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Li N, Teng SW, Zhao L, Li JR, Xu JL, Li N, Shuai JC, Chen ZY. Carboxypeptidase E Regulates Activity-Dependent TrkB Neuronal Surface Insertion and Hippocampal Memory. J Neurosci 2021; 41:6987-7002. [PMID: 34266900 PMCID: PMC8372023 DOI: 10.1523/jneurosci.0236-21.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 05/14/2021] [Accepted: 07/09/2021] [Indexed: 11/21/2022] Open
Abstract
Activity-dependent insertion of the tropomyosin-related kinase B (TrkB) receptor into the plasma membrane can explain, in part, the preferential effect of brain-derived neurotrophic factor (BDNF) on active neurons and synapses; however, the underlying molecular mechanisms remain obscure. Here, we report a novel function for carboxypeptidase E (CPE) in controlling chemical long-term potentiation stimuli-induced TrkB surface delivery in hippocampal neurons. Total internal reflection fluorescence assays and line plot assays showed that CPE facilitates TrkB transport from dendritic shafts to the plasma membrane. The Box2 domain in the juxtamembrane region of TrkB and the C terminus of CPE are critical for the activity-dependent plasma membrane insertion of TrkB. Moreover, the transactivator of transcription TAT-CPE452-466, which could block the association between CPE and TrkB, significantly inhibited neuronal activity-enhanced BDNF signaling and dendritic spine morphologic plasticity in cultured hippocampal neurons. Microinfusion of TAT-CPE452-466 into the dorsal hippocampus of male C57BL/6 mice inhibited the endogenous interaction between TrkB and CPE and diminished fear-conditioning-induced TrkB phosphorylation, which might lead to an impairment in hippocampal memory acquisition and consolidation but not retrieval. These results suggest that CPE modulates activity-induced TrkB surface insertion and hippocampal-dependent memory and sheds light on our understanding of the role of CPE in TrkB-dependent synaptic plasticity and memory modulation.SIGNIFICANCE STATEMENT It is well known that BDNF acts preferentially on active neurons; however, the underlying molecular mechanism is not fully understood. In this study, we found that the cytoplasmic tail of CPE could interact with TrkB and facilitate the neuronal activity-dependent movement of TrkB vesicles to the plasma membrane. Blocking the association between CPE and TrkB decreased fear-conditioning-induced TrkB phosphorylation and led to hippocampal memory deficits. These findings provide novel insights into the role of CPE in TrkB intracellular trafficking as well as in mediating BDNF/TrkB function in synaptic plasticity and hippocampal memory.
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Affiliation(s)
- Na Li
- Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education, Chinese National Health Commission and Chinese Academy of Medical Sciences, State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Department of Cardiology, Qilu Hospital, Cheeloo College of Medicine, Shandong University, Jinan 250012, China
| | | | - Ling Zhao
- Cell Biology, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, 250012, China
| | - Jing-Rui Li
- College of Life Sciences, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, Institute of Biomedical Sciences, Shandong Normal University, Jinan 250014, China
| | - Jia-Ling Xu
- Institution of Traditional Chinese Medicine Innovation Research, Shandong University of Traditional Chinese Medicine, Jinan, 250355 China
| | - Na Li
- Departments of Anatomy and Neurobiology and
| | | | - Zhe-Yu Chen
- Departments of Anatomy and Neurobiology and
- Institute of Brain Science, Shuguang Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
- Institution of Traditional Chinese Medicine Innovation Research, Shandong University of Traditional Chinese Medicine, Jinan, 250355 China
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Brunstein M, Teremetz M, Hérault K, Tourain C, Oheim M. Eliminating unwanted far-field excitation in objective-type TIRF. Part I. identifying sources of nonevanescent excitation light. Biophys J 2014; 106:1020-32. [PMID: 24606927 DOI: 10.1016/j.bpj.2013.12.049] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 12/18/2013] [Accepted: 12/23/2013] [Indexed: 11/18/2022] Open
Abstract
Total internal reflection fluorescence microscopy (TIRFM) achieves subdiffraction axial sectioning by confining fluorophore excitation to a thin layer close to the cell/substrate boundary. However, it is often unknown how thin this light sheet actually is. Particularly in objective-type TIRFM, large deviations from the exponential intensity decay expected for pure evanescence have been reported. Nonevanescent excitation light diminishes the optical sectioning effect, reduces contrast, and renders TIRFM-image quantification uncertain. To identify the sources of this unwanted fluorescence excitation in deeper sample layers, we here combine azimuthal and polar beam scanning (spinning TIRF), atomic force microscopy, and wavefront analysis of beams passing through the objective periphery. Using a variety of intracellular fluorescent labels as well as negative staining experiments to measure cell-induced scattering, we find that azimuthal beam spinning produces TIRFM images that more accurately portray the real fluorophore distribution, but these images are still hampered by far-field excitation. Furthermore, although clearly measureable, cell-induced scattering is not the dominant source of far-field excitation light in objective-type TIRF, at least for most types of weakly scattering cells. It is the microscope illumination optical path that produces a large cell- and beam-angle invariant stray excitation that is insensitive to beam scanning. This instrument-induced glare is produced far from the sample plane, inside the microscope illumination optical path. We identify stray reflections and high-numerical aperture aberrations of the TIRF objective as one important source. This work is accompanied by a companion paper (Pt.2/2).
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Affiliation(s)
- Maia Brunstein
- CNRS, UMR 8154, Paris, F-75006 France; INSERM, U603, Paris, F-75006 France; Laboratoire de Neurophysiologie et Nouvelles Microscopies, Université Paris Descartes, PRES Sorbonne Paris Cité, Paris, F-75006 France
| | - Maxime Teremetz
- CNRS, UMR 8154, Paris, F-75006 France; INSERM, U603, Paris, F-75006 France; Laboratoire de Neurophysiologie et Nouvelles Microscopies, Université Paris Descartes, PRES Sorbonne Paris Cité, Paris, F-75006 France; Master Programme: Biologie Cellulaire, Physiologie et Pathologies (BCPP), Université Paris Diderot, PRES Sorbonne Paris Cité, Paris, France
| | - Karine Hérault
- CNRS, UMR 8154, Paris, F-75006 France; INSERM, U603, Paris, F-75006 France; Laboratoire de Neurophysiologie et Nouvelles Microscopies, Université Paris Descartes, PRES Sorbonne Paris Cité, Paris, F-75006 France
| | - Christophe Tourain
- CNRS, UMR 8154, Paris, F-75006 France; INSERM, U603, Paris, F-75006 France; Laboratoire de Neurophysiologie et Nouvelles Microscopies, Université Paris Descartes, PRES Sorbonne Paris Cité, Paris, F-75006 France; Service Commun de Microscopie (SCM), Institut Fédératif de Recherche en Neurosciences, Paris, F-75006 France
| | - Martin Oheim
- CNRS, UMR 8154, Paris, F-75006 France; INSERM, U603, Paris, F-75006 France; Laboratoire de Neurophysiologie et Nouvelles Microscopies, Université Paris Descartes, PRES Sorbonne Paris Cité, Paris, F-75006 France.
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Brunstein M, Hérault K, Oheim M. Eliminating unwanted far-field excitation in objective-type TIRF. Part II. combined evanescent-wave excitation and supercritical-angle fluorescence detection improves optical sectioning. Biophys J 2014; 106:1044-56. [PMID: 24606929 PMCID: PMC4026779 DOI: 10.1016/j.bpj.2013.12.051] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 12/18/2013] [Accepted: 12/23/2013] [Indexed: 12/29/2022] Open
Abstract
Azimuthal beam scanning makes evanescent-wave (EW) excitation isotropic, thereby producing total internal reflection fluorescence (TIRF) images that are evenly lit. However, beam spinning does not fundamentally address the problem of propagating excitation light that is contaminating objective-type TIRF. Far-field excitation depends more on the specific objective than on cell scattering. As a consequence, the excitation impurities in objective-type TIRF are only weakly affected by changes of azimuthal or polar beam angle. These are the main results of the first part of this study (Eliminating unwanted far-field excitation in objective-type TIRF. Pt.1. Identifying sources of nonevanescent excitation light). This second part focuses on exactly where up beam in the illumination system stray light is generated that gives rise to nonevanescent components in TIRF. Using dark-field imaging of scattered excitation light we pinpoint the objective, intermediate lenses and, particularly, the beam scanner as the major sources of stray excitation. We study how adhesion-molecule coating and astrocytes or BON cells grown on the coverslip surface modify the dark-field signal. On flat and weakly scattering cells, most background comes from stray reflections produced far from the sample plane, in the beam scanner and the objective lens. On thick, optically dense cells roughly half of the scatter is generated by the sample itself. We finally show that combining objective-type EW excitation with supercritical-angle fluorescence (SAF) detection efficiently rejects the fluorescence originating from deeper sample regions. We demonstrate that SAF improves the surface selectivity of TIRF, even at shallow penetration depths. The coplanar microscopy scheme presented here merges the benefits of beam spinning EW excitation and SAF detection and provides the conditions for quantitative wide-field imaging of fluorophore dynamics at or near the plasma membrane.
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Affiliation(s)
- Maia Brunstein
- CNRS, UMR 8154, Paris, F-75006 France; INSERM, U603, Paris, F-75006 France; Laboratoire de Neurophysiologie et Nouvelles Microscopies, Université Paris Descartes, PRES Sorbonne Paris Cité, Paris, F-75006 France
| | - Karine Hérault
- CNRS, UMR 8154, Paris, F-75006 France; INSERM, U603, Paris, F-75006 France; Laboratoire de Neurophysiologie et Nouvelles Microscopies, Université Paris Descartes, PRES Sorbonne Paris Cité, Paris, F-75006 France
| | - Martin Oheim
- CNRS, UMR 8154, Paris, F-75006 France; INSERM, U603, Paris, F-75006 France; Laboratoire de Neurophysiologie et Nouvelles Microscopies, Université Paris Descartes, PRES Sorbonne Paris Cité, Paris, F-75006 France.
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