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Trus M, Atlas D. Non-ionotropic voltage-gated calcium channel signaling. Channels (Austin) 2024; 18:2341077. [PMID: 38601983 PMCID: PMC11017947 DOI: 10.1080/19336950.2024.2341077] [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: 02/09/2024] [Accepted: 04/04/2024] [Indexed: 04/12/2024] Open
Abstract
Voltage-gated calcium channels (VGCCs) are the major conduits for calcium ions (Ca2+) within excitable cells. Recent studies have highlighted the non-ionotropic functionality of VGCCs, revealing their capacity to activate intracellular pathways independently of ion flow. This non-ionotropic signaling mode plays a pivotal role in excitation-coupling processes, including gene transcription through excitation-transcription (ET), synaptic transmission via excitation-secretion (ES), and cardiac contraction through excitation-contraction (EC). However, it is noteworthy that these excitation-coupling processes require extracellular calcium (Ca2+) and Ca2+ occupancy of the channel ion pore. Analogous to the "non-canonical" characterization of the non-ionotropic signaling exhibited by the N-methyl-D-aspartate receptor (NMDA), which requires extracellular Ca2+ without the influx of ions, VGCC activation requires depolarization-triggered conformational change(s) concomitant with Ca2+ binding to the open channel. Here, we discuss the contributions of VGCCs to ES, ET, and EC coupling as Ca2+ binding macromolecules that transduces external stimuli to intracellular input prior to elevating intracellular Ca2+. We emphasize the recognition of calcium ion occupancy within the open ion-pore and its contribution to the excitation coupling processes that precede the influx of calcium. The non-ionotropic activation of VGCCs, triggered by the upstroke of an action potential, provides a conceptual framework to elucidate the mechanistic aspects underlying the microseconds nature of synaptic transmission, cardiac contractility, and the rapid induction of first-wave genes.
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Affiliation(s)
- Michael Trus
- Department of Biological Chemistry, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Daphne Atlas
- Department of Biological Chemistry, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
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2
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Gonzalez-Rodriguez P, Zampese E, Surmeier DJ. Disease mechanisms as Subtypes: Mitochondrial and bioenergetic dysfunction. HANDBOOK OF CLINICAL NEUROLOGY 2023; 193:53-66. [PMID: 36803823 DOI: 10.1016/b978-0-323-85555-6.00007-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Parkinson disease (PD) is the second most common neurodegenerative disease in the world. Despite its enormous human and societal cost, there is no disease-modifying therapy for PD. This unmet medical need reflects our limited understanding of PD pathogenesis. One of the most important clues comes from the recognition that PD motor symptoms arises from the dysfunction and degeneration of a very select group of neurons in the brain. These neurons have a distinctive set of anatomic and physiologic traits that reflect their role in brain function. These traits elevate mitochondrial stress, potentially making them particularly vulnerable to age, as well as to genetic mutations and environmental toxins linked to PD incidence. In this chapter, the literature supporting this model is outlined, along with gaps in our knowledge base. The translational implications of this hypothesis are then discussed, with a focus on why disease-modification trials have failed to date and what this means for the development of new strategies for altering disease course.
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Affiliation(s)
- Patricia Gonzalez-Rodriguez
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla and CIBERNED, Seville, Spain
| | - Enrico Zampese
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - D James Surmeier
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States.
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Dixon RE, Trimmer JS. Endoplasmic Reticulum-Plasma Membrane Junctions as Sites of Depolarization-Induced Ca 2+ Signaling in Excitable Cells. Annu Rev Physiol 2023; 85:217-243. [PMID: 36202100 PMCID: PMC9918718 DOI: 10.1146/annurev-physiol-032122-104610] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Membrane contact sites between endoplasmic reticulum (ER) and plasma membrane (PM), or ER-PM junctions, are found in all eukaryotic cells. In excitable cells they play unique roles in organizing diverse forms of Ca2+ signaling as triggered by membrane depolarization. ER-PM junctions underlie crucial physiological processes such as excitation-contraction coupling, smooth muscle contraction and relaxation, and various forms of activity-dependent signaling and plasticity in neurons. In many cases the structure and molecular composition of ER-PM junctions in excitable cells comprise important regulatory feedback loops linking depolarization-induced Ca2+ signaling at these sites to the regulation of membrane potential. Here, we describe recent findings on physiological roles and molecular composition of native ER-PM junctions in excitable cells. We focus on recent studies that provide new insights into canonical forms of depolarization-induced Ca2+ signaling occurring at junctional triads and dyads of striated muscle, as well as the diversity of ER-PM junctions in these cells and in smooth muscle and neurons.
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Affiliation(s)
- Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California, USA;
| | - James S Trimmer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California, USA;
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4
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Shkryl VM. The spatio-temporal properties of calcium transients in hippocampal pyramidal neurons in vitro. Front Cell Neurosci 2022; 16:1054950. [PMID: 36589284 PMCID: PMC9795003 DOI: 10.3389/fncel.2022.1054950] [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: 09/28/2022] [Accepted: 11/24/2022] [Indexed: 12/15/2022] Open
Abstract
The spatio-temporal properties of calcium signals were studied in cultured pyramidal neurons of the hippocampus using two-dimensional fluorescence microscopy and ratiometric dye Fura-2. Depolarization-induced Ca2+ transients revealed an asynchronous delayed increase in free Ca2+ concentration. We found that the level of free resting calcium in the cell nucleus is significantly lower compared to the soma, sub-membrane, and dendritic tree regions. Calcium release from the endoplasmic reticulum under the action of several stimuli (field stimulation, high K+ levels, and caffeine) occurs in all areas studied. Under depolarization, calcium signals developed faster in the dendrites than in other areas, while their amplitude was significantly lower since larger and slower responses inside the soma. The peak value of the calcium response to the application of 10 mM caffeine, ryanodine receptors (RyRs) agonist, does not differ in the sub-membrane zone, central region, and nucleus but significantly decreases in the dendrites. In the presence of caffeine, the delay of Ca2+ signals between various areas under depolarization significantly declined. Thirty percentage of the peak amplitude of Ca2+ transients at prolonged electric field stimulation corresponded to calcium release from the ER store by RyRs, while short-term stimulation did not depend on them. 20 μM dantrolene, RyRs inhibitor, significantly reduces Ca2+ transient under high K+ levels depolarization of the neuron. RyRs-mediated enhancement of the Ca2+ signal is more pronounced in the central part and nucleus compared to the sub-membrane or dendrites regions of the neuron. In summary, using the ratiometric imaging allowed us to obtain additional information about the involvement of RyRs in the intracellular dynamics of Ca2+ signals induced by depolarization or electrical stimulation train, with an underlying change in Ca2+ concentration in various regions of interest in hippocampal pyramidal neurons.
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Ion Channel Partnerships: Odd and Not-So-Odd Couples Controlling Neuronal Ion Channel Function. Int J Mol Sci 2022; 23:ijms23041953. [PMID: 35216068 PMCID: PMC8878034 DOI: 10.3390/ijms23041953] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 02/05/2022] [Accepted: 02/08/2022] [Indexed: 12/04/2022] Open
Abstract
The concerted function of the large number of ion channels expressed in excitable cells, including brain neurons, shapes diverse signaling events by controlling the electrical properties of membranes. It has long been recognized that specific groups of ion channels are functionally coupled in mediating ionic fluxes that impact membrane potential, and that these changes in membrane potential impact ion channel gating. Recent studies have identified distinct sets of ion channels that can also physically and functionally associate to regulate the function of either ion channel partner beyond that afforded by changes in membrane potential alone. Here, we review canonical examples of such ion channel partnerships, in which a Ca2+ channel is partnered with a Ca2+-activated K+ channel to provide a dedicated route for efficient coupling of Ca2+ influx to K+ channel activation. We also highlight examples of non-canonical ion channel partnerships between Ca2+ channels and voltage-gated K+ channels that are not intrinsically Ca2+ sensitive, but whose partnership nonetheless yields enhanced regulation of one or the other ion channel partner. We also discuss how these ion channel partnerships can be shaped by the subcellular compartments in which they are found and provide perspectives on how recent advances in techniques to identify proteins in close proximity to one another in native cells may lead to an expanded knowledge of other ion channel partnerships.
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Sahu G, Turner RW. The Molecular Basis for the Calcium-Dependent Slow Afterhyperpolarization in CA1 Hippocampal Pyramidal Neurons. Front Physiol 2022; 12:759707. [PMID: 35002757 PMCID: PMC8730529 DOI: 10.3389/fphys.2021.759707] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 11/01/2021] [Indexed: 12/02/2022] Open
Abstract
Neuronal signal transmission depends on the frequency, pattern, and timing of spike output, each of which are shaped by spike afterhyperpolarizations (AHPs). There are classically three post-spike AHPs of increasing duration categorized as fast, medium and slow AHPs that hyperpolarize a cell over a range of 10 ms to 30 s. Intensive early work on CA1 hippocampal pyramidal cells revealed that all three AHPs incorporate activation of calcium-gated potassium channels. The ionic basis for a fAHP was rapidly attributed to the actions of big conductance (BK) and the mAHP to small conductance (SK) or Kv7 potassium channels. In stark contrast, the ionic basis for a prominent slow AHP of up to 30 s duration remained an enigma for over 30 years. Recent advances in pharmacological, molecular, and imaging tools have uncovered the expression of a calcium-gated intermediate conductance potassium channel (IK, KCa3.1) in central neurons that proves to contribute to the slow AHP in CA1 hippocampal pyramidal cells. Together the data show that the sAHP arises in part from a core tripartite complex between Cav1.3 (L-type) calcium channels, ryanodine receptors, and IK channels at endoplasmic reticulum-plasma membrane junctions. Work on the sAHP in CA1 pyramidal neurons has again quickened pace, with identified contributions by both IK channels and the Na-K pump providing answers to several mysteries in the pharmacological properties of the sAHP.
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Affiliation(s)
- Giriraj Sahu
- National Institute of Pharmaceutical Education and Research Ahmedabad, Ahmedabad, India
| | - Ray W Turner
- Department Cell Biology & Anatomy, Cumming School of Medicine, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
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Rufenach B, Van Petegem F. Structure and function of STAC proteins: Calcium channel modulators and critical components of muscle excitation-contraction coupling. J Biol Chem 2021; 297:100874. [PMID: 34129875 PMCID: PMC8258685 DOI: 10.1016/j.jbc.2021.100874] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 06/02/2021] [Accepted: 06/11/2021] [Indexed: 12/26/2022] Open
Abstract
In skeletal muscle tissue, an intriguing mechanical coupling exists between two ion channels from different membranes: the L-type voltage-gated calcium channel (CaV1.1), located in the plasma membrane, and ryanodine receptor 1 (RyR1) located in the sarcoplasmic reticulum membrane. Excitable cells rely on Cavs to initiate Ca2+ entry in response to action potentials. RyRs can amplify this signal by releasing Ca2+ from internal stores. Although this process can be mediated through Ca2+ as a messenger, an overwhelming amount of evidence suggests that RyR1 has recruited CaV1.1 directly as its voltage sensor. The exact mechanisms that underlie this coupling have been enigmatic, but a recent wave of reports have illuminated the coupling protein STAC3 as a critical player. Without STAC3, the mechanical coupling between Cav1.1 and RyR1 is lost, and muscles fail to contract. Various sequence variants of this protein have been linked to congenital myopathy. Other STAC isoforms are expressed in the brain and may serve as regulators of L-type CaVs. Despite the short length of STACs, several points of contacts have been proposed between them and CaVs. However, it is currently unclear whether STAC3 also forms direct interactions with RyR1, and whether this modulates RyR1 function. In this review, we discuss the 3D architecture of STAC proteins, the biochemical evidence for their interactions, the relevance of these connections for functional modulation, and their involvement in myopathy.
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Affiliation(s)
- Britany Rufenach
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
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8
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Vierra NC, Kirmiz M, van der List D, Santana LF, Trimmer JS. Kv2.1 mediates spatial and functional coupling of L-type calcium channels and ryanodine receptors in mammalian neurons. eLife 2019; 8:49953. [PMID: 31663850 PMCID: PMC6839919 DOI: 10.7554/elife.49953] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 10/29/2019] [Indexed: 12/16/2022] Open
Abstract
The voltage-gated K+ channel Kv2.1 serves a major structural role in the soma and proximal dendrites of mammalian brain neurons, tethering the plasma membrane (PM) to endoplasmic reticulum (ER). Although Kv2.1 clustering at neuronal ER-PM junctions (EPJs) is tightly regulated and highly conserved, its function remains unclear. By identifying and evaluating proteins in close spatial proximity to Kv2.1-containing EPJs, we discovered that a significant role of Kv2.1 at EPJs is to promote the clustering and functional coupling of PM L-type Ca2+ channels (LTCCs) to ryanodine receptor (RyR) ER Ca2+ release channels. Kv2.1 clustering also unexpectedly enhanced LTCC opening at polarized membrane potentials. This enabled Kv2.1-LTCC-RyR triads to generate localized Ca2+ release events (i.e., Ca2+ sparks) independently of action potentials. Together, these findings uncover a novel mode of LTCC regulation and establish a unique mechanism whereby Kv2.1-associated EPJs provide a molecular platform for localized somatodendritic Ca2+ signals in mammalian brain neurons.
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Affiliation(s)
- Nicholas C Vierra
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, United States.,Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, United States
| | - Michael Kirmiz
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, United States
| | - Deborah van der List
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, United States.,Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, United States
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, United States
| | - James S Trimmer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, United States.,Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, United States
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9
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Naderi R, Esmaeili-Mahani S, Abbasnejad M. Extracellular calcium influx through L-type calcium channels, intracellular calcium currents and extracellular signal-regulated kinase signaling are involved in the abscisic acid-induced precognitive and anti-anxiety effects. Biomed Pharmacother 2019; 109:582-588. [DOI: 10.1016/j.biopha.2018.10.141] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Revised: 10/14/2018] [Accepted: 10/24/2018] [Indexed: 10/27/2022] Open
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10
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Zhong W, Chebolu S, Darmani NA. Intracellular emetic signaling evoked by the L-type Ca 2+ channel agonist FPL64176 in the least shrew (Cryptotis parva). Eur J Pharmacol 2018; 834:157-168. [PMID: 29966616 DOI: 10.1016/j.ejphar.2018.06.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/09/2018] [Accepted: 06/28/2018] [Indexed: 12/20/2022]
Abstract
Ca2+ plays a major role in maintaining cellular homeostasis and regulates processes including apoptotic cell death and side-effects of cancer chemotherapy including vomiting. Currently we explored the emetic mechanisms of FPL64176, an L-type Ca2+ channel (LTCC) agonist with maximal emetogenic effect at its 10 mg/kg dose. FPL64176 evoked c-Fos immunoreactivity in shrew brainstem sections containing the vomit-associated nuclei, nucleus tractus solitarius (NTS) and dorsal motor nucleus of the vagus. FPL64176 also increased phosphorylation of proteins ERK1/2, PKCα/βII and Akt in the brainstem. Moreover, their corresponding inhibitors (PD98059, GF 109203X and LY294002, respectively) reduced FPL64176-evoked vomiting. A 30 min subcutaneous (s.c.) pretreatment with the LTCC antagonist nifedipine (10 mg/kg) abolished FPL64176-elicited vomiting, c-Fos expression, and emetic effector phosphorylation. Ryanodine receptors (RyRs) and inositol trisphosphate receptors (IP3Rs) mediate intracellular Ca2+ release from the sarcoplasmic/endoplasmic reticulum. The RyR antagonist dantrolene (i.p.), or a combination of low doses of nifedipine and dantrolene, but not the IP3R antagonist 2-APB, significantly attenuated FPL64176-induced vomiting. The serotonin type 3 receptor (5-HT3R) antagonist palonosetron (s.c.), the neurokinin 1 receptor (NK1R) antagonist netupitant (i.p.) or a combination of non-effective doses of netupitant and palonosetron showed antiemetic potential against FPL64176-evoked vomiting. Serotonin (5-HT) and substance P immunostaining revealed FPL64176-induced emesis was accompanied by an increase in 5-HT but not SP-immunoreactivity in the dorsomedial subdivision of the NTS. These findings demonstrate that Ca2+ mobilization through LTCCs and RyRs, and subsequent emetic effector phosphorylation and 5-HT release play important roles in FPL64176-induced emesis which can be prevented by 5-HT3R and NK1R antagonists.
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Affiliation(s)
- Weixia Zhong
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, 309 E. Second Street, Pomona, CA 91766, United States
| | - Seetha Chebolu
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, 309 E. Second Street, Pomona, CA 91766, United States
| | - Nissar A Darmani
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, 309 E. Second Street, Pomona, CA 91766, United States.
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11
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Maimaiti S, Frazier HN, Anderson KL, Ghoweri AO, Brewer LD, Porter NM, Thibault O. Novel calcium-related targets of insulin in hippocampal neurons. Neuroscience 2017; 364:130-142. [PMID: 28939258 DOI: 10.1016/j.neuroscience.2017.09.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 09/07/2017] [Accepted: 09/08/2017] [Indexed: 01/28/2023]
Abstract
Both insulin signaling disruption and Ca2+ dysregulation are closely related to memory loss during aging and increase the vulnerability to Alzheimer's disease (AD). In hippocampal neurons, aging-related changes in calcium regulatory pathways have been shown to lead to higher intracellular calcium levels and an increase in the Ca2+-dependent afterhyperpolarization (AHP), which is associated with cognitive decline. Recent studies suggest that insulin reduces the Ca2+-dependent AHP. Given the sensitivity of neurons to insulin and evidence that brain insulin signaling is reduced with age, insulin-mediated alterations in calcium homeostasis may underlie the beneficial actions of insulin in the brain. Indeed, increasing insulin signaling in the brain via intranasal delivery has yielded promising results such as improving memory in both clinical and animal studies. However, while several mechanisms have been proposed, few have focused on regulation on intracellular Ca2+. In the present study, we further examined the effects of acute insulin on calcium pathways in primary hippocampal neurons in culture. Using the whole-cell patch-clamp technique, we found that acute insulin delivery reduced voltage-gated calcium currents. Fura-2 imaging was used to also address acute insulin effects on spontaneous and depolarization-mediated Ca2+ transients. Results indicate that insulin reduced Ca2+ transients, which appears to have involved a reduction in ryanodine receptor function. Together, these results suggest insulin regulates pathways that control intracellular Ca2+ which may reduce the AHP and improve memory. This may be one mechanism contributing to improved memory recall in response to intranasal insulin therapy in the clinic.
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Affiliation(s)
- Shaniya Maimaiti
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, UKMC, MS-310; 800 Rose Street, Lexington, KY 40536, United States
| | - Hilaree N Frazier
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, UKMC, MS-310; 800 Rose Street, Lexington, KY 40536, United States
| | - Katie L Anderson
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, UKMC, MS-310; 800 Rose Street, Lexington, KY 40536, United States
| | - Adam O Ghoweri
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, UKMC, MS-310; 800 Rose Street, Lexington, KY 40536, United States
| | - Lawrence D Brewer
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, UKMC, MS-310; 800 Rose Street, Lexington, KY 40536, United States
| | - Nada M Porter
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, UKMC, MS-310; 800 Rose Street, Lexington, KY 40536, United States
| | - Olivier Thibault
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, UKMC, MS-310; 800 Rose Street, Lexington, KY 40536, United States.
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Zhong W, Picca AJ, Lee AS, Darmani NA. Ca2+ signaling and emesis: Recent progress and new perspectives. Auton Neurosci 2017; 202:18-27. [DOI: 10.1016/j.autneu.2016.07.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 07/21/2016] [Accepted: 07/22/2016] [Indexed: 02/07/2023]
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Khuzakhmetova VF, Nurullin LF, Bukharaeva EA, Nikolsky EE. Involvement of dihydropyridine-sensitive calcium channels in high asynchrony of transmitter release in neuromuscular synapses of newborn rats. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2016; 470:220-223. [PMID: 27822757 DOI: 10.1134/s0012496616050124] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Indexed: 06/06/2023]
Abstract
Experiments on neuromuscular synapses of rats at different stages of ontogenesis have been performed. It has been found that one of the reasons of higher asynchrony of the release of single quanta of acetylcholine in the synapses of newborn animals is the activity of the presynaptic dihydropyridine-sensitive calcium channels of the L-type.
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Affiliation(s)
- V F Khuzakhmetova
- Kazan Institute of Biochemistry and Biophysics, Kazan Scientific Center, Russian Academy of Sciences, Kazan, Tatarstan, Russia
- Kazan (Volga Region) Federal University, Kazan, Tatarstan, Russia
| | - L F Nurullin
- Kazan Institute of Biochemistry and Biophysics, Kazan Scientific Center, Russian Academy of Sciences, Kazan, Tatarstan, Russia
- Kazan (Volga Region) Federal University, Kazan, Tatarstan, Russia
| | - E A Bukharaeva
- Kazan Institute of Biochemistry and Biophysics, Kazan Scientific Center, Russian Academy of Sciences, Kazan, Tatarstan, Russia.
- Kazan (Volga Region) Federal University, Kazan, Tatarstan, Russia.
| | - E E Nikolsky
- Kazan Institute of Biochemistry and Biophysics, Kazan Scientific Center, Russian Academy of Sciences, Kazan, Tatarstan, Russia
- Kazan (Volga Region) Federal University, Kazan, Tatarstan, Russia
- Kazan State Medical University, Kazan, Tatarstan, Russia
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Zhong W, Chebolu S, Darmani NA. Thapsigargin-induced activation of Ca(2+)-CaMKII-ERK in brainstem contributes to substance P release and induction of emesis in the least shrew. Neuropharmacology 2015; 103:195-210. [PMID: 26631534 DOI: 10.1016/j.neuropharm.2015.11.023] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 10/06/2015] [Accepted: 11/23/2015] [Indexed: 11/29/2022]
Abstract
Cytoplasmic calcium (Ca(2+)) mobilization has been proposed to be an important factor in the induction of emesis. The selective sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA) inhibitor thapsigargin, is known to deplete intracellular Ca(2+) stores, which consequently evokes extracellular Ca(2+) entry through cell membrane-associated channels, accompanied by a prominent rise in cytosolic Ca(2+). A pro-drug form of thapsigargin is currently under clinical trial as a targeted cancer chemotherapeutic. We envisioned that the intracellular effects of thapsigargin could cause emesis and planned to investigate its mechanisms of emetic action. Indeed, thapsigargin did induce vomiting in the least shrew in a dose-dependent and bell-shaped manner, with maximal efficacy (100%) at 0.5 mg/kg (i.p.). Thapsigargin (0.5 mg/kg) also caused increases in c-Fos immunoreactivity in the brainstem emetic nuclei including the area postrema (AP), nucleus tractus solitarius (NTS) and dorsal motor nucleus of the vagus (DMNX), as well as enhancement of substance P (SP) immunoreactivity in DMNX. In addition, thapsigargin (0.5 mg/kg, i.p.) led to vomit-associated and time-dependent increases in phosphorylation of Ca(2+)/calmodulin kinase IIα (CaMKIIα) and extracellular signal-regulated protein kinase 1/2 (ERK1/2) in the brainstem. We then explored the suppressive potential of diverse chemicals against thapsigargin-evoked emesis including antagonists of: i) neurokinin-1 receptors (netupitant), ii) the type 3 serotonin receptors (palonosetron), iii) store-operated Ca(2+) entry (YM-58483), iv) L-type Ca(2+) channels (nifedipine), and v) SER Ca(2+)-release channels inositol trisphosphate (IP3Rs) (2-APB)-, and ryanodine (RyRs) (dantrolene)-receptors. In addition, the antiemetic potential of inhibitors of CaMKII (KN93) and ERK1/2 (PD98059) were investigated. All tested antagonists/blockers attenuated emetic parameters to varying degrees except palonosetron, however a combination of non-effective doses of netupitant and palonosetron exhibited additive antiemetic efficacy. A low-dose combination of nifedipine and 2-APB plus dantrolene mixture completely abolished thapsigargin-evoked vomiting, CaMKII-ERK1/2 activation and SP elevation. In addition, pretreatment with KN93 or PD98059 suppressed thapsigargin-induced increases in SP and ERK1/2 activation. Intracerebroventricular injection of netupitant suppressed vomiting caused by thapsigargin which suggests that the principal site of evoked emesis is the brainstem. In sum, this is the first study to demonstrate that thapsigargin causes vomiting via the activation of the Ca(2+)-CaMKII-ERK1/2 cascade, which is associated with an increase in the brainstem tissue content of SP, and the evoked emesis occurs through SP-induced activation of neurokinin-1 receptors.
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Affiliation(s)
- Weixia Zhong
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona CA 91766, USA
| | - Seetha Chebolu
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona CA 91766, USA
| | - Nissar A Darmani
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona CA 91766, USA.
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Gant JC, Blalock EM, Chen KC, Kadish I, Porter NM, Norris CM, Thibault O, Landfield PW. FK506-binding protein 1b/12.6: a key to aging-related hippocampal Ca2+ dysregulation? Eur J Pharmacol 2013; 739:74-82. [PMID: 24291098 DOI: 10.1016/j.ejphar.2013.10.070] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 10/16/2013] [Accepted: 10/17/2013] [Indexed: 12/25/2022]
Abstract
It has been recognized for some time that the Ca(2+)-dependent slow afterhyperpolarization (sAHP) is larger in hippocampal neurons of aged compared with young animals. In addition, extensive studies since have shown that other Ca(2+)-mediated electrophysiological responses are increased in hippocampus with aging, including Ca(2+) transients, L-type voltage-gated Ca(2+) channel activity, Ca(2+) spike duration and action potential accommodation. Elevated Ca(2+)-induced Ca(2+) release from ryanodine receptors (RyRs) appears to drive amplification of the Ca(2+) responses. Components of this Ca(2+) dysregulation phenotype correlate with deficits in cognitive function and plasticity, indicating they may play critical roles in aging-related impairment of brain function. However, the molecular mechanisms underlying aging-related Ca(2+) dysregulation are not well understood. FK506-binding proteins 1a and 1b (FKBP1a/1b, also known as FKBP12/12.6) are immunophilin proteins that bind the immunosuppressant drugs FK506 and rapamycin. In muscle cells, FKBP1a/1b also bind RyRs and inhibits Ca(2+)-induced Ca(2+) release, but it is not clear whether FKBPs act similarly in brain cells. Recently, we found that selectively disrupting hippocampal FKBP1b function in young rats, either by microinjecting adeno-associated viral vectors expressing siRNA, or by treatment with rapamycin, increases the sAHP and recapitulates much of the hippocampal Ca(2+) dysregulation phenotype. Moreover, in microarray studies, we found FKBP1b gene expression was downregulated in hippocampus of aging rats and early-stage Alzheimer's disease subjects. These results suggest the novel hypothesis that declining FKBP function is a key factor in aging-related Ca(2+) dysregulation in the brain and point to potential new therapeutic targets for counteracting unhealthy brain aging.
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Affiliation(s)
- J C Gant
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, 800 Rose St., UKMC Lexington, KY 40536, United States
| | - E M Blalock
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, 800 Rose St., UKMC Lexington, KY 40536, United States
| | - K-C Chen
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, 800 Rose St., UKMC Lexington, KY 40536, United States
| | - I Kadish
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, 800 Rose St., UKMC Lexington, KY 40536, United States
| | - N M Porter
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, 800 Rose St., UKMC Lexington, KY 40536, United States
| | - C M Norris
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, 800 Rose St., UKMC Lexington, KY 40536, United States
| | - O Thibault
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, 800 Rose St., UKMC Lexington, KY 40536, United States
| | - P W Landfield
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, 800 Rose St., UKMC Lexington, KY 40536, United States.
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16
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Rebello MR, Maliphol AB, Medler KF. Ryanodine Receptors Selectively Interact with L Type Calcium Channels in Mouse Taste Cells. PLoS One 2013; 8:e68174. [PMID: 23826376 PMCID: PMC3694925 DOI: 10.1371/journal.pone.0068174] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 05/27/2013] [Indexed: 12/04/2022] Open
Abstract
Introduction We reported that ryanodine receptors are expressed in two different types of mammalian peripheral taste receptor cells: Type II and Type III cells. Type II cells lack voltage-gated calcium channels (VGCCs) and chemical synapses. In these cells, ryanodine receptors contribute to the taste-evoked calcium signals that are initiated by opening inositol trisphosphate receptors located on internal calcium stores. In Type III cells that do have VGCCs and chemical synapses, ryanodine receptors contribute to the depolarization-dependent calcium influx. Methodology/Principal Findings The goal of this study was to establish if there was selectivity in the type of VGCC that is associated with the ryanodine receptor in the Type III taste cells or if the ryanodine receptor opens irrespective of the calcium channels involved. We also wished to determine if the ryanodine receptors and VGCCs require a physical linkage to interact or are simply functionally associated with each other. Using calcium imaging and pharmacological inhibitors, we found that ryanodine receptors are selectively associated with L type VGCCs but likely not through a physical linkage. Conclusions/Significance Taste cells are able to undergo calcium induced calcium release through ryanodine receptors to increase the initial calcium influx signal and provide a larger calcium response than would otherwise occur when L type channels are activated in Type III taste cells.
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Affiliation(s)
- Michelle R. Rebello
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, New York, United States of America
| | - Amanda B. Maliphol
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, New York, United States of America
| | - Kathryn F. Medler
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, New York, United States of America
- * E-mail:
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17
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Baker KD, Edwards TM, Rickard NS. The role of intracellular calcium stores in synaptic plasticity and memory consolidation. Neurosci Biobehav Rev 2013; 37:1211-39. [PMID: 23639769 DOI: 10.1016/j.neubiorev.2013.04.011] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 04/18/2013] [Accepted: 04/22/2013] [Indexed: 12/20/2022]
Abstract
Memory processing requires tightly controlled signalling cascades, many of which are dependent upon intracellular calcium (Ca(2+)). Despite this, most work investigating calcium signalling in memory formation has focused on plasma membrane channels and extracellular sources of Ca(2+). The intracellular Ca(2+) release channels, ryanodine receptors (RyRs) and inositol (1,4,5)-trisphosphate receptors (IP3Rs) have a significant capacity to regulate intracellular Ca(2+) signalling. Evidence at both cellular and behavioural levels implicates both RyRs and IP3Rs in synaptic plasticity and memory formation. Pharmacobehavioural experiments using young chicks trained on a single-trial discrimination avoidance task have been particularly useful by demonstrating that RyRs and IP3Rs have distinct roles in memory formation. RyR-dependent Ca(2+) release appears to aid the consolidation of labile memory into a persistent long-term memory trace. In contrast, IP3Rs are required during long-term memory. This review discusses various functions for RyRs and IP3Rs in memory processing, including neuro- and glio-transmitter release, dendritic spine remodelling, facilitating vasodilation, and the regulation of gene transcription and dendritic excitability. Altered Ca(2+) release from intracellular stores also has significant implications for neurodegenerative conditions.
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Affiliation(s)
- Kathryn D Baker
- School of Psychology and Psychiatry, Monash University, Clayton 3800, Victoria, Australia.
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18
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Thr136Ile polymorphism of human vesicular monoamine transporter-1 (SLC18A1 gene) influences its transport activity in vitro. Neural Plast 2013; 2012:945373. [PMID: 23213575 PMCID: PMC3504448 DOI: 10.1155/2012/945373] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 09/22/2012] [Accepted: 09/23/2012] [Indexed: 12/23/2022] Open
Abstract
The hippocampus has the extraordinary capacity to process and store information. Consequently, there is an intense interest in the mechanisms that underline learning and memory. Synaptic plasticity has been hypothesized to be the neuronal substrate for learning. Ca2+ and Ca2+-activated kinases control cellular processes of most forms of hippocampal synapse plasticity. In this paper, I aim to integrate our current understanding of Ca2+-mediated synaptic plasticity and metaplasticity in motivational and reward-related learning in the hippocampus. I will introduce two representative neuromodulators that are widely studied in reward-related learning (e.g., ghrelin and endocannabinoids) and show how they might contribute to hippocampal neuron activities and Ca2+-mediated signaling processes in synaptic plasticity. Additionally, I will discuss functional significance of these two systems and their signaling pathways for its relevance to maladaptive reward learning leading to addiction.
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19
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Miyazaki K, Manita S, Ross WN. Developmental profile of localized spontaneous Ca(2+) release events in the dendrites of rat hippocampal pyramidal neurons. Cell Calcium 2012; 52:422-32. [PMID: 22951184 DOI: 10.1016/j.ceca.2012.08.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 07/03/2012] [Accepted: 08/02/2012] [Indexed: 10/28/2022]
Abstract
Recent experiments demonstrate that localized spontaneous Ca(2+) release events can be detected in the dendrites of pyramidal cells in the hippocampus and other neurons (J. Neurosci. 29 (2009) 7833-7845). These events have some properties that resemble ryanodine receptor mediated "sparks" in myocytes, and some that resemble IP(3) receptor mediated "puffs" in oocytes. They can be detected in the dendrites of rats of all tested ages between P3 and P80 (with sparser sampling in older rats), suggesting that they serve a general signaling function and are not just important in development. However, in younger rats the amplitudes of the events are larger than the amplitudes in older animals and almost as large as the amplitudes of Ca(2+) signals from backpropagating action potentials (bAPs). The rise time of the event signal is fast at all ages and is comparable to the rise time of the bAP fluorescence signal at the same dendritic location. The decay time is slower in younger animals, primarily because of weaker Ca(2+) extrusion mechanisms at that age. Diffusion away from a brief localized source is the major determinant of decay at all ages. A simple computational model closely simulates these events with extrusion rate the only age dependent variable.
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Affiliation(s)
- Kenichi Miyazaki
- Department of Physiology, New York Medical College, Valhalla, NY 10595, United States
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20
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Beltran-Parrazal L, Fernandez-Ruiz J, Toledo R, Manzo J, Morgado-Valle C. Inhibition of endoplasmic reticulum Ca²⁺ ATPase in preBötzinger complex of neonatal rat does not affect respiratory rhythm generation. Neuroscience 2012; 224:116-24. [PMID: 22906476 DOI: 10.1016/j.neuroscience.2012.08.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 08/03/2012] [Accepted: 08/13/2012] [Indexed: 10/28/2022]
Abstract
PreBötzinger complex (preBötC) neurons in the brainstem underlie respiratory rhythm generation in vitro. As a result of network interactions, preBötC neurons burst synchronously to produce rhythmic premotor inspiratory activity. Each inspiratory neuron has a characteristic 10-20 mV, 0.3-0.8 s synchronous depolarization known as the inspiratory drive potential or inspiratory envelope, topped by action potentials (APs). Mechanisms involving Ca(2+) fluxes have been proposed to underlie the initiation of the inspiratory drive potential. An important source of intracellular Ca(2+) is the endoplasmic reticulum (ER) in which active Ca(2+) sequestration is mediated by a class of transporters termed sarco/endoplasmic reticulum Ca(2+) ATPases (SERCAs). We aim to test the hypothesis that disruption of Ca(2+) sequestration into the ER affects respiratory rhythm generation. We examined the effect of inhibiting SERCA on respiratory rhythm generation in an in vitro slice preparation. Bath application of the potent SERCA inhibitors thapsigargin or cyclopiazonic acid (CPA) for up to 90 min did not significantly affect the period or amplitude of respiratory-related motor output or integral and duration of inspiratory drive in preBötC neurons. We promoted the depletion of intracellular Ca(2+) stores by a transient bath application of 30 mM K(+) (high K(+)) in the continuous presence of thapsigargin or CPA. After washing out the high K(+), respiratory rhythm period and amplitude returned to baseline values. These results show that after inhibition of SERCA and depletion of intracellular Ca(2+) stores, respiratory rhythm remains substantially the same, suggesting that this source of Ca(2+) does not significantly contribute to rhythm generation in the preBötC in vitro.
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Affiliation(s)
- L Beltran-Parrazal
- Centro de Investigaciones Cerebrales, Direccion General de Investigaciones, Universidad Veracruzana, Mexico
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21
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Abstract
All cells use changes in intracellular calcium concentration ([Ca(2+)](i)) to regulate cell signalling events. In neurons, with their elaborate dendritic and axonal arborizations, there are clear examples of both localized and widespread Ca(2+) signals. [Ca(2+)](i) changes that are generated by Ca(2+) entry through voltage- and ligand-gated channels are the best characterized. In addition, the release of Ca(2+) from intracellular stores can result in increased [Ca(2+)](i); the signals that trigger this release have been less well-studied, in part because they are not usually associated with specific changes in membrane potential. However, recent experiments have revealed dramatic widespread Ca(2+) waves and localized spark-like events, particularly in dendrites. Here we review emerging data on the nature of these signals and their functions.
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Jungbluth H, Dowling JJ, Ferreiro A, Muntoni F. 182nd ENMC International Workshop: RYR1-related myopathies, 15-17th April 2011, Naarden, The Netherlands. Neuromuscul Disord 2012; 22:453-62. [PMID: 22226685 DOI: 10.1016/j.nmd.2011.12.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 12/04/2011] [Indexed: 11/15/2022]
Affiliation(s)
- Heinz Jungbluth
- Clinical Neuroscience Division, IOP, King's College, London, United Kingdom.
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23
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Abstract
This review lays out the emerging evidence for the fundamental role of Ca(2+) stores and store-operated channels in the Ca(2+) homeostasis of rods and cones. Calcium-induced calcium release (CICR) is a major contributor to steady-state and light-evoked photoreceptor Ca(2+) homeostasis in the darkness whereas store-operated Ca(2+) channels play a more significant role under sustained illumination conditions. The homeostatic response includes dynamic interactions between the plasma membrane, endoplasmic reticulum (ER), mitochondria and/or outer segment disk organelles which dynamically sequester, accumulate and release Ca(2+). Coordinated activation of SERCA transporters, ryanodine receptors (RyR), inositol triphosphate receptors (IP3Rs) and TRPC channels amplifies cytosolic voltage-operated signals but also provides a memory trace of previous exposures to light. Store-operated channels, activated by the STIM1 sensor, prevent pathological decrease in [Ca(2+)]i mediated by excessive activation of PMCA transporters in saturating light. CICR and SOCE may also modulate the transmission of afferent and efferent signals in the outer retina. Thus, Ca(2+) stores provide additional complexity, adaptability, tuneability and speed to photoreceptor signaling.
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Affiliation(s)
- David Križaj
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
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Type 1 ryanodine receptor knock-in mutation causing central core disease of skeletal muscle also displays a neuronal phenotype. Proc Natl Acad Sci U S A 2011; 109:610-5. [PMID: 22203976 DOI: 10.1073/pnas.1115111108] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The type 1 ryanodine receptor (RyR1) is expressed widely in the brain, with high levels in the cerebellum, hippocampus, and hypothalamus. We have shown that L-type Ca(2+) channels in terminals of hypothalamic magnocellular neurons are coupled to RyRs, as they are in skeletal muscle, allowing voltage-induced Ca(2+) release (VICaR) from internal Ca(2+) stores without Ca(2+) influx. Here we demonstrate that RyR1 plays a role in VICaR in nerve terminals. Furthermore, in heterozygotes from the Ryr1(I4895T/WT) (IT/+) mouse line, carrying a knock-in mutation corresponding to one that causes a severe form of human central core disease, VICaR is absent, demonstrating that type 1 RyR mediates VICaR and that these mice have a neuronal phenotype. The absence of VICaR was shown in two ways: first, depolarization in the absence of Ca(2+) influx elicited Ca(2+)syntillas (scintilla, spark, in a nerve terminal, a SYNaptic structure) in WT, but not in mutant terminals; second, in the presence of extracellular Ca(2+), IT/+ terminals showed a twofold decrease in global Ca(2+) transients, with no change in plasmalemmal Ca(2+) current. From these studies we draw two conclusions: (i) RyR1 plays a role in VICaR in hypothalamic nerve terminals; and (ii) a neuronal alteration accompanies the myopathy in IT/+ mice, and, possibly in humans carrying the corresponding RyR1 mutation.
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25
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Structural and functional differences between L-type calcium channels: crucial issues for future selective targeting. Trends Pharmacol Sci 2011; 32:366-75. [DOI: 10.1016/j.tips.2011.02.012] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 02/07/2011] [Accepted: 02/17/2011] [Indexed: 11/21/2022]
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Disrupting function of FK506-binding protein 1b/12.6 induces the Ca²+-dysregulation aging phenotype in hippocampal neurons. J Neurosci 2011; 31:1693-703. [PMID: 21289178 DOI: 10.1523/jneurosci.4805-10.2011] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
With aging, multiple Ca(2+)-associated electrophysiological processes exhibit increased magnitude in hippocampal pyramidal neurons, including the Ca(2+)-dependent slow afterhyperpolarization (sAHP), L-type voltage-gated Ca(2+) channel (L-VGCC) activity, Ca(2+)-induced Ca(2+) release (CICR) from ryanodine receptors (RyRs), and Ca(2+) transients. This pattern of Ca(2+) dysregulation correlates with reduced neuronal excitability/plasticity and impaired learning/memory and has been proposed to contribute to unhealthy brain aging and Alzheimer's disease. However, little is known about the underlying molecular mechanisms. In cardiomyocytes, FK506-binding protein 1b/12.6 (FKBP1b) binds and stabilizes RyR2 in the closed state, inhibiting RyR-mediated Ca(2+) release. Moreover, we recently found that hippocampal Fkbp1b expression is downregulated, whereas Ryr2 and Frap1/Mtor (mammalian target of rapamycin) expression is upregulated with aging in rats. Here, we tested the hypothesis that disrupting FKBP1b function also destabilizes Ca(2+) homeostasis in hippocampal neurons and is sufficient to induce the aging phenotype of Ca(2+) dysregulation in young animals. Selective knockdown of Fkbp1b with interfering RNA in vitro (96 h) enhanced voltage-gated Ca(2+) current in cultured neurons, whereas in vivo Fkbp1b knockdown by microinjection of viral vector (3-4 weeks) dramatically increased the sAHP in hippocampal slice neurons from young-adult rats. Rapamycin, which displaces FKBP1b from RyRs in myocytes, similarly enhanced VGCC current and the sAHP and also increased CICR. Moreover, FKBP1b knockdown in vivo was associated with upregulation of RyR2 and mTOR protein expression. Thus, disruption of FKBP1b recapitulated much of the Ca(2+)-dysregulation aging phenotype in young rat hippocampus, supporting a novel hypothesis that declining FKBP function plays a major role in unhealthy brain aging.
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Rebello MR, Medler KF. Ryanodine receptors selectively contribute to the formation of taste-evoked calcium signals in mouse taste cells. Eur J Neurosci 2010; 32:1825-35. [PMID: 20955474 DOI: 10.1111/j.1460-9568.2010.07463.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The peripheral taste system uses multiple signaling pathways to transduce a stimulus into an output signal that activates afferent neurons. All of these signaling pathways depend on transient increases in intracellular calcium, but current understanding of these calcium signals is not well developed. Using molecular and physiological techniques, this study establishes that ryanodine receptors (RyRs), specifically isoform 1, are expressed in taste cells and that their physiological function differs among cell types employing different signaling pathways. RyR1 contributes to some taste-evoked signals that rely on calcium release from internal stores but can also supplement the calcium signal that is initiated by opening voltage-gated calcium channels. In taste cells expressing both signaling pathways, RyR1 contributes to the depolarization-induced calcium signal but not to the calcium signal that depends on calcium release from stores. These data suggest that RyR1 is an important regulator of calcium signaling and that its physiological role in taste cells is dictated by the nature of the calcium signaling mechanisms expressed.
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Affiliation(s)
- Michelle R Rebello
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
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