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Shen J, Zhao X, Bai X, Zhu W, Li Z, Yang Z, Wang Q, Ji J. Phosphoproteomic analysis reveals CDK5-Mediated phosphorylation of MTDH inhibits protein synthesis in microglia. Biochem Biophys Res Commun 2024; 735:150669. [PMID: 39260336 DOI: 10.1016/j.bbrc.2024.150669] [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: 07/12/2024] [Revised: 09/02/2024] [Accepted: 09/05/2024] [Indexed: 09/13/2024]
Abstract
CDK5 plays a crucial role in maintaining normal central nervous system (CNS) development and synaptic function, while microglia are the primary immune cells present in the CNS and play vital physiological roles in CNS development, immune surveillance, and regulation of synaptic plasticity. Despite this, our understanding of both the substrate proteins and functional mechanisms of CDK5 in microglia remains limited. To address this, we utilized CRISPR-Cas9 knockout of Cdk5 in BV2 cells and conducted quantitative phosphoproteomics analysis to systematically screen potential CDK5 substrates in microglia. Our findings identified 335 phosphorylation sites on 234 proteins as potential CDK5 substrates in microglia based on the reported sequence motif. Through in vitro kinase assay and intracellular inhibition and knockout of CDK5 experiments, we confirmed that ER proteins MTDH (protein LYRIC) and Calnexin are novel substrate proteins of CDK5. Moreover, we demonstrated for the first time a critical mechanism for regulating protein synthesis in microglia, that the phosphorylation of S565 site on MTDH, a key protein mediating cell growth, by CDK5 inhibits protein synthesis. Our data provide valuable insights for the discovery of new substrate proteins of CDK5 and the in-depth investigation of the function and mechanism of CDK5 in microglia.
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Affiliation(s)
- Jian Shen
- Department of General Surgery, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China
| | - Xuyang Zhao
- Institute of Systems Biomedicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Xue Bai
- State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Wenyuan Zhu
- State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Zeyang Li
- State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Zihao Yang
- State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Qingsong Wang
- State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China.
| | - Jianguo Ji
- State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China.
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2
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Wolf D, Röder C, Sendtner M, Lüningschrör P. An Essential Role for Calnexin in ER-Phagy and the Unfolded Protein Response. Cells 2024; 13:1498. [PMID: 39273068 PMCID: PMC11394613 DOI: 10.3390/cells13171498] [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: 07/26/2024] [Revised: 08/24/2024] [Accepted: 09/03/2024] [Indexed: 09/15/2024] Open
Abstract
ER-phagy is a specialized form of autophagy, defined by the lysosomal degradation of ER subdomains. ER-phagy has been implicated in relieving the ER from misfolded proteins during ER stress upon activation of the unfolded protein response (UPR). Here, we identified an essential role for the ER chaperone calnexin in regulating ER-phagy and the UPR in neurons. We showed that chemical induction of ER stress triggers ER-phagy in the somata and axons of primary cultured motoneurons. Under basal conditions, the depletion of calnexin leads to an enhanced ER-phagy in axons. However, upon ER stress induction, ER-phagy did not further increase in calnexin-deficient motoneurons. In addition to increased ER-phagy under basal conditions, we also detected an elevated proteasomal turnover of insoluble proteins, suggesting enhanced protein degradation by default. Surprisingly, we detected a diminished UPR in calnexin-deficient early cortical neurons under ER stress conditions. In summary, our data suggest a central role for calnexin in orchestrating both ER-phagy and the UPR to maintain protein homeostasis within the ER.
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Affiliation(s)
- Daniel Wolf
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Chiara Röder
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Michael Sendtner
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Patrick Lüningschrör
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, Versbacher Str. 5, 97078 Würzburg, Germany
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3
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Michalak M. Calreticulin: Endoplasmic reticulum Ca 2+ gatekeeper. J Cell Mol Med 2024; 28:e17839. [PMID: 37424156 PMCID: PMC10902585 DOI: 10.1111/jcmm.17839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 06/21/2023] [Accepted: 06/27/2023] [Indexed: 07/11/2023] Open
Abstract
Endoplasmic reticulum (ER) luminal Ca2+ is vital for the function of the ER and regulates many cellular processes. Calreticulin is a highly conserved, ER-resident Ca2+ binding protein and lectin-like chaperone. Over four decades of studying calreticulin demonstrate that this protein plays a crucial role in maintaining Ca2+ supply under different physiological conditions, in managing access to Ca2+ and how Ca2+ is used depending on the environmental events and in making sure that Ca2+ is not misused. Calreticulin plays a role of ER luminal Ca2+ sensor to manage Ca2+-dependent ER luminal events including maintaining interaction with its partners, Ca2+ handling molecules, substrates and stress sensors. The protein is strategically positioned in the lumen of the ER from where the protein manages access to and distribution of Ca2+ for many cellular Ca2+-signalling events. The importance of calreticulin Ca2+ pool extends beyond the ER and includes influence of cellular processes involved in many aspects of cellular pathophysiology. Abnormal handling of the ER Ca2+ contributes to many pathologies from heart failure to neurodegeneration and metabolic diseases.
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Affiliation(s)
- Marek Michalak
- Department of BiochemistryUniversity of AlbertaEdmontonAlbertaCanada
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4
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Lüningschrör P, Andreska T, Veh A, Wolf D, Giridhar NJ, Moradi M, Denzel A, Sendtner M. Calnexin controls TrkB cell surface transport and ER-phagy in mouse cerebral cortex development. Dev Cell 2023; 58:1733-1747.e6. [PMID: 37506696 DOI: 10.1016/j.devcel.2023.07.004] [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: 09/27/2022] [Revised: 05/23/2023] [Accepted: 07/05/2023] [Indexed: 07/30/2023]
Abstract
Transactivation of Tropomyosin receptor kinase B (TrkB) by EGF leads to cell surface transport of TrkB, promoting its signaling responsiveness to brain-derived neurotrophic factor (BDNF), a critical process for proper cortical plate development. However, the mechanisms that regulate the transport of TrkB to the cell surface are not fully understood. Here, we identified Calnexin as a regulator for targeting TrkB either to the cell surface or toward autophagosomal processing. Calnexin-deficient mouse embryos show impaired cortical plate formation and elevated levels of transactivated TrkB. In Calnexin-depleted mouse neuronal precursor cells, we detected an impaired cell surface transport of TrkB in response to EGF and an impaired delivery to autophagosomes. Mechanistically, we show that Calnexin facilitates the interaction of TrkB with the ER-phagy receptor Fam134b, thereby targeting TrkB to ER-phagy. This mechanism appears as a critical process for fine-tuning the sensitivity of neurons to BDNF.
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Affiliation(s)
- Patrick Lüningschrör
- Institute of Clinical Neurobiology, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Thomas Andreska
- Institute of Clinical Neurobiology, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Alexander Veh
- Institute of Clinical Neurobiology, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Daniel Wolf
- Institute of Clinical Neurobiology, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Neha Jadhav Giridhar
- Institute of Clinical Neurobiology, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Mehri Moradi
- Institute of Clinical Neurobiology, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Angela Denzel
- Imperial Cancer Research Fund now Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Michael Sendtner
- Institute of Clinical Neurobiology, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany.
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Babačić H, Christ W, Araújo JE, Mermelekas G, Sharma N, Tynell J, García M, Varnaite R, Asgeirsson H, Glans H, Lehtiö J, Gredmark-Russ S, Klingström J, Pernemalm M. Comprehensive proteomics and meta-analysis of COVID-19 host response. Nat Commun 2023; 14:5921. [PMID: 37739942 PMCID: PMC10516886 DOI: 10.1038/s41467-023-41159-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 08/24/2023] [Indexed: 09/24/2023] Open
Abstract
COVID-19 is characterised by systemic immunological perturbations in the human body, which can lead to multi-organ damage. Many of these processes are considered to be mediated by the blood. Therefore, to better understand the systemic host response to SARS-CoV-2 infection, we performed systematic analyses of the circulating, soluble proteins in the blood through global proteomics by mass-spectrometry (MS) proteomics. Here, we show that a large part of the soluble blood proteome is altered in COVID-19, among them elevated levels of interferon-induced and proteasomal proteins. Some proteins that have alternating levels in human cells after a SARS-CoV-2 infection in vitro and in different organs of COVID-19 patients are deregulated in the blood, suggesting shared infection-related changes.The availability of different public proteomic resources on soluble blood proteome alterations leaves uncertainty about the change of a given protein during COVID-19. Hence, we performed a systematic review and meta-analysis of MS global proteomics studies of soluble blood proteomes, including up to 1706 individuals (1039 COVID-19 patients), to provide concluding estimates for the alteration of 1517 soluble blood proteins in COVID-19. Finally, based on the meta-analysis we developed CoViMAPP, an open-access resource for effect sizes of alterations and diagnostic potential of soluble blood proteins in COVID-19, which is publicly available for the research, clinical, and academic community.
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Affiliation(s)
- Haris Babačić
- Science for Life Laboratory and Department of Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden.
| | - Wanda Christ
- Centre for Infectious Medicine, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - José Eduardo Araújo
- Science for Life Laboratory and Department of Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Georgios Mermelekas
- Science for Life Laboratory and Department of Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Nidhi Sharma
- Science for Life Laboratory and Department of Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Janne Tynell
- Centre for Infectious Medicine, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Marina García
- Centre for Infectious Medicine, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Renata Varnaite
- Centre for Infectious Medicine, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Hilmir Asgeirsson
- Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
- Unit of Infectious Diseases, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Hedvig Glans
- Centre for Infectious Medicine, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
- Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Janne Lehtiö
- Science for Life Laboratory and Department of Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Sara Gredmark-Russ
- Centre for Infectious Medicine, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
- Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå, Sweden
| | - Jonas Klingström
- Centre for Infectious Medicine, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
- Division of Molecular Medicine and Virology (MMV), Department of Biomedical and Clinical Sciences (BKV), Linköping University, Linköping, Sweden
| | - Maria Pernemalm
- Science for Life Laboratory and Department of Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden.
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Bhardwaj R, Bhardwaj A, Dhawan DK, Tandon C, Kaur T. 4-PBA rescues hyperoxaluria induced nephrolithiasis by modulating urinary glycoproteins: Cross talk between endoplasmic reticulum, calcium homeostasis and mitochondria. Life Sci 2022; 305:120786. [PMID: 35809664 DOI: 10.1016/j.lfs.2022.120786] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 06/28/2022] [Accepted: 07/01/2022] [Indexed: 12/15/2022]
Abstract
AIM Urinary glycoproteins such as Tamm Horsfall Protein (THP) and Osteopontin (OPN) are well established key regulators of renal stone formation. Additionally, recent revelations have highlighted the influence of Endoplasmic Reticulum (ER) and mitochondria of crucial importance in nephrolithiasis. However, till date conclusive approach highlighting the influence of ER stress on urinary glycoproteins and chaperone in nephrolithiasis remains elusive. Therefore, the present study was focussed on deciphering the possible effect of 4-PBA mitigating ER stress on urinary glycoproteins and calnexin (chaperone) with emphasis on interlinking calcium homeostasis in hyperoxaluric rats. MATERIAL AND METHODS Post 9 days of treatment, animals were sacrificed, and renal tissues were investigated for urinary glycoproteins, calnexin, calcium homeostasis, ER environment, redox status, and mitochondrial linkage. KEY FINDINGS 4-PBA appreciably reversed the altered levels of THP, OPN, and calnexin observed along with curtailing the disrupted calcium homeostasis when assessed for SERCA activity and intra-cellular calcium levels. Additionally, significant improvement in the perturbed ER environment as verified by escalated ER stress markers, disturbed protein folding-aggregation-degradation (congo red assay) pathway, and redox status was found post 4-PBA intervention. Interestingly, linkage of ER stress and mitochondria was established under hyperoxaluric conditions when assessed for protein levels of VDAC1 and GRP75. SIGNIFICANCE 4-PBA treatment resulted in rectifying the repercussions of ER-mitochondrial caused distress when assessed for protein folding/aggregation/degradation events along with disturbed calcium homeostasis. The present study advocates the necessity to adopt a holistic vision towards hyperoxaluria with emphasis on glycoproteins and ER environment.
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Affiliation(s)
- Rishi Bhardwaj
- Department of Biophysics, Panjab University, Chandigarh, India
| | - Ankita Bhardwaj
- Department of Biophysics, Panjab University, Chandigarh, India
| | | | | | - Tanzeer Kaur
- Department of Biophysics, Panjab University, Chandigarh, India.
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7
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Regulation of SLC6A14 trafficking in breast cancer cells by heat shock protein HSP90β. Biochem Biophys Res Commun 2022; 614:41-46. [DOI: 10.1016/j.bbrc.2022.05.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 05/04/2022] [Indexed: 11/20/2022]
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8
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Xu DM, Zhang ZW, Yi JX, Xie L, Yu WJ, Qiu JF, Xu CW, He CL, Xu XR, Yin J. Role of Ca 2+, Calnexin and Calreticulin in Platelet from Adult Patients with Chronic Immune Thrombocytopenic Purpura. Int J Gen Med 2022; 15:2119-2125. [PMID: 35237072 PMCID: PMC8885122 DOI: 10.2147/ijgm.s347301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 01/25/2022] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Adult chronic immune thrombocytopenia (chronic ITP) is a common autoimmune hemorrhagic disease characterized by decreased platelet production and increased platelet destruction, leading to thrombocytopenia. In this study, Ca2+, calnexin (CNX) and calreticulin (CRT) within platelets from adult patients with chronic ITP were investigated. METHODS Platelets were isolated from blood specimen collected from 20 adult patients with chronic ITP and 20 healthy volunteers. Ca2+, CNX and CRT were determined by flow cytometry, and the results were analyzed with EXPO32 ADC software. RESULTS Flow cytometry showed the expressions of Ca2+ (74.19±19.40% vs 22.79±10.47%) was elevated (P<0.05). However, CNX (15.10±7.32% vs 41.79±14.45%) and CRT (25.11±12.66% vs 38.58±12.02%) were decreased markedly in platelets from adult patients with chronic ITP (P<0.05 compared with healthy volunteers). CONCLUSION Based on enhanced expression of Ca2+ and attenuated expression of CNX and CRT in patients with chronic ITP, Ca2+ concentration and its associated down-regulated proteins may be important regulatory signals in the pathogenesis of chronic ITP.
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Affiliation(s)
- Da-Ming Xu
- Division of Urological Surgery, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
| | - Ze-Wen Zhang
- Division of Hematology, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
| | - Jing-Xing Yi
- Department of Clinical Laboratory Medicine, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
| | - Long Xie
- Department of Clinical Laboratory Medicine, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
| | - Wen-Jun Yu
- Division of Hematology, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
| | - Jin-Feng Qiu
- Division of Respirology, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
| | - Cheng-Wei Xu
- Department of Blood Purification, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
| | - Chun-Ling He
- Department of Pathology, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
| | - Xian-Ru Xu
- Division of Inventional Ultrasonic Therapeutics, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
| | - Jun Yin
- Department of Clinical Laboratory Medicine, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong Province, People’s Republic of China
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Yang C, Guo X, Shan Y, He Z, Jiang D, Wang X, Wang L. The expression profile of calnexin in Patinopecten yessoensis after acute high temperature stress. FISH AND SHELLFISH IMMUNOLOGY REPORTS 2021; 2:100016. [DOI: 10.1016/j.fsirep.2021.100016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 06/23/2021] [Accepted: 07/01/2021] [Indexed: 11/29/2022] Open
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10
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Mast N, Petrov AM, Prendergast E, Bederman I, Pikuleva IA. Brain Acetyl-CoA Production and Phosphorylation of Cytoskeletal Proteins Are Targets of CYP46A1 Activity Modulation and Altered Sterol Flux. Neurotherapeutics 2021; 18:2040-2060. [PMID: 34235635 PMCID: PMC8609074 DOI: 10.1007/s13311-021-01079-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/23/2021] [Indexed: 02/04/2023] Open
Abstract
Cholesterol and 24-hydroxycholesterol are the most abundant brain sterols and represent the substrate and product, respectively, of cytochrome P450 46A1 (CYP46A1), a CNS-specific enzyme. CYP46A1 controls cholesterol elimination and turnover in the brain, the two processes that determine the rate of brain sterol flux through the plasma membranes and thereby the properties of these membranes. Brain sterol flux is decreased in Cyp46a1-/- mice compared to wild-type mice and increased in 5XFAD mice (a model of Alzheimer's disease) when they are treated with a small dose of efavirenz, a CYP46A1 activator. Herein, we first assessed the brain proteome (synaptosomal fractions) and phospho-proteome (synaptosomal fractions and brain homogenates) of efavirenz-treated and control 5XFAD mice. Then, based on the pattern of protein abundance change, we conducted acetyl-CoA measurements (brain homogenates and mitochondria) and metabolic profiling (brain homogenates). The phospho-proteomics datasets were used for comparative analyses with the datasets obtained by us previously on mice with the same changes (efavirenz-treated and control 5XFAD mice from a different treatment paradigm) or with changes in the opposite direction (Cyp46a1-/- vs wild-type mice) in brain sterol flux. We found that CYP46A1 activity or the rate of brain sterol flux affects acetyl-CoA-related metabolic pathways as well as phosphorylation of cytoskeletal and other proteins. Knowledge of the key roles of acetyl-CoA and cytoskeletal phosphorylation in cell biology expands our understanding of the significance of CYP46A1-mediated cholesterol 24-hydroxylation in the brain and provides an additional explanation for why CYP46A1 activity modulations are beneficial in mouse models of different brain diseases.
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Affiliation(s)
- Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Alexey M Petrov
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center, Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, Box 30, 420111, Kazan, Russia
- Institute of Neuroscience, Kazan State Medial University, 49 Butlerova Street, 420012, Kazan, Russia
| | - Erin Prendergast
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Ilya Bederman
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA.
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11
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Gao CC, Li GW, Wang TT, Gao L, Wang FF, Shang HW, Yang ZJ, Guo YX, Wang BY, Xu JD. Rhubarb extract relieves constipation by stimulating mucus production in the colon and altering the intestinal flora. Biomed Pharmacother 2021; 138:111479. [PMID: 33774313 DOI: 10.1016/j.biopha.2021.111479] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 03/05/2021] [Accepted: 03/06/2021] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Constipation, mainly characterized by the difficulty in defecation, is a clinical symptom caused by a variety of factors. It can be manifested as normal or slow colonic transport abnormalities, which can occur alone or concurrently with defecation disorders. As there is not uniform definition and assessment standard, no clear plan could be used for the treatment of constipation. Although rhubarb, a traditional Chinese medicine, plays a therapeutic role in diseases involving constipation symptoms, the detailed mechanism of it in treating constipation remains unclear. METHODS A model of constipation-induced by diphenoxylate was prepared. Immunofluorescent staining was used to detect the expression of mucin 2 (MUC2), calnexin and chymase in colon. Western blotting was used to detect changes of tryptase and calnexin in the colon. And real-time polymerase chain reaction (PCR) was utilized to detect the changes of immunoglobulin-binding protein (Bip), X-box binding protein 1 (Xbp1) and C/EBP homologous protein (CHOP) of colonic goblet cells in mRNA levels. ELISA and biochemical kits were utilized to detect the changes of MUC2, Trefoil factor 3 (TFF3), acetylcholine, histamine and C-C motif chemokine ligand 5 (CCL5) in the colon. And the changes of colonic mucosa and intestinal flora of constipation model mice caused by rhubarb extract (RE) were analyzed to identify the mechanism of RE on the treatment of constipation. RESULTS RE promotes the secretion of colonic mucus by recruiting mast cells and enhancing the content of histamine and Ach in the mice colon. In the process, RE causes up-regulation of Bip and CHOP mRNA expression and down-regulation of Xbp1 and Xbp1s mRNA expression that induces ER stress of colonic epithelium associated with changes in the intestinal flora diversity and short-chain fatty acids content. CONCLUSION RE could relieve constipation by promoting the secretion of colonic mucus via mast cells activation and improving the intestinal microenvironment.
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Affiliation(s)
- Chen-Chen Gao
- Department of Physiology and Pathophysiology, Basic Medical College, Capital Medical University, Beijing 100069, China
| | - Guang-Wen Li
- Department of Physiology and Pathophysiology, Basic Medical College, Capital Medical University, Beijing 100069, China
| | - Tian-Tian Wang
- Department of Physiology and Pathophysiology, Basic Medical College, Capital Medical University, Beijing 100069, China
| | - Lei Gao
- Department of Bioinformatics, College of Bioengineering, Capital Medical University, Beijing 100069, China
| | - Fei-Fei Wang
- Department of Clinical Medicine, Basic Medical College, Capital Medical University, Beijing 100069, China
| | - Hong-Wei Shang
- Experimental Center for Morphological Research Platform, Capital Medical University, Beijing 100069, China
| | - Ze-Jun Yang
- Department of Clinical Medicine, Basic Medical College, Capital Medical University, Beijing 100069, China
| | - Yue-Xin Guo
- Department of Oral Medicine, Basic Medical College, Capital Medical University, Beijing 100069, China
| | - Bo-Ya Wang
- Undergraduate Student of 2018 Eight Program of Clinical Medicine, Peking University Health Science Center, Beijing 100081, China
| | - Jing-Dong Xu
- Department of Physiology and Pathophysiology, Basic Medical College, Capital Medical University, Beijing 100069, China.
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12
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Adams BM, Canniff NP, Guay KP, Hebert DN. The Role of Endoplasmic Reticulum Chaperones in Protein Folding and Quality Control. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2021; 59:27-50. [PMID: 34050861 PMCID: PMC9185992 DOI: 10.1007/978-3-030-67696-4_3] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Molecular chaperones assist the folding of nascent chains in the cell. Chaperones also aid in quality control decisions as persistent chaperone binding can help to sort terminal misfolded proteins for degradation. There are two major molecular chaperone families in the endoplasmic reticulum (ER) that assist proteins in reaching their native structure and evaluating the fidelity of the maturation process. The ER Hsp70 chaperone, BiP, supports adenine nucleotide-regulated binding to non-native proteins that possess exposed hydrophobic regions. In contrast, the carbohydrate-dependent chaperone system involving the membrane protein calnexin and its soluble paralogue calreticulin recognize a specific glycoform of an exposed hydrophilic protein modification for which the composition is controlled by a series of glycosidases and transferases. Here, we compare and contrast the properties, mechanisms of action and functions of these different chaperones systems that work in parallel, as well as together, to assist a large variety of substrates that traverse the eukaryotic secretory pathway.
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Affiliation(s)
- Benjamin M Adams
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA, USA
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Amherst, MA, USA
| | - Nathan P Canniff
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA, USA
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Amherst, MA, USA
| | - Kevin P Guay
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA, USA
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Amherst, MA, USA
| | - Daniel N Hebert
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA, USA.
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Amherst, MA, USA.
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13
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Nałęcz KA. Amino Acid Transporter SLC6A14 (ATB 0,+) - A Target in Combined Anti-cancer Therapy. Front Cell Dev Biol 2020; 8:594464. [PMID: 33195271 PMCID: PMC7609839 DOI: 10.3389/fcell.2020.594464] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 09/30/2020] [Indexed: 12/12/2022] Open
Abstract
Cancer cells are characterized by quick growth and proliferation, demanding constant supply of various nutrients. Several plasma membrane transporters delivering such compounds are upregulated in cancer. Solute carrier family 6 member 14 (SLC6A14), known as amino acid transporter B0,+ (ATB0,+) transports all amino acids with exception of the acidic ones: aspartate and glutamate. Its malfunctioning is correlated with several pathological states and it is upregulated in solid tumors. The high expression of SLC6A14 is prognostic and unfavorable in pancreatic cancer, while in breast cancer it is expressed in estrogen receptor positive cells. As many plasma membrane transporters it resides in endoplasmic reticulum (ER) membrane after translation before further trafficking through Golgi to the cell surface. Transporter exit from ER is strictly controlled. The proper folding of SLC6A14 was shown to be controlled from the cytoplasmic side by heat shock proteins, further exit from ER and formation of coatomer II (COPII) coated vesicles depends on specific interaction with COPII cargo-recognizing subunit SEC24C, phosphorylated by kinase AKT. Inhibition of heat shock proteins, known to be upregulated in cancer, directs SLC6A14 to degradation. Targeting proteins regulating SLC6A14 trafficking is proposed as an additional pharmacological treatment of cancer.
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Affiliation(s)
- Katarzyna A Nałęcz
- Laboratory of Transport Through Biomembranes, Nencki Institute of Experimental Biology, Warsaw, Poland
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14
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Manning JR, Wijeratne AB, Oloizia BB, Zhang Y, Greis KD, Schultz JEJ. Phosphoproteomic analysis identifies phospho-Threonine-17 site of phospholamban important in low molecular weight isoform of fibroblast growth factor 2-induced protection against post-ischemic cardiac dysfunction. J Mol Cell Cardiol 2020; 148:1-14. [PMID: 32853649 DOI: 10.1016/j.yjmcc.2020.08.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 07/04/2020] [Accepted: 08/09/2020] [Indexed: 10/23/2022]
Abstract
RATIONALE Among its many biological roles, fibroblast growth factor 2 (FGF2) protects the heart from dysfunction and damage associated with an ischemic attack. Our laboratory demonstrated that its protection against myocardial dysfunction occurs by the low molecular weight (LMW) isoform of FGF2, while the high molecular weight (HMW) isoforms are associated with a worsening in post-ischemic recovery of cardiac function. LMW FGF2-mediated cardioprotection is facilitated by activation of multiple kinases, including PKCalpha, PKCepsilon, and ERK, and inhibition of p38 and JNK. OBJECTIVE Yet, the substrates of those kinases associated with LMW FGF2-induced cardioprotection against myocardial dysfunction remain to be elucidated. METHODS AND RESULTS To identify substrates in LMW FGF2 improvement of post-ischemic cardiac function, mouse hearts expressing only LMW FGF2 were subjected to ischemia-reperfusion (I/R) injury and analyzed by a mass spectrometry (MS)-based quantitative phosphoproteomic strategy. MS analysis identified 50 phosphorylation sites from 7 sarcoendoplasmic reticulum (SR) proteins that were significantly altered in I/R-treated hearts only expressing LMW FGF2 compared to those hearts lacking FGF2. One of those phosphorylated SR proteins identified was phospholamban (PLB), which exhibited rapid, increased phosphorylation at Threonine-17 (Thr17) after I/R in hearts expressing only LMW FGF2; this was further validated using Selected Reaction Monitoring-based MS workflow. To demonstrate a mechanistic role of phospho-Thr17 PLB in LMW FGF2-mediated cardioprotection, hearts only expressing LMW FGF2 and those expressing only LMW FGF2 with a mutant PLB lacking phosphorylatable Thr17 (Thr17Ala PLB) were subjected to I/R. Hearts only expressing LMW FGF2 showed significantly improved recovery of cardiac function following I/R (p < 0.05), and this functional improvement was significantly abrogated in hearts expressing LMW FGF2 and Thr17Ala PLB (p < 0.05). CONCLUSION The findings indicate that LMW FGF2 modulates intracellular calcium handling/cycling via regulatory changes in SR proteins essential for recovery from I/R injury, and thereby protects the heart from post-ischemic cardiac dysfunction.
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Affiliation(s)
- Janet R Manning
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, United States of America
| | - Aruna B Wijeratne
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, United States of America
| | - Brian B Oloizia
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, United States of America
| | - Yu Zhang
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, United States of America
| | - Kenneth D Greis
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, United States of America
| | - Jo El J Schultz
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, United States of America.
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15
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Lee S, Shin Y, Kim K, Song Y, Kim Y, Kang SW. Protein Translocation Acquires Substrate Selectivity Through ER Stress-Induced Reassembly of Translocon Auxiliary Components. Cells 2020; 9:cells9020518. [PMID: 32102453 PMCID: PMC7072789 DOI: 10.3390/cells9020518] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 02/20/2020] [Accepted: 02/24/2020] [Indexed: 11/16/2022] Open
Abstract
Protein import across the endoplasmic reticulum membrane is physiologically regulated in a substrate-selective manner to ensure the protection of stressed ER from the overload of misfolded proteins. However, it is poorly understood how different types of substrates are accurately distinguished and disqualified during translocational regulation. In this study, we found poorly assembled translocon-associated protein (TRAP) complexes in stressed ER. Immunoaffinity purification identified calnexin in the TRAP complex in which poor assembly inhibited membrane insertion of the prion protein (PrP) in a transmembrane sequence-selective manner, through translocational regulation. This reaction was induced selectively by redox perturbation, rather than calcium depletion, in the ER. The liberation of ERp57 from calnexin appeared to be the reason for the redox sensitivity. Stress-independent disruption of the TRAP complex prevented a pathogenic transmembrane form of PrP (ctmPrP) from accumulating in the ER. This study uncovered a previously unappreciated role for calnexin in assisting the redox-sensitive function of the TRAP complex and provided insights into the ER stress-induced reassembly of translocon auxiliary components as a key mechanism by which protein translocation acquires substrate selectivity.
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Affiliation(s)
- Sohee Lee
- Department of Biomedical Sciences, University of Ulsan College of Medicine, Seoul 138-736, Korea; (S.L.); (Y.S.); (Y.S.)
- Asan Medical Institute of Convergence Science and Technology, Asan Medical Center, Seoul 05505, Korea
| | - Yejin Shin
- Department of Biomedical Sciences, University of Ulsan College of Medicine, Seoul 138-736, Korea; (S.L.); (Y.S.); (Y.S.)
- Asan Medical Institute of Convergence Science and Technology, Asan Medical Center, Seoul 05505, Korea
| | - Kyunggon Kim
- Department of Convergence Medicine, Asan Medical Center, Seoul 05505, Korea;
| | - Youngsup Song
- Department of Biomedical Sciences, University of Ulsan College of Medicine, Seoul 138-736, Korea; (S.L.); (Y.S.); (Y.S.)
- Asan Medical Institute of Convergence Science and Technology, Asan Medical Center, Seoul 05505, Korea
| | - Yongsub Kim
- Department of Biomedical Sciences, University of Ulsan College of Medicine, Seoul 138-736, Korea; (S.L.); (Y.S.); (Y.S.)
- Asan Medical Institute of Convergence Science and Technology, Asan Medical Center, Seoul 05505, Korea
| | - Sang-Wook Kang
- Department of Biomedical Sciences, University of Ulsan College of Medicine, Seoul 138-736, Korea; (S.L.); (Y.S.); (Y.S.)
- Asan Medical Institute of Convergence Science and Technology, Asan Medical Center, Seoul 05505, Korea
- Correspondence: ; Tel.: +82-2-3010-2205
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16
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The Expression of Myeloproliferative Neoplasm-Associated Calreticulin Variants Depends on the Functionality of ER-Associated Degradation. Cancers (Basel) 2019; 11:cancers11121921. [PMID: 31810292 PMCID: PMC6966542 DOI: 10.3390/cancers11121921] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 11/26/2019] [Accepted: 11/28/2019] [Indexed: 12/15/2022] Open
Abstract
Background: Mutations in CALR observed in myeloproliferative neoplasms (MPN) were recently shown to be pathogenic via their interaction with MPL and the subsequent activation of the Janus Kinase – Signal Transducer and Activator of Transcription (JAK-STAT) pathway. However, little is known on the impact of those variant CALR proteins on endoplasmic reticulum (ER) homeostasis. Methods: The impact of the expression of Wild Type (WT) or mutant CALR on ER homeostasis was assessed by quantifying the expression level of Unfolded Protein Response (UPR) target genes, splicing of X-box Binding Protein 1 (XBP1), and the expression level of endogenous lectins. Pharmacological and molecular (siRNA) screens were used to identify mechanisms involved in CALR mutant proteins degradation. Coimmunoprecipitations were performed to define more precisely actors involved in CALR proteins disposal. Results: We showed that the expression of CALR mutants alters neither ER homeostasis nor the sensitivity of hematopoietic cells towards ER stress-induced apoptosis. In contrast, the expression of CALR variants is generally low because of a combination of secretion and protein degradation mechanisms mostly mediated through the ER-Associated Degradation (ERAD)-proteasome pathway. Moreover, we identified a specific ERAD network involved in the degradation of CALR variants. Conclusions: We propose that this ERAD network could be considered as a potential therapeutic target for selectively inhibiting CALR mutant-dependent proliferation associated with MPN, and therefore attenuate the associated pathogenic outcomes.
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17
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Kovalchuk V, Samluk Ł, Juraszek B, Jurkiewicz-Trząska D, Sucic S, Freissmuth M, Nałęcz KA. Trafficking of the amino acid transporter B 0,+ (SLC6A14) to the plasma membrane involves an exclusive interaction with SEC24C for its exit from the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1866:252-263. [PMID: 30445147 PMCID: PMC6314439 DOI: 10.1016/j.bbamcr.2018.11.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 11/02/2018] [Accepted: 11/12/2018] [Indexed: 12/16/2022]
Abstract
A plasma membrane amino acid transporter B0,+ (ATB0,+), encoded by the SLC6A14 gene, is specific for neutral and basic amino acids. It is up-regulated in several types of malignant cancers. Neurotransmitter transporters of the SLC6 family interact with specific SEC24 proteins of the COPII complex along their pathway from the endoplasmic reticulum (ER) to Golgi. This study focused on the possible role of SEC24 proteins in ATB0,+ trafficking. Rat ATB0,+ was expressed in HEK293 cells, its localization and trafficking were examined by Western blot, deglycosylation, immunofluorescence (co-localization with ER and trans-Golgi markers) and biotinylation. The expression of ATB0,+ at the plasma membrane was decreased by dominant negative mutants of SAR1, a GTPase, whose activity triggers the formation of the COPII complex. ATB0,+ co-precipitated with SEC24C (but not with the remaining isoforms A, B and D). This interaction was confirmed by immunocytochemistry and the proximity ligation assay. Co-localization of SEC24C with endogenous ATB0,+ was also observed in MCF-7 breast cancer cells. Contrary to the endogenous transporter, part of the overexpressed ATB0,+ is directed to proteolysis, a process significantly reversed by a proteasome inhibitor bortezomib. Co-transfection with a SEC24C dominant negative mutant attenuated ATB0,+ expression at the plasma membrane, due to proteolytic degradation. These results support a hypothesis that lysine at position +2 downstream of the ER export "RI" motif on the cargo protein is crucial for SEC24C binding and for further trafficking to the Golgi. Moreover, there is an equilibrium between ER export and degradation mechanisms in case of overexpressed transporter.
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Affiliation(s)
- Vasylyna Kovalchuk
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland
| | - Łukasz Samluk
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland
| | - Barbara Juraszek
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland
| | - Dominika Jurkiewicz-Trząska
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Katarzyna A Nałęcz
- Laboratory of Transport through Biomembranes, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland.
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18
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Hareza A, Bakun M, Świderska B, Dudkiewicz M, Koscielny A, Bajur A, Jaworski J, Dadlez M, Pawłowski K. Phosphoproteomic insights into processes influenced by the kinase-like protein DIA1/C3orf58. PeerJ 2018; 6:e4599. [PMID: 29666759 PMCID: PMC5896498 DOI: 10.7717/peerj.4599] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 03/21/2018] [Indexed: 12/27/2022] Open
Abstract
Many kinases are still ‘orphans,’ which means knowledge about their substrates, and often also about the processes they regulate, is lacking. Here, DIA1/C3orf58, a member of a novel predicted kinase-like family, is shown to be present in the endoplasmic reticulum and to influence trafficking via the secretory pathway. Subsequently, DIA1 is subjected to phosphoproteomics analysis to cast light on its signalling pathways. A liquid chromatography–tandem mass spectrometry proteomic approach with phosphopeptide enrichment is applied to membrane fractions of DIA1-overexpressing and control HEK293T cells, and phosphosites dependent on the presence of DIA1 are elucidated. Most of these phosphosites belonged to CK2- and proline-directed kinase types. In parallel, the proteomics of proteins immunoprecipitated with DIA1 reported its probable interactors. This pilot study provides the basis for deeper studies of DIA1 signalling.
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Affiliation(s)
- Agnieszka Hareza
- Department of Experimental Design and Bioinformatics, Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Warszawa, Poland.,International Institute of Molecular and Cellular Biology, Warszawa, Poland
| | - Magda Bakun
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warszawa, Poland
| | - Bianka Świderska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warszawa, Poland
| | - Małgorzata Dudkiewicz
- Department of Experimental Design and Bioinformatics, Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Warszawa, Poland
| | - Alicja Koscielny
- International Institute of Molecular and Cellular Biology, Warszawa, Poland
| | - Anna Bajur
- Department of Experimental Design and Bioinformatics, Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Warszawa, Poland.,International Institute of Molecular and Cellular Biology, Warszawa, Poland.,Current affiliation: Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Jacek Jaworski
- International Institute of Molecular and Cellular Biology, Warszawa, Poland
| | - Michał Dadlez
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warszawa, Poland
| | - Krzysztof Pawłowski
- Department of Experimental Design and Bioinformatics, Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Warszawa, Poland.,Department of Translational Medicine, Clinical Sciences, Lund University, Lund, Sweden
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19
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Jung J, Eggleton P, Robinson A, Wang J, Gutowski N, Holley J, Newcombe J, Dudek E, Paul AM, Zochodne D, Kraus A, Power C, Agellon LB, Michalak M. Calnexin is necessary for T cell transmigration into the central nervous system. JCI Insight 2018. [PMID: 29515033 DOI: 10.1172/jci.insight.98410] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
In multiple sclerosis (MS), a demyelinating inflammatory disease of the CNS, and its animal model (experimental autoimmune encephalomyelitis; EAE), circulating immune cells gain access to the CNS across the blood-brain barrier to cause inflammation, myelin destruction, and neuronal damage. Here, we discovered that calnexin, an ER chaperone, is highly abundant in human brain endothelial cells of MS patients. Conversely, mice lacking calnexin exhibited resistance to EAE induction, no evidence of immune cell infiltration into the CNS, and no induction of inflammation markers within the CNS. Furthermore, calnexin deficiency in mice did not alter the development or function of the immune system. Instead, the loss of calnexin led to a defect in brain endothelial cell function that resulted in reduced T cell trafficking across the blood-brain barrier. These findings identify calnexin in brain endothelial cells as a potentially novel target for developing strategies aimed at managing or preventing the pathogenic cascade that drives neuroinflammation and destruction of the myelin sheath in MS.
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Affiliation(s)
- Joanna Jung
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Paul Eggleton
- University of Exeter Medical School, Exeter, Devon, United Kingdom.,UCB Pharma, Slough, Berkshire, United Kingdom
| | - Alison Robinson
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Jessica Wang
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Nick Gutowski
- University of Exeter Medical School, Exeter, Devon, United Kingdom
| | - Janet Holley
- University of Exeter Medical School, Exeter, Devon, United Kingdom
| | - Jia Newcombe
- NeuroResource, UCL Institute of Neurology, University College London, London, United Kingdom
| | - Elzbieta Dudek
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Amber M Paul
- Multiple Sclerosis Centre and.,Department of Medicine (Neurology), University of Alberta, Edmonton Alberta, Canada
| | - Douglas Zochodne
- Department of Medicine (Neurology), University of Alberta, Edmonton Alberta, Canada
| | - Allison Kraus
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Christopher Power
- Multiple Sclerosis Centre and.,Department of Medicine (Neurology), University of Alberta, Edmonton Alberta, Canada
| | - Luis B Agellon
- School of Human Nutrition, McGill University, Ste. Anne de Bellevue, Quebec, Canada
| | - Marek Michalak
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.,Multiple Sclerosis Centre and
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20
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Guo H, Zhang J, Wang Y, Bu C, Zhou Y, Fang Q. Comparative Proteomic Analysis of Lysine Acetylation in Fish CIK Cells Infected with Aquareovirus. Int J Mol Sci 2017; 18:E2419. [PMID: 29135940 PMCID: PMC5713387 DOI: 10.3390/ijms18112419] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 11/10/2017] [Accepted: 11/12/2017] [Indexed: 01/06/2023] Open
Abstract
Grass carp (Ctenopharyngodon idellus) is an important worldwide commercial freshwater culture species. However, grass carp reovirus (GCRV) causes serious hemorrhagic disease in fingerlings and yearlings of fishes. To understand the molecular pathogenesis of host cells during GCRV infection, intensive proteomic quantification analysis of lysine acetylation in Ctenopharyngodon idella kidney (CIK) cells was performed. Using dimethylation labeling-based quantitative proteomics, 832 acetylated proteins with 1391 lysine acetylation sites were identified in response to GCRV infection, among which 792 proteins with 1323 sites were quantifiable. Bioinformatics analysis showed that differentially expressed lysine acetylated proteins are involved in diverse cellular processes and associated with multifarious functions, suggesting that extensive intracellular activities were changed upon viral infection. In addition, extensive alterations on host-protein interactions at the lysine acetylation level were also detected. Further biological experiments showed that the histone deacetylases (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) could significantly suppress the GCRV replication. To our knowledge, this is the first to reveal the proteome-wide changes in host cell acetylome with aquatic virus infection. The results provided in this study laid a basis for further understanding the host response to aquareovirus infection in the post-translational modification aspect by regulating cell lysine acetylation conducive to viral replication.
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Affiliation(s)
- Hong Guo
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
| | - Jie Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
| | - Yaping Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
| | - Chen Bu
- Jingjie PTM BioLab (Hangzhou) Co., Ltd., Hangzhou 310018, China.
| | - Yanyan Zhou
- Jingjie PTM BioLab (Hangzhou) Co., Ltd., Hangzhou 310018, China.
| | - Qin Fang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
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21
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Jung J, Wang J, Groenendyk J, Lee D, Michalak M, Agellon LB. Fatty acid binding protein (Fabp) 5 interacts with the calnexin cytoplasmic domain at the endoplasmic reticulum. Biochem Biophys Res Commun 2017; 493:202-206. [PMID: 28911862 DOI: 10.1016/j.bbrc.2017.09.046] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 09/09/2017] [Indexed: 10/18/2022]
Abstract
Calnexin is a type 1 integral endoplasmic reticulum membrane molecular chaperone with an endoplasmic reticulum luminal chaperone domain and a highly conserved C-terminal domain oriented to the cytoplasm. Fabp5 is a cytoplasmic protein that binds long-chain fatty acids and other lipophilic ligands. Using a yeast two-hybrid screen, immunoprecipitation, microscale thermophoresis analysis and cellular fractionation, we discovered that Fabp5 interacts with the calnexin cytoplasmic C-tail domain at the endoplasmic reticulum. These observations identify Fabp5 as a previously unrecognized calnexin binding partner.
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Affiliation(s)
- Joanna Jung
- Departments of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Jessica Wang
- Departments of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Jody Groenendyk
- Departments of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Dukgyu Lee
- School of Human Nutrition, McGill University, Ste. Anne de Bellevue, Quebec, H9X 3V9, Canada
| | - Marek Michalak
- Departments of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Luis B Agellon
- School of Human Nutrition, McGill University, Ste. Anne de Bellevue, Quebec, H9X 3V9, Canada.
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22
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De Almeida I, Oliveira NMM, Randall RA, Hill CS, McCoy JM, Stern CD. Calreticulin is a secreted BMP antagonist, expressed in Hensen's node during neural induction. Dev Biol 2017; 421:161-170. [PMID: 27919666 PMCID: PMC5231319 DOI: 10.1016/j.ydbio.2016.12.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 11/29/2016] [Accepted: 12/01/2016] [Indexed: 11/27/2022]
Abstract
Hensen's node is the "organizer" of the avian and mammalian early embryo. It has many functions, including neural induction and patterning of the ectoderm and mesoderm. Some of the signals responsible for these activities are known but these do not explain the full complexity of organizer activity. Here we undertake a functional screen to discover new secreted factors expressed by the node at this time of development. Using a Signal Sequence Trap in yeast, we identify several candidates. Here we focus on Calreticulin. We show that in addition to its known functions in intracellular Calcium regulation and protein folding, Calreticulin is secreted, it can bind to BMP4 and act as a BMP antagonist in vivo and in vitro. Calreticulin is not sufficient to account for all organizer functions but may contribute to the complexity of its activity.
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Affiliation(s)
- Irene De Almeida
- Department of Cell & Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Nidia M M Oliveira
- Department of Cell & Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | | | | | | | - Claudio D Stern
- Department of Cell & Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
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23
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Dai P, Luo F, Wang Y, Jiang H, Wang L, Zhang G, Zhu L, Hu M, Wang X, Lu L, Liu Z. Species- and gender-dependent differences in the glucuronidation of a flavonoid glucoside and its aglycone determined using expressed UGT enzymes and microsomes. Biopharm Drug Dispos 2016; 36:622-35. [PMID: 26317684 DOI: 10.1002/bdd.1989] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 08/13/2015] [Accepted: 08/22/2015] [Indexed: 11/09/2022]
Abstract
Flavonoids occur naturally as glucosides and aglycones. Their common phenolic hydroxyl groups may trigger extensive UDP-glucuronosyltransferase (UGT)- catalysed metabolism. Unlike aglycones, glucosides contain glucose moieties. However, the influence of these glucose moieties on glucuronidation of glucosides and aglycones remains unclear. In this study, the flavonoid glucoside tilianin and its aglycone acacetin were used as model compounds. The glucuronidation characteristics and enzyme kinetics of tilianin and acacetin were compared using human UGT isoforms, liver microsomes and intestinal microsomes obtained from different animal species. Tilianin and acacetin were metabolized into different glucuronides, with UGT1A8 produced as the main isoform. Assessment of enzyme kinetics in UGT1A8, human liver microsomes and human intestinal microsomes revealed that compared with tilianin, acacetin displayed lower Km (0.6-, 0.7- and 0.6-fold, respectively), higher Vmax (20-, 60- and 230-fold, respectively) and higher clearance (30-, 80- and 300-fold, respectively). Furthermore, glucuronidation of acacetin and tilianin showed significant species- and gender-dependent differences. In conclusion, glucuronidation of flavonoid aglycones is faster than that of glucosides in the intestine and the liver. Understanding the metabolism and species- and gender-dependent differences between glucosides and aglycones is crucial for the development of drugs from flavonoids.
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Affiliation(s)
- Peimin Dai
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, 510515, China.,International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, China
| | - Feifei Luo
- International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, China
| | - Ying Wang
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, 510515, China.,International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, China
| | - Huangyu Jiang
- International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, China
| | - Liping Wang
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, 510515, China.,First Affiliated Hospital of the Medical College, Shihezi University, Xin Jiang, 832008, China
| | - Guiyu Zhang
- International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, China
| | - Lijun Zhu
- International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, China
| | - Ming Hu
- International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, China.,Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, 1441 Moursund Street, Houston, Texas, 77030, USA
| | - Xinchun Wang
- First Affiliated Hospital of the Medical College, Shihezi University, Xin Jiang, 832008, China
| | - Linlin Lu
- International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, China
| | - Zhongqiu Liu
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, 510515, China.,International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, 510006, China
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24
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Song J, Che J, You Z, Ye L, Li J, Zhang Y, Qian Q, Zhong B. Phosphoproteomic analysis of the posterior silk gland of Bombyx mori provides novel insight into phosphorylation regulating the silk production. J Proteomics 2016; 148:194-201. [DOI: 10.1016/j.jprot.2016.08.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Revised: 08/03/2016] [Accepted: 08/09/2016] [Indexed: 11/28/2022]
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25
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Model-Driven Understanding of Palmitoylation Dynamics: Regulated Acylation of the Endoplasmic Reticulum Chaperone Calnexin. PLoS Comput Biol 2016; 12:e1004774. [PMID: 26900856 PMCID: PMC4765739 DOI: 10.1371/journal.pcbi.1004774] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 01/25/2016] [Indexed: 11/29/2022] Open
Abstract
Cellular functions are largely regulated by reversible post-translational modifications of proteins which act as switches. Amongst these, S-palmitoylation is unique in that it confers hydrophobicity. Due to technical difficulties, the understanding of this modification has lagged behind. To investigate principles underlying dynamics and regulation of palmitoylation, we have here studied a key cellular protein, the ER chaperone calnexin, which requires dual palmitoylation for function. Apprehending the complex inter-conversion between single-, double- and non- palmitoylated species required combining experimental determination of kinetic parameters with extensive mathematical modelling. We found that calnexin, due to the presence of two cooperative sites, becomes stably acylated, which not only confers function but also a remarkable increase in stability. Unexpectedly, stochastic simulations revealed that palmitoylation does not occur soon after synthesis, but many hours later. This prediction guided us to find that phosphorylation actively delays calnexin palmitoylation in resting cells. Altogether this study reveals that cells synthesize 5 times more calnexin than needed under resting condition, most of which is degraded. This unused pool can be mobilized by preventing phosphorylation or increasing the activity of the palmitoyltransferase DHHC6. The endoplasmic reticulum (ER) is the largest intracellular organelle of mammalian cells. It is responsible for many fundamental cellular functions, such as folding, quality control of membrane and secreted protein, lipid biosynthesis, control of apoptosis and calcium storage. Recent studies have shown that many ER membrane proteins are lipid modified. We therefore hypothesized that palmitoyltransferases, the enzymes responsible for this modifications, act as a regulator of the mammalian ER, controlling the function of a network of key proteins through reversible acylation. In this work we combine computational methods with experimental determination of parameters to study the mechanisms and properties of ER palmitoylation, using as a model the palmitoylation of the ER protein calnexin. The systematic analysis of the mathematical model, built and calibrated with the help of experimental data, shows that Calnexin palmitoylation leads to a 9-fold increase in half-life and that a long delay separates synthesis from palmitoylation in unstimulated cells. Surprisingly during this delay, 75% of synthesized calnexin is degraded before being palmitoylated. We hypothesize that this unexpected apparent inefficiency is a design principle that provides the cell with a means to post-translationally tune the calnexin content.
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26
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Dudek E, Millott R, Liu WX, Beauchamp E, Berthiaume LG, Michalak M. N-Myristoyltransferase 1 interacts with calnexin at the endoplasmic reticulum. Biochem Biophys Res Commun 2015; 468:889-93. [PMID: 26603938 DOI: 10.1016/j.bbrc.2015.11.052] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2015] [Accepted: 11/11/2015] [Indexed: 11/28/2022]
Abstract
Calnexin is a type 1 integral endoplasmic reticulum (ER) membrane molecular chaperone with a highly conserved C-terminal domain oriented to the cytoplasm. Protein N-myristoylation plays an important role in a wide variety of cellular signal transduction pathways and it is catalyzed by N-myristoyltransferase (NMT), a cytoplasmic and ER associated enzyme. Here using yeast two-hybrid screen, Western blot analysis, immunoprecipitation, immunolocalization and cellular fractionation we discovered that N-myristoyltransferase 1 interacts with calnexin at the ER. These observations point at a previously unrecognized contribution of calnexin to the retention of NMT1 at the ER membrane.
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Affiliation(s)
- Elzbieta Dudek
- Departments of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Robyn Millott
- Departments of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Wen-Xin Liu
- Departments of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Erwan Beauchamp
- Departments of Cell Biology, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Luc G Berthiaume
- Departments of Cell Biology, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Marek Michalak
- Departments of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada.
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27
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Kwon OK, Sim J, Kim SJ, Sung E, Kim JY, Jeong TC, Lee S. Comprehensive Analysis of in Vivo Phosphoproteome of Mouse Liver Microsomes. J Proteome Res 2015; 14:5215-24. [PMID: 26487105 DOI: 10.1021/acs.jproteome.5b00812] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Protein phosphorylation at serine, threonine, and tyrosine residues are some of the most widespread reversible post-translational modifications. Microsomes are vesicle-like bodies, not ordinarily present within living cells, which form from pieces of the endoplasmic reticulum (ER), plasma membrane, mitochondria, or Golgi apparatus of broken eukaryotic cells. Here we investigated the total phosphoproteome of mouse liver microsomes (MLMs) using TiO2 enrichment of phosphopeptides coupled to on-line 2D-LC-MS/MS. In total, 699 phosphorylation sites in 527 proteins were identified in MLMs. When compared with the current phosphoSitePlus database, 155 novel phosphoproteins were identified in MLM. The distributions of phosphosites were 89.4, 8.0, and 2.6% for phosphoserine, phosphotheronine, and phosphotyrosine, respectively. By Motif-X analysis, eight Ser motifs and one Thr motif were found, and five acidic, two basophilic-, and two proline-directed motifs were assigned. The potential functions of phosphoproteins in MLM were assigned by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. In GO annotation, phosphorylated microsomal proteins were involved in mRNA processing, mRNA metabolic processes, and RNA splicing. In the KEGG pathway analysis, phosphorylated microsomal proteins were highly enriched in ribosome protein processing in ER and ribosomes and in RNA transport. Furthermore, we determined that 52 and 23 phosphoproteins were potential substrates of cAMP-dependent protein kinase A and casein kinase II, respectively, many of which are 40S/60S ribosomal proteins. Overall, our results provide an overview of features of protein phosphorylation in MLMs that should be a valuable resource for the future understanding of protein synthesis or translation involving phosphorylation.
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Affiliation(s)
- Oh Kwang Kwon
- College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University , Daegu 41566, Republic of Korea
| | - JuHee Sim
- College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University , Daegu 41566, Republic of Korea
| | - Sun Ju Kim
- College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University , Daegu 41566, Republic of Korea
| | - Eunji Sung
- College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University , Daegu 41566, Republic of Korea
| | - Jin Young Kim
- Mass Spectrometry Research Center, Korea Basic Science Institute , Ochang, Chungbuk 28115, Republic of Korea
| | - Tae Cheon Jeong
- College of Pharmacy, Yeungnam University , Gyeongsan 38541, Republic of Korea
| | - Sangkyu Lee
- College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University , Daegu 41566, Republic of Korea
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28
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Abstract
The endoplasmic reticulum (ER) supports many cellular processes and performs diverse functions, including protein synthesis, translocation across the membrane, integration into the membrane, folding, and posttranslational modifications including N-linked glycosylation; and regulation of Ca2+ homeostasis. In mammalian systems, the majority of proteins synthesized by the rough ER have N-linked glycans critical for protein maturation. The N-linked glycan is used as a quality control signal in the secretory protein pathway. A series of chaperones, folding enzymes, glucosidases, and carbohydrate transferases support glycoprotein synthesis and processing. Perturbation of ER-associated functions such as disturbed ER glycoprotein quality control, protein glycosylation and protein folding results in activation of an ER stress coping response. Collectively this ER stress coping response is termed the unfolded protein response (UPR), and occurs through the activation of complex cytoplasmic and nuclear signaling pathways. Cellular and ER homeostasis depends on balanced activity of the ER protein folding, quality control, and degradation pathways; as well as management of the ER stress coping response.
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29
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Lee D, Kraus A, Prins D, Groenendyk J, Aubry I, Liu WX, Li HD, Julien O, Touret N, Sykes BD, Tremblay ML, Michalak M. UBC9-dependent association between calnexin and protein tyrosine phosphatase 1B (PTP1B) at the endoplasmic reticulum. J Biol Chem 2015; 290:5725-38. [PMID: 25586181 DOI: 10.1074/jbc.m114.635474] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Calnexin is a type I integral endoplasmic reticulum (ER) membrane protein, molecular chaperone, and a component of the translocon. We discovered a novel interaction between the calnexin cytoplasmic domain and UBC9, a SUMOylation E2 ligase, which modified the calnexin cytoplasmic domain by the addition of SUMO. We demonstrated that calnexin interaction with the SUMOylation machinery modulates an interaction with protein tyrosine phosphatase 1B (PTP1B), an ER-associated protein tyrosine phosphatase involved in the negative regulation of insulin and leptin signaling. We showed that calnexin and PTP1B form UBC9-dependent complexes, revealing a previously unrecognized contribution of calnexin to the retention of PTP1B at the ER membrane. This work shows that the SUMOylation machinery links two ER proteins from divergent pathways to potentially affect cellular protein quality control and energy metabolism.
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Affiliation(s)
- Dukgyu Lee
- From the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Allison Kraus
- From the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Daniel Prins
- From the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Jody Groenendyk
- From the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Isabelle Aubry
- McGill Cancer Centre, Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Wen-Xin Liu
- From the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Hao-Dong Li
- From the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Olivier Julien
- From the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Nicolas Touret
- From the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Brian D Sykes
- From the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Michel L Tremblay
- McGill Cancer Centre, Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Marek Michalak
- McGill Cancer Centre, Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
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30
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Zhang Q, Wang XQ, Jiang HS, Jia WM, Zhao XF, Wang JX. Calnexin functions in antibacterial immunity of Marsupenaeus japonicus. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 46:356-363. [PMID: 24858031 DOI: 10.1016/j.dci.2014.05.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 05/04/2014] [Accepted: 05/04/2014] [Indexed: 06/03/2023]
Abstract
Calnexin (Cnx) is an endoplasmic reticulum membrane-bound lectin chaperone that comprises a dedicated maturation system with another lectin chaperone calreticulin (Crt). This maturation system is known as the Cnx/Crt cycle. The main functions of Cnx are Ca(2+) storage, glycoprotein folding, and quality control of synthesis. Recent studies have shown that Cnx is important in phagocytosis and in optimizing dendritic cell immunity. However, the functions of Cnx in invertebrate innate immunity remain unclear. In this research, we characterized Cnx in the kuruma shrimp Marsupenaeus japonicus (designated as MjCnx) and detected its function in shrimp immunity. The expression of MjCnx was upregulated in several tissues challenged with Vibrio anguillarum. Recombinant MjCnx could bind to bacteria by binding polysaccharides. MjCnx protein existed in the cytoplasm and on the membrane of hemocytes and was upregulated by bacterial challenge. The recombinant MjCnx enhanced the clearance of V. anguillarum in vivo, and the clearance effects were impaired after silencing MjCnx with RNA interference assay. Recombinant MjCnx promoted phagocytosis efficiency of hemocytes. These results suggest that MjCnx functions as one of the pattern recognition receptors and has crucial functions in shrimp antibacterial immunity.
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Affiliation(s)
- Qing Zhang
- MOE Key Laboratory of Plant Cell Engineering and Germplasm Innovation/Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong 250100, China
| | - Xiu-Qing Wang
- School of Clinical Laboratory of Medicine, Ningxia Medical University, Yinchuan, Ningxia 750004, China
| | - Hai-Shan Jiang
- MOE Key Laboratory of Plant Cell Engineering and Germplasm Innovation/Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong 250100, China
| | - Wen-Ming Jia
- MOE Key Laboratory of Plant Cell Engineering and Germplasm Innovation/Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong 250100, China
| | - Xiao-Fan Zhao
- MOE Key Laboratory of Plant Cell Engineering and Germplasm Innovation/Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong 250100, China
| | - Jin-Xing Wang
- MOE Key Laboratory of Plant Cell Engineering and Germplasm Innovation/Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong 250100, China.
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31
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Negroni L, Taouji S, Arma D, Pallares-Lupon N, Leong K, Beausang LA, Latterich M, Bossé R, Balabaud C, Schmitter JM, Bioulac-Sage P, Zucman-Rossi J, Rosenbaum J, Chevet E. Integrative quantitative proteomics unveils proteostasis imbalance in human hepatocellular carcinoma developed on nonfibrotic livers. Mol Cell Proteomics 2014; 13:3473-83. [PMID: 25225353 DOI: 10.1074/mcp.m114.043174] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Proteomics-based clinical studies represent promising resources for the discovery of novel biomarkers or for unraveling molecular mechanisms underlying particular diseases. Here, we present a discovery study of hepatocellular carcinoma developed on nonfibrotic liver (nfHCC) that combines complementary quantitative iTRAQ-based proteomics and phosphoproteomics approaches. Using both approaches, we compared a set of 24 samples (18 nfHCC versus six nontumor liver tissue). We identified 43 proteins (67 peptides) differentially expressed and 32 peptides differentially phosphorylated between the experimental groups. The functional analysis of the two data sets pointed toward the deregulation of a protein homeostasis (proteostasis) network including the up-regulation of the Endoplasmic Reticulum (ER) resident HSPA5, HSP90B1, PDIA6, and P4HB and of the cytosolic HSPA1B, HSP90AA1, HSPA9, UBC, CNDP2, TXN, and VCP as well as the increased phosphorylation of the ER resident calnexin at Ser583. Antibody-based validation approaches (immunohistochemistry, immunoblot, Alphascreen(®), and AMMP(®)) on independent nfHCC tumor sets (up to 77 samples) confirmed these observations, thereby indicating a common mechanism occurring in nfHCC tumors. Based on these results we propose that adaptation to proteostasis imbalance in nfHCC tumors might confer selective advantages to those tumors. As such, this model could provide an additional therapeutic opportunity for those tumors arising on normal liver by targeting the tumor proteostasis network. Data are available via ProteomeXchange with identifier PXD001253.
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Affiliation(s)
- Luc Negroni
- From the ‡UMR 5248 CNRS-Université Bordeaux-IPB, Bordeaux, France; §Université de Bordeaux, Bordeaux, France
| | - Said Taouji
- §Université de Bordeaux, Bordeaux, France; ¶INSERM, UMR-U1053, Team ≪ Endoplasmic Reticulum Stress and Cancer ≫, Bordeaux, France. ‖BMYscreen, Bordeaux, France
| | - Daniela Arma
- From the ‡UMR 5248 CNRS-Université Bordeaux-IPB, Bordeaux, France; ¶INSERM, UMR-U1053, Team ≪ Endoplasmic Reticulum Stress and Cancer ≫, Bordeaux, France. **INSERM, UMR-U1053, ≪ Repteam ≫, Bordeaux, France
| | - Nestor Pallares-Lupon
- §Université de Bordeaux, Bordeaux, France; ¶INSERM, UMR-U1053, Team ≪ Endoplasmic Reticulum Stress and Cancer ≫, Bordeaux, France
| | - Kristen Leong
- ‡‡BioScale, Inc., 4 Maguire Rd, Lexington, MA 02421, USA
| | | | - Martin Latterich
- ‡‡BioScale, Inc., 4 Maguire Rd, Lexington, MA 02421, USA; §§Proteogenomics Research Institute for Systems Medicine, San Diego, California 92121
| | | | - Charles Balabaud
- §Université de Bordeaux, Bordeaux, France; **INSERM, UMR-U1053, ≪ Repteam ≫, Bordeaux, France
| | - Jean-Marie Schmitter
- From the ‡UMR 5248 CNRS-Université Bordeaux-IPB, Bordeaux, France; §Université de Bordeaux, Bordeaux, France
| | - Paulette Bioulac-Sage
- §Université de Bordeaux, Bordeaux, France; **INSERM, UMR-U1053, ≪ Repteam ≫, Bordeaux, France
| | - Jessica Zucman-Rossi
- ‖‖Inserm, UMR-1162, Génomique fonctionnelle des Tumeurs solides, IUH, Paris, F-75010 France; Université Paris Descartes, Labex Immuno-Oncology, Sorbonne Paris Cité, Faculté de Médecine, Paris, France; Université Paris 13, Sorbonne Paris Cité, UFR SMBH, F-93000 Bobigny, France; Université Paris Diderot, F-75013 Paris
| | - Jean Rosenbaum
- §Université de Bordeaux, Bordeaux, France; **INSERM, UMR-U1053, ≪ Repteam ≫, Bordeaux, France
| | - Eric Chevet
- §Université de Bordeaux, Bordeaux, France; ¶INSERM, UMR-U1053, Team ≪ Endoplasmic Reticulum Stress and Cancer ≫, Bordeaux, France. ‖BMYscreen, Bordeaux, France; Centre Régional de Lutte Contre le Cancer Eugène Marquis, 35000 Rennes, France
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32
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Carvalho AS, Ribeiro H, Voabil P, Penque D, Jensen ON, Molina H, Matthiesen R. Global mass spectrometry and transcriptomics array based drug profiling provides novel insight into glucosamine induced endoplasmic reticulum stress. Mol Cell Proteomics 2014; 13:3294-307. [PMID: 25128556 DOI: 10.1074/mcp.m113.034363] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We investigated the molecular effects of glucosamine supplements, a popular and safe alternative to nonsteroidal anti-inflammatory drugs, for decreasing pain, inflammation, and maintaining healthy joints. Numerous studies have reported an array of molecular effects after glucosamine treatment. We questioned whether the differences in the effects observed in previous studies were associated with the focus on a specific subproteome or with the use of specific cell lines or tissues. To address this question, global mass spectrometry- and transcription array-based glucosamine drug profiling was performed on malignant cell lines from different stages of lymphocyte development. We combined global label-free MS-based protein quantitation with an open search for modifications to obtain the best possible proteome coverage. Our data were largely consistent with previous studies in a variety of cellular models. We mainly observed glucosamine induced O-GlcNAcylation/O-GalNAcylation (O-HexNAcylation); however, we also observed global and local changes in acetylation, methylation, and phosphorylation. For example, our data provides two additional examples of "yin-yang" between phosphorylation and O-HexNAcylation. Furthermore, we mapped novel O-HexNAc sites on GLU2B and calnexin. GLU2B and calnexin are known to be located in the endoplasmic reticulum (ER) and involved in protein folding and quality control. The O-HexNAc sites were regulated by glucosamine treatment and correlated with the up-regulation of the ER stress marker GRP78. The occupancy of O-HexNAc on GLU2B and calnexin sites differed between the cytosolic and nuclear fractions with a higher occupancy in the cytosolic fraction. Based on our data we propose the hypothesis that O-HexNAc either inactivates calnexin and/or targets it to the cytosolic fraction. Further, we hypothesize that O-HexNAcylation induced by glucosamine treatment enhances protein trafficking.
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Affiliation(s)
- Ana Sofia Carvalho
- From the ‡Proteolysis in Diseases, IPATIMUP, Institute of Molecular Pathology and Immunology of the University of Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal; §Human Genetics Department, National Institute of Health Dr Ricardo Jorge, Av. Padre Cruz, 1649-016 Lisboa, Portugal
| | - Helena Ribeiro
- From the ‡Proteolysis in Diseases, IPATIMUP, Institute of Molecular Pathology and Immunology of the University of Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal
| | - Paula Voabil
- From the ‡Proteolysis in Diseases, IPATIMUP, Institute of Molecular Pathology and Immunology of the University of Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal
| | - Deborah Penque
- §Human Genetics Department, National Institute of Health Dr Ricardo Jorge, Av. Padre Cruz, 1649-016 Lisboa, Portugal
| | - Ole N Jensen
- ¶Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense
| | - Henrik Molina
- ‖Proteomics Resource Center, The Rockefeller University, 1230 York Avenue, New York, New York 10065-6399
| | - Rune Matthiesen
- From the ‡Proteolysis in Diseases, IPATIMUP, Institute of Molecular Pathology and Immunology of the University of Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal; §Human Genetics Department, National Institute of Health Dr Ricardo Jorge, Av. Padre Cruz, 1649-016 Lisboa, Portugal;
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Yang L, Zhao D, Ren J, Yang J. Endoplasmic reticulum stress and protein quality control in diabetic cardiomyopathy. Biochim Biophys Acta Mol Basis Dis 2014; 1852:209-18. [PMID: 24846717 DOI: 10.1016/j.bbadis.2014.05.006] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 05/03/2014] [Accepted: 05/06/2014] [Indexed: 12/20/2022]
Abstract
Endoplasmic reticulum (ER) stress, together with the unfolded protein response (UPR), is initially considered an adaptive response aiming at maintenance of ER homeostasis. Nonetheless, ER stress, when in excess, can eventually trigger cell apoptosis and loss of function. UPR is mediated by three major transmembrane proteins, including inositol-requiring enzyme 1 (IRE1), protein kinase RNA-like ER kinase (PERK), and activating transcription factor (ATF) 6. A unique role has been speculated for ER stress in the pathogenesis of diabetes mellitus (DM) and its complications. Recent studies have shown that ER stress is an early event associated with diabetic cardiomyopathy, and may be triggered by hyperglycemia, free fatty acids (FFAs) and inflammation. In this mini-review, we attempted to discuss the activation machinery for ER stress in response to these triggers en route to disrupted ER function and cellular autophagy or apoptosis, ultimately insulin resistance and development of diabetic cardiomyopathy. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.
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Affiliation(s)
- Lifang Yang
- Department of Anesthesiology, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China; Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, WY 82071, USA
| | - Dajun Zhao
- Department of Cardiac Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China
| | - Jun Ren
- Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, WY 82071, USA.
| | - Jian Yang
- Department of Cardiac Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China.
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Pavli M, Farmaki E, Merkourea S, Vastardis H, Sklavounou A, Tzerbos F, Chatzistamou I. Endoplasmic Reticulum Stress-Associated Chaperones, Bip/GRP78 and Calnexin are Overexpressed in Keratocystic Odontogenic Tumours. EJOURNAL OF ORAL MAXILLOFACIAL RESEARCH 2014; 5:e3. [PMID: 24800053 PMCID: PMC4007369 DOI: 10.5037/jomr.2014.5103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 03/28/2014] [Indexed: 12/18/2022]
Abstract
Objectives Odontogenic keratocysts (OKCs) are developmental
cysts that have been reclassified according World Health Organization
(WHO), to keratocystic odontogenic tumours (KCOTs), a term that better
reflects their neoplastic nature. The aim of present study is to
evaluate the induction of stress of the endoplasmic reticulum and
execution of the resulting unfolded protein response in keratinocystic
odontogenic tumours. Material and Methods We analyzed by
immunohistochemistry the expression of the chaperones BiP/GRP78 and calnexin in
24 cases of KCOTs. As controls, we have used 9 cases of periapical or radicular
cysts (PACs) and 5 cases of Fibromas (FBs). The PACs and the FBs were included
in the analysis, as PACs are the most common type of inflammatory odontogenic
cysts of and FBs, as lesions of the connective tissue with unaffected
epithelium. Results Analysis revealed a strong association between
both BiP/GRP78 and calnexin expression and KCOTs: 18 out of 24 (75%) KCOTs
expressed BiP/GRP78 as opposed to 1 out of 9 (13%) PACs, and none of 5 FBs
evaluated (P < 0.001, x2-test). Calnexin was expressed in 11 out of
24 KCOTs (46%) but only one out of 9 (13%) PACs, and none of the 5 FBs analyzed
(P < 0.001, x2-test). Conclusions Study results imply
that induction of endoplasmic reticulum stress maybe of diagnostic value in
keratocystic odontogenic tumours characterization. In addition to recent
findings suggesting that endoplasmic reticulum stress plays a causative role in
keratinization of epithelia, pharmacological interference with the execution of
the unfolded protein response should be considered for the management of
keratocystic odontogenic tumours.
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Affiliation(s)
- Maria Pavli
- Clinic of Oral and Maxillofacial Surgery, Dental School, National and Kapodistrian University of Athens Greece
| | - Elena Farmaki
- Department of Biochemistry, Medical School, National and Kapodistrian University of Athens Greece
| | - Stavroula Merkourea
- Department of Oral Medicine and Pathology, Dental School, National and Kapodistrian University of Athens Greece
| | - Helen Vastardis
- Department of Basic Sciences, Dental School, National and Kapodistrian University of Athens Greece
| | - Alexandra Sklavounou
- Department of Biochemistry, Medical School, National and Kapodistrian University of Athens Greece
| | - Fotios Tzerbos
- Clinic of Oral and Maxillofacial Surgery, Dental School, National and Kapodistrian University of Athens Greece
| | - Ioulia Chatzistamou
- Department of Basic Sciences, Dental School, National and Kapodistrian University of Athens Greece
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SEO SOYOUNG, KWON YOUNGSOOK, YU KWEON, KIM SEUNGWHAN, KWON OYU, KANG KYUNGHEE, KWON KISANG. Naloxone induces endoplasmic reticulum stress in PC12 cells. Mol Med Rep 2014; 9:1395-9. [DOI: 10.3892/mmr.2014.1935] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 01/29/2014] [Indexed: 11/05/2022] Open
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Sever L, Vo NT, Bols NC, Dixon B. Rainbow trout (Oncorhynchus mykiss) contain two calnexin genes which encode distinct proteins. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 42:211-9. [PMID: 24060503 PMCID: PMC7103213 DOI: 10.1016/j.dci.2013.09.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 05/15/2023]
Abstract
Calnexin (IP90/P88) is an integral membrane protein of the endoplasmic reticulum that binds newly synthesized N-linked glycoproteins during their folding in the ER including MHC class I molecule. This manuscript reports the identification of two unique cDNA clones of calnexin in rainbow trout. Both encode putative mature proteins of 579 and 592 aa respectively in addition to a 24 aa signal peptide. Sequence analysis revealed that only one of the two cDNA clones encodes a putative ER retention signal, K/QEDDL, followed by a serine phosphorylation site conserved with mammalian homologs. Amino acid sequence alignment illustrated conservation of the calnexin luminal domain, which consists of a globular and a P domain, in both copies. Southern blotting revealed that there are at least two copies of the calnexin gene in the trout genome and northern blotting showed a wide tissue distribution of an estimated 3 kbp calnexin transcript with an additional minor transcript of 2.3 kbp expressed only in head kidney, spleen PBLs and strongly in RTS11. Importantly, the smaller transcript was predominantly upregulated in RTS11 after a 24h treatment with the calcium ionophore A23187. In western blots, calnexin was detected primarily as a 120 kDa protein and upon A23187 treatment; a 100 kDa band was most prominently expressed. These results suggest that in salmonids there are two differentiated versions of the calnexin gene which encode proteins that may have diverged to perform unique biological functions.
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Affiliation(s)
| | | | | | - Brian Dixon
- Corresponding author. Tel.: +1 (519)888 4567x32665.
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Kübler D, Seidler J, André S, Kumar S, Schwartz-Albiez R, Lehmann WD, Gabius HJ. Phosphorylation of multifunctional galectins by protein kinases CK1, CK2, and PKA. Anal Biochem 2013; 449:109-17. [PMID: 24333252 DOI: 10.1016/j.ab.2013.12.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 11/21/2013] [Accepted: 12/03/2013] [Indexed: 02/07/2023]
Abstract
Phosphorylation is known to have a strong impact on protein functions. We analyzed members of the lectin family of multifunctional galectins as targets of the protein kinases CK1, CK2, and PKA. Galectins are potent growth regulators able to bind both glycan and peptide motifs at intra- and extracellular sites. Performing in vitro kinase assays, galectin phosphorylation was detected by phosphoprotein staining and autoradiography. The insertion of phosphoryl groups varied to a large extent depending on the type of kinase applied and the respective galectin substrate. Sites of phosphorylation observed in the recombinant galectins were determined by a strategic combination of phosphopeptide enrichment and nano-ultra-performance liquid chromatography tandem mass spectrometry (nanoUPLC-MS/MS). By in silico modeling, phosphorylation sites were visualized three-dimensionally. Our results reveal galectin-type-specific Ser-/Thr-dependent phosphorylation beyond the known example of galectin-3. These data are the basis for functional studies and also illustrate the analytical sensitivity of the applied methods for further work on human lectins.
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Affiliation(s)
- Dieter Kübler
- Biomolecular Interactions, German Cancer Research Center, 69120 Heidelberg, Germany.
| | | | - Sabine André
- Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig Maximilians University Munich, 80539 Munich, Germany
| | - Sonu Kumar
- Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | | | - Wolf-Dieter Lehmann
- Core Facility Molecular Structural Analysis, German Cancer Research Center, 69120 Heidelberg, Germany
| | - Hans-Joachim Gabius
- Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig Maximilians University Munich, 80539 Munich, Germany
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Cabrera-Wrooman A, Janovick JA, Conn PM. Species sequence differences determine the interaction of GnRH receptor with the cellular quality control system. Mol Cell Endocrinol 2013; 381:1-7. [PMID: 23891857 PMCID: PMC3795929 DOI: 10.1016/j.mce.2013.07.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 06/29/2013] [Accepted: 07/15/2013] [Indexed: 01/04/2023]
Abstract
Plasma membrane expression (PME) of the human GnRHR (hGnRHR) is regulated by a primate-specific Lys(191) which destabilizes a Cys(14)-Cys(200) bridge required by the cellular quality control system (QCS). A 4-amino, non-contiguous "motif" (Leu(112), Gln(208), Leu(300), Asp(302)) is required for this effect. The hGnRHR sequence, with or without Lys(191), decreases PME and inositol phosphate (IP) production when co-expressed with calnexin, a QCS chaperone. WT rat GnRHR, decreases PME and IP production, when co-expressed with calnexin, but to a lesser degree than hGnRH. When the human sequence contains the rat motif, IP production is closer to that of rat GnRHR. When Lys(191) is deleted from hGnRHR and co-expressed with calnexin, IP production is similar to the rat sequence. When rat GnRHR containing Lys(191) and the human motif is co-expressed with calnexin, IP production is similar to cells expressing the hGnRHR. The motif sequence appears to be a determinant of calnexin recognition.
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Affiliation(s)
- Alejandro Cabrera-Wrooman
- Oregon National Primate Research Center, Oregon Health and Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA.
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Sarwat M, Naqvi AR. Heterologous expression of rice calnexin (OsCNX) confers drought tolerance in Nicotiana tabacum. Mol Biol Rep 2013; 40:5451-64. [PMID: 23681551 DOI: 10.1007/s11033-013-2643-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2012] [Accepted: 05/07/2013] [Indexed: 12/20/2022]
Abstract
Calnexin (CNX) is an integral membrane protein of endoplasmic reticulum (ER) and is a critical component of ER quality control machinery. It acts as a chaperone and ensures proper folding of newly synthesised glycoproteins. CNX shares a considerable homology with its luminal counterpart calreticulin (CRT). Together, they constitute CNX/CRT cycle which is imperative for proper folding of nascent proteins. CNX deficient organisms develop severe complications because of improper folding of proteins and consequently ER stress. CNX maintains calcium homeostasis by binding to the Ca(2+) which is a central node in various signaling pathways. Phosphorylation of cytoplasmic tail of CNX controls the sarco endoplasmic reticulum calcium ATPase and thus the movement of Ca(2+) in and out of its store-house, i.e. ER. Our studies on Oryza sativa CNX (OsCNX) reveal constitutive expression at various developmental stages and various tissues, thereby proving its requirement throughout the plant development. Further, its expression under various stress conditions gives an insight of the crosstalk existing between ER stress and abiotic stress signaling. This was confirmed by heterologous expression of OsCNX (OsCNX-HE) in tobacco and the OsCNX-HE lines were observed to exhibit better germination under mannitol stress and survival under dehydration stress conditions. The dehydration tolerance conferred by OsCNX appears to be ABA-dependent pathway.
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Affiliation(s)
- Maryam Sarwat
- Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, 110067, India.
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Marques PI, Ferreira Z, Martins M, Figueiredo J, Silva DI, Castro P, Morales-Hojas R, Simões-Correia J, Seixas S. SERPINA2 is a novel gene with a divergent function from SERPINA1. PLoS One 2013; 8:e66889. [PMID: 23826168 PMCID: PMC3691238 DOI: 10.1371/journal.pone.0066889] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Accepted: 05/11/2013] [Indexed: 11/23/2022] Open
Abstract
Serine protease inhibitors (SERPINs) are a superfamily of highly conserved proteins that play a key role in controlling the activity of proteases in diverse biological processes. The SERPIN cluster located at the 14q32.1 region includes the gene coding for SERPINA1, and a highly homologous sequence, SERPINA2, which was originally thought to be a pseudogene. We have previously shown that SERPINA2 is expressed in different tissues, namely leukocytes and testes, suggesting that it is a functional SERPIN. To investigate the function of SERPINA2, we used HeLa cells stably transduced with the different variants of SERPINA2 and SERPINA1 (M1, S and Z) and leukocytes as the in vivo model. We identified SERPINA2 as a 52 kDa intracellular glycoprotein, which is localized at the endoplasmic reticulum (ER), independently of the variant analyzed. SERPINA2 is not significantly regulated by proteasome, proposing that ER localization is not due to misfolding. Specific features of SERPINA2 include the absence of insoluble aggregates and the insignificant response to cell stress, suggesting that it is a non-polymerogenic protein with divergent activity of SERPINA1. Using phylogenetic analysis, we propose an origin of SERPINA2 in the crown of primates, and we unveiled the overall conservation of SERPINA2 and A1. Nonetheless, few SERPINA2 residues seem to have evolved faster, contributing to the emergence of a new advantageous function, possibly as a chymotrypsin-like SERPIN. Herein, we present evidences that SERPINA2 is an active gene, coding for an ER-resident protein, which may act as substrate or adjuvant of ER-chaperones.
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Affiliation(s)
- Patrícia Isabel Marques
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto, Portugal
| | - Zélia Ferreira
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Department of Biology, Faculty of Sciences, University of Porto, Porto, Portugal
| | - Manuella Martins
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
| | - Joana Figueiredo
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Medical Faculty, University of Porto, Porto, Portugal
| | - Diana Isabel Silva
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
| | - Patrícia Castro
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
| | - Ramiro Morales-Hojas
- Molecular Evolution, Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
| | - Joana Simões-Correia
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Institute of Biomedical Research on Light and Image, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Susana Seixas
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- * E-mail: (SS)
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Cigna D, D'Anna C, Zizzo C, Francofonte D, Sorrentino I, Colomba P, Albeggiani G, Armini A, Bianchi L, Bini L, Duro G. Alteration of proteomic profiles in PBMC isolated from patients with Fabry disease: preliminary findings. MOLECULAR BIOSYSTEMS 2013; 9:1162-8. [PMID: 23385635 DOI: 10.1039/c3mb25402j] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Fabry disease (FD) is an X-linked progressive multisystem disease due to mutations in the gene encoding the lysosomal enzyme α-galactosidase A (α-GalA). The deficiency in α-GalA activity leads to an intra-lysosomal accumulation of neutral glycosphingolipids, mainly globotriaosylceramide (Gb3), in various organs and systems. Enzyme replacement therapy is available and alternative therapeutic approaches are being explored. No diagnostic test, other than sequencing of the α-galactosidase A gene, is available, no biomarker has been proven useful to screen for and predict the disease, and underlying mechanisms are still elusive. The aim of this study is to identify FD specific biomarkers and to better understand the pathophysiological changes that occur over time in FD. We compared peripheral blood mononuclear cells (PBMC) from FD patients (n = 8) with control PBMC from healthy individuals (n = 6), by two-dimensional electrophoresis (2DE) and the detected differentially expressed proteins were then subjected to matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). In FD patients we identified, among the down-regulated proteins, Calnexin, Rho GDP-dissociation inhibitor 2, Rho GDP-dissociation inhibitor 1, Chloride intracellular channel protein 1; on the other hand γ-enolase, 14-3-3 protein theta, 14-3-3 protein zeta/delta, and galectin-1 were identified as up-regulated proteins. Calnexin and Rho GDP-dissociation inhibitor-1,2 are related to protein folding, signal transduction and cell proliferation. This is the first time that γ-enolase and galectin-1 are described to be up-regulated in Fabry patients. Levels of γ-enolase increase dramatically in cardiovascular accidents and cerebral trauma, whereas galectins are regulators of acute and chronic inflammation. These findings may improve our understanding of the molecular mechanisms underlying the pathology and provide new insight and knowledge for future studies in this field.
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Affiliation(s)
- Diego Cigna
- Laboratory of Proteomics, Institute of Biomedicine and Molecular Immunology (IBIM), CNR, Palermo, Italy
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Smirle J, Au CE, Jain M, Dejgaard K, Nilsson T, Bergeron J. Cell biology of the endoplasmic reticulum and the Golgi apparatus through proteomics. Cold Spring Harb Perspect Biol 2013; 5:a015073. [PMID: 23284051 DOI: 10.1101/cshperspect.a015073] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Enriched endoplasmic reticulum (ER) and Golgi membranes subjected to mass spectrometry have uncovered over a thousand different proteins assigned to the ER and Golgi apparatus of rat liver. This, in turn, led to the uncovering of several hundred proteins of poorly understood function and, through hierarchical clustering, showed that proteins distributed in patterns suggestive of microdomains in cognate organelles. This has led to new insights with respect to their intracellular localization and function. Another outcome has been the critical testing of the cisternal maturation hypothesis showing overwhelming support for a predominant role of COPI vesicles in the transport of resident proteins of the ER and Golgi apparatus (as opposed to biosynthetic cargo). Here we will discuss new insights gained and also highlight new avenues undertaken to further explore the cell biology of the ER and the Golgi apparatus through tandem mass spectrometry.
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Affiliation(s)
- Jeffrey Smirle
- The Research Institute of the McGill University Health Centre and the Department of Medicine, McGill University, Montreal, Quebec H3A 1A1, Canada
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Palmitoylated calnexin is a key component of the ribosome-translocon complex. EMBO J 2012; 31:1823-35. [PMID: 22314232 DOI: 10.1038/emboj.2012.15] [Citation(s) in RCA: 132] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 01/03/2012] [Indexed: 12/11/2022] Open
Abstract
A third of the human genome encodes N-glycosylated proteins. These are co-translationally translocated into the lumen/membrane of the endoplasmic reticulum (ER) where they fold and assemble before they are transported to their final destination. Here, we show that calnexin, a major ER chaperone involved in glycoprotein folding is palmitoylated and that this modification is mediated by the ER palmitoyltransferase DHHC6. This modification leads to the preferential localization of calnexin to the perinuclear rough ER, at the expense of ER tubules. Moreover, palmitoylation mediates the association of calnexin with the ribosome-translocon complex (RTC) leading to the formation of a supercomplex that recruits the actin cytoskeleton, leading to further stabilization of the assembly. When formation of the calnexin-RTC supercomplex was affected by DHHC6 silencing, mutation of calnexin palmitoylation sites or actin depolymerization, folding of glycoproteins was impaired. Our findings thus show that calnexin is a stable component of the RTC in a manner that is exquisitely dependent on its palmitoylation status. This association is essential for the chaperone to capture its client proteins as they emerge from the translocon, acquire their N-linked glycans and initiate folding.
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Gannon J, Bergeron JJM, Nilsson T. Golgi and related vesicle proteomics: simplify to identify. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a005421. [PMID: 21813401 DOI: 10.1101/cshperspect.a005421] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Despite more than six decades of successful Golgi research, the fundamental question as to how biosynthetic material is transported through the secretory pathway remains unanswered. New technologies such as live cell imaging and correlative microscopy have highlighted the plastic nature of the Golgi, one that is sensitive to perturbation yet highly efficient in regaining both structure and function. Single molecule-microscopy and super resolution-microscopy further adds to this picture. Various models for protein transport have been put forward, each with its own merits and pitfalls but we are far from resolving whether one is more correct than the other. As such, our laboratory considers multiple mechanisms of Golgi transport until proven otherwise. This includes the two classical modes of transport, vesicular transport and cisternal progression/maturation as well as more recent models such as tubular inter- and intra-cisternal connections (long lasting or transient) and inter-Golgi stack transport. In this article, we focus on an emerging inductive technology, mass spectrometry-based proteomics that has already enabled insight into the relative composition of compartments and subcompartments of the secretory pathway including mechanistic aspects of protein transport. We note that proteomics, as with any other technology, is not a stand-alone technology but one that works best alongside complementary approaches.
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Affiliation(s)
- Joan Gannon
- The Research Institute of the McGill University Health Centre and the Department of Medicine, Montreal, Quebec, Canada
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Verhaar R, Drukarch B, Bol JGJM, Jongenelen CAM, Musters RJP, Wilhelmus MMM. Increase in endoplasmic reticulum-associated tissue transglutaminase and enzymatic activation in a cellular model of Parkinson's disease. Neurobiol Dis 2011; 45:839-50. [PMID: 22051113 DOI: 10.1016/j.nbd.2011.10.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 10/12/2011] [Accepted: 10/16/2011] [Indexed: 12/15/2022] Open
Abstract
Parkinson's disease (PD) is characterized by accumulation of α-synuclein aggregates and degeneration of melanized, catecholaminergic neurons. The tissue transglutaminase (tTG) enzyme catalyzes molecular protein cross-linking. In PD, tTG levels are increased and cross-linking has been identified as an important factor in α-synuclein aggregation. In our quest to link tTGs distribution in the human brain to the hallmarks of PD pathology, we recently reported that catecholaminergic neurons in PD disease-affected brain areas display typical endoplasmic reticulum (ER) granules showing tTG immunoreactivity. In the present study, we set out to elucidate the nature of the interaction between tTG and the ER in PD pathogenesis, using retinoic-acid differentiated SH-SY5Y cells exposed to the PD-mimetic 1-methyl-4-phenylpyridinium (MPP(+)). Alike our observations in PD brain, MPP(+)-treated cells displayed typical TG-positive granules, that were also induced by other PD mimetics and by ER-stress inducing toxins. Additional immunocytochemical and biochemical investigation revealed that tTG is indeed associated to the ER, in particular at the cytoplasmic face of the ER. Upon MPP(+) exposure, additional recruitment of tTG toward the ER was found. In addition, we observed that MPP(+)-induced tTG activity results in transamidation of ER membrane proteins, like calnexin. Our data provide strong evidence for a, so far unrecognized, localization of tTG at the ER, at least in catecholaminergic neurons, and suggests that in PD activation of tTG may have a direct impact on ER function, in particular via post-translational modification of ER membrane proteins.
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Affiliation(s)
- Robin Verhaar
- Department of Anatomy and Neurosciences, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
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Groenendyk J, Sreenivasaiah PK, Kim DH, Agellon LB, Michalak M. Biology of endoplasmic reticulum stress in the heart. Circ Res 2010; 107:1185-97. [PMID: 21071716 DOI: 10.1161/circresaha.110.227033] [Citation(s) in RCA: 233] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The endoplasmic reticulum (ER) is a multifunctional intracellular organelle supporting many processes required by virtually every mammalian cell, including cardiomyocytes. It performs diverse functions, including protein synthesis, translocation across the membrane, integration into the membrane, folding, posttranslational modification including N-linked glycosylation, and synthesis of phospholipids and steroids on the cytoplasmic side of the ER membrane, and regulation of Ca(2+) homeostasis. Perturbation of ER-associated functions results in ER stress via the activation of complex cytoplasmic and nuclear signaling pathways, collectively termed the unfolded protein response (UPR) (also known as misfolded protein response), leading to upregulation of expression of ER resident chaperones, inhibition of protein synthesis and activation of protein degradation. The UPR has been associated with numerous human pathologies, and it may play an important role in the pathophysiology of the heart. ER stress responses, ER Ca(2+) buffering, and protein and lipid turnover impact many cardiac functions, including energy metabolism, cardiogenesis, ischemic/reperfusion, cardiomyopathies, and heart failure. ER proteins and ER stress-associated pathways may play a role in the development of novel UPR-targeted therapies for cardiovascular diseases.
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Affiliation(s)
- Jody Groenendyk
- Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta, Canada
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Song H, Rohrs H, Tan M, Wohltmann M, Ladenson JH, Turk J. Effects of endoplasmic reticulum stress on group VIA phospholipase A2 in beta cells include tyrosine phosphorylation and increased association with calnexin. J Biol Chem 2010; 285:33843-57. [PMID: 20732873 DOI: 10.1074/jbc.m110.153197] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Group VIA phospholipase A(2) (iPLA(2)β) hydrolyzes glycerophospholipids at the sn-2-position to yield a free fatty acid and a 2-lysophospholipid, and iPLA(2)β has been reported to participate in apoptosis, phospholipid remodeling, insulin secretion, transcriptional regulation, and other processes. Induction of endoplasmic reticulum (ER) stress in β-cells and vascular myocytes with SERCA inhibitors activates iPLA(2)β, resulting in hydrolysis of arachidonic acid from membrane phospholipids, by a mechanism that is not well understood. Regulatory proteins interact with iPLA(2)β, including the Ca(2+)/calmodulin-dependent protein kinase IIβ, and we have characterized the iPLA(2)β interactome further using affinity capture and LC/electrospray ionization/MS/MS. An iPLA(2)β-FLAG fusion protein was expressed in an INS-1 insulinoma cell line and then adsorbed to an anti-FLAG matrix after cell lysis. iPLA(2)β and any associated proteins were then displaced with FLAG peptide and analyzed by SDS-PAGE. Gel sections were digested with trypsin, and the resultant peptide mixtures were analyzed by LC/MS/MS with database searching. This identified 37 proteins that associate with iPLA(2)β, and nearly half of them reside in ER or mitochondria. They include the ER chaperone calnexin, whose association with iPLA(2)β increases upon induction of ER stress. Phosphorylation of iPLA(2)β at Tyr(616) also occurs upon induction of ER stress, and the phosphoprotein associates with calnexin. The activity of iPLA(2)β in vitro increases upon co-incubation with calnexin, and overexpression of calnexin in INS-1 cells results in augmentation of ER stress-induced, iPLA(2)β-catalyzed hydrolysis of arachidonic acid from membrane phospholipids, reflecting the functional significance of the interaction. Similar results were obtained with mouse pancreatic islets.
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Affiliation(s)
- Haowei Song
- Mass Spectrometry Resource, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St Louis, Missouri 63110, USA
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Simmen T, Lynes EM, Gesson K, Thomas G. Oxidative protein folding in the endoplasmic reticulum: tight links to the mitochondria-associated membrane (MAM). BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1465-73. [PMID: 20430008 DOI: 10.1016/j.bbamem.2010.04.009] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Revised: 04/15/2010] [Accepted: 04/16/2010] [Indexed: 12/18/2022]
Abstract
The production of secretory proteins at the ER (endoplasmic reticulum) depends on a ready supply of energy and metabolites as well as the close monitoring of the chemical conditions that favor oxidative protein folding. ER oxidoreductases and chaperones fold nascent proteins into their export-competent three-dimensional structure. Interference with these protein folding enzymes leads to the accumulation of unfolded proteins within the ER lumen, causing an acute organellar stress that triggers the UPR (unfolded protein response). The UPR increases the transcription of ER chaperones commensurate with the load of newly synthesized proteins and can protect the cell from ER stress. Persistant stress, however, can force the UPR to commit cells to undergo apoptotic cell death, which requires the emptying of ER calcium stores. Conversely, a continuous ebb and flow of calcium occurs between the ER and mitochondria during resting conditions on a domain of the ER that forms close contacts with mitochondria, the MAM (mitochondria-associated membrane). On the MAM, ER folding chaperones such as calnexin and calreticulin and oxidoreductases such as ERp44, ERp57 and Ero1alpha regulate calcium flux from the ER through reversible, calcium and redox-dependent interactions with IP3Rs (inositol 1,4,5-trisphophate receptors) and with SERCAs (sarcoplasmic/endoplasmic reticulum calcium ATPases). During apoptosis progression and depending on the identity of the ER chaperone and oxidoreductase, these interactions increase or decrease, suggesting that the extent of MAM targeting of ER chaperones and oxidoreductases could shift the readout of ER-mitochondria calcium exchange from housekeeping to apoptotic. However, little is known about the cytosolic factors that mediate the on/off interactions between ER chaperones and oxidoreductases with ER calcium channels and pumps. One candidate regulator is the multi-functional molecule PACS-2 (phosphofurin acidic cluster sorting protein-2). Recent studies suggest that PACS-2 mediates localization of a mobile pool of calnexin to the MAM in addition to regulating homeostatic ER calcium signaling as well as MAM integrity. Together, these findings suggest that cytosolic, membrane and lumenal proteins combine to form a two-way switch that determines the rate of protein secretion by providing ions and metabolites and that appears to participate in the pro-apoptotic ER-mitochondria calcium transfer.
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Affiliation(s)
- Thomas Simmen
- Faculty of Medicine and Dentistry, School of Molecular and Systems Medicine, Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada.
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