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Jatczak-Śliwa M, Terejko K, Brodzki M, Michałowski MA, Czyzewska MM, Nowicka JM, Andrzejczak A, Srinivasan R, Mozrzymas JW. Distinct Modulation of Spontaneous and GABA-Evoked Gating by Flurazepam Shapes Cross-Talk Between Agonist-Free and Liganded GABA A Receptor Activity. Front Cell Neurosci 2018; 12:237. [PMID: 30210295 PMCID: PMC6121034 DOI: 10.3389/fncel.2018.00237] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [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: 04/25/2018] [Accepted: 07/17/2018] [Indexed: 11/13/2022] Open
Abstract
GABAA receptors (GABAARs) play a crucial inhibitory role in the CNS. Benzodiazepines (BDZs) are positive modulators of specific subtypes of GABAARs, but the underlying mechanism remains obscure. Early studies demonstrated the major impact of BDZs on binding and more recent investigations indicated gating, but it is unclear which transitions are affected. Moreover, the upregulation of GABAAR spontaneous activity by BDZs indicates their impact on receptor gating but the underlying mechanisms remain unknown. Herein, we investigated the effect of a BDZ (flurazepam) on the spontaneous and GABA-induced activity for wild-type (WT, α1β2γ2) and mutated (at the orthosteric binding site α1F64) GABAARs. Surprisingly, in spite of the localization at the binding site, these mutations increased the spontaneous activity. Flurazepam (FLU) upregulated this activity for mutants and WT receptors to a similar extent by affecting opening/closing transitions. Spontaneous activity affected GABA-evoked currents and is manifested as an overshoot after agonist removal that depended on the modulation by BDZs. We explain the mechanism of this phenomenon as a cross-desensitization of ligand-activated and spontaneously active receptors. Moreover, due to spontaneous activity, FLU-pretreatment and co-application (agonist + FLU) protocols yielded distinct results. We provide also the first evidence that GABAAR may enter the desensitized state in the absence of GABA in a FLU-dependent manner. Based on our data and model simulations, we propose that FLU affects agonist-induced gating by modifying primarily preactivation and desensitization. We conclude that the mechanisms of modulation of spontaneous and ligand-activated GABAAR activity concerns gating but distinct transitions are affected in spontaneous and agonist-evoked activity.
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Affiliation(s)
- Magdalena Jatczak-Śliwa
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Katarzyna Terejko
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | - Marek Brodzki
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Michał A Michałowski
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Marta M Czyzewska
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | - Joanna M Nowicka
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | - Anna Andrzejczak
- Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | | | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
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Brodzki M, Rutkowski R, Jatczak M, Kisiel M, Czyzewska MM, Mozrzymas JW. Comparison of kinetic and pharmacological profiles of recombinant α1γ2L and α1β2γ2L GABAA receptors - A clue to the role of intersubunit interactions. Eur J Pharmacol 2016; 784:81-9. [PMID: 27179992 DOI: 10.1016/j.ejphar.2016.05.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [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: 12/29/2015] [Revised: 05/10/2016] [Accepted: 05/10/2016] [Indexed: 11/25/2022]
Abstract
The fastest inhibitory mechanism in the CNS is mediated by ionotropic GABAA receptors and it is known that subunit composition critically determines their properties. While a typical GABAA receptor consists of two α, two β and one γ/δ subunit, there are some exceptions, e.g. αβ receptors. Functional α1γ2 GABAA receptors can be expressed in recombinant model (Verdoorn et al., 1990) and although their role remains unknown, it seems appealing to extend their characterization to further explore the structure-function relationship of GABAA receptors. Intriguingly, this receptor is lacking canonical GABA binding sites but it can be activated by GABA and dose-response relationships for α1β2γ2L and α1γ2L receptors overlap. Deactivation kinetics was similar for both receptors but the percentage of the fast component was smaller in the case of α1γ2L receptors and, consequently, the mean deactivation time constant was slower. The rate and extent of macroscopic desensitization were smaller in the case of α1γ2L receptors but they showed slower recovery. Both receptor types had a similar proton sensitivity showing only subtle but significant differences in pH effects on deactivation. Flurazepam exerted a similar effect on both receptors but the rapid deactivation components were differently affected and an opposite effect was observed on desensitization extent. Rebound currents evoked by pentobarbital were undistinguishable for both receptor types. Taking altogether, although some significant differences were found, α1β2γ2L and α1γ2L receptors showed unforeseen similarity. We propose that functioning of GABAA receptors might rely on subunit-subunit cooperative interactions to a larger extent than believed so far.
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Affiliation(s)
- Marek Brodzki
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland; Department of Animal Molecular Physiology, Institute of Experimental Biology, University of Wrocław, ul. Cybulskiego 30, 50-205 Wrocław, Poland.
| | - Radoslaw Rutkowski
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
| | - Magdalena Jatczak
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland; Department of Animal Molecular Physiology, Institute of Experimental Biology, University of Wrocław, ul. Cybulskiego 30, 50-205 Wrocław, Poland
| | - Magdalena Kisiel
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
| | - Marta M Czyzewska
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland; Department of Animal Molecular Physiology, Institute of Experimental Biology, University of Wrocław, ul. Cybulskiego 30, 50-205 Wrocław, Poland
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Pantakani DVK, Czyzewska MM, Sikorska A, Bodda C, Mannan AU. Oligomerization of ZFYVE27 (Protrudin) is necessary to promote neurite extension. PLoS One 2011; 6:e29584. [PMID: 22216323 PMCID: PMC3247280 DOI: 10.1371/journal.pone.0029584] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Accepted: 12/01/2011] [Indexed: 11/20/2022] Open
Abstract
ZFYVE27 (Protrudin) was originally identified as an interacting partner of spastin, which is most frequently mutated in hereditary spastic paraplegia. ZFYVE27 is a novel member of FYVE family, which is implicated in the formation of neurite extensions by promoting directional membrane trafficking in neurons. Now, through a yeast two-hybrid screen, we have identified that ZFYVE27 interacts with itself and the core interaction region resides within the third hydrophobic region (HR3) of the protein. We confirmed the ZFYVE27's self-interaction in the mammalian cells by co-immunoprecipitation and co-localization studies. To decipher the oligomeric nature of ZFYVE27, we performed sucrose gradient centrifugation and showed that ZFYVE27 oligomerizes into dimer/tetramer forms. Sub-cellular fractionation and Triton X-114 membrane phase separation analysis indicated that ZFYVE27 is a peripheral membrane protein. Furthermore, ZFYVE27 also binds to phosphatidylinositol 3-phosphate lipid moiety. Interestingly, cells expressing ZFYVE27ΔHR3 failed to produce protrusions instead caused swelling of cell soma. When ZFYVE27ΔHR3 was co-expressed with wild-type ZFYVE27 (ZFYVE27WT), it exerted a dominant negative effect on ZFYVE27WT as the cells co-expressing both proteins were also unable to induce protrusions and showed cytoplasmic swelling. Altogether, it is evident that a functionally active form of oligomer is crucial for ZFYVE27 ability to promote neurite extensions.
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Affiliation(s)
| | - Marta M. Czyzewska
- Institute of Human Genetics, University of Goettingen, Goettingen, Germany
| | - Anna Sikorska
- Institute of Human Genetics, University of Goettingen, Goettingen, Germany
| | - Chiranjeevi Bodda
- Institute of Human Genetics, University of Goettingen, Goettingen, Germany
| | - Ashraf U. Mannan
- Institute of Human Genetics, University of Goettingen, Goettingen, Germany
- * E-mail:
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