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Glyakina AV, Suvorina MY, Dovidchenko NV, Katina NS, Surin AK, Galzitskaya OV. Exploring Compactness and Dynamics of Apomyoglobin. Proteins 2025; 93:997-1008. [PMID: 39713842 DOI: 10.1002/prot.26786] [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: 07/08/2024] [Revised: 12/02/2024] [Accepted: 12/09/2024] [Indexed: 12/24/2024]
Abstract
Hydrogen-deuterium exchange mass spectrometry (HDX-MS) approach has become a valuable analytical complement to traditional methods. HDX-MS allows the identification of dynamic surfaces in proteins. We have shown that the introduction of various mutations into the amino acid sequence of whale apomyoglobin (apoMb) leads to a change in the number of exchangeable hydrogen atoms, which is associated with a change in its compactness in the native-like condition. Thus, amino acid substitutions V10A, A15S, P120G, and M131A result in an increase in the number of exchangeable hydrogen atoms at the native-like condition, while the mutant form A144S leads to a decrease in the number of exchangeable hydrogen atoms. This may be due to a decrease and increase in the compactness of apoMb structure compared to the wild-type apoMb, respectively. The L9F and L9E mutations did not affect the compactness of the molecule compared to the wild type. We have demonstrated that V10A and M131A substitutions lead to the maximum and large increase correspondently in the average number of exchangeable hydrogen atoms for deuterium, since these substitutions lead to the loss of contacts between important parts of myoglobin structure: helices A, G, and H, which are structured at the early stage of folding.
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Affiliation(s)
- Anna V Glyakina
- Institute of Mathematical Problems of Biology, Russian Academy of Sciences, the Branch of Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, Moscow, Russia
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Russia
| | - Mariya Y Suvorina
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Russia
| | - Nikita V Dovidchenko
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Russia
- Gamaleya Research Centre of Epidemiology and Microbiology, Moscow, Russia
| | - Natalya S Katina
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Russia
- The Branch of the Institute of Bioorganic Chemistry, Russian Academy of Sciences, Pushchino, Russia
| | - Alexey K Surin
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Russia
- The Branch of the Institute of Bioorganic Chemistry, Russian Academy of Sciences, Pushchino, Russia
- State Research Center for Applied Microbiology and Biotechnology, Russia
| | - Oxana V Galzitskaya
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Russia
- Gamaleya Research Centre of Epidemiology and Microbiology, Moscow, Russia
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Russia
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HBV Infection-Related PDZK1 Plays an Oncogenic Role by Regulating the PI3K-Akt Pathway and Fatty Acid Metabolism and Enhances Immunosuppression. J Immunol Res 2022; 2022:8785567. [PMID: 36052278 PMCID: PMC9427290 DOI: 10.1155/2022/8785567] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 07/15/2022] [Indexed: 11/18/2022] Open
Abstract
Background and Aim. Chronic hepatitis B virus (HBV) infection is the leading global cause of hepatocellular carcinoma (HCC). Few studies have been conducted concerning the HBV infection-related genes and their function. Methods. We compared differentially expressed genes (DGEs) in HBV-positive and -negative tumor samples and conducted a Spearman correlation study between the DGEs and HBV titers within The Cancer Genome Atlas (TCGA). Moreover, we validated the results of our in-house samples. Results. In this study, we discovered a series of genes that correlated statistically with HBV infection based on the TCGA database. These genes were related to increased inflammation and some oncogenic signaling pathways via Gene Set Enrichment Analysis (GSEA). PDZK1 is an ideal gene, which mostly relates positively to HBV infection; moreover, it is overexpressed in human HCC, especially in those HBV-infected HCCs. After analyzing the TCGA data and performing a verification study using our own samples, PDZK1 expression was investigated to be significantly associated with PI3K-Akt signaling and fatty acid metabolism. Further, single-sample GSEA analysis of tumor immune cell infiltration gene sets revealed that high PDZK1expression in HCC tissues was significantly associated with increased tumor-associated macrophages (TAMs) and regulatory T cells(Tregs). Conclusions. PDZK1 is an HBV infection-related gene, which plays oncogenic roles, possibly due to enhancing PI3K-Akt, fatty acid usage in tumor cells and TAMs, and Treg-induced immunosuppression.
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Yu H. HDL and Scavenger Receptor Class B Type I (SRBI). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1377:79-93. [DOI: 10.1007/978-981-19-1592-5_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Wan W, Shi Y, Ji L, Li X, Xu X, Zhao D. Interleukin-37 contributes to the pathogenesis of gout by affecting PDZ domain-containing 1 protein through the nuclear factor-kappa B pathway. J Int Med Res 2021; 48:300060520948717. [PMID: 32910705 PMCID: PMC7488913 DOI: 10.1177/0300060520948717] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
OBJECTIVE Our objective was to explore the molecular pathogenesis of the onset of gout and the mechanism underlying the effect of interleukin (IL)-37 on PDZ domain-containing 1 (PDZK1) protein through the nuclear factor-κB signaling pathway. METHODS Real-time PCR and western blotting were used to detect expression of PDZK1 mRNA and protein, respectively, in the HK-2 cell line. The inhibitors pyrrolidine dithiocarbamate (PDTC) and wortmannin were added to HK-2 cells stimulated by IL-37, and changes in PDZK1 protein were detected by western blotting. RESULTS Based on our previous research, we used 10 µmol/L PDTC. We detected no significant change in PDZK1 at the mRNA level among the IL-37, PDTC+IL-37, and wortmannin+IL-37 groups. With increasing IL-37 concentration, the protein level of PDZK1 increased. After adding wortmannin, the protein level of PDZK1 increased with increasing concentration of IL-37, albeit not significantly, and the level of PDZK1 remained lower than that with IL-37 alone. After adding PDTC, the protein level of PDZK1 showed a trend to decrease with increasing concentrations of IL-37 up to 40 ng/mL. The immunofluorescence results supported the western blot results. CONCLUSIONS IL-37 can affect protein expression of PDZK1, but not at the translational level, in the pathogenesis of gout.
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Affiliation(s)
- Wei Wan
- Department of Rheumatology and Immunology, Changhai Hospital, Affiliated to Naval Military Medical University, Shanghai, China
| | - Yeqing Shi
- Department of Rheumatology and Immunology, Changhai Hospital, Affiliated to Naval Military Medical University, Shanghai, China
| | - Lianmei Ji
- Department of Rheumatology and Immunology, Changhai Hospital, Affiliated to Naval Military Medical University, Shanghai, China
| | - Xiaofang Li
- Department of Rheumatology and Immunology, Changhai Hospital, Affiliated to Naval Military Medical University, Shanghai, China
| | - Xia Xu
- Department of Rheumatology and Immunology, Changhai Hospital, Affiliated to Naval Military Medical University, Shanghai, China
| | - Dongbao Zhao
- Department of Rheumatology and Immunology, Changhai Hospital, Affiliated to Naval Military Medical University, Shanghai, China
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Marques PE, Nyegaard S, Collins RF, Troise F, Freeman SA, Trimble WS, Grinstein S. Multimerization and Retention of the Scavenger Receptor SR-B1 in the Plasma Membrane. Dev Cell 2019; 50:283-295.e5. [DOI: 10.1016/j.devcel.2019.05.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 04/05/2019] [Accepted: 05/10/2019] [Indexed: 10/26/2022]
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Shen WJ, Asthana S, Kraemer FB, Azhar S. Scavenger receptor B type 1: expression, molecular regulation, and cholesterol transport function. J Lipid Res 2018; 59:1114-1131. [PMID: 29720388 DOI: 10.1194/jlr.r083121] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 04/26/2018] [Indexed: 12/16/2022] Open
Abstract
Cholesterol is required for maintenance of plasma membrane fluidity and integrity and for many cellular functions. Cellular cholesterol can be obtained from lipoproteins in a selective pathway of HDL-cholesteryl ester (CE) uptake without parallel apolipoprotein uptake. Scavenger receptor B type 1 (SR-B1) is a cell surface HDL receptor that mediates HDL-CE uptake. It is most abundantly expressed in liver, where it provides cholesterol for bile acid synthesis, and in steroidogenic tissues, where it delivers cholesterol needed for storage or steroidogenesis in rodents. SR-B1 transcription is regulated by trophic hormones in the adrenal gland, ovary, and testis; in the liver and elsewhere, SR-B1 is subject to posttranscriptional and posttranslational regulation. SR-B1 operates in several metabolic processes and contributes to pathogenesis of atherosclerosis, inflammation, hepatitis C virus infection, and other conditions. Here, we summarize characteristics of the selective uptake pathway and involvement of microvillar channels as facilitators of selective HDL-CE uptake. We also present the potential mechanisms of SR-B1-mediated selective cholesterol transport; the transcriptional, posttranscriptional, and posttranslational regulation of SR-B1; and the impact of gene variants on expression and function of human SR-B1. A better understanding of this unique pathway and SR-B1's role may yield improved therapies for a wide variety of conditions.
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Affiliation(s)
- Wen-Jun Shen
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
| | - Shailendra Asthana
- Drug Discovery Research Center (DDRC), Translational Health Science and Technology Institute (THSTI), NCR Biotech Science Cluster, Faridabad 121001, Haryana, India
| | - Fredric B Kraemer
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
| | - Salman Azhar
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
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Al-Jezawi NK, Al-Shamsi AM, Suleiman J, Ben-Salem S, John A, Vijayan R, Ali BR, Al-Gazali L. Compound heterozygous variants in the multiple PDZ domain protein (MPDZ) cause a case of mild non-progressive communicating hydrocephalus. BMC MEDICAL GENETICS 2018; 19:34. [PMID: 29499638 PMCID: PMC5834892 DOI: 10.1186/s12881-018-0540-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 02/12/2018] [Indexed: 02/08/2023]
Abstract
BACKGROUND Congenital hydrocephalus (CH) results from the accumulation of excessive amounts of cerebrospinal fluid (CSF) in the brain, often leading to severe neurological impairments. However, the adverse effects of CH can be reduced if the condition is detected and treated early. Earlier reports demonstrated that some CH cases are caused by mutations in L1CAM gene encoding the neural cell adhesion molecule L1. On the other hand, recent studies have implicated the multiple PDZ domain (MPDZ) gene in some severe forms of CH, inherited in an autosomal recessive pattern. METHODS In this study, whole-exome and Sanger sequencing were performed on a 9 months old Emirati child clinically diagnosed by CH. In addition, in silico, cellular, and molecular assays have been conducted to confirm pathogenicity of the identified variants and to establish disease mechanism. RESULTS Whole exome sequencing revealed two compound heterozygous novel variants (c.394G > A and c.1744C > G) in the affected child within the MPDZ gene. Segregation analysis revealed that each of the parents is heterozygous for one of the two variants and therefore passed that variant to their child. The outcome of the in silico and bioinformatics analyses came in line with the experimental data, suggesting that the two variants are most likely disease causing. CONCLUSIONS The compound heterozygous variants identified in this study are the most likely cause of CH in the affected child. The study further confirms MPDZ as a gene underlying some CH cases.
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Affiliation(s)
- Nesreen K. Al-Jezawi
- Department of Pathology, College of Medicine and Heath Sciences, United Arab Emirates University, P.O. Box 17666, Al-Ain, United Arab Emirates
| | | | - Jehan Suleiman
- Department of Paediatrics, College of Medicine and Heath Sciences, United Arab Emirates University, P.O. Box 17666, Al-Ain, United Arab Emirates
| | - Salma Ben-Salem
- Department of Pathology, College of Medicine and Heath Sciences, United Arab Emirates University, P.O. Box 17666, Al-Ain, United Arab Emirates
| | - Anne John
- Department of Pathology, College of Medicine and Heath Sciences, United Arab Emirates University, P.O. Box 17666, Al-Ain, United Arab Emirates
| | - Ranjit Vijayan
- Department of Biology, College of Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Bassam R. Ali
- Department of Pathology, College of Medicine and Heath Sciences, United Arab Emirates University, P.O. Box 17666, Al-Ain, United Arab Emirates
| | - Lihadh Al-Gazali
- Department of Paediatrics, College of Medicine and Heath Sciences, United Arab Emirates University, P.O. Box 17666, Al-Ain, United Arab Emirates
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Abstract
PURPOSE OF REVIEW To outline the roles of SR-B1 and PDZK1 in hepatic selective HDL cholesterol uptake and reverse cholesterol transport and the consequences for atherosclerosis development. RECENT FINDINGS Much of our understanding of the physiological roles of SR-B1 and PDZK1 in HDL metabolism and atherosclerosis comes from studies of genetically manipulated mice. These show SR-B1 and PDZK1 play key roles in HDL metabolism and protection against atherosclerosis. The recent identification of rare loss of function mutations in the human SCARB1 gene verifies that it plays similar roles in HDL metabolism in humans. Other rare mutations in both the human SCARB1 and PDZK1 genes remain to be characterized but may have potentially devastating consequences to SR-B1 function. SUMMARY Identification of carriers of rare mutations in human SCARB1 and PDZK1 that impair the function of their gene products and characterization of the effects of these mutations on HDL cholesterol levels and atherosclerosis will add to our understanding of the importance of HDL function and cholesterol flux, as opposed to HDL-cholesterol levels, per se, for protection against cardiovascular disease.
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Affiliation(s)
- Bernardo L Trigatti
- aDepartment of Biochemistry and Biomedical Sciences, McMaster University bThrombosis and Atherosclerosis Research Institute, Hamilton Health Sciences and McMaster University, Hamilton, Ontario, Canada
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Pal R, Ke Q, Pihan GA, Yesilaltay A, Penman ML, Wang L, Chitraju C, Kang PM, Krieger M, Kocher O. Carboxy-terminal deletion of the HDL receptor reduces receptor levels in liver and steroidogenic tissues, induces hypercholesterolemia, and causes fatal heart disease. Am J Physiol Heart Circ Physiol 2016; 311:H1392-H1408. [PMID: 27694217 DOI: 10.1152/ajpheart.00463.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 09/13/2016] [Indexed: 01/15/2023]
Abstract
The HDL receptor SR-BI mediates the transfer of cholesteryl esters from HDL to cells and controls HDL abundance and structure. Depending on the genetic background, loss of SR-BI causes hypercholesterolemia, anemia, reticulocytosis, splenomegaly, thrombocytopenia, female infertility, and fatal coronary heart disease (CHD). The carboxy terminus of SR-BI (505QEAKL509) must bind to the cytoplasmic adaptor PDZK1 for normal hepatic-but not steroidogenic cell-expression of SR-BI protein. To determine whether SR-BI's carboxy terminus is also required for normal protein levels in steroidogenic cells, we introduced into SR-BI's gene a 507Ala/STOP mutation that produces a truncated receptor (SR-BIΔCT). As expected, the dramatic reduction of hepatic receptor protein in SR-BIΔCT mice was similar to that in PDZK1 knockout (KO) mice. Unlike SR-BI KO females, SR-BIΔCT females were fertile. The severity of SR-BIΔCT mice's hypercholesterolemia was intermediate between those of SR-BI KO and PDZK1 KO mice. Substantially reduced levels of the receptor in adrenal cortical cells, ovarian cells, and testicular Leydig cells in SR-BIΔCT mice suggested that steroidogenic cells have an adaptor(s) functionally analogous to hepatic PDZK1. When SR-BIΔCT mice were crossed with apolipoprotein E KO mice (SR-BIΔCT/apoE KO), pathologies including hypercholesterolemia, macrocytic anemia, hepatic and splenic extramedullary hematopoiesis, massive splenomegaly, reticulocytosis, thrombocytopenia, and rapid-onset and fatal occlusive coronary arterial atherosclerosis and CHD (median age of death: 9 wk) were observed. These results provide new insights into the control of SR-BI in steroidogenic cells and establish SR-BIΔCT/apoE KO mice as a new animal model for the study of CHD.
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Affiliation(s)
- Rinku Pal
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Qingen Ke
- Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - German A Pihan
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Ayce Yesilaltay
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Marsha L Penman
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Li Wang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Chandramohan Chitraju
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts
| | - Peter M Kang
- Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Monty Krieger
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Olivier Kocher
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts;
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Affiliation(s)
- Gregory
F. Pirrone
- Department of Chemistry and
Chemical Biology, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 United States
| | - Roxana E. Iacob
- Department of Chemistry and
Chemical Biology, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 United States
| | - John R. Engen
- Department of Chemistry and
Chemical Biology, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 United States
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Shen WJ, Hu J, Hu Z, Kraemer FB, Azhar S. Scavenger receptor class B type I (SR-BI): a versatile receptor with multiple functions and actions. Metabolism 2014; 63:875-86. [PMID: 24854385 PMCID: PMC8078058 DOI: 10.1016/j.metabol.2014.03.011] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 03/12/2014] [Accepted: 03/18/2014] [Indexed: 11/16/2022]
Abstract
Scavenger receptor class B type I (SR-BI), is a physiologically relevant HDL receptor that mediates selective uptake of lipoprotein (HDL)-derived cholesteryl ester (CE) in vitro and in vivo. Mammalian SR-BI is a 509-amino acid, ~82 kDa glycoprotein that contains N- and C-terminal cytoplasmic domains, two-transmembrane domains, as well as a large extracellular domain containing 5-6 cysteine residues and multiple sites for N-linked glycosylation. The size and structural characteristics of SR-BI, however, vary considerably among lower vertebrates and insects. Recently, significant progress has been made in understanding the molecular mechanisms involved in the posttranscriptional/posttranslational regulation of SR-BI in a tissue specific manner. The purpose of this review is to summarize the current body of knowledge about the events and molecules connected with the posttranscriptional/posttranslational regulation of SR-BI and to update the molecular and functional characteristics of the insect SR-BI orthologs.
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MESH Headings
- Animals
- Biological Transport
- Gene Expression Regulation
- Glycosylation
- Humans
- Insect Proteins/chemistry
- Insect Proteins/genetics
- Insect Proteins/metabolism
- Lipoproteins, HDL/chemistry
- Lipoproteins, HDL/genetics
- Lipoproteins, HDL/metabolism
- Liver/metabolism
- Organ Specificity
- Protein Conformation
- Protein Processing, Post-Translational
- Receptors, Lipoprotein/chemistry
- Receptors, Lipoprotein/genetics
- Receptors, Lipoprotein/metabolism
- Scavenger Receptors, Class B/chemistry
- Scavenger Receptors, Class B/genetics
- Scavenger Receptors, Class B/metabolism
- Species Specificity
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Affiliation(s)
- Wen-Jun Shen
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304; Division of Endocrinology, Stanford University, Stanford, California 94305
| | - Jie Hu
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304
| | - Zhigang Hu
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304; Division of Endocrinology, Stanford University, Stanford, California 94305
| | - Fredric B Kraemer
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304; Division of Endocrinology, Stanford University, Stanford, California 94305
| | - Salman Azhar
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304; Division of Gastroenterology and Hepatology, Stanford University, Stanford, California 94305.
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Yang J, Singh V, Chen TE, Sarker R, Xiong L, Cha B, Jin S, Li X, Tse CM, Zachos NC, Donowitz M. NHERF2/NHERF3 protein heterodimerization and macrocomplex formation are required for the inhibition of NHE3 activity by carbachol. J Biol Chem 2014; 289:20039-53. [PMID: 24867958 DOI: 10.1074/jbc.m114.562413] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
NHERF1, NHERF2, and NHERF3 belong to the NHERF (Na(+)/H(+) exchanger regulatory factor) family of PSD-95/Discs-large/ZO-1 (PDZ) scaffolding proteins. Individually, each NHERF protein has been shown to be involved in the regulation of multiple receptors or transporters including Na(+)/H(+) exchanger 3 (NHE3). Although NHERF dimerizations have been reported, results have been inconsistent, and the physiological function of NHERF dimerizations is still unknown. The current study semiquantitatively compared the interaction strength among all possible homodimerizations and heterodimerizations of these three NHERF proteins by pulldown and co-immunoprecipitation assays. Both methods showed that NHERF2 and NHERF3 heterodimerize as the strongest interaction among all NHERF dimerizations. In vivo NHERF2/NHERF3 heterodimerization was confirmed by FRET and FRAP (fluorescence recovery after photobleach). NHERF2/NHERF3 heterodimerization is mediated by PDZ domains of NHERF2 and the C-terminal PDZ domain recognition motif of NHERF3. The NHERF3-4A mutant is defective in heterodimerization with NHERF2 and does not support the inhibition of NHE3 by carbachol. This suggests a role for NHERF2/NHERF3 heterodimerization in the regulation of NHE3 activity. In addition, both PDZ domains of NHERF2 could be simultaneously occupied by NHERF3 and another ligand such as NHE3, α-actinin-4, and PKCα, promoting formation of NHE3 macrocomplexes. This study suggests that NHERF2/NHERF3 heterodimerization mediates the formation of NHE3 macrocomplexes, which are required for the inhibition of NHE3 activity by carbachol.
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Affiliation(s)
- Jianbo Yang
- From the Department of Medicine, Division of Gastroenterology and
| | - Varsha Singh
- From the Department of Medicine, Division of Gastroenterology and
| | - Tian-E Chen
- From the Department of Medicine, Division of Gastroenterology and
| | - Rafiquel Sarker
- From the Department of Medicine, Division of Gastroenterology and
| | - Lishou Xiong
- From the Department of Medicine, Division of Gastroenterology and
| | - Boyoung Cha
- From the Department of Medicine, Division of Gastroenterology and
| | - Shi Jin
- From the Department of Medicine, Division of Gastroenterology and
| | - Xuhang Li
- From the Department of Medicine, Division of Gastroenterology and
| | - C Ming Tse
- From the Department of Medicine, Division of Gastroenterology and
| | | | - Mark Donowitz
- From the Department of Medicine, Division of Gastroenterology and Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Challenges in using cultured primary rodent hepatocytes or cell lines to study hepatic HDL receptor SR-BI regulation by its cytoplasmic adaptor PDZK1. PLoS One 2013; 8:e69725. [PMID: 23936087 PMCID: PMC3720616 DOI: 10.1371/journal.pone.0069725] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 06/12/2013] [Indexed: 12/15/2022] Open
Abstract
Background PDZK1 is a four PDZ-domain containing cytoplasmic protein that binds to a variety of membrane proteins via their C-termini and can influence the abundance, localization and/or function of its target proteins. One of these targets in hepatocytes in vivo is the HDL receptor SR-BI. Normal hepatic expression of SR-BI protein requires PDZK1 - <5% of normal hepatic SR-BI is seen in the livers of PDZK1 knockout mice. Progress has been made in identifying features of PDZK1 required to control hepatic SR-BI in vivo using hepatic expression of wild-type and mutant forms of PDZK1 in wild-type and PDZK1 KO transgenic mice. Such in vivo studies are time consuming and expensive, and cannot readily be used to explore many features of the underlying molecular and cellular mechanisms. Methodology/Principal Findings Here we have explored the potential to use either primary rodent hepatocytes in culture using 2D collagen gels with newly developed optimized conditions or PDZK1/SR-BI co-transfected cultured cell lines (COS, HEK293) for such studies. SR-BI and PDZK1 protein and mRNA expression levels fell rapidly in primary hepatocyte cultures, indicating this system does not adequately mimic hepatocytes in vivo for analysis of the PDZK1 dependence of SR-BI. Although PDZK1 did alter SR-BI protein expression in the cell lines, its influence was independent of SR-BI’s C-terminus, and thus is not likely to occur via the same mechanism as that which occurs in hepatocytes in vivo. Conclusions/Significance Caution must be exercised in using primary hepatocytes or cultured cell lines when studying the mechanism underlying the regulation of hepatic SR-BI by PDZK1. It may be possible to use SR-BI and PDZK1 expression as sensitive markers for the in vivo-like state of hepatocytes to further improve primary hepatocyte cell culture conditions.
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