1
|
Akizawa H, Lopes EM, Fissore RA. Zn 2+ is essential for Ca 2+ oscillations in mouse eggs. eLife 2023; 12:RP88082. [PMID: 38099643 PMCID: PMC10723796 DOI: 10.7554/elife.88082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2023] Open
Abstract
Changes in the intracellular concentration of free calcium (Ca2+) underpin egg activation and initiation of development in animals and plants. In mammals, the Ca2+ release is periodical, known as Ca2+ oscillations, and mediated by the type 1 inositol 1,4,5-trisphosphate receptor (IP3R1). Another divalent cation, zinc (Zn2+), increases exponentially during oocyte maturation and is vital for meiotic transitions, arrests, and polyspermy prevention. It is unknown if these pivotal cations interplay during fertilization. Here, using mouse eggs, we showed that basal concentrations of labile Zn2+ are indispensable for sperm-initiated Ca2+ oscillations because Zn2+-deficient conditions induced by cell-permeable chelators abrogated Ca2+ responses evoked by fertilization and other physiological and pharmacological agonists. We also found that chemically or genetically generated eggs with lower levels of labile Zn2+ displayed reduced IP3R1 sensitivity and diminished ER Ca2+ leak despite the stable content of the stores and IP3R1 mass. Resupplying Zn2+ restarted Ca2+ oscillations, but excessive Zn2+ prevented and terminated them, hindering IP3R1 responsiveness. The findings suggest that a window of Zn2+ concentrations is required for Ca2+ responses and IP3R1 function in eggs, ensuring optimal response to fertilization and egg activation.
Collapse
Affiliation(s)
- Hiroki Akizawa
- Department of Veterinary and Animal Sciences, University of Massachusetts AmherstAmherstUnited States
| | - Emily M Lopes
- Department of Veterinary and Animal Sciences, University of Massachusetts AmherstAmherstUnited States
- Molecular and Cellular Biology Graduate Program, University of MassachusettsAmherstUnited States
| | - Rafael A Fissore
- Department of Veterinary and Animal Sciences, University of Massachusetts AmherstAmherstUnited States
| |
Collapse
|
2
|
Akizawa H, Lopes E, Fissore RA. Zn 2+ is Essential for Ca 2+ Oscillations in Mouse Eggs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.13.536745. [PMID: 37131581 PMCID: PMC10153198 DOI: 10.1101/2023.04.13.536745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Changes in the intracellular concentration of free calcium (Ca2+) underpin egg activation and initiation of development in animals and plants. In mammals, the Ca2+ release is periodical, known as Ca2+ oscillations, and mediated by the type 1 inositol 1,4,5-trisphosphate receptor (IP3R1). Another divalent cation, zinc (Zn2+), increases exponentially during oocyte maturation and is vital for meiotic transitions, arrests, and polyspermy prevention. It is unknown if these pivotal cations interplay during fertilization. Here, using mouse eggs, we showed that basal concentrations of labile Zn2+ are indispensable for sperm-initiated Ca2+ oscillations because Zn2+-deficient conditions induced by cell-permeable chelators abrogated Ca2+ responses evoked by fertilization and other physiological and pharmacological agonists. We also found that chemically- or genetically generated eggs with lower levels of labile Zn2+ displayed reduced IP3R1 sensitivity and diminished ER Ca2+ leak despite the stable content of the stores and IP3R1 mass. Resupplying Zn2+ restarted Ca2+ oscillations, but excessive Zn2+ prevented and terminated them, hindering IP3R1 responsiveness. The findings suggest that a window of Zn2+ concentrations is required for Ca2+ responses and IP3R1 function in eggs, ensuring optimal response to fertilization and egg activation.
Collapse
Affiliation(s)
- Hiroki Akizawa
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, 661 North Pleasant Street, Amherst, Massachusetts, 01003, United States
| | - Emily Lopes
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, 661 North Pleasant Street, Amherst, Massachusetts, 01003, United States
- Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, Massachusetts, 01003, United States
| | - Rafael A. Fissore
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, 661 North Pleasant Street, Amherst, Massachusetts, 01003, United States
| |
Collapse
|
3
|
Dorward AM, Stewart AJ, Pitt SJ. The role of Zn2+ in shaping intracellular Ca2+ dynamics in the heart. J Gen Physiol 2023; 155:e202213206. [PMID: 37326614 PMCID: PMC10276528 DOI: 10.1085/jgp.202213206] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 04/18/2023] [Accepted: 05/22/2023] [Indexed: 06/17/2023] Open
Abstract
Increasing evidence suggests that Zn2+ acts as a second messenger capable of transducing extracellular stimuli into intracellular signaling events. The importance of Zn2+ as a signaling molecule in cardiovascular functioning is gaining traction. In the heart, Zn2+ plays important roles in excitation-contraction (EC) coupling, excitation-transcription coupling, and cardiac ventricular morphogenesis. Zn2+ homeostasis in cardiac tissue is tightly regulated through the action of a combination of transporters, buffers, and sensors. Zn2+ mishandling is a common feature of various cardiovascular diseases. However, the precise mechanisms controlling the intracellular distribution of Zn2+ and its variations during normal cardiac function and during pathological conditions are not fully understood. In this review, we consider the major pathways by which the concentration of intracellular Zn2+ is regulated in the heart, the role of Zn2+ in EC coupling, and discuss how Zn2+ dyshomeostasis resulting from altered expression levels and efficacy of Zn2+ regulatory proteins are key drivers in the progression of cardiac dysfunction.
Collapse
Affiliation(s)
- Amy M. Dorward
- School of Medicine, University of St Andrews, St Andrews, UK
| | - Alan J. Stewart
- School of Medicine, University of St Andrews, St Andrews, UK
| | | |
Collapse
|
4
|
Tambeaux A, Aguilar-Sánchez Y, Santiago DJ, Mascitti M, DiNovo KM, Mejía-Alvarez R, Fill M, Wayne Chen SR, Ramos-Franco J. Ligand sensitivity of type-1 inositol 1,4,5-trisphosphate receptor is enhanced by the D2594K mutation. Pflugers Arch 2023; 475:569-581. [PMID: 36881190 PMCID: PMC10105685 DOI: 10.1007/s00424-023-02796-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 02/06/2023] [Accepted: 02/12/2023] [Indexed: 03/08/2023]
Abstract
Inositol 1,4,5-trisphosphate receptor (IP3R) and ryanodine receptor (RyR) are homologous cation channels that mediate release of Ca2+ from the endoplasmic/sarcoplasmic reticulum (ER/SR) and thereby are involved in many physiological processes. In previous studies, we determined that when the D2594 residue, located at or near the gate of the IP3R type 1, was replaced by lysine (D2594K), a gain of function was obtained. This mutant phenotype was characterized by increased IP3 sensitivity. We hypothesized the IP3R1-D2594 determines the ligand sensitivity of the channel by electrostatically affecting the stability of the closed and open states. To test this possibility, the relationship between the D2594 site and IP3R1 regulation by IP3, cytosolic, and luminal Ca2+ was determined at the cellular, subcellular, and single-channel levels using fluorescence Ca2+ imaging and single-channel reconstitution. We found that in cells, D2594K mutation enhances the IP3 ligand sensitivity. Single-channel IP3R1 studies revealed that the conductance of IP3R1-WT and -D2594K channels is similar. However, IP3R1-D2594K channels exhibit higher IP3 sensitivity, with substantially greater efficacy. In addition, like its wild type (WT) counterpart, IP3R1-D2594K showed a bell-shape cytosolic Ca2+-dependency, but D2594K had greater activity at each tested cytosolic free Ca2+ concentration. The IP3R1-D2594K also had altered luminal Ca2+ sensitivity. Unlike IP3R1-WT, D2594K channel activity did not decrease at low luminal Ca2+ levels. Taken together, our functional studies indicate that the substitution of a negatively charged residue by a positive one at the channels' pore cytosolic exit affects the channel's gating behavior thereby explaining the enhanced ligand-channel's sensitivity.
Collapse
Affiliation(s)
- Allison Tambeaux
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA
| | - Yuriana Aguilar-Sánchez
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA.,Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Demetrio J Santiago
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA.,Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain
| | | | - Karyn M DiNovo
- Department of Physiology, Midwestern University, Downers Grove, IL, USA
| | | | - Michael Fill
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA
| | - S R Wayne Chen
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA.,Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, AB, Canada
| | - Josefina Ramos-Franco
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA.
| |
Collapse
|
5
|
Neumann J, Van Nieuwenhove E, Terry LE, Staels F, Knebel TR, Welkenhuyzen K, Ahmadzadeh K, Baker MR, Gerbaux M, Willemsen M, Barber JS, Serysheva II, De Waele L, Vermeulen F, Schlenner S, Meyts I, Yule DI, Bultynck G, Schrijvers R, Humblet-Baron S, Liston A. Disrupted Ca 2+ homeostasis and immunodeficiency in patients with functional IP 3 receptor subtype 3 defects. Cell Mol Immunol 2023; 20:11-25. [PMID: 36302985 PMCID: PMC9794825 DOI: 10.1038/s41423-022-00928-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 09/12/2022] [Indexed: 11/27/2022] Open
Abstract
Calcium signaling is essential for lymphocyte activation, with genetic disruptions of store-operated calcium (Ca2+) entry resulting in severe immunodeficiency. The inositol 1,4,5-trisphosphate receptor (IP3R), a homo- or heterotetramer of the IP3R1-3 isoforms, amplifies lymphocyte signaling by releasing Ca2+ from endoplasmic reticulum stores following antigen stimulation. Although knockout of all IP3R isoforms in mice causes immunodeficiency, the seeming redundancy of the isoforms is thought to explain the absence of variants in human immunodeficiency. In this study, we identified compound heterozygous variants of ITPR3 (a gene encoding IP3R subtype 3) in two unrelated Caucasian patients presenting with immunodeficiency. To determine whether ITPR3 variants act in a nonredundant manner and disrupt human immune responses, we characterized the Ca2+ signaling capacity, the lymphocyte response, and the clinical phenotype of these patients. We observed disrupted Ca2+ signaling in patient-derived fibroblasts and immune cells, with abnormal proliferation and activation responses following T-cell receptor stimulation. Reconstitution of IP3R3 in IP3R knockout cell lines led to the identification of variants as functional hypomorphs that showed reduced ability to discriminate between homeostatic and induced states, validating a genotype-phenotype link. These results demonstrate a functional link between defective endoplasmic reticulum Ca2+ channels and immunodeficiency and identify IP3Rs as diagnostic targets for patients with specific inborn errors of immunity. These results also extend the known cause of Ca2+-associated immunodeficiency from store-operated entry to impaired Ca2+ mobilization from the endoplasmic reticulum, revealing a broad sensitivity of lymphocytes to genetic defects in Ca2+ signaling.
Collapse
Affiliation(s)
- Julika Neumann
- VIB Center for Brain and Disease Research, Leuven, Belgium
- Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium
| | - Erika Van Nieuwenhove
- VIB Center for Brain and Disease Research, Leuven, Belgium
- Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium
- UZ Leuven, Leuven, Belgium
| | - Lara E Terry
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY, 14526, USA
| | - Frederik Staels
- Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium
- UZ Leuven, Leuven, Belgium
| | - Taylor R Knebel
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY, 14526, USA
| | - Kirsten Welkenhuyzen
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Leuven Kankerinstituut, KU Leuven, Leuven, Belgium
| | - Kourosh Ahmadzadeh
- Laboratory of Immunobiology, Department Microbiology and Immunology, Rega Institute, KU Leuven, Leuven, Belgium
| | - Mariah R Baker
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, 77030, USA
| | - Margaux Gerbaux
- Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium
- Pediatric Department, Academic Children Hospital Queen Fabiola, Université Libre de Bruxelles, Brussels, Belgium
| | - Mathijs Willemsen
- VIB Center for Brain and Disease Research, Leuven, Belgium
- Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium
| | - John S Barber
- VIB Center for Brain and Disease Research, Leuven, Belgium
- Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium
| | - Irina I Serysheva
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, 77030, USA
| | - Liesbeth De Waele
- Department of Pediatric Neurology, University Hospitals Leuven, Leuven, Belgium
| | | | - Susan Schlenner
- Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium
| | - Isabelle Meyts
- UZ Leuven, Leuven, Belgium.
- Laboratory for Inborn Errors of Immunity, Department of Immunology and Microbiology, KU Leuven, Leuven, Belgium.
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY, 14526, USA
| | - Geert Bultynck
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Leuven Kankerinstituut, KU Leuven, Leuven, Belgium
| | - Rik Schrijvers
- UZ Leuven, Leuven, Belgium.
- Laboratory for Allergy and Clinical Immunology and Immunogenetics Research Group, Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium.
| | | | - Adrian Liston
- VIB Center for Brain and Disease Research, Leuven, Belgium.
- Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium.
- Immunology Programme, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK.
| |
Collapse
|
6
|
Binding of the erlin1/2 complex to the third intralumenal loop of IP 3R1 triggers its ubiquitin-proteasomal degradation. J Biol Chem 2022; 298:102026. [PMID: 35568199 PMCID: PMC9168715 DOI: 10.1016/j.jbc.2022.102026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 05/04/2022] [Accepted: 05/05/2022] [Indexed: 11/21/2022] Open
Abstract
Long-term activation of inositol 1,4,5-trisphosphate receptors (IP3Rs) leads to their degradation by the ubiquitin–proteasome pathway. The first and rate-limiting step in this process is thought to be the association of conformationally active IP3Rs with the erlin1/2 complex, an endoplasmic reticulum–located oligomer of erlin1 and erlin2 that recruits the E3 ubiquitin ligase RNF170, but the molecular determinants of this interaction remain unknown. Here, through mutation of IP3R1, we show that the erlin1/2 complex interacts with the IP3R1 intralumenal loop 3 (IL3), the loop between transmembrane (TM) helices 5 and 6, and in particular, with a region close to TM5, since mutation of amino acids D-2471 and R-2472 can specifically block erlin1/2 complex association. Surprisingly, we found that additional mutations in IL3 immediately adjacent to TM5 (e.g., D2465N) almost completely abolish IP3R1 Ca2+ channel activity, indicating that the integrity of this region is critical to IP3R1 function. Finally, we demonstrate that inhibition of the ubiquitin-activating enzyme UBE1 by the small-molecule inhibitor TAK-243 completely blocked IP3R1 ubiquitination and degradation without altering erlin1/2 complex association, confirming that association of the erlin1/2 complex is the primary event that initiates IP3R1 processing and that IP3R1 ubiquitination mediates IP3R1 degradation. Overall, these data localize the erlin1/2 complex–binding site on IP3R1 to IL3 and show that the region immediately adjacent to TM5 is key to the events that facilitate channel opening.
Collapse
|
7
|
Gaburjakova J, Gaburjakova M. The Cardiac Ryanodine Receptor Provides a Suitable Pathway for the Rapid Transport of Zinc (Zn2+). Cells 2022; 11:cells11050868. [PMID: 35269490 PMCID: PMC8909583 DOI: 10.3390/cells11050868] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 02/25/2022] [Accepted: 03/01/2022] [Indexed: 12/13/2022] Open
Abstract
The sarcoplasmic reticulum (SR) in cardiac muscle is suggested to act as a dynamic storage for Zn2+ release and reuptake, albeit it is primarily implicated in the Ca2+ signaling required for the cardiac cycle. A large Ca2+ release from the SR is mediated by the cardiac ryanodine receptor (RYR2), and while this has a prominent conductance for Ca2+ in vivo, it also conducts other divalent cations in vitro. Since Zn2+ and permeant Mg2+ have similar physical properties, we tested if the RYR2 channel also conducts Zn2+. Using the method of planar lipid membranes, we evidenced that the RYR2 channel is permeable to Zn2+ with a considerable conductance of 81.1 ± 2.4 pS, which was significantly lower than the values for Ca2+ (127.5 ± 1.8 pS) and Mg2+ (95.3 ± 1.4 pS), obtained under the same asymmetric conditions. Despite similar physical properties, the intrinsic Zn2+ permeability (PCa/PZn = 2.65 ± 0.19) was found to be ~2.3-fold lower than that of Mg2+ (PCa/PMg = 1.146 ± 0.071). Further, we assessed whether the channel itself could be a direct target of the Zn2+ current, having the Zn2+ finger extended into the cytosolic vestibular portion of the permeation pathway. We attempted to displace Zn2+ from the RYR2 Zn2+ finger to induce its structural defects, which are associated with RYR2 dysfunction. Zn2+ chelators were added to the channel cytosolic side or strongly competing cadmium cations (Cd2+) were allowed to permeate the RYR2 channel. Only the Cd2+ current was able to cause the decay of channel activity, presumably as a result of Zn2+ to Cd2+ replacement. Our findings suggest that the RYR2 channel can provide a suitable pathway for rapid Zn2+ escape from the cardiac SR; thus, the channel may play a role in local and/or global Zn2+ signaling in cardiomyocytes.
Collapse
|
8
|
Baker MR, Fan G, Seryshev AB, Agosto MA, Baker ML, Serysheva II. Cryo-EM structure of type 1 IP 3R channel in a lipid bilayer. Commun Biol 2021; 4:625. [PMID: 34035440 PMCID: PMC8149723 DOI: 10.1038/s42003-021-02156-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 04/26/2021] [Indexed: 12/11/2022] Open
Abstract
Type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) is the predominant Ca2+-release channel in neurons. IP3R1 mediates Ca2+ release from the endoplasmic reticulum into the cytosol and thereby is involved in many physiological processes. Here, we present the cryo-EM structures of full-length rat IP3R1 reconstituted in lipid nanodisc and detergent solubilized in the presence of phosphatidylcholine determined in ligand-free, closed states by single-particle electron cryo-microscopy. Notably, both structures exhibit the well-established IP3R1 protein fold and reveal a nearly complete representation of lipids with similar locations of ordered lipids bound to the transmembrane domains. The lipid-bound structures show improved features that enabled us to unambiguously build atomic models of IP3R1 including two membrane associated helices that were not previously resolved in the TM region. Our findings suggest conserved locations of protein-bound lipids among homotetrameric ion channels that are critical for their structural and functional integrity despite the diversity of structural mechanisms for their gating. 3D structure of full-length rat type 1 inositol 1,4,5-trisphosphate receptor reconstituted in lipid nanodisc is determined using single-particle cryo-electron microscopy. The study suggests conserved locations of protein-bound lipids among structurally diverse, homo-tetrameric ion channels.
Collapse
Affiliation(s)
- Mariah R Baker
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Guizhen Fan
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Alexander B Seryshev
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Melina A Agosto
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
| | - Matthew L Baker
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Irina I Serysheva
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA.
| |
Collapse
|
9
|
Ivanova H, Vervliet T, Monaco G, Terry LE, Rosa N, Baker MR, Parys JB, Serysheva II, Yule DI, Bultynck G. Bcl-2-Protein Family as Modulators of IP 3 Receptors and Other Organellar Ca 2+ Channels. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035089. [PMID: 31501195 DOI: 10.1101/cshperspect.a035089] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The pro- and antiapoptotic proteins belonging to the B-cell lymphoma-2 (Bcl-2) family exert a critical control over cell-death processes by enabling or counteracting mitochondrial outer membrane permeabilization. Beyond this mitochondrial function, several Bcl-2 family members have emerged as critical modulators of intracellular Ca2+ homeostasis and dynamics, showing proapoptotic and antiapoptotic functions. Bcl-2 family proteins specifically target several intracellular Ca2+-transport systems, including organellar Ca2+ channels: inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs), Ca2+-release channels mediating Ca2+ flux from the endoplasmic reticulum, as well as voltage-dependent anion channels (VDACs), which mediate Ca2+ flux across the mitochondrial outer membrane into the mitochondria. Although the formation of protein complexes between Bcl-2 proteins and these channels has been extensively studied, a major advance during recent years has been elucidating the complex interaction of Bcl-2 proteins with IP3Rs. Distinct interaction sites for different Bcl-2 family members were identified in the primary structure of IP3Rs. The unique molecular profiles of these Bcl-2 proteins may account for their distinct functional outcomes when bound to IP3Rs. Furthermore, Bcl-2 inhibitors used in cancer therapy may affect IP3R function as part of their proapoptotic effect and/or as an adverse effect in healthy cells.
Collapse
Affiliation(s)
- Hristina Ivanova
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, B-3000 Leuven, Belgium
| | - Tim Vervliet
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, B-3000 Leuven, Belgium
| | - Giovanni Monaco
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, B-3000 Leuven, Belgium
| | - Lara E Terry
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642
| | - Nicolas Rosa
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, B-3000 Leuven, Belgium
| | - Mariah R Baker
- Department of Biochemistry and Molecular Biology, McGovern Medical School at The University of Texas Health Science Center at Houston, Structural Biology Imaging Center, Houston, Texas 77030
| | - Jan B Parys
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, B-3000 Leuven, Belgium
| | - Irina I Serysheva
- Department of Biochemistry and Molecular Biology, McGovern Medical School at The University of Texas Health Science Center at Houston, Structural Biology Imaging Center, Houston, Texas 77030
| | - David I Yule
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642
| | - Geert Bultynck
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, B-3000 Leuven, Belgium
| |
Collapse
|
10
|
Cao X, Chen J, Li D, Xie P, Xu M, Lin W, Li S, Pan G, Tang Y, Xu J, Olkkonen VM, Yan D, Zhong W. ORP4L couples IP 3 to ITPR1 in control of endoplasmic reticulum calcium release. FASEB J 2019; 33:13852-13865. [PMID: 31648575 DOI: 10.1096/fj.201900933rr] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Oxysterol-binding protein-related protein (ORP) 4L acts as a scaffold protein assembling CD3-ε, G-αq/11, and PLC-β3 into a complex at the plasma membrane that mediates inositol (1,4,5)-trisphosphate (IP3)-induced endoplasmic reticulum (ER) Ca2+ release and oxidative phosphorylation in T-cell acute lymphoblastic leukemia cells. Here, we offer new evidence that ORP4L interacts with the carboxyl terminus of the IP3 receptor type 1 (ITPR1) in Jurkat T cells. ORP4L enables IP3 binding to ITPR1; a truncated construct that lacks the ITPR1-binding region retains the ability to increase IP3 production but fails to mediate IP3 and ITPR1 binding. In association with this ability of ORP4L, it enhances Ca2+ release from the ER and subsequent cytosolic and mitochondrial parallel Ca2+ spike oscillations that stimulate mitochondrial energetics and thus maintains cell survival. These data support a novel model in which ORP4L is a cofactor of ITPR1, which increases ITPR1 sensitivity to IP3 and enables ER Ca2+ release.-Cao, X., Chen, J., Li, D., Xie, P., Xu, M., Lin, W., Li, S., Pan, G., Tang, Y., Xu, J., Olkkonen, V. M., Yan, D., Zhong, W. ORP4L couples IP3 to ITPR1 in control of endoplasmic reticulum calcium release.
Collapse
Affiliation(s)
- Xiuye Cao
- Department of Biology, Jinan University, Guangzhou, China
| | - Jianuo Chen
- Department of Biology, Jinan University, Guangzhou, China
| | - Dan Li
- Department of Biology, Jinan University, Guangzhou, China
| | - Peipei Xie
- Department of Biology, Jinan University, Guangzhou, China
| | - Mengyang Xu
- Department of Biology, Jinan University, Guangzhou, China
| | - Weize Lin
- Department of Biology, Jinan University, Guangzhou, China
| | - Shiqian Li
- Department of Biology, Jinan University, Guangzhou, China
| | - Guoping Pan
- Department of Biology, Jinan University, Guangzhou, China
| | - Yong Tang
- Department of Biology, Jinan University, Guangzhou, China
| | - Jun Xu
- Research Center for Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Helsinki, Finland
| | - Daoguang Yan
- Department of Biology, Jinan University, Guangzhou, China
| | - Wenbin Zhong
- Department of Biology, Jinan University, Guangzhou, China
| |
Collapse
|
11
|
Cryo-EM reveals ligand induced allostery underlying InsP 3R channel gating. Cell Res 2018; 28:1158-1170. [PMID: 30470765 PMCID: PMC6274648 DOI: 10.1038/s41422-018-0108-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/02/2018] [Accepted: 10/22/2018] [Indexed: 01/06/2023] Open
Abstract
Inositol-1,4,5-trisphosphate receptors (InsP3Rs) are cation channels that mobilize Ca2+ from intracellular stores in response to a wide range of cellular stimuli. The paradigm of InsP3R activation is the coupled interplay between binding of InsP3 and Ca2+ that switches the ion conduction pathway between closed and open states to enable the passage of Ca2+ through the channel. However, the molecular mechanism of how the receptor senses and decodes ligand-binding signals into gating motion remains unknown. Here, we present the electron cryo-microscopy structure of InsP3R1 from rat cerebellum determined to 4.1 Å resolution in the presence of activating concentrations of Ca2+ and adenophostin A (AdA), a structural mimetic of InsP3 and the most potent known agonist of the channel. Comparison with the 3.9 Å-resolution structure of InsP3R1 in the Apo-state, also reported herein, reveals the binding arrangement of AdA in the tetrameric channel assembly and striking ligand-induced conformational rearrangements within cytoplasmic domains coupled to the dilation of a hydrophobic constriction at the gate. Together, our results provide critical insights into the mechanistic principles by which ligand-binding allosterically gates InsP3R channel.
Collapse
|
12
|
Terry LE, Alzayady KJ, Furati E, Yule DI. Inositol 1,4,5-trisphosphate Receptor Mutations associated with Human Disease. MESSENGER (LOS ANGELES, CALIF. : PRINT) 2018; 6:29-44. [PMID: 30197841 PMCID: PMC6128530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Calcium release into the cytosol via the inositol 1,4,5-trisphosphate receptor (IP3R) calcium channel is important for a variety of cellular processes. As a result, impairment or inhibition of this release can result in disease. Recently, mutations in all four domains of the IP3R have been suggested to cause diseases such as ataxia, cancer, and anhidrosis; however, most of these mutations have not been functionally characterized. In this review we summarize the reported mutations, as well as the associated symptoms. Additionally, we use clues from transgenic animals, receptor stoichiometry, and domain location of mutations to speculate on the effects of individual mutations on receptor structure and function and the overall mechanism of disease.
Collapse
Affiliation(s)
- Lara E Terry
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Kamil J Alzayady
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Esraa Furati
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| |
Collapse
|
13
|
Egorova PA, Bezprozvanny IB. Inositol 1,4,5-trisphosphate receptors and neurodegenerative disorders. FEBS J 2018; 285:3547-3565. [PMID: 29253316 DOI: 10.1111/febs.14366] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 11/27/2017] [Accepted: 12/12/2017] [Indexed: 12/15/2022]
Abstract
The inositol 1,4,5-trisphosphate receptor (IP3 R) is an intracellular ion channel that mediates the release of calcium ions from the endoplasmic reticulum. It plays a role in basic biological functions, such as cell division, differentiation, fertilization and cell death, and is involved in developmental processes including learning, memory and behavior. Deregulation of neuronal calcium signaling results in disturbance of cell homeostasis, synaptic loss and dysfunction, eventually leading to cell death. Three IP3 R subtypes have been identified in mammalian cells and the predominant isoform in neurons is IP3 R type 1. Dysfunction of IP3 R type 1 may play a role in the pathogenesis of certain neurodegenerative diseases as enhanced activity of the IP3 R was observed in models of Huntington's disease, spinocerebellar ataxias and Alzheimer's disease. These results suggest that IP3 R-mediated signaling is a potential target for treatment of these disorders. In this review we discuss the structure, functions and regulation of the IP3 R in healthy neurons and in conditions of neurodegeneration.
Collapse
Affiliation(s)
- Polina A Egorova
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg Polytechnic University, St Petersburg, Russia
| | - Ilya B Bezprozvanny
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg Polytechnic University, St Petersburg, Russia.,Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| |
Collapse
|
14
|
Yeste M, Jones C, Amdani SN, Coward K. Oocyte Activation and Fertilisation: Crucial Contributors from the Sperm and Oocyte. Results Probl Cell Differ 2017; 59:213-239. [PMID: 28247051 DOI: 10.1007/978-3-319-44820-6_8] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This chapter intends to summarise the importance of sperm- and oocyte-derived factors in the processes of sperm-oocyte binding and oocyte activation. First, we describe the initial interaction between sperm and the zona pellucida, with particular regard to acrosome exocytosis. We then describe how sperm and oocyte membranes fuse, with special reference to the discovery of the sperm protein IZUMO1 and its interaction with the oocyte membrane receptor JUNO. We then focus specifically upon oocyte activation, the fundamental process by which the oocyte is alleviated from metaphase II arrest by a sperm-soluble factor. The identity of this sperm factor has been the source of much debate recently, although mounting evidence, from several different laboratories, provides strong support for phospholipase C ζ (PLCζ), a sperm-specific phospholipase. Herein, we discuss the evidence in support of PLCζ and evaluate the potential role of other candidate proteins, such as post-acrosomal WW-binding domain protein (PAWP/WBP2NL). Since the cascade of downstream events triggered by the sperm-borne oocyte activation factor heavily relies upon specialised cellular machinery within the oocyte, we also discuss the critical role of oocyte-borne factors, such as the inositol trisphosphate receptor (IP3R), protein kinase C (PKC), store-operated calcium entry (SOCE) and calcium/calmodulin-dependent protein kinase II (CaMKII), during the process of oocyte activation. In order to place the implications of these various factors and processes into a clinical context, we proceed to describe their potential association with oocyte activation failure and discuss how clinical techniques such as the in vitro maturation of oocytes may affect oocyte activation ability. Finally, we contemplate the role of artificial oocyte activating agents in the clinical rescue of oocyte activation deficiency and discuss options for more endogenous alternatives.
Collapse
Affiliation(s)
- Marc Yeste
- Unit of Cell Biology, Department of Biology, Faculty of Sciences, University of Girona, C/ Maria Aurèlia Campany, 69, Campus Montilivi, E-17071, Girona, Spain. .,Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, UK.
| | - Celine Jones
- Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, UK
| | - Siti Nornadhirah Amdani
- Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, UK
| | - Kevin Coward
- Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, UK
| |
Collapse
|
15
|
Wang L, Alzayady KJ, Yule DI. Proteolytic fragmentation of inositol 1,4,5-trisphosphate receptors: a novel mechanism regulating channel activity? J Physiol 2015; 594:2867-76. [PMID: 26486785 DOI: 10.1113/jp271140] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 09/30/2015] [Indexed: 12/15/2022] Open
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3 Rs) are a family of ubiquitously expressed intracellular Ca(2+) release channels. Regulation of channel activity by Ca(2+) , nucleotides, phosphorylation, protein binding partners and other cellular factors is thought to play a major role in defining the specific spatiotemporal characteristics of intracellular Ca(2+) signals. These properties are, in turn, believed pivotal for the selective and specific physiological activation of Ca(2+) -dependent effectors. IP3 Rs are also substrates for the intracellular cysteine proteases, calpain and caspase. Cleavage of the IP3 R has been proposed to play a role in apoptotic cell death by uncoupling regions important for IP3 binding from the channel domain, leaving an unregulated leaky Ca(2+) pore. Contrary to this hypothesis, we demonstrate following proteolysis that N- and C-termini of IP3 R1 remain associated, presumably through non-covalent interactions. Further, we show that complementary fragments of IP3 R1 assemble into tetrameric structures and retain their ability to be regulated robustly by IP3 . While peptide continuity is clearly not necessary for IP3 -gating of the channel, we propose that cleavage of the IP3 R peptide chain may alter other important regulatory events to modulate channel activity. In this scenario, stimulation of the cleaved IP3 R may support distinct spatiotemporal Ca(2+) signals and activation of specific effectors. Notably, in many adaptive physiological events, the non-apoptotic activities of caspase and calpain are demonstrated to be important, but the substrates of the proteases are poorly defined. We speculate that proteolytic fragmentation may represent a novel form of IP3 R regulation, which plays a role in varied adaptive physiological processes.
Collapse
Affiliation(s)
- Liwei Wang
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Avenue, Rochester, NY, 14642, USA
| | - Kamil J Alzayady
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Avenue, Rochester, NY, 14642, USA
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Avenue, Rochester, NY, 14642, USA
| |
Collapse
|
16
|
Fan G, Baker ML, Wang Z, Baker MR, Sinyagovskiy PA, Chiu W, Ludtke SJ, Serysheva II. Gating machinery of InsP3R channels revealed by electron cryomicroscopy. Nature 2015; 527:336-41. [PMID: 26458101 DOI: 10.1038/nature15249] [Citation(s) in RCA: 174] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 07/24/2015] [Indexed: 12/12/2022]
Abstract
Inositol-1,4,5-trisphosphate receptors (InsP3Rs) are ubiquitous ion channels responsible for cytosolic Ca(2+) signalling and essential for a broad array of cellular processes ranging from contraction to secretion, and from proliferation to cell death. Despite decades of research on InsP3Rs, a mechanistic understanding of their structure-function relationship is lacking. Here we present the first, to our knowledge, near-atomic (4.7 Å) resolution electron cryomicroscopy structure of the tetrameric mammalian type 1 InsP3R channel in its apo-state. At this resolution, we are able to trace unambiguously ∼85% of the protein backbone, allowing us to identify the structural elements involved in gating and modulation of this 1.3-megadalton channel. Although the central Ca(2+)-conduction pathway is similar to other ion channels, including the closely related ryanodine receptor, the cytosolic carboxy termini are uniquely arranged in a left-handed α-helical bundle, directly interacting with the amino-terminal domains of adjacent subunits. This configuration suggests a molecular mechanism for allosteric regulation of channel gating by intracellular signals.
Collapse
Affiliation(s)
- Guizhen Fan
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, The University of Texas Medical School at Houston, 6431 Fannin Street, Houston, Texas 77030, USA
| | - Matthew L Baker
- National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
| | - Zhao Wang
- National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
| | - Mariah R Baker
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, The University of Texas Medical School at Houston, 6431 Fannin Street, Houston, Texas 77030, USA
| | - Pavel A Sinyagovskiy
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, The University of Texas Medical School at Houston, 6431 Fannin Street, Houston, Texas 77030, USA
| | - Wah Chiu
- National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
| | - Steven J Ludtke
- National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
| | - Irina I Serysheva
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, The University of Texas Medical School at Houston, 6431 Fannin Street, Houston, Texas 77030, USA
| |
Collapse
|
17
|
Yeste M, Jones C, Amdani SN, Patel S, Coward K. Oocyte activation deficiency: a role for an oocyte contribution? Hum Reprod Update 2015; 22:23-47. [DOI: 10.1093/humupd/dmv040] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 08/13/2015] [Indexed: 12/11/2022] Open
|
18
|
Stable expression and function of the inositol 1,4,5-triphosphate receptor requires palmitoylation by a DHHC6/selenoprotein K complex. Proc Natl Acad Sci U S A 2014; 111:16478-83. [PMID: 25368151 DOI: 10.1073/pnas.1417176111] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Calcium (Ca(2+)) is a secondary messenger in cells and Ca(2+) flux initiated from endoplasmic reticulum (ER) stores via inositol 1,4,5-triphosphate (IP3) binding to the IP3 receptor (IP3R) is particularly important for the activation and function of immune cells. Previous studies demonstrated that genetic deletion of selenoprotein K (Selk) led to decreased Ca(2+) flux in a variety of immune cells and impaired immunity, but the mechanism was unclear. Here we show that Selk deficiency does not affect receptor-induced IP3 production, but Selk deficiency through genetic deletion or low selenium in culture media leads to low expression of the IP3R due to a defect in IP3R palmitoylation. Bioinformatic analysis of the DHHC (letters represent the amino acids aspartic acid, histidine, histidine, and cysteine in the catalytic domain) family of enzymes that catalyze protein palmitoylation revealed that one member, DHHC6, contains a predicted Src-homology 3 (SH3) domain and DHHC6 is localized to the ER membrane. Because Selk is also an ER membrane protein and contains an SH3 binding domain, immunofluorescence and coimmunoprecipitation experiments were conducted and revealed DHHC6/Selk interactions in the ER membrane that depended on SH3/SH3 binding domain interactions. DHHC6 knockdown using shRNA in stably transfected cell lines led to decreased expression of the IP3R and impaired IP3R-dependent Ca(2+) flux. Mass spectrophotometric and bioinformatic analyses of the IP3R protein identified two palmitoylated cysteine residues and another potentially palmitoylated cysteine, and mutation of these three cysteines to alanines resulted in decreased IP3R palmitoylation and function. These findings reveal IP3R palmitoylation as a critical regulator of Ca(2+) flux in immune cells and define a previously unidentified DHHC/Selk complex responsible for this process.
Collapse
|
19
|
Alzayady KJ, Wagner LE, Chandrasekhar R, Monteagudo A, Godiska R, Tall GG, Joseph SK, Yule DI. Functional inositol 1,4,5-trisphosphate receptors assembled from concatenated homo- and heteromeric subunits. J Biol Chem 2013; 288:29772-84. [PMID: 23955339 DOI: 10.1074/jbc.m113.502203] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Vertebrate genomes code for three subtypes of inositol 1,4,5-trisphosphate (IP3) receptors (IP3R1, -2, and -3). Individual IP3R monomers are assembled to form homo- and heterotetrameric channels that mediate Ca(2+) release from intracellular stores. IP3R subtypes are regulated differentially by IP3, Ca(2+), ATP, and various other cellular factors and events. IP3R subtypes are seldom expressed in isolation in individual cell types, and cells often express different complements of IP3R subtypes. When multiple subtypes of IP3R are co-expressed, the subunit composition of channels cannot be specifically defined. Thus, how the subunit composition of heterotetrameric IP3R channels contributes to shaping the spatio-temporal properties of IP3-mediated Ca(2+) signals has been difficult to evaluate. To address this question, we created concatenated IP3R linked by short flexible linkers. Dimeric constructs were expressed in DT40-3KO cells, an IP3R null cell line. The dimeric proteins were localized to membranes, ran as intact dimeric proteins on SDS-PAGE, and migrated as an ∼1100-kDa band on blue native gels exactly as wild type IP3R. Importantly, IP3R channels formed from concatenated dimers were fully functional as indicated by agonist-induced Ca(2+) release. Using single channel "on-nucleus" patch clamp, the channels assembled from homodimers were essentially indistinguishable from those formed by the wild type receptor. However, the activity of channels formed from concatenated IP3R1 and IP3R2 heterodimers was dominated by IP3R2 in terms of the characteristics of regulation by ATP. These studies provide the first insight into the regulation of heterotetrameric IP3R of defined composition. Importantly, the results indicate that the properties of these channels are not simply a blend of those of the constituent IP3R monomers.
Collapse
Affiliation(s)
- Kamil J Alzayady
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | | | | | | | | | | | | | | |
Collapse
|
20
|
Alzayady KJ, Chandrasekhar R, Yule DI. Fragmented inositol 1,4,5-trisphosphate receptors retain tetrameric architecture and form functional Ca2+ release channels. J Biol Chem 2013; 288:11122-34. [PMID: 23479737 DOI: 10.1074/jbc.m113.453241] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Inositol 1,4,5-trisphosphate receptor isoforms are a family of ubiquitously expressed ligand-gated channels encoded by three individual genes. The proteins are localized to membranes of intracellular Ca(2+) stores and play pivotal roles in Ca(2+) homeostasis. Previous studies have demonstrated that IP3R1 is cleaved by the intracellular proteases calpain and caspase both in vivo and in vitro. However, the resultant cleavage products are poorly defined, and the functional consequences of these proteolytic events are not fully understood. We demonstrate that IP3R1 is cleaved during staurosporine-induced apoptosis, yielding N-terminal fragments encompassing the ligand-binding domain and the majority of the central modulatory domain together with a C-terminal fragment containing the channel domain and cytosolic tail. Notably, these fragments remain associated with the membrane after initiation of apoptotic cleavage. Furthermore, when recombinant IP3R1 fragments, corresponding to those predicted to be generated by caspase or calpain cleavage, are stably coexpressed in cells, they physically associate and form functional channels. These data provide novel insights regarding the regulation of IP3R1 during proteolysis and provide direct evidence that polypeptide continuity is not required for IP3R activation and Ca(2+) release.
Collapse
Affiliation(s)
- Kamil J Alzayady
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642, USA
| | | | | |
Collapse
|