaling pathway inhibitors and chemical agents, ERK(1/2) was found to be activated in a sustained way after endocytosis, followed by downstream immediate early genes (c-fos and egr-1) modulation. We propose that the intriguing properties of cellular internalization of HCV non-enveloped particles can induce specific ERK(1/2)-MAPKs events that could be important in HCV life cycle and pathogenesis of HCV infection.
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Affiliation(s)
| | - Alexandros Α. Lavdas
- Laboratory of Cellular and Molecular Neurobiology, Hellenic Pasteur Institute, Athens, Greece
| | - Panagiota Tsitoura
- Present Address: Insect Molecular Genetics and Biotechnology, Institute of Biology, NCSR Demokritos, Athens, Greece
| | - Elisavet Serti
- Molecular Virology Laboratory, Hellenic Pasteur Institute, Athens, Greece
| | | | - Penelope Mavromara
- Molecular Virology Laboratory, Hellenic Pasteur Institute, Athens, Greece
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16
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May V, Lutz E, MacKenzie C, Schutz KC, Dozark K, Braas KM. Pituitary adenylate cyclase-activating polypeptide (PACAP)/PAC1HOP1 receptor activation coordinates multiple neurotrophic signaling pathways: Akt activation through phosphatidylinositol 3-kinase gamma and vesicle endocytosis for neuronal survival. J Biol Chem 2010; 285:9749-9761. [PMID: 20093365 PMCID: PMC2843224 DOI: 10.1074/jbc.m109.043117] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
MAPK and Akt pathways are predominant mediators of trophic signaling for many neuronal systems. Among the vasoactive intestinal peptide/secretin/glucagon family of related peptides, pituitary adenylate cyclase-activating polypeptide (PACAP) binding to specific PAC(1) receptor isoforms can engage multiple signaling pathways and promote neuroprotection through mechanisms that are not well understood. Using a primary sympathetic neuronal system, the current studies demonstrate that PACAP activation of PAC(1)HOP1 receptors engages both MAPK and Akt neurotrophic pathways in an integrated program to facilitate neuronal survival after growth factor withdrawal. PACAP not only stimulated prosurvival ERK1/2 and ERK5 activation but also abrogated SAPK/JNK and p38 MAPK signaling in parallel. In contrast to the potent and rapid effects of PACAP in ERK1/2 phosphorylation, PACAP stimulated Akt phosphorylation in a late phase of PAC(1)HOP1 receptor signaling. From inhibitor and immunoprecipitation analyses, the PACAP/PAC(1)HOP1 receptor-mediated Akt responses did not represent transactivation mechanisms but appeared to depend on G alpha(q)/phosphatidylinositol 3-kinase gamma activity and vesicular internalization pathways. Phosphatidylinositol 3-kinase gamma-selective inhibitors blocked PACAP-stimulated Akt phosphorylation in primary neuronal cultures and in PAC(1)HOP1-overexpressing cell lines; RNA interference-mediated knockdown of the receptor effectors attenuated PACAP-mediated Akt activation. Similarly, perturbation of endocytic pathways also blocked Akt phosphorylation. Between ERK and Akt pathways, PACAP-stimulated Akt signaling was the primary cascade that attenuated cultured neuron apoptosis after growth factor withdrawal. The partitioning of PACAP-mediated Akt signaling in endosomes may be a key mechanism contributing to the high spatial and temporal specificity in signal transduction necessary for survival pathways.
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Affiliation(s)
- Victor May
- Departments of Anatomy and Neurobiology and of Pharmacology, The University of Vermont College of Medicine, Burlington, Vermont 05405.
| | - Eve Lutz
- University of Strathclyde, Strathclyde Institute of Pharmacy and Biomedical Sciences, Royal College, 204 George Street, Glasgow G1 1XW, Scotland, United Kingdom
| | - Christopher MacKenzie
- University of Strathclyde, Strathclyde Institute of Pharmacy and Biomedical Sciences, Royal College, 204 George Street, Glasgow G1 1XW, Scotland, United Kingdom
| | - Kristin C Schutz
- Departments of Anatomy and Neurobiology and of Pharmacology, The University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Kate Dozark
- Departments of Anatomy and Neurobiology and of Pharmacology, The University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Karen M Braas
- Departments of Anatomy and Neurobiology and of Pharmacology, The University of Vermont College of Medicine, Burlington, Vermont 05405
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17
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Lin WJ, Yang CY, Lin YC, Tsai MC, Yang CW, Tung CY, Ho PY, Kao FJ, Lin CH. Phafin2 modulates the structure and function of endosomes by a Rab5-dependent mechanism. Biochem Biophys Res Commun 2009; 391:1043-8. [PMID: 19995552 DOI: 10.1016/j.bbrc.2009.12.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2009] [Accepted: 12/03/2009] [Indexed: 12/20/2022]
Abstract
By regulating the amount of protein receptors on the cell membrane and the metabolisms of receptor-bound ligands, endocytosis represents one of the fundamental biological activities that regulate how cells respond to the environment. We report here that a Fab1-YotB-Vac1p-EEA1 (FYVE) domain-containing lipid associated protein, called Phafin2, is preferentially expressed in the human hepatocellular carcinoma (HCC) and is involved in the biogenesis of endosomes. Over-expression of Phafin2 or its FYVE domain results in the formation of enlarged endosomes that are still functional for endocytosis; the biogenesis of such abnormal organelles is mediated by phosphoinositide 3-kinases (PI3K) and Rab5 signaling. Using fluorescence resonance energy transfer measured by fluorescence lifetime imaging microscopy (FLIM-FRET), we further demonstrate in live cells that Phafin2 can directly activate Rab5. By modulating the receptor internalization/recycling and Rab5 activation, Phafin2 affects the density of membranous insulin receptors, and regulates the transcriptional activity of AP-1 that is downstream of the insulin signaling pathway. These results provide a vivid example that an endosome modulator, such as Phafin2, may control the cells' responses to the extracellular cues.
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Affiliation(s)
- Wen-Jie Lin
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan
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18
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Jopling HM, Odell A, Hooper NM, Zachary IC, Walker JH, Ponnambalam S. Rab GTPase regulation of VEGFR2 trafficking and signaling in endothelial cells. Arterioscler Thromb Vasc Biol 2009; 29:1119-24. [PMID: 19372461 PMCID: PMC2704050 DOI: 10.1161/atvbaha.109.186239] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Vascular endothelial growth factor receptor 2 (VEGFR2) is a receptor tyrosine kinase that regulates vascular physiology. However, mechanism(s) by which VEGFR2 signaling and trafficking is coordinated are not clear. Here, we have tested endocytic Rab GTPases for regulation of VEGFR2 trafficking and signaling linked to endothelial cell migration. METHODS AND RESULTS Quiescent VEGFR2 displays endosomal localization and colocalization with the Rab5a GTPase, an early endosome fusion regulator. Expression of GTP or GDP-bound Rab5a mutants block activated VEGFR2 trafficking and degradation. Manipulation of Rab7a GTPase activity associated with late endosomes using overexpression of wild-type or mutant proteins blocks activated VEGFR2 trafficking and degradation. Depletion of Rab7a decreased VEGFR2 Y1175 phosphorylation but increased p42/44 (pERK1/2) MAPK phosphorylation. Endothelial cell migration was increased by Rab5a depletion but decreased by Rab7a depletion. CONCLUSIONS Rab5a and Rab7a regulate VEGFR2 trafficking toward early and late endosomes. Our data suggest that VEGFR2-mediated regulation of endothelial function is dependent on different but specific Rab-mediated GTP hydrolysis activity required for endosomal trafficking.
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Affiliation(s)
- Helen M. Jopling
- Endothelial Cell Biology Unit, Institute for Molecular & Cellular Biology, LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, UK
| | - Adam Odell
- Endothelial Cell Biology Unit, Institute for Molecular & Cellular Biology, LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, UK
| | - Nigel M. Hooper
- Proteolysis Research Group, Institute for Molecular & Cellular Biology, LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, UK
| | - Ian C. Zachary
- Centre for Cardiovascular Biology and Medicine, Rayne Institute, University College London, London WC1E 6JJ, UK
| | - John H. Walker
- Endothelial Cell Biology Unit, Institute for Molecular & Cellular Biology, LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, UK
| | - Sreenivasan Ponnambalam
- Endothelial Cell Biology Unit, Institute for Molecular & Cellular Biology, LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, UK
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19
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Endocytosis of adiponectin receptor 1 through a clathrin- and Rab5-dependent pathway. Cell Res 2009; 19:317-27. [PMID: 18982021 DOI: 10.1038/cr.2008.299] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In eukaryotic cells, receptor endocytosis is a key event regulating signaling transduction. Adiponectin receptors belong to a new receptor family that is distinct from G-protein-coupled receptors and has critical roles in the pathogenesis of diabetes and metabolic syndrome. Here, we analyzed the endocytosis of adiponectin and adiponectin receptor 1 (AdipoR1) and found that they are both internalized into transferrin-positive compartments that follow similar traffic routes. Blocking clathrin-mediated endocytosis by expressing Eps15 mutants or depleting K(+) trapped AdipoR1 at the plasma membrane, and K(+) depletion abolished adiponectin internalization, indicating that the endocytosis of AdipoR1 and adiponectin is clathrin-dependent. Depletion of K(+) and overexpression of Eps15 mutants enhance adiponectin-stimulated AMP-activated protein kinase phosphorylation, suggesting that the endocytosis of AdipoR1 might downregulate adiponectin signaling. In addition, AdipoR1 colocalizes with the small GTPase Rab5, and a dominant negative Rab5 abrogates AdipoR1 endocytosis. These data indicate that AdipoR1 is internalized through a clathrin- and Rab5-dependent pathway and that endocytosis may play a role in the regulation of adiponectin signaling.
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20
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Iwasaki H. Involvement of PRMT1 in hnRNPQ activation and internalization of insulin receptor. Biochem Biophys Res Commun 2008; 372:314-9. [DOI: 10.1016/j.bbrc.2008.05.051] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2008] [Accepted: 05/11/2008] [Indexed: 10/22/2022]
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21
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Schenck A, Goto-Silva L, Collinet C, Rhinn M, Giner A, Habermann B, Brand M, Zerial M. The endosomal protein Appl1 mediates Akt substrate specificity and cell survival in vertebrate development. Cell 2008; 133:486-97. [PMID: 18455989 DOI: 10.1016/j.cell.2008.02.044] [Citation(s) in RCA: 309] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2007] [Revised: 12/11/2007] [Accepted: 02/26/2008] [Indexed: 11/25/2022]
Abstract
During development of multicellular organisms, cells respond to extracellular cues through nonlinear signal transduction cascades whose principal components have been identified. Nevertheless, the molecular mechanisms underlying specificity of cellular responses remain poorly understood. Spatial distribution of signaling proteins may contribute to signaling specificity. Here, we tested this hypothesis by investigating the role of the Rab5 effector Appl1, an endosomal protein that interacts with transmembrane receptors and Akt. We show that in zebrafish, Appl1 regulates Akt activity and substrate specificity, controlling GSK-3beta but not TSC2. Consistent with this pattern, Appl1 is selectively required for cell survival, most critically in highly expressing tissues. Remarkably, Appl1 function requires its endosomal localization. Indeed, Akt and GSK-3beta, but not TSC2, dynamically associate with Appl1 endosomes upon growth factor stimulation. We propose that partitioning of Akt and selected effectors onto endosomal compartments represents a key mechanism contributing to the specificity of signal transduction in vertebrate development.
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Affiliation(s)
- Annette Schenck
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
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22
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ALS2/alsin deficiency in neurons leads to mild defects in macropinocytosis and axonal growth. Biochem Biophys Res Commun 2008; 370:87-92. [PMID: 18358238 DOI: 10.1016/j.bbrc.2008.01.177] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Accepted: 01/30/2008] [Indexed: 12/11/2022]
Abstract
Loss of function mutations in the ALS2 gene account for a number of juvenile/infantile recessive motor neuron diseases, indicating that its gene product, ALS2/alsin, plays a crucial role in maintenance and survival for a subset of neurons. ALS2 acts as a guanine nucleotide exchange factor (GEF) for the small GTPase Rab5 and is implicated in endosome dynamics in cells. However, the role of ALS2 in neurons remains unclear. To elucidate the neuronal ALS2 functions, we investigate cellular phenotypes of ALS2-deficient primary cultured neurons derived from Als2-knockout (KO) mice. Here, we show that ALS2 deficiency results not only in the delay of axon outgrowth in hippocampal neurons, but also in a decreased level of the fluid phase horseradish peroxidase (HRP) uptake, which represents the activity for macropinocytic endocytosis, in cortical neurons. Thus, ALS2 may act as a modulator in neuronal differentiation and/or development through regulation of membrane dynamics.
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