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Alghalayini A, Hossain KR, Moghaddasi S, Turkewitz DR, D’Amario C, Wallach M, Valenzuela SM. In Vitro Enzymatic Studies Reveal pH and Temperature Sensitive Properties of the CLIC Proteins. Biomolecules 2023; 13:1394. [PMID: 37759794 PMCID: PMC10526857 DOI: 10.3390/biom13091394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 09/09/2023] [Accepted: 09/10/2023] [Indexed: 09/29/2023] Open
Abstract
Chloride intracellular ion channel (CLIC) proteins exist as both soluble and integral membrane proteins, with CLIC1 capable of shifting between two distinct structural conformations. New evidence has emerged indicating that members of the CLIC family act as moonlighting proteins, referring to the ability of a single protein to carry out multiple functions. In addition to their ion channel activity, CLIC family members possess oxidoreductase enzymatic activity and share significant structural and sequence homology, along with varying overlaps in their tissue distribution and cellular localization. In this study, the 2-hydroxyethyl disulfide (HEDS) assay system was used to characterize kinetic properties, as well as the temperature and pH profiles of three CLIC protein family members (CLIC1, CLIC3, CLIC4). We also assessed the effects of the drugs rapamycin and amphotericin B, on the three CLIC proteins' enzymatic activity in the HEDS assay. Our results demonstrate CLIC1 to be highly heat-sensitive, with optimal enzymatic activity observed at neutral pH7 and at a temperature of 37 °C, while CLIC3 had higher oxidoreductase activity in more acidic pH5 and was found to be relatively heat stable. CLIC4, like CLIC1, was temperature sensitive with optimal enzymatic activity observed at 37 °C; however, it showed optimal activity in more alkaline conditions of pH8. Our current study demonstrates individual differences in the enzymatic activity between the three CLIC proteins, suggesting each CLIC protein is likely regulated in discrete ways, involving changes in the subcellular milieu and microenvironment.
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Affiliation(s)
- Amani Alghalayini
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
- ARC Research Hub for Integrated Device for End-User Analysis at Low-Levels (IDEAL), Faculty of Science, University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Khondker Rufaka Hossain
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
- ARC Research Hub for Integrated Device for End-User Analysis at Low-Levels (IDEAL), Faculty of Science, University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Saba Moghaddasi
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
| | - Daniel R. Turkewitz
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
| | - Claudia D’Amario
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
| | - Michael Wallach
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
| | - Stella M. Valenzuela
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
- ARC Research Hub for Integrated Device for End-User Analysis at Low-Levels (IDEAL), Faculty of Science, University of Technology Sydney, Sydney, NSW 2007, Australia
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Hossain KR, Turkewitz DR, Holt SA, Le Brun AP, Valenzuela SM. Sterol Structural Features' Impact on the Spontaneous Membrane Insertion of CLIC1 into Artificial Lipid Membranes. Langmuir 2023; 39:3286-3300. [PMID: 36821411 DOI: 10.1021/acs.langmuir.2c03129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Background: A membrane protein interaction with lipids shows distinct specificity in terms of the sterol structure. The structure of the sterol's polar headgroup, steroidal rings, and aliphatic side chains have all been shown to influence protein membrane interactions, including the initial binding and subsequent oligomerization to form functional channels. Previous studies have provided some insights into the regulatory role that cholesterol plays in the spontaneous membrane insertion of the chloride intracellular ion channel protein, CLIC1. However, the manner in which cholesterol interacts with CLIC1 is yet largely unknown. Method: In this study, the CLIC1 interaction with different lipid:sterol monolayers was studied using the Langmuir trough and neutron reflectometry in order to investigate the structural features of cholesterol essential for the spontaneous membrane insertion of the CLIC1 protein. Molecular docking simulations were also performed to study the binding affinities between CLIC1 and the different sterol molecules. Results: This study, for the first time, highlights the vital role of the free sterol 3β-OH group as an essential structural requirement for the interaction of CLIC1 with cholesterol. Furthermore, the presence of additional hydroxyl groups, methylation of the sterol skeleton, and the structure of the sterol alkyl side chain have also been shown to modulate the magnitude of CLIC1 interaction with sterols and hence their spontaneous membrane insertion. This study also reports the ability of CLIC1 to interact with other naturally existing sterol molecules. General Significance: Like the sterol molecules, CLIC proteins are evolutionarily conserved with almost all vertebrates expressing six CLIC proteins (CLIC1-6), and CLIC-like proteins are also present in invertebrates and have also been reported in plants. This discovery of CLIC1 protein interaction with other natural sterols and the sterol structural requirements for CLIC membrane insertion provide key information to explore the feasibility of exploiting these properties for therapeutic and prophylactic purposes.
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Affiliation(s)
- Khondker R Hossain
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, New South Wales 2234, Australia
| | - Daniel R Turkewitz
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Stephen A Holt
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, New South Wales 2234, Australia
| | - Anton P Le Brun
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, New South Wales 2234, Australia
| | - Stella M Valenzuela
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia
- Institute for Biomedical Materials and Devices (IBMD), University of Technology Sydney, Sydney, New South Wales 2007, Australia
- ARC Research Hub for Integrated Device for End-User Analysis at Low-Levels (IDEAL Hub), Faculty of Science, University of Technology Sydney, , Sydney, New South Wales 2007, Australia
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Simonett SP, Shin S, Herring JA, Bacher R, Smith LA, Dong C, Rabaglia ME, Stapleton DS, Schueler KL, Choi J, Bernstein MN, Turkewitz DR, Perez-Cervantes C, Spaeth J, Stein R, Tessem JS, Kendziorski C, Keleş S, Moskowitz IP, Keller MP, Attie AD. Identification of direct transcriptional targets of NFATC2 that promote β cell proliferation. J Clin Invest 2021; 131:e144833. [PMID: 34491912 PMCID: PMC8553569 DOI: 10.1172/jci144833] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 09/02/2021] [Indexed: 12/13/2022] Open
Abstract
The transcription factor NFATC2 induces β cell proliferation in mouse and human islets. However, the genomic targets that mediate these effects have not been identified. We expressed active forms of Nfatc2 and Nfatc1 in human islets. By integrating changes in gene expression with genomic binding sites for NFATC2, we identified approximately 2200 transcriptional targets of NFATC2. Genes induced by NFATC2 were enriched for transcripts that regulate the cell cycle and for DNA motifs associated with the transcription factor FOXP. Islets from an endocrine-specific Foxp1, Foxp2, and Foxp4 triple-knockout mouse were less responsive to NFATC2-induced β cell proliferation, suggesting the FOXP family works to regulate β cell proliferation in concert with NFATC2. NFATC2 induced β cell proliferation in both mouse and human islets, whereas NFATC1 did so only in human islets. Exploiting this species difference, we identified approximately 250 direct transcriptional targets of NFAT in human islets. This gene set enriches for cell cycle-associated transcripts and includes Nr4a1. Deletion of Nr4a1 reduced the capacity of NFATC2 to induce β cell proliferation, suggesting that much of the effect of NFATC2 occurs through its induction of Nr4a1. Integration of noncoding RNA expression, chromatin accessibility, and NFATC2 binding sites enabled us to identify NFATC2-dependent enhancer loci that mediate β cell proliferation.
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Affiliation(s)
- Shane P. Simonett
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Sunyoung Shin
- Department of Mathematical Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Jacob A. Herring
- Nutrition, Dietetics and Food Science Department, Brigham Young University, Provo, Utah, USA
| | - Rhonda Bacher
- Department of Biostatistics, University of Florida, Gainesville, Florida, USA
| | - Linsin A. Smith
- Departments of Pediatrics, Pathology, and Human Genetics, University of Chicago, Chicago, Illinois, USA
| | - Chenyang Dong
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Mary E. Rabaglia
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Donnie S. Stapleton
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Kathryn L. Schueler
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Jeea Choi
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | | | - Daniel R. Turkewitz
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Carlos Perez-Cervantes
- Departments of Pediatrics, Pathology, and Human Genetics, University of Chicago, Chicago, Illinois, USA
| | - Jason Spaeth
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Roland Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Jeffery S. Tessem
- Nutrition, Dietetics and Food Science Department, Brigham Young University, Provo, Utah, USA
| | - Christina Kendziorski
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Sündüz Keleş
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Ivan P. Moskowitz
- Departments of Pediatrics, Pathology, and Human Genetics, University of Chicago, Chicago, Illinois, USA
| | - Mark P. Keller
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Alan D. Attie
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
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Turkewitz DR, Moghaddasi S, Alghalayini A, D'Amario C, Ali HM, Wallach M, Valenzuela SM. Comparative study of His- and Non-His-tagged CLIC proteins, reveals changes in their enzymatic activity. Biochem Biophys Rep 2021; 26:101015. [PMID: 34036185 PMCID: PMC8138732 DOI: 10.1016/j.bbrep.2021.101015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 04/15/2021] [Accepted: 05/02/2021] [Indexed: 10/29/2022] Open
Abstract
The chloride intracellular ion channel protein (CLIC) family are a unique set of ion channels that can exist as soluble and integral membrane proteins. New evidence has emerged that demonstrates CLICs' possess oxidoreductase enzymatic activity and may function as either membrane-spanning ion channels or as globular enzymes. To further characterize the enzymatic profile of members of the CLIC family and to expand our understanding of their functions, we expressed and purified recombinant CLIC1, CLIC3, and a non-functional CLIC1-Cys24A mutant using a Histidine tag, bacterial protein expression system. We demonstrate that the presence of the six-polyhistidine tag at the amino terminus of the proteins led to a decrease in their oxidoreductase enzymatic activity compared to their non-His-tagged counterparts, when assessed using 2-hydroxyethyl disulfide as a substrate. These results strongly suggest the six-polyhistidine tag alters CLIC's structure at the N-terminus, which also contains the enzyme active site. It also raises the need for caution in use of His-tagged proteins when assessing oxidoreductase protein enzymatic function.
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Affiliation(s)
- Daniel R Turkewitz
- School of Life Sciences, University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Saba Moghaddasi
- School of Life Sciences, University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Amani Alghalayini
- School of Life Sciences, University of Technology Sydney, Sydney, NSW, 2007, Australia.,ARC Research Hub for Integrated Device for End-user Analysis at Low-levels (IDEAL), Faculty of Science, University of Technology Sydney, NSW, 2007, Australia
| | - Claudia D'Amario
- School of Life Sciences, University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Hala M Ali
- School of Life Sciences, University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Michael Wallach
- School of Life Sciences, University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Stella M Valenzuela
- School of Life Sciences, University of Technology Sydney, Sydney, NSW, 2007, Australia.,ARC Research Hub for Integrated Device for End-user Analysis at Low-levels (IDEAL), Faculty of Science, University of Technology Sydney, NSW, 2007, Australia
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Hossain KR, Turkewitz DR, Holt SA, Herson L, Brown LJ, Cornell BA, Curmi PMG, Valenzuela SM. A conserved GXXXG motif in the transmembrane domain of CLIC proteins is essential for their cholesterol-dependant membrane interaction. Biochim Biophys Acta Gen Subj 2019; 1863:1243-1253. [PMID: 31075359 DOI: 10.1016/j.bbagen.2019.04.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 04/25/2019] [Accepted: 04/29/2019] [Indexed: 12/21/2022]
Abstract
BACKGROUND Sterols have been reported to modulate conformation and hence the function of several membrane proteins. One such group is the Chloride Intracellular Ion Channel (CLIC) family of proteins. The CLIC protein family consists of six evolutionarily conserved protein members in vertebrates. These proteins exist as both monomeric soluble proteins and as membrane bound proteins. To date, the structure of their membrane-bound form remains unknown. In addition to several studies indicating cellular redox environment and pH as facilitators of CLIC1 insertion into membranes, we have also demonstrated that the spontaneous membrane insertion of CLIC1 is regulated by membrane cholesterol. METHOD We have performed Langmuir-film, Impedance Spectroscopy and Molecular Docking Simulations to study the role of this GXXXG motif in CLIC1 interaction with cholesterol. RESULTS Unlike CLIC1-wild-type protein, the G18A and G22A mutants, that form part of the GXXXG motif, showed much slower initial kinetics and lower ion channel activity compared to the native protein. This difference can be attributed to the significantly reduced membrane interaction and insertion rate of the mutant proteins and/or slower formation of the final membrane configuration of the mutant proteins once in the membrane. CONCLUSION In this study, our findings uncover the identification of a GXXXG motif in CLIC1, which likely serves as the cholesterol-binding domain, that facilitates the protein's membrane interaction and insertion. Furthermore, we were able to postulate a model by which CLIC1 can autonomously insert into membranes to form functional ion channels. GENERAL SIGNIFICANCE Members of the CLIC family of proteins demonstrate unusual structural and dual functional properties - as ion channels and enzymes. Elucidating how the CLIC proteins' interact with membranes, thus allowing them to switch between their soluble and membrane form, will provide key information as to a mechanism of moonlighting activity and a novel regulatory role for cholesterol in such a process.
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Affiliation(s)
- Khondker Rufaka Hossain
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Daniel R Turkewitz
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Stephen A Holt
- Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Height, Australian Centre for Neutron Scattering, New South Wales 2234, Australia
| | - Leonie Herson
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Louise J Brown
- Department of Molecular Sciences, Macquarie University, New South Wales 2109, Australia
| | - Bruce A Cornell
- Surgical Diagnostics Pty Ltd., Roseville, Sydney 2069, Australia; Institute for Biomedical Materials and Devices, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Paul M G Curmi
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Stella M Valenzuela
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia; Institute for Biomedical Materials and Devices, University of Technology Sydney, Sydney, New South Wales 2007, Australia.
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Monesson-Olson B, McClain JJ, Case AE, Dorman HE, Turkewitz DR, Steiner AB, Downes GB. Expression of the eight GABAA receptor α subunits in the developing zebrafish central nervous system. PLoS One 2018; 13:e0196083. [PMID: 29702678 PMCID: PMC5922542 DOI: 10.1371/journal.pone.0196083] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 04/05/2018] [Indexed: 11/26/2022] Open
Abstract
GABA is a robust regulator of both developing and mature neural networks. It exerts many of its effects through GABAA receptors, which are heteropentamers assembled from a large array of subunits encoded by distinct genes. In mammals, there are 19 different GABAA subunit types, which are divided into the α, β, γ, δ, ε, π, θ and ρ subfamilies. The immense diversity of GABAA receptors is not fully understood. However, it is known that specific isoforms, with their distinct biophysical properties and expression profiles, tune responses to GABA. Although larval zebrafish are well-established as a model system for neural circuit analysis, little is known about GABAA receptors diversity and expression in this system. Here, using database analysis, we show that the zebrafish genome contains at least 23 subunits. All but the mammalian θ and ε subunits have at least one zebrafish ortholog, while five mammalian GABAA receptor subunits have two zebrafish orthologs. Zebrafish contain one subunit, β4, which does not have a clear mammalian ortholog. Similar to mammalian GABAA receptors, the zebrafish α subfamily is the largest and most diverse of the subfamilies. In zebrafish there are eight α subunits, and RNA in situ hybridization across early zebrafish development revealed that they demonstrate distinct patterns of expression in the brain, spinal cord, and retina. Some subunits were very broadly distributed, whereas others were restricted to small populations of cells. Subunit-specific expression patterns in zebrafish resembled were those found in frogs and rodents, which suggests that the roles of different GABAA receptor isoforms are largely conserved among vertebrates. This study provides a platform to examine isoform specific roles of GABAA receptors within zebrafish neural circuits and it highlights the potential of this system to better understand the remarkable heterogeneity of GABAA receptors.
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Affiliation(s)
- Bryan Monesson-Olson
- Neuroscience and Behavior Graduate Program, University of Massachusetts, Amherst, MA, United States of America
- Biology Department, University of Massachusetts, Amherst, MA, United States of America
| | - Jon J. McClain
- Biology Department, University of Massachusetts, Amherst, MA, United States of America
| | - Abigail E. Case
- Biology Department, University of Massachusetts, Amherst, MA, United States of America
| | - Hanna E. Dorman
- Biology Department, University of Massachusetts, Amherst, MA, United States of America
| | - Daniel R. Turkewitz
- Department of Biology and Health Sciences, Pace University, Pleasantville, NY, United States of America
| | - Aaron B. Steiner
- Department of Biology and Health Sciences, Pace University, Pleasantville, NY, United States of America
| | - Gerald B. Downes
- Neuroscience and Behavior Graduate Program, University of Massachusetts, Amherst, MA, United States of America
- Biology Department, University of Massachusetts, Amherst, MA, United States of America
- * E-mail:
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