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Müller WEG, Neufurth M, Wang S, Schröder HC, Wang X. The Physiological Inorganic Polymers Biosilica and Polyphosphate as Key Drivers for Biomedical Materials in Regenerative Nanomedicine. Int J Nanomedicine 2024; 19:1303-1337. [PMID: 38348175 PMCID: PMC10860874 DOI: 10.2147/ijn.s446405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 01/18/2024] [Indexed: 02/15/2024] Open
Abstract
There is a need for novel nanomaterials with properties not yet exploited in regenerative nanomedicine. Based on lessons learned from the oldest metazoan phylum, sponges, it has been recognized that two previously ignored or insufficiently recognized principles play an essential role in tissue regeneration, including biomineral formation/repair and wound healing. Firstly, the dependence on enzymes as a driving force and secondly, the availability of metabolic energy. The discovery of enzymatic synthesis and regenerative activity of amorphous biosilica that builds the mineral skeleton of siliceous sponges formed the basis for the development of successful strategies for the treatment of osteochondral impairments in humans. In addition, the elucidation of the functional significance of a second regeneratively active inorganic material, namely inorganic polyphosphate (polyP) and its amorphous nanoparticles, present from sponges to humans, has pushed forward the development of innovative materials for both soft (skin, cartilage) and hard tissue (bone) repair. This energy-rich molecule exhibits a property not shown by any other biopolymer: the delivery of metabolic energy, even extracellularly, necessary for the ATP-dependent tissue regeneration. This review summarizes the latest developments in nanobiomaterials based on these two evolutionarily old, regeneratively active materials, amorphous silica and amorphous polyP, highlighting their specific, partly unique properties and mode of action, and discussing their possible applications in human therapy. The results of initial proof-of-concept studies on patients demonstrating complete healing of chronic wounds are outlined.
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Affiliation(s)
- Werner E G Müller
- ERC Advanced Investigator Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Meik Neufurth
- ERC Advanced Investigator Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Shunfeng Wang
- ERC Advanced Investigator Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Heinz C Schröder
- ERC Advanced Investigator Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Xiaohong Wang
- ERC Advanced Investigator Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
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2
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Tashima AK, de Castro LM, Fricker LD. Quantitative Peptidomics Using Reductive Methylation of Amines. Methods Mol Biol 2024; 2758:109-124. [PMID: 38549011 DOI: 10.1007/978-1-0716-3646-6_6] [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] [Indexed: 04/02/2024]
Abstract
A number of different approaches have been used for quantitative peptidomics. In this protocol, we describe the method in which peptides are reacted with formaldehyde and sodium cyanoborohydride, which converts primary and secondary amines into tertiary amines. By using different combinations of regular reagents, deuterated reagents (2H), and reagents containing deuterium and 13C, it is possible to produce five isotopically distinct forms of the methylated peptides, which can be quantified by mass spectrometry. Peptides with free N-termini that are primary amines incorporate two methyl groups using this procedure, which differ by 2 Da for each of the five isotopic combinations. Peptides that contain unmodified lysine residues incorporate additional pairs of methyl groups, leading to larger mass differences between isotopic forms. The reagents are commercially available, relatively inexpensive, and chemically stable.
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Affiliation(s)
- Alexandre K Tashima
- Department of Biochemistry, Escola Paulista de Medicina, Federal University of Sao Paulo, Sao Paulo, SP, Brazil.
| | - Leandro M de Castro
- Biodiversity of Coastal Environments Postgraduate Program, Bioscience Institute, São Paulo State University, São Vicente, SP, Brazil
| | - Lloyd D Fricker
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
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3
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Du S, Zhu C, Ren X, Chen X, Cui X, Guan S. Regulation of secretory pathway kinase or kinase-like proteins in human cancers. Front Immunol 2023; 14:942849. [PMID: 36825005 PMCID: PMC9941534 DOI: 10.3389/fimmu.2023.942849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 01/24/2023] [Indexed: 02/09/2023] Open
Abstract
Secretory pathway kinase or kinase-like proteins (SPKKPs) are effective in the lumen of the endoplasmic reticulum (ER), Golgi apparatus (GA), and extracellular space. These proteins are involved in secretory signaling pathways and are distinctive from typical protein kinases. Various reports have shown that SPKKPs regulate the tumorigenesis and progression of human cancer via the phosphorylation of various substrates, which is essential in physiological and pathological processes. Emerging evidence has revealed that the expression of SPKKPs in human cancers is regulated by multiple factors. This review summarizes the current understanding of the contribution of SPKKPs in tumorigenesis and the progression of immunity. With the epidemic trend of immunotherapy, targeting SPKKPs may be a novel approach to anticancer therapy. This study briefly discusses the recent advances regarding SPKKPs.
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Affiliation(s)
- Shaonan Du
- Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, China
| | - Chen Zhu
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, China
| | - Xiaolin Ren
- Department of Neurosurgery, Shenyang Red Cross Hospital, Shenyang, China
| | - Xin Chen
- Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, China
| | - Xiao Cui
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, China
| | - Shu Guan
- Department of Surgical Oncology and Breast Surgery, The First Hospital of China Medical University, Shenyang, China
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Li L, Wang N, Xiong Y, Guo G, Zhu M, Gu Y. Transcription Factor FOSL1 Enhances Drug Resistance of Breast Cancer Through DUSP7-Mediated Dephosphorylation of PEA15. Mol Cancer Res 2021; 20:515-526. [PMID: 34907034 DOI: 10.1158/1541-7786.mcr-21-0658] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 11/02/2021] [Accepted: 12/07/2021] [Indexed: 11/16/2022]
Abstract
Breast cancer (BC) represents one of the commonest and deadliest malignancies in women. However, drug resistance has always been a major obstacle to cancer treatment. Transcription factors have been reported to have close association with drug resistance of tumors. Recently, by analyzing the data from Gene Expression Omnibus (GEO) database (id: GSE76540), we found that transcription factor FOSL1 was significantly up-regulated in the transcriptome of doxorubicin-resistant BC cells compared with that in sensitive parental cells. Therefore, we aim to explore the regulatory mechanism of FOSL1 in affecting the drug resistance of BC cells. FOSL1 expression in doxorubicin-resistant BC cells was firstly examined through RT-qPCR, and then its influence on the drug resistance of BC cells was explored through a series of in vitro and in vivo mechanism assays. Results showed that FOSL1 promoted the drug resistance of BC cells to doxorubicin both in intro and in vivo. It positively regulated the transcription of DUSP7 in BC doxorubicin-resistant cells and DUSP7 also enhanced the drug resistance of BC cells. Furthermore, FOSL1 promoted the dephosphorylation of PEA15 through DUSP7. In conclusion, it was verified that FOSL1 promoted the drug resistance in breast cancer through DUSP7-mediated dephosphorylation of PEA15. Implications: These initial findings suggest that the FOSL1/DUSP7/PEA15 pathway may provide a theoretical guidance for BC treatment.
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Affiliation(s)
- Lin Li
- First Affiliated Hospital of Zhengzhou University
| | - Nan Wang
- First Affiliated Hospital of Zhengzhou University
| | - Youyi Xiong
- First Affiliated Hospital of Zhengzhou University
| | | | - Mingzhi Zhu
- First Affiliated Hospital of Zhengzhou University
| | - Yuanting Gu
- Department of Breast Surgery, First Affiliated Hospital of Zhengzhou University
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5
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The ABCs of the atypical Fam20 secretory pathway kinases. J Biol Chem 2021; 296:100267. [PMID: 33759783 PMCID: PMC7948968 DOI: 10.1016/j.jbc.2021.100267] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 01/05/2021] [Accepted: 01/06/2021] [Indexed: 12/12/2022] Open
Abstract
The study of extracellular phosphorylation was initiated in late 19th century when the secreted milk protein, casein, and egg-yolk protein, phosvitin, were shown to be phosphorylated. However, it took more than a century to identify Fam20C, which phosphorylates both casein and phosvitin under physiological conditions. This kinase, along with its family members Fam20A and Fam20B, defined a new family with altered amino acid sequences highly atypical from the canonical 540 kinases comprising the kinome. Fam20B is a glycan kinase that phosphorylates xylose residues and triggers peptidoglycan biosynthesis, a role conserved from sponges to human. The protein kinase, Fam20C, conserved from nematodes to humans, phosphorylates well over 100 substrates in the secretory pathway with overall functions postulated to encompass endoplasmic reticulum homeostasis, nutrition, cardiac function, coagulation, and biomineralization. The preferred phosphorylation motif of Fam20C is SxE/pS, and structural studies revealed that related member Fam20A allosterically activates Fam20C by forming a heterodimeric/tetrameric complex. Fam20A, a pseudokinase, is observed only in vertebrates. Loss-of-function genetic alterations in the Fam20 family lead to human diseases such as amelogenesis imperfecta, nephrocalcinosis, lethal and nonlethal forms of Raine syndrome with major skeletal defects, and altered phosphate homeostasis. Together, these three members of the Fam20 family modulate a diverse network of secretory pathway components playing crucial roles in health and disease. The overarching theme of this review is to highlight the progress that has been made in the emerging field of extracellular phosphorylation and the key roles secretory pathway kinases play in an ever-expanding number of cellular processes.
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Du S, Guan S, Zhu C, Guo Q, Cao J, Guan G, Cheng W, Cheng P, Wu A. Secretory Pathway Kinase FAM20C, a Marker for Glioma Invasion and Malignancy, Predicts Poor Prognosis of Glioma. Onco Targets Ther 2020; 13:11755-11768. [PMID: 33239887 PMCID: PMC7680683 DOI: 10.2147/ott.s275452] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Accepted: 10/21/2020] [Indexed: 12/15/2022] Open
Abstract
Purpose Glioblastoma (GBM) is the most lethal primary cancer in adult central nervous system, and new strategies are desperately needed. The secretory pathway kinase or kinase-like proteins (SPKKPs) have been shown to mediate multiple physiological functions by phosphorylating extracellular proteins and proteoglycans. However, their roles in cancers, especially GBM, remain poorly defined. Methods The least absolute shrinkage and selection operator (LASSO) regression was employed for establishing the SPKKPs signature for IDH wild type (wt) GBM prognosis. Integrative analyses with multiple datasets were employed to identify the core member of this gene family in glioma. The receiver operator characteristic (ROC) curves and immunohistochemistry were further used for evaluating its association with progressive malignancy in glioma and GBM patients’ survival, respectively. Gene set enrichment analysis (GSEA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to interpret its functions in GBM, which were further verified in vitro. Results A SPKKPs classifier was constructed with 3 genes of this family. This signature could effectively distinguish IDH wt GBM survival. Family with sequence similarity 20 C (FAM20C) was further identified as the core member of this family in glioma. Elevated FAM20C expression was not only closely correlated with glioma malignancy progression and the mesenchymal subtype of GBM but also indicated unfavorable survival of GBM patients. FAM20C was also found to be associated with the disrupted immune response in GBM microenvironment and was required for the migration of glioma and immune cells. Conclusion These data indicate that the potential of FAM20C serving as a predictive molecule and a therapeutic target for GBM.
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Affiliation(s)
- Shaonan Du
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, People's Republic of China
| | - Shu Guan
- Department of Surgical Oncology and Breast Surgery, The First Hospital of China Medical University, Shenyang, People's Republic of China
| | - Chen Zhu
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, People's Republic of China
| | - Qing Guo
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, People's Republic of China
| | - Jingyuan Cao
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, People's Republic of China
| | - Gefei Guan
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, People's Republic of China
| | - Wen Cheng
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, People's Republic of China
| | - Peng Cheng
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, People's Republic of China
| | - Anhua Wu
- Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, People's Republic of China.,College of Applied Technology, China Medical University, Shenyang, Liaoning 110122, People's Republic of China
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Miao N, Zhan Y, Xu Y, Yuan H, Qin C, Lin F, Xie X, Mu S, Yuan M, Mu H, Guo S, Li Y, Zhang B. Loss of Fam20c causes defects in the acinar and duct structure of salivary glands in mice. Int J Mol Med 2019; 43:2103-2117. [PMID: 30864688 PMCID: PMC6443332 DOI: 10.3892/ijmm.2019.4126] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 03/01/2019] [Indexed: 12/11/2022] Open
Abstract
Family with sequence similarity 20-member C (FAM20C), a recently characterized Golgi kinase, performs numerous biological functions by phosphorylating more than 100 secreted proteins. However, the role of FAM20C in the salivary glands remains undefined. The present study demonstrated that FAM20C is mainly located in the cytoplasm of duct epithelial cells in the salivary glands. Fam20cf/f; Mmtv-Cre mice were created in which Fam20c was inactivated in the salivary gland cells and observed that the number of ducts and the ductal cross-sectional area increased significantly, while the number of acinar cells was reduced. The granular convoluted tubules (GCTs) exhibited an accumulation of aberrant secretory granules, along with a reduced expression and altered distribution patterns of β nerve growth factor, α-amylase and bone morphogenetic protein (BMP) 4. This abnormality suggested that the GCT cells were immature and exhibited defects in developmental and secretory functions. In accordance with the morphological alterations and the reduced number of acinar cells, FAM20C deficiency in the salivary glands significantly decreased the salivary flow rate. The Na+, Cl− and K+ concentrations in the saliva were all significantly increased due to dysfunction of the ducts. Furthermore, Fam20c deficiency significantly increased BMP2 and BMP7 expression, decreased BMP4 expression, and attenuated the canonical and noncanonical BMP signaling pathways in the salivary glands. Collectively, the results of the present study demonstrate that FAM20C is a key regulator of acinar and duct structure and duct maturation and provide a novel avenue for investigating novel therapeutic targets for oral diseases including xerostomia.
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Affiliation(s)
- Nan Miao
- Institute of Hard Tissue Development and Regeneration, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Yuanbo Zhan
- Department of Periodontology and Oral Mucosa, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150086, P.R. China
| | - Yingying Xu
- Institute of Hard Tissue Development and Regeneration, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Haoze Yuan
- Institute of Hard Tissue Development and Regeneration, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Chunlin Qin
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, TX 75246, USA
| | - Feng Lin
- Department of General Surgery, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150086, P.R. China
| | - Xiaohua Xie
- Institute of Hard Tissue Development and Regeneration, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Sen Mu
- Department of Periodontology and Oral Mucosa, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150086, P.R. China
| | - Mengtong Yuan
- The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Haibin Mu
- Institute of Hard Tissue Development and Regeneration, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Shouli Guo
- The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Ying Li
- Institute of Hard Tissue Development and Regeneration, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Bin Zhang
- Institute of Hard Tissue Development and Regeneration, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
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Zhang H, Zhu Q, Cui J, Wang Y, Chen MJ, Guo X, Tagliabracci VS, Dixon JE, Xiao J. Structure and evolution of the Fam20 kinases. Nat Commun 2018; 9:1218. [PMID: 29572475 PMCID: PMC5865150 DOI: 10.1038/s41467-018-03615-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 02/28/2018] [Indexed: 01/04/2023] Open
Abstract
The Fam20 proteins are novel kinases that phosphorylate secreted proteins and proteoglycans. Fam20C phosphorylates hundreds of secreted proteins and is activated by the pseudokinase Fam20A. Fam20B phosphorylates a xylose residue to regulate proteoglycan synthesis. Despite these wide-ranging and important functions, the molecular and structural basis for the regulation and substrate specificity of these kinases are unknown. Here we report molecular characterizations of all three Fam20 kinases, and show that Fam20C is activated by the formation of an evolutionarily conserved homodimer or heterodimer with Fam20A. Fam20B has a unique active site for recognizing Galβ1-4Xylβ1, the initiator disaccharide within the tetrasaccharide linker region of proteoglycans. We further show that in animals the monomeric Fam20B preceded the appearance of the dimeric Fam20C, and the dimerization trait of Fam20C emerged concomitantly with a change in substrate specificity. Our results provide comprehensive structural, biochemical, and evolutionary insights into the function of the Fam20 kinases.
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Affiliation(s)
- Hui Zhang
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China
| | - Qinyu Zhu
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China
| | - Jixin Cui
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Yuxin Wang
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China
| | - Mark J Chen
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN, 38015, USA
| | - Xing Guo
- The Life Sciences Institute, Zhejiang University, 310058, Hangzhou, China
| | - Vincent S Tagliabracci
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Jack E Dixon
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Junyu Xiao
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China.
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Dasgupta S, Castro LM, Tashima AK, Fricker L. Quantitative Peptidomics Using Reductive Methylation of Amines. Methods Mol Biol 2018; 1719:161-174. [PMID: 29476510 DOI: 10.1007/978-1-4939-7537-2_10] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A number of different approaches have been used for quantitative peptidomics. In this protocol we describe the method in which peptides are reacted with formaldehyde and sodium cyanoborohydride, which converts primary and secondary amines into tertiary amines. By using different combinations of regular reagents, deuterated reagents (2H), and reagents containing deuterium and 13C, it is possible to produce five isotopically distinct forms of the methylated peptides which can be quantified by mass spectrometry. Peptides with free N-termini that are primary amines incorporate two methyl groups using this procedure, which differ by 2 Da for each of the five isotopic combinations. Peptides that contain unmodified lysine residues incorporate additional pairs of methyl groups, leading to larger mass differences between isotopic forms. The reagents are commercially available, relatively inexpensive, and chemically stable.
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Affiliation(s)
- Sayani Dasgupta
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Leandro M Castro
- Bioscience Institute, São Paulo State University, São Vicente, SP, Brazil
| | - Alexandre K Tashima
- Department of Biochemistry, Escola Paulista de Medicina, Federal University of São Paulo, São Paulo, SP, Brazil
| | - Lloyd Fricker
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA. .,Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA.
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10
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Liu C, Zhang H, Jani P, Wang X, Lu Y, Li N, Xiao J, Qin C. FAM20C regulates osteoblast behaviors and intracellular signaling pathways in a cell-autonomous manner. J Cell Physiol 2017; 233:3476-3486. [PMID: 28926103 DOI: 10.1002/jcp.26200] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 09/08/2017] [Indexed: 12/29/2022]
Abstract
Recent studies indicate that Family with sequence similarity 20 member C (FAM20C) catalyzes the phosphorylation of secreted proteins, and participates in a variety of biological processes, including cell proliferation, migration, mineralization, and phosphate homeostasis. To explore the local influences of FAM20C on osteoblast, Fam20c-deficient osteoblasts were generated by treating the immortalized Fam20cf/f osteoblasts with CMV-Cre-IRES-EGFP lentivirus. Compared with the normal Fam20cf/f osteoblasts, the expression of Bone sialoprotein (Bsp), Osteocalcin (Ocn), Fibroblast growth factor 23 (Fgf23), and transcription factors that promote osteoblast maturation were up-regulated in the Fam20c-deficient osteoblasts. In contrast, the expression of Dental matrix protein 1 (Dmp1), Dentin sialophosphoprotein (Dspp), Osteopontin (Opn), type I Collagen a 1 (Col1a1), and Alkine phosphatase (Alp) were down-regulated in the Fam20c-deficient cells. These alterations disclosed the primary regulation of Fam20c on gene expression. The Fam20c-deficient osteoblasts showed a remarkable reduction in the ability of forming mineralized nodules. However, supplements of extracellular matrix proteins extracted from the normal bone failed to rescue the reduced mineralization, suggesting that FAM20C may affect the biomineralization by the means more than local phosphorylation of extracellular matrix proteins and systemic phosphorus homeostasis. Moreover, although Fam20c deficiency had little impact on cell proliferation, it significantly reduced cell migration and lowered the levels of p-Smad1/5/8, p-Erk and p-p38, suggesting that the kinase activity of FAM20C might be essential to cell mobility and the activity of BMP ligands. In summary, these findings provide evidences that FAM20C may regulate osteoblast maturation, migration, mineralization, and BMP signaling pathways in a cell-autonomous manner.
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Affiliation(s)
- Chao Liu
- Department of Oral Biology, College of Stomatology, Dalian Medical University, Dalian, Liaoning, China.,Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas
| | - Hua Zhang
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas
| | - Priyam Jani
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas
| | - Xiaofang Wang
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas
| | - Yongbo Lu
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas
| | - Nan Li
- Department of Oral Biology, College of Stomatology, Dalian Medical University, Dalian, Liaoning, China
| | - Jing Xiao
- Department of Oral Biology, College of Stomatology, Dalian Medical University, Dalian, Liaoning, China
| | - Chunlin Qin
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas
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Qin Z, Wang P, Li X, Zhang S, Tian M, Dai Y, Fu L. Systematic network-based discovery of a Fam20C inhibitor (FL-1607) with apoptosis modulation in triple-negative breast cancer. MOLECULAR BIOSYSTEMS 2017; 12:2108-18. [PMID: 27113542 DOI: 10.1039/c6mb00111d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Family with sequence similarity 20, member C (Fam20C) is a physiological Golgi casein kinase that phosphorylates multiple secreted proteins. Recently, it has been reported that Fam20C can be identified as a novel kinase target for therapeutic development. Thus, inhibition of Fam20C will be a potential therapeutic strategy to prevent tumor cell progression and metastasis. In our study, based upon the systems-biology network, molecular modeling and molecular dynamics (MD) simulations, we discovered a novel Fam20C inhibitor (FL-1607) with potent anti-proliferative effects on triple-negative breast cancer (TNBC) cells. Subsequently, we found that this Fam20C inhibitor could induce apoptosis and inhibit cell migration in MDA-MB-468 cells. Together, these findings would provide a new clue to the exploration of more novel Fam20C inhibitors for future TNBC therapy.
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Affiliation(s)
- Ziyi Qin
- Institute of Traditional Chinese Medicine & Natural Products, Jinan University, Guangzhou 510632, China.
| | - Peiqi Wang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
| | - Xinyi Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
| | - Shouyue Zhang
- State Key Laboratory of Biotherapy & Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China.
| | - Mao Tian
- State Key Laboratory of Biotherapy & Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China.
| | - Yi Dai
- Institute of Traditional Chinese Medicine & Natural Products, Jinan University, Guangzhou 510632, China.
| | - Leilei Fu
- State Key Laboratory of Biotherapy & Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China.
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12
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Cui J, Zhu Q, Zhang H, Cianfrocco MA, Leschziner AE, Dixon JE, Xiao J. Structure of Fam20A reveals a pseudokinase featuring a unique disulfide pattern and inverted ATP-binding. eLife 2017; 6. [PMID: 28432788 PMCID: PMC5413348 DOI: 10.7554/elife.23990] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 04/20/2017] [Indexed: 12/19/2022] Open
Abstract
Mutations in FAM20A cause tooth enamel defects known as Amelogenesis Imperfecta (AI) and renal calcification. We previously showed that Fam20A is a secretory pathway pseudokinase and allosterically activates the physiological casein kinase Fam20C to phosphorylate secreted proteins important for biomineralization (Cui et al., 2015). Here we report the nucleotide-free and ATP-bound structures of Fam20A. Fam20A exhibits a distinct disulfide bond pattern mediated by a unique insertion region. Loss of this insertion due to abnormal mRNA splicing interferes with the structure and function of Fam20A, resulting in AI. Fam20A binds ATP in the absence of divalent cations, and strikingly, ATP is bound in an inverted orientation compared to other kinases. Fam20A forms a dimer in the crystal, and residues in the dimer interface are critical for Fam20C activation. Together, these results provide structural insights into the function of Fam20A and shed light on the mechanism by which Fam20A mutations cause disease. DOI:http://dx.doi.org/10.7554/eLife.23990.001
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Affiliation(s)
- Jixin Cui
- Department of Pharmacology, University of California, San Diego, United States
| | - Qinyu Zhu
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.,The State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Hui Zhang
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.,The State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Michael A Cianfrocco
- Department of Cellular and Molecular Medicine, University of California, San Diego, United States
| | - Andres E Leschziner
- Department of Cellular and Molecular Medicine, University of California, San Diego, United States
| | - Jack E Dixon
- Department of Pharmacology, University of California, San Diego, United States.,Department of Cellular and Molecular Medicine, University of California, San Diego, United States.,Department of Chemistry and Biochemistry, University of California, San Diego, United States
| | - Junyu Xiao
- The State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
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13
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Zhu Q, Venzke D, Walimbe AS, Anderson ME, Fu Q, Kinch LN, Wang W, Chen X, Grishin NV, Huang N, Yu L, Dixon JE, Campbell KP, Xiao J. Structure of protein O-mannose kinase reveals a unique active site architecture. eLife 2016; 5. [PMID: 27879205 PMCID: PMC5142810 DOI: 10.7554/elife.22238] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 11/22/2016] [Indexed: 12/20/2022] Open
Abstract
The ‘pseudokinase’ SgK196 is a protein O-mannose kinase (POMK) that catalyzes an essential phosphorylation step during biosynthesis of the laminin-binding glycan on α-dystroglycan. However, the catalytic mechanism underlying this activity remains elusive. Here we present the crystal structure of Danio rerio POMK in complex with Mg2+ ions, ADP, aluminum fluoride, and the GalNAc-β3-GlcNAc-β4-Man trisaccharide substrate, thereby providing a snapshot of the catalytic transition state of this unusual kinase. The active site of POMK is established by residues located in non-canonical positions and is stabilized by a disulfide bridge. GalNAc-β3-GlcNAc-β4-Man is recognized by a surface groove, and the GalNAc-β3-GlcNAc moiety mediates the majority of interactions with POMK. Expression of various POMK mutants in POMK knockout cells further validated the functional requirements of critical residues. Our results provide important insights into the ability of POMK to function specifically as a glycan kinase, and highlight the structural diversity of the human kinome. DOI:http://dx.doi.org/10.7554/eLife.22238.001
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Affiliation(s)
- Qinyu Zhu
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.,Academy for Advanced Interdisciplinary Studies, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - David Venzke
- Department of Molecular Physiology and Biophysics, Howard Hughes Medical Institute, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa City, United States.,Department of Neurology, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa, United States.,Department of Internal Medicine, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa, United States
| | - Ameya S Walimbe
- Department of Molecular Physiology and Biophysics, Howard Hughes Medical Institute, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa City, United States.,Department of Neurology, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa, United States.,Department of Internal Medicine, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa, United States
| | - Mary E Anderson
- Department of Molecular Physiology and Biophysics, Howard Hughes Medical Institute, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa City, United States.,Department of Neurology, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa, United States.,Department of Internal Medicine, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa, United States
| | - Qiuyu Fu
- National Institute of Biological Sciences, Beijing, China
| | - Lisa N Kinch
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
| | - Wei Wang
- Academy for Advanced Interdisciplinary Studies, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China.,Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China.,Synthetic and Functional Biomolecules Center, Peking University, Beijing, China.,Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Peking University, Beijing, China
| | - Xing Chen
- Academy for Advanced Interdisciplinary Studies, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China.,Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China.,Synthetic and Functional Biomolecules Center, Peking University, Beijing, China.,Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Peking University, Beijing, China
| | - Nick V Grishin
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
| | - Niu Huang
- National Institute of Biological Sciences, Beijing, China
| | - Liping Yu
- Medical Nuclear Magnetic Resonance Facility, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa, United States
| | - Jack E Dixon
- Department of Pharmacology, University of California, San Diego, La Jolla, United States.,Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, United States.,Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, United States
| | - Kevin P Campbell
- Department of Molecular Physiology and Biophysics, Howard Hughes Medical Institute, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa City, United States.,Department of Neurology, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa, United States.,Department of Internal Medicine, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa, United States
| | - Junyu Xiao
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.,Academy for Advanced Interdisciplinary Studies, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
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14
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Tagliabracci VS, Wiley SE, Guo X, Kinch LN, Durrant E, Wen J, Xiao J, Cui J, Nguyen KB, Engel JL, Coon JJ, Grishin N, Pinna LA, Pagliarini DJ, Dixon JE. A Single Kinase Generates the Majority of the Secreted Phosphoproteome. Cell 2015; 161:1619-32. [PMID: 26091039 DOI: 10.1016/j.cell.2015.05.028] [Citation(s) in RCA: 236] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 03/05/2015] [Accepted: 05/06/2015] [Indexed: 01/12/2023]
Abstract
The existence of extracellular phosphoproteins has been acknowledged for over a century. However, research in this area has been undeveloped largely because the kinases that phosphorylate secreted proteins have escaped identification. Fam20C is a kinase that phosphorylates S-x-E/pS motifs on proteins in milk and in the extracellular matrix of bones and teeth. Here, we show that Fam20C generates the majority of the extracellular phosphoproteome. Using CRISPR/Cas9 genome editing, mass spectrometry, and biochemistry, we identify more than 100 secreted phosphoproteins as genuine Fam20C substrates. Further, we show that Fam20C exhibits broader substrate specificity than previously appreciated. Functional annotations of Fam20C substrates suggest roles for the kinase beyond biomineralization, including lipid homeostasis, wound healing, and cell migration and adhesion. Our results establish Fam20C as the major secretory pathway protein kinase and serve as a foundation for new areas of investigation into the role of secreted protein phosphorylation in human biology and disease.
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Affiliation(s)
- Vincent S Tagliabracci
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Sandra E Wiley
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Xiao Guo
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Lisa N Kinch
- Department of Biophysics, University of Texas, Southwestern Medical Center, Dallas, TX 75390-9050, USA
| | - Eric Durrant
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jianzhong Wen
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Junyu Xiao
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jixin Cui
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Kim B Nguyen
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - James L Engel
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Joshua J Coon
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Nick Grishin
- Department of Biophysics, University of Texas, Southwestern Medical Center, Dallas, TX 75390-9050, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Lorenzo A Pinna
- Department of Biomedical Sciences, University of Padova, 35121 Padova, Italy; Venetian Institute of Molecular Medicine, 35129 Padova, Italy
| | - David J Pagliarini
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jack E Dixon
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.
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15
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Orizio F, Damiati E, Giacopuzzi E, Benaglia G, Pianta S, Schauer R, Schwartz-Albiez R, Borsani G, Bresciani R, Monti E. Human sialic acid acetyl esterase: Towards a better understanding of a puzzling enzyme. Glycobiology 2015; 25:992-1006. [DOI: 10.1093/glycob/cwv034] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 05/17/2015] [Indexed: 01/09/2023] Open
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16
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Sreelatha A, Kinch LN, Tagliabracci VS. The secretory pathway kinases. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1687-93. [PMID: 25862977 DOI: 10.1016/j.bbapap.2015.03.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 03/31/2015] [Indexed: 12/16/2022]
Abstract
Protein phosphorylation is a nearly universal post-translation modification involved in a plethora of cellular events. Even though phosphorylation of extracellular proteins had been observed, the identity of the kinases that phosphorylate secreted proteins remained a mystery until only recently. Advances in genome sequencing and genetic studies have paved the way for the discovery of a new class of kinases that localize within the endoplasmic reticulum, Golgi apparatus and the extracellular space. These novel kinases phosphorylate proteins and proteoglycans in the secretory pathway and appear to regulate various extracellular processes. Mutations in these kinases cause human disease, thus underscoring the biological importance of phosphorylation within the secretory pathway. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases.
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Affiliation(s)
- Anju Sreelatha
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Lisa N Kinch
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Vincent S Tagliabracci
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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17
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Abstract
We have come a long way in the 55 years since Edmond Fischer and the late Edwin Krebs discovered that the activity of glycogen phosphorylase is regulated by reversible protein phosphorylation. Many of the fundamental molecular mechanisms that operate in biological signaling have since been characterized and the vast web of interconnected pathways that make up the cellular signaling network has been mapped in considerable detail. Nonetheless, it is important to consider how fast this field is still moving and the issues at the current boundaries of our understanding. One must also appreciate what experimental strategies have allowed us to attain our present level of knowledge. We summarize here some key issues (both conceptual and methodological), raise unresolved questions, discuss potential pitfalls, and highlight areas in which our understanding is still rudimentary. We hope these wide-ranging ruminations will be useful to investigators who carry studies of signal transduction forward during the rest of the 21st century.
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18
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Tagliabracci VS, Engel JL, Wiley SE, Xiao J, Gonzalez DJ, Nidumanda Appaiah H, Koller A, Nizet V, White KE, Dixon JE. Dynamic regulation of FGF23 by Fam20C phosphorylation, GalNAc-T3 glycosylation, and furin proteolysis. Proc Natl Acad Sci U S A 2014; 111:5520-5. [PMID: 24706917 PMCID: PMC3992636 DOI: 10.1073/pnas.1402218111] [Citation(s) in RCA: 223] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The family with sequence similarity 20, member C (Fam20C) has recently been identified as the Golgi casein kinase. Fam20C phosphorylates secreted proteins on Ser-x-Glu/pSer motifs and loss-of-function mutations in the kinase cause Raine syndrome, an often-fatal osteosclerotic bone dysplasia. Fam20C is potentially an upstream regulator of the phosphate-regulating hormone fibroblast growth factor 23 (FGF23), because humans with FAM20C mutations and Fam20C KO mice develop hypophosphatemia due to an increase in full-length, biologically active FGF23. However, the mechanism by which Fam20C regulates FGF23 is unknown. Here we show that Fam20C directly phosphorylates FGF23 on Ser(180), within the FGF23 R(176)XXR(179)/S(180)AE subtilisin-like proprotein convertase motif. This phosphorylation event inhibits O-glycosylation of FGF23 by polypeptide N-acetylgalactosaminyltransferase 3 (GalNAc-T3), and promotes FGF23 cleavage and inactivation by the subtilisin-like proprotein convertase furin. Collectively, our results provide a molecular mechanism by which FGF23 is dynamically regulated by phosphorylation, glycosylation, and proteolysis. Furthermore, our findings suggest that cross-talk between phosphorylation and O-glycosylation of proteins in the secretory pathway may be an important mechanism by which secreted proteins are regulated.
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Affiliation(s)
| | | | | | | | | | - Hitesh Nidumanda Appaiah
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202; and
| | - Antonius Koller
- Stony Brook University Proteomics Center, School of Medicine, Stony Brook University, Stony Brook, NY 11794
| | - Victor Nizet
- Pediatrics
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093
| | - Kenneth E. White
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202; and
| | - Jack E. Dixon
- Departments of Pharmacology
- Cellular and Molecular Medicine, and
- Chemistry and Biochemistry and
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19
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Dawn of the dead: protein pseudokinases signal new adventures in cell biology. Biochem Soc Trans 2013; 41:969-74. [DOI: 10.1042/bst20130115] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recent studies of proteins containing kinase-like domains that lack catalytic residue(s) classically required for phosphotransfer, termed pseudokinases, have uncovered important roles in cell signalling across the kingdoms of life. Additionally, mutations within pseudokinase domains are known to underlie human diseases, suggesting that these proteins may represent new and unexplored therapeutic targets. To date, few pseudokinases have been studied in intricate detail, but as described in the present article and in the subsequent papers in this issue of Biochemical Society Transactions, several new studies have provided an advanced template and an improved framework for interrogating the roles of pseudokinases in signal transduction. In the present article, we review landmarks in the establishment of this field of study, highlight some experimental challenges and propose a simple scheme for definition of these domains based on their primary sequences, rather than experimentally defined nucleotide-binding or catalytic activities.
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