1
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Ren L, Thai PN, Gopireddy RR, Timofeyev V, Ledford HA, Woltz RL, Park S, Puglisi JL, Moreno CM, Santana LF, Conti AC, Kotlikoff MI, Xiang YK, Yarov-Yarovoy V, Zaccolo M, Zhang XD, Yamoah EN, Navedo MF, Chiamvimonvat N. Adenylyl cyclase isoform 1 contributes to sinoatrial node automaticity via functional microdomains. JCI Insight 2022; 7:e162602. [PMID: 36509290 PMCID: PMC9746826 DOI: 10.1172/jci.insight.162602] [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] [Received: 06/13/2022] [Accepted: 10/05/2022] [Indexed: 11/22/2022] Open
Abstract
Sinoatrial node (SAN) cells are the heart's primary pacemaker. Their activity is tightly regulated by β-adrenergic receptor (β-AR) signaling. Adenylyl cyclase (AC) is a key enzyme in the β-AR pathway that catalyzes the production of cAMP. There are current gaps in our knowledge regarding the dominant AC isoforms and the specific roles of Ca2+-activated ACs in the SAN. The current study tests the hypothesis that distinct AC isoforms are preferentially expressed in the SAN and compartmentalize within microdomains to orchestrate heart rate regulation during β-AR signaling. In contrast to atrial and ventricular myocytes, SAN cells express a diverse repertoire of ACs, with ACI as the predominant Ca2+-activated isoform. Although ACI-KO (ACI-/-) mice exhibit normal cardiac systolic or diastolic function, they experience SAN dysfunction. Similarly, SAN-specific CRISPR/Cas9-mediated gene silencing of ACI results in sinus node dysfunction. Mechanistically, hyperpolarization-activated cyclic nucleotide-gated 4 (HCN4) channels form functional microdomains almost exclusively with ACI, while ryanodine receptor and L-type Ca2+ channels likely compartmentalize with ACI and other AC isoforms. In contrast, there were no significant differences in T-type Ca2+ and Na+ currents at baseline or after β-AR stimulation between WT and ACI-/- SAN cells. Due to its central characteristic feature as a Ca2+-activated isoform, ACI plays a unique role in sustaining the rise of local cAMP and heart rates during β-AR stimulation. The findings provide insights into the critical roles of the Ca2+-activated isoform of AC in sustaining SAN automaticity that is distinct from contractile cardiomyocytes.
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Affiliation(s)
- Lu Ren
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California, USA
| | - Phung N. Thai
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
| | | | - Valeriy Timofeyev
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
| | - Hannah A. Ledford
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
| | - Ryan L. Woltz
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
| | - Seojin Park
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, Nevada, USA
- Prestige Biopharma Korea, Myongjigukje 7-ro, Gangseo-gu, Busan, South Korea
| | - Jose L. Puglisi
- College of Medicine. California North State University, Sacramento, California, USA
| | - Claudia M. Moreno
- Department of Physiology and Membrane Biology, UCD, Davis, California, USA
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington, USA
| | | | - Alana C. Conti
- Research & Development Service, John D. Dingell VA Medical Center, and
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA
| | | | - Yang Kevin Xiang
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
- Department of Pharmacology, UCD, Davis, California, USA
| | | | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, United Kingdom
| | - Xiao-Dong Zhang
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, Nevada, USA
| | | | - Nipavan Chiamvimonvat
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
- Department of Pharmacology, UCD, Davis, California, USA
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2
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Chen J, Ding Q, An L, Wang H. Ca2+-stimulated adenylyl cyclases as therapeutic targets for psychiatric and neurodevelopmental disorders. Front Pharmacol 2022; 13:949384. [PMID: 36188604 PMCID: PMC9523369 DOI: 10.3389/fphar.2022.949384] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 09/05/2022] [Indexed: 11/13/2022] Open
Abstract
As the main secondary messengers, cyclic AMP (cAMP) and Ca2+ trigger intracellular signal transduction cascade and, in turn, regulate many aspects of cellular function in developing and mature neurons. The group I adenylyl cyclase (ADCY, also known as AC) isoforms, including ADCY1, 3, and 8 (also known as AC1, AC3, and AC8), are stimulated by Ca2+ and thus functionally positioned to integrate cAMP and Ca2+ signaling. Emerging lines of evidence have suggested the association of the Ca2+-stimulated ADCYs with bipolar disorder, schizophrenia, major depressive disorder, post-traumatic stress disorder, and autism. In this review, we discuss the molecular and cellular features as well as the physiological functions of ADCY1, 3, and 8. We further discuss the recent therapeutic development to target the Ca2+-stimulated ADCYs for potential treatments of psychiatric and neurodevelopmental disorders.
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3
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Mansour A, Nagi K, Dallaire P, Lukasheva V, Le Gouill C, Bouvier M, Pineyro G. Comprehensive Signaling Profiles Reveal Unsuspected Functional Selectivity of δ-Opioid Receptor Agonists and Allow the Identification of Ligands with the Greatest Potential for Inducing Cyclase Superactivation. ACS Pharmacol Transl Sci 2021; 4:1483-1498. [PMID: 34661070 PMCID: PMC8506601 DOI: 10.1021/acsptsci.1c00019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Indexed: 11/29/2022]
Abstract
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Prolonged exposure
to opioid receptor agonists triggers adaptations
in the adenylyl cyclase (AC) pathway that lead to enhanced production
of cyclic adenosine monophosphate (cAMP) upon withdrawal. This cellular
phenomenon contributes to withdrawal symptoms, hyperalgesia and analgesic
tolerance that interfere with clinical management of chronic pain
syndromes. Since δ-opioid receptors (DOPrs) are a promising
target for chronic pain management, we were interested in finding
out if cell-based signaling profiles as generated for drug discovery
purposes could inform us of the ligand potential to induce sensitization
of the cyclase path. For this purpose, signaling of DOPr agonists
was monitored at multiple effectors. The resulting signaling profiles
revealed marked functional selectivity, particularly for Met-enkephalin
(Met-ENK) whose signaling bias profile differed from those of synthetic
ligands like SNC-80 and ARM390. Signaling diversity among ligands
was systematized by clustering agonists according to similarities
in Emax and Log(τ) values for the
different responses. The classification process revealed that the
similarity in Gα/Gβγ, but not in β-arrestin
(βarr), responses was correlated with the potential of Met-ENK,
deltorphin II, (d-penicillamine2,5)-enkephalin (DPDPE), ARM390,
and SNC-80 to enhance cAMP production, all of which required Ca2+ mobilization to produce this response. Moreover, superactivation
by Met-ENK, which was the most-effective Ca2+ mobilizing
agonist, required Gαi/o activation, availability of Gβγ
subunits at the membrane, and activation of Ca2+ effectors
such as calmodulin and protein kinase C (PKC). In contrast, superactivation by (N-(l-tyrosyl)-(3S)-1,2,3,4-tetrahydroisoquinoline-3-carbonyl)-l-phenylalanyl-l-phenylalanine (TIPP), which was set
in a distinct category through clustering, required activation of
Gαi/o subunits but was independent of the Gβγ dimer
and Ca2+ mobilization, relying instead on Src and Raf-1
to induce this cellular adaptation.
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Affiliation(s)
- Ahmed Mansour
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, Quebec H3T 1J4, Canada.,CHU Sainte-Justine Research Center, Montréal, Quebec H3T 1C5, Canada
| | - Karim Nagi
- College of Medicine, QU Health, Qatar University, P.O. Box 2713, Doha, Qatar
| | - Paul Dallaire
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, Quebec H3T 1J4, Canada.,CHU Sainte-Justine Research Center, Montréal, Quebec H3T 1C5, Canada
| | - Viktoriya Lukasheva
- Institute for Research in Immunology and Cancer, Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Quebec H3T 1J4, Canada
| | - Christian Le Gouill
- Institute for Research in Immunology and Cancer, Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Quebec H3T 1J4, Canada
| | - Michel Bouvier
- Institute for Research in Immunology and Cancer, Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Quebec H3T 1J4, Canada
| | - Graciela Pineyro
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, Quebec H3T 1J4, Canada.,CHU Sainte-Justine Research Center, Montréal, Quebec H3T 1C5, Canada
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4
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Capel RA, Bose SJ, Collins TP, Rajasundaram S, Ayagama T, Zaccolo M, Burton RAB, Terrar DA. IP 3-mediated Ca 2+ release regulates atrial Ca 2+ transients and pacemaker function by stimulation of adenylyl cyclases. Am J Physiol Heart Circ Physiol 2020; 320:H95-H107. [PMID: 33064562 PMCID: PMC7864251 DOI: 10.1152/ajpheart.00380.2020] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inositol trisphosphate (IP3) is a Ca2+-mobilizing second messenger shown to modulate atrial muscle contraction and is thought to contribute to atrial fibrillation. Cellular pathways underlying IP3 actions in cardiac tissue remain poorly understood, and the work presented here addresses the question whether IP3-mediated Ca2+ release from the sarcoplasmic reticulum is linked to adenylyl cyclase activity including Ca2+-stimulated adenylyl cyclases (AC1 and AC8) that are selectively expressed in atria and sinoatrial node (SAN). Immunocytochemistry in guinea pig atrial myocytes identified colocalization of type 2 IP3 receptors with AC8, while AC1 was located in close vicinity. Intracellular photorelease of IP3 by UV light significantly enhanced the amplitude of the Ca2+ transient (CaT) evoked by electrical stimulation of atrial myocytes (31 ± 6% increase 60 s after photorelease, n = 16). The increase in CaT amplitude was abolished by inhibitors of adenylyl cyclases (MDL-12,330) or protein kinase A (H89), showing that cAMP signaling is required for this effect of photoreleased IP3. In mouse, spontaneously beating right atrial preparations, phenylephrine, an α-adrenoceptor agonist with effects that depend on IP3-mediated Ca2+ release, increased the maximum beating rate by 14.7 ± 0.5%, n = 10. This effect was substantially reduced by 2.5 µmol/L 2-aminoethyl diphenylborinate and abolished by a low dose of MDL-12,330, observations which are again consistent with a functional interaction between IP3 and cAMP signaling involving Ca2+ stimulation of adenylyl cyclases in the SAN pacemaker. Understanding the interaction between IP3 receptor pathways and Ca2+-stimulated adenylyl cyclases provides important insights concerning acute mechanisms for initiation of atrial arrhythmias. NEW & NOTEWORTHY This study provides evidence supporting the proposal that IP3 signaling in cardiac atria and sinoatrial node involves stimulation of Ca2+-activated adenylyl cyclases (AC1 and AC8) by IP3-evoked Ca2+ release from junctional sarcoplasmic reticulum. AC8 and IP3 receptors are shown to be located close together, while AC1 is nearby. Greater understanding of these novel aspects of the IP3 signal transduction mechanism is important for future study in atrial physiology and pathophysiology, particularly atrial fibrillation.
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Affiliation(s)
- Rebecca A Capel
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Samuel J Bose
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thomas P Collins
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Skanda Rajasundaram
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thamali Ayagama
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Rebecca-Ann Beatrice Burton
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Derek A Terrar
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
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5
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Zakhvataev VE. Tidal variations of background ionizing radiation and circadian timing of the suprachiasmatic nucleus clock. Med Hypotheses 2020; 140:109667. [PMID: 32182557 DOI: 10.1016/j.mehy.2020.109667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/03/2020] [Accepted: 03/05/2020] [Indexed: 02/06/2023]
Abstract
Recently, correlations of different physiological processes in humans with variations in the local lunisolar gravitational tide force have been observed under highly controlled laboratory conditions. Understanding of the physical nature of this phenomenon needs a comprehensive study of its possible molecular mechanisms. One of the possible timing cues is the strong periodic variation of the emanation fields of radon-222 and its progeny produced by tidal deformations of geological environment. In the present work, we argue that this variation could induce temporal modulation of radiation-induced bystander signaling pathways associated with fundamental regulators of gene expression in the suprachiasmatic nucleus clock.
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Affiliation(s)
- V E Zakhvataev
- Federal Research Center "Krasnoyarsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences", 660036 Krasnoyarsk, Russia; Siberian Federal University, 660041 Krasnoyarsk, Russia.
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6
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Stress-induced bystander signaling as a possible factor contributing to neuronal excitability and seizure generation/epileptogenesis. Med Hypotheses 2016; 90:57-62. [DOI: 10.1016/j.mehy.2016.03.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 03/10/2016] [Indexed: 01/23/2023]
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7
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Zakhvataev VE. Possible scenarios of the influence of low-dose ionizing radiation on neural functioning. Med Hypotheses 2015; 85:723-35. [PMID: 26526727 DOI: 10.1016/j.mehy.2015.10.020] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 10/05/2015] [Accepted: 10/20/2015] [Indexed: 12/30/2022]
Abstract
Possible scenarios of the influence of ionizing radiation on neural functioning and the CNS are suggested. We argue that the radiation-induced bystander mechanisms associated with Ca(2+) flows, reactive nitrogen and oxygen species, and cytokines might lead to modulation of certain neuronal signaling pathways. The considered scenarios of conjugation of the bystander signaling and the neuronal signaling might result in modulation of certain synaptic receptors, neurogenesis, neurotransmission, channel conductance, synaptic signaling, different forms of neural plasticity, memory formation and storage, and learning. On this basis, corresponding new possible strategies for treating neurodegenerative deceases and mental disorders are proposed. The mechanisms considered might also be associated with neuronal survival and relevant to the treatment for brain injuries. At the same time, these mechanisms might be associated with detrimental effects and might facilitate the development of some neurological and psychiatric disorders.
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Affiliation(s)
- Vladimir E Zakhvataev
- Neuroinformatics Department, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands; Laboratory of Biological Action of Low-Intensity Factors, Siberian Federal University, 79 Svobodny pr., 660041 Krasnoyarsk, Russia.
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8
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Abstract
SOCE (store-operated Ca2+ entry) is mediated via specific plasma membrane channels in response to ER (endoplasmic reticulum) Ca2+ store depletion. This route of Ca2+ entry is central to the dynamic interplay between Ca2+ and cAMP signalling in regulating the activity of Ca2+-sensitive adenylate cyclase isoforms (AC1, AC5, AC6 and AC8). Two proteins have been identified as key components of SOCE: STIM1 (stromal interaction molecule 1), which senses ER Ca2+ store content and translocates to the plasma membrane upon store depletion, where it then activates Orai1, the pore-forming component of the CRAC (Ca2+ release-activated Ca2+) channel. Previous studies reported that co-expression of STIM1 and Orai1 in HEK-293 (human embryonic kidney 293) cells enhances Ca2+-stimulated AC8 activity and that AC8 and Orai1 directly interact to enhance this regulation. Nonetheless, the additional involvement of TRPC (transient receptor potential canonical) channels in SOCE has also been proposed. In the present study, we evaluate the contribution of TRPC1 to SOCE-mediated regulation of Ca2+-sensitive ACs in HEK-293 cells stably expressing AC8 (HEK-AC8) and HSG (human submandibular gland) cells expressing an endogenous Ca2+-inhibited AC6. We demonstrate a role for TRPC1 as an integral component of SOCE, alongside STIM1 and Orai1, in regulating Ca2+ fluxes within AC microdomains and influencing cAMP production.
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9
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Abstract
Recent advances in the AC (adenylate cyclase)/cAMP field reveal overarching roles for the ACs. Whereas few processes are unaffected by cAMP in eukaryotes, ranging from the rapid modulation of ion channel kinetics to the slowest developmental effects, the large number of cellular processes modulated by only three intermediaries, i.e. PKA (protein kinase A), Epacs (exchange proteins directly activated by cAMP) and CNG (cyclic nucleotide-gated) channels, poses the question of how selectivity and fine control is achieved by cAMP. One answer rests on the number of differently regulated and distinctly expressed AC species. Specific ACs are implicated in processes such as insulin secretion, immunological responses, sino-atrial node pulsatility and memory formation, and specific ACs are linked with particular diseased conditions or predispositions, such as cystic fibrosis, Type 2 diabetes and dysrhythmias. However, much of the selectivity and control exerted by cAMP lies in the sophisticated properties of individual ACs, in terms of their coincident responsiveness, dynamic protein scaffolding and organization of cellular microassemblies. The ACs appear to be the centre of highly organized microdomains, where both cAMP and Ca2+, the other major influence on ACs, change in patterns quite discrete from the broad cellular milieu. How these microdomains are organized is beginning to become clear, so that ACs may now be viewed as fundamental signalling centres, whose properties exceed their production of cAMP. In the present review, we summarize how ACs are multiply regulated and the steps that are put in place to ensure discrimination in their signalling. This includes scaffolding of targets and modulators by the ACs and assembling of signalling nexuses in discrete cellular domains. We also stress how these assemblies are cell-specific, context-specific and dynamic, and may be best addressed by targeted biosensors. These perspectives on the organization of ACs uncover new strategies for intervention in systems mediated by cAMP, which promise far more informed specificity than traditional approaches.
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10
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Jiang LI, Wang JE, Sternweis PC. Regions on adenylyl cyclase VII required for selective regulation by the G13 pathway. Mol Pharmacol 2012; 83:587-93. [PMID: 23229509 DOI: 10.1124/mol.112.082446] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Regulation of multiple adenylyl cyclases (AC) provides unique inputs to mediate the synthesis of cAMP, a ubiquitous second messenger that controls many aspects of cellular function. On stimulation by G(s), the activities of ACs can be further selectively modulated by other pathways to ensure precise control of intracellular cAMP responses to specific stimuli. Recently, we reported that one of the AC isoforms, AC7, is uniquely regulated by the G(13) pathway. To understand more fully the molecular mechanism of this regulation, we compared the regulation of AC7 with that of AC2 in bone marrow-derived macrophages devoid of AC7. Although both enzymes could fully restore regulation of cAMP by Gβγ, activation of the G(13) pathway preferentially synergized with AC7. Exchange of domains between the two isoforms indicates that the C1b domain and the N-terminus of the C1a domain are important for directing selective regulation of AC7 by the G(13) pathway. A mutagenesis screen identified more specific regions of AC7 that differentially mediate its regulation by distinct pathways.
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Affiliation(s)
- Lily I Jiang
- Department of Pharmacology, University of Texas-Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas, USA 74390-9041, USA
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11
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Masada N, Schaks S, Jackson SE, Sinz A, Cooper DMF. Distinct mechanisms of calmodulin binding and regulation of adenylyl cyclases 1 and 8. Biochemistry 2012; 51:7917-29. [PMID: 22971080 PMCID: PMC3466776 DOI: 10.1021/bi300646y] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Calmodulin (CaM), by mediating the stimulation of the activity of two adenylyl cyclases (ACs), plays a key role in integrating the cAMP and Ca(2+) signaling systems. These ACs, AC1 and AC8, by decoding discrete Ca(2+) signals can contribute to fine-tuning intracellular cAMP dynamics, particularly in neurons where they predominate. CaM comprises an α-helical linker separating two globular regions at the N-terminus and the C-terminus that each bind two Ca(2+) ions. These two lobes have differing affinities for Ca(2+), and they can interact with target proteins independently. This study explores previous indications that the two lobes of CaM can regulate AC1 and AC8 differently and thereby yield different responses to cellular transitions in [Ca(2+)](i). We first compared by glutathione S-transferase pull-down assays and offline nanoelectrospray ionization mass spectrometry the interaction of CaM and Ca(2+)-binding deficient mutants of CaM with the internal CaM binding domain (CaMBD) of AC1 and the two terminal CaMBDs of AC8. We then examined the influence of these three CaMBDs on Ca(2+) binding by native and mutated CaM in stopped-flow experiments to quantify their interactions. The three CaMBDs show quite distinct interactions with the two lobes of CaM. These findings establish the critical kinetic differences between the mechanisms of Ca(2+)-CaM activation of AC1 and AC8, which may underpin their different physiological roles.
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Affiliation(s)
- Nanako Masada
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
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12
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Organization of cAMP signalling microdomains for optimal regulation by Ca2+ entry. Biochem Soc Trans 2012; 40:246-50. [PMID: 22260699 DOI: 10.1042/bst20110613] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cross-talk between cAMP and Ca2+ signalling pathways plays a critical role in cellular homoeostasis. Several AC (adenylate cyclase) isoforms, catalysing the production of cAMP from ATP, display sensitivity to submicromolar changes in intracellular Ca2+ and, as a consequence, are key sites for Ca2+ and cAMP interplay. Interestingly, these Ca2+-regulated ACs are not equally responsive to equivalent Ca2+ rises within the cell, but display a remarkable selectivity for regulation by SOCE (store-operated Ca2+ entry). Over the years, considerable efforts at investigating this phenomenon have provided indirect evidence of an intimate association between Ca2+-sensitive AC isoforms and sites of SOCE. Now, recent identification of the molecular components of SOCE [namely STIM1 (stromal interaction molecule 1) and Orai1], coupled with significant advances in the generation of high-resolution targeted biosensors for Ca2+ and cAMP, have provided the first detailed insight into the organization of the cellular microdomains associated with Ca2+-regulated ACs. In the present review, I summarize the findings that have helped to provide our most definitive understanding of the selective regulation of cAMP signalling by SOCE.
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13
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Willoughby D, Everett KL, Halls ML, Pacheco J, Skroblin P, Vaca L, Klussmann E, Cooper DMF. Direct binding between Orai1 and AC8 mediates dynamic interplay between Ca2+ and cAMP signaling. Sci Signal 2012; 5:ra29. [PMID: 22494970 DOI: 10.1126/scisignal.2002299] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The interplay between calcium ion (Ca(2+)) and cyclic adenosine monophosphate (cAMP) signaling underlies crucial aspects of cell homeostasis. The membrane-bound Ca(2+)-regulated adenylyl cyclases (ACs) are pivotal points of this integration. These enzymes display high selectivity for Ca(2+) entry arising from the activation of store-operated Ca(2+) (SOC) channels, and they have been proposed to functionally colocalize with SOC channels to reinforce crosstalk between the two signaling pathways. Using a multidisciplinary approach, we have identified a direct interaction between the amino termini of Ca(2+)-stimulated AC8 and Orai1, the pore component of SOC channels. High-resolution biosensors targeted to the AC8 and Orai1 microdomains revealed that this protein-protein interaction is responsible for coordinating subcellular changes in both Ca(2+) and cAMP. The demonstration that Orai1 functions as an integral component of a highly organized signaling complex to coordinate Ca(2+) and cAMP signals underscores how SOC channels can be recruited to maximize the efficiency of the interplay between these two ubiquitous signaling pathways.
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Affiliation(s)
- Debbie Willoughby
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK
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14
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Collins TP, Terrar DA. Ca(2+)-stimulated adenylyl cyclases regulate the L-type Ca(2+) current in guinea-pig atrial myocytes. J Physiol 2012; 590:1881-93. [PMID: 22351635 DOI: 10.1113/jphysiol.2011.227066] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Ca(2+)-stimulated adenylyl cyclases (ACs) have recently been shown to play important roles in pacemaking in the sino-atrial node. Here we present evidence that Ca(2+)-stimulated ACs are functionally active in guinea-pig atrial myocytes. Basal activity of an AC in isolated atrial myocytes was demonstrated by the observations that MDL 12,330A (10 μm), an AC inhibitor, reduced L-type Ca(2+) current (I(CaL)) amplitude, while inhibition of phosphodiesterases with IBMX (100 μm) increased I(CaL) amplitude. Buffering of cytosolic Ca(2+) by exposure of myocytes to BAPTA-AM (5 μm) reduced I(CaL) amplitude, as did inhibition of Ca(2+) release from the sarcoplasmic reticulum with ryanodine (2 μm) and thapsigargin (1 μm). [Ca(2+)]i-activated calmodulin kinase II (CaMKII) inhibition with KN-93 (1 μm) reduced I(CaL), but subsequent application of BAPTA-AM further reduced I(CaL). This effect of BAPTA-AM, in the presence of CaMKII inhibition, demonstrates that there is an additional Ca(2+)-modulated pathway (not dependent on CaMKII) that regulates I(CaL) in atrial myocytes. The effects of BAPTA could be reversed by forskolin (10 μm), a direct stimulator of all AC isoforms, which would restore cAMP levels. In the presence of BAPTA-AM, the actions of IBMX were reduced. In addition, inclusion of cAMP in the patch electrode in the whole-cell configuration prevented the effects of BAPTA. These effects are all consistent with a role for Ca(2+)-stimulated AC in the regulation of atrial myocyte I(CaL).
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Affiliation(s)
- Thomas P Collins
- National Heart and Lung Institute, Imperial College, Guy Scadding Building, Dovehouse Street, London SW3 6LY, UK.
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15
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Mine N, Yamamoto S, Saito N, Yamazaki S, Suda C, Ishigaki M, Kufe DW, Von Hoff DD, Kawabe T. CBP501-calmodulin binding contributes to sensitizing tumor cells to cisplatin and bleomycin. Mol Cancer Ther 2011; 10:1929-38. [PMID: 21831962 DOI: 10.1158/1535-7163.mct-10-1139] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
CBP501 is an anticancer drug currently in randomized phase II clinical trials for patients with non-small cell lung cancer and malignant pleural mesothelioma. CBP501 was originally described as a unique G(2) checkpoint-directed agent that binds to 14-3-3, inhibiting the actions of Chk1, Chk2, mitogen-activated protein kinase-activated protein kinase 2, and C-Tak1. However, unlike a G(2) checkpoint inhibitor, CBP501 clearly enhances the accumulation of tumor cells at G(2)-M phase that is induced by cisplatin or bleomycin at low doses and short exposure. By contrast, CBP501 does not similarly affect the accumulation of tumor cells at G(2)-M that is induced by radiation, doxorubicin, or 5-fluorouracil treatment. Our recent findings point to an additional mechanism of action for CBP501. The enhanced accumulation of tumor cells at G(2)-M upon combined treatment with cisplatin and CBP501 results from an increase in intracellular platinum concentrations, which leads to increased binding of platinum to DNA. The observed CBP501-enhanced platinum accumulation is negated in the presence of excess Ca(2+). Some calmodulin inhibitors behave similarly to, although less potently than, CBP501. Furthermore, analysis by surface plasmon resonance reveals a direct, high-affinity molecular interaction between CBP501 and CaM (K(d) = 4.62 × 10(-8) mol/L) that is reversed by Ca(2+), whereas the K(d) for the complex between CBP501 and 14-3-3 is approximately 10-fold weaker and is Ca(2+) independent. We conclude that CaM inhibition contributes to CBP501's activity in sensitizing cancer cells to cisplatin or bleomycin. This article presents an additional mechanism of action which might explain the clinical activity of the CBP501-cisplatin combination.
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Affiliation(s)
- Naoki Mine
- CanBas Co., Ltd., 2-2-1 Otemachi, Numazu City 410-0801, Japan
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Memon I, Khan KM, Siddiqui S, Perveen S, Ishaq M. Temporal expression of calcium/calmodulin-dependent adenylyl cyclase isoforms in rat articular chondrocytes: RT-PCR and immunohistochemical localization. J Anat 2011; 217:574-87. [PMID: 20698909 DOI: 10.1111/j.1469-7580.2010.01273.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
A multitude of signalling cascades are implicated in the homeostasis of articular chondrocytes. However, the identity of these signalling pathways is not fully established. The 3, 5'-cyclic AMP-mediated signalling system is considered to be a prototype. Adenylyl cyclase (AC) is an effector enzyme responsible for the synthesis of cAMP. There are 10 mammalian AC isoforms and some of these are differentially regulated by calcium/calmodulin (Ca²(+) /CaM). Ca²(+) is known to play an important role in the development and maintenance of skeletal tissues. Ca²(+) /CaM-dependent AC isoforms and their temporal expression in articular chondrocytes in rats were identified using RT-PCR and immunohistochemistry techniques. All Ca²(+) /CaM-dependent AC isoforms were expressed in chondrocytes from all age groups examined. Each isoform was differentially expressed in developing and adult articular chondrocytes. Generally, expression of AC isoforms was observed to increase with age, but the increase was not uniform for all Ca²(+) /CaM-dependent AC isoforms. Expression of Ca²(+) /CaM-dependent AC isoforms along with other signalling molecules known to be present in articular chondrocytes indicate complicated and multifactorial signalling cascades involved in the development and homeostasis of articular cartilage. The significance of these findings in terms of articular chondrocyte physiology is discussed.
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Affiliation(s)
- Ismail Memon
- Department of Biological & Biomedical Sciences, Aga Khan University, Karachi, Pakistan.
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Lin AH, Cohen JE, Wan Q, Niu K, Shrestha P, Bernstein SL, Abrams TW. Serotonin stimulation of cAMP-dependent plasticity in Aplysia sensory neurons is mediated by calmodulin-sensitive adenylyl cyclase. Proc Natl Acad Sci U S A 2010; 107:15607-12. [PMID: 20702764 PMCID: PMC2932616 DOI: 10.1073/pnas.1004451107] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Calmodulin (CaM)-sensitive adenylyl cyclase (AC) in sensory neurons (SNs) in Aplysia has been proposed as a molecular coincidence detector during conditioning. We identified four putative ACs in Aplysia CNS. CaM binds to a sequence in the C1b region of AC-AplA that resembles the CaM-binding sequence in the C1b region of AC1 in mammals. Recombinant AC-AplA was stimulated by Ca(2+)/CaM. AC-AplC is most similar to the Ca(2+)-inhibited AC5 and AC6 in mammals. Recombinant AC-AplC was directly inhibited by Ca(2+), independent of CaM. AC-AplA and AC-AplC are expressed in SNs, whereas AC-AplB and AC-AplD are not. Knockdown of AC-AplA demonstrated that serotonin stimulation of cAMP-dependent plasticity in SNs is predominantly mediated by this CaM-sensitive AC. We propose that the coexpression of a Ca(2+)-inhibited AC in SNs, together with a Ca(2+)/CaM-stimulated AC, would enhance the associative requirement for coincident Ca(2+) influx and serotonin for effective stimulation of cAMP levels and initiation of plasticity mediated by AC-AplA.
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Affiliation(s)
| | | | | | | | | | - Steven L. Bernstein
- Department of Ophthalmology, University of Maryland School of Medicine, Baltimore, MD 21201-1559
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Tekmen M, Gleason E. Multiple Ca2+-dependent mechanisms regulate L-type Ca2+ current in retinal amacrine cells. J Neurophysiol 2010; 104:1849-66. [PMID: 20685929 DOI: 10.1152/jn.00031.2010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Understanding the regulation of L-type voltage-gated Ca(2+) current is an important component of elucidating the signaling capabilities of retinal amacrine cells. Here we ask how the cytosolic Ca(2+) environment and the balance of Ca(2+)-dependent effectors shape native L-type Ca(2+) channel function in these cells. To achieve this, whole cell voltage clamp recordings were made from cultured amacrine cells under conditions that address the contribution of mitochondrial Ca(2+) uptake (MCU), Ca(2+)/calmodulin (CaM)-dependent channel inactivation (CDI), protein kinase A (PKA), and Ca(2+)-induced Ca(2+) release (CICR). Under control conditions, repeated activation of the L-type channels produces a progressive enhancement of the current. Inhibition of MCU causes a reduction in the Ca(2+) current amplitude that is dependent on Ca(2+) influx as well as cytosolic Ca(2+) buffering, consistent with CDI. Including the Ca(2+) buffer bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA) internally can shift the balance between enhancement and inhibition such that inhibition of MCU can enhance the current. Inhibition of PKA can remove the enhancing effect of BAPTA suggesting that cyclic AMP-dependent phosphorylation is involved. Inhibition of CaM suppresses CDI but spares the enhancement, consistent with the substantially higher sensitivity of the Ca(2+)-sensitive adenylate cyclase 1 (AC1) to Ca(2+)/CaM. Inhibition of the ryanodine receptor reduces the current amplitude, suggesting that CICR might normally amplify the activation of AC1 and stimulation of PKA activity. These experiments reveal that the amplitude of L-type Ca(2+) currents in retinal amacrine cells are both positively and negatively regulated by Ca(2+)-dependent mechanisms.
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Affiliation(s)
- Merve Tekmen
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
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Sakamoto T, Kitaura H, Minami M, Honda Y, Watanabe T, Ueda A, Suzuki K, Irie T. Transcriptional effect of a calmodulin inhibitor, W-7, on the ligninolytic enzyme genes in Phanerochaete chrysosporium. Curr Genet 2010; 56:401-10. [PMID: 20532887 DOI: 10.1007/s00294-010-0309-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Revised: 05/15/2010] [Accepted: 05/22/2010] [Indexed: 10/19/2022]
Abstract
We investigated the effects of a calmodulin (CaM) inhibitor, W-7, on the expression of lignin peroxidase (LiP) and manganese peroxidase (MnP) genes in Phanerochaete chrysosporium to consider the role of cam gene, which was upregulated in parallel with the total activities of LiP and MnP in our previous transcriptomic analysis. The addition of 100 μM W-7 to the fungal cultures repressed the total activities of LiP and MnP, whereas the addition of 100 μM W-5, which is a control drug of W-7, retained approximately half of them, indicating that the effect of W-7 was attributable to CaM inhibition. Real-time reverse transcription polymerase chain reaction analysis revealed that most of lip and mnp isozyme genes predicted from whole-genome data were significantly inhibited by W-7 at the transcription level (P ≤ 0.05). These results suggest that CaM has an important role for the expression of isozyme genes of LiP and MnP at the transcription level.
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Willoughby D, Wachten S, Masada N, Cooper DMF. Direct demonstration of discrete Ca2+ microdomains associated with different isoforms of adenylyl cyclase. J Cell Sci 2010; 123:107-17. [PMID: 20016071 DOI: 10.1242/jcs.062067] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Ca(2+)-sensitive adenylyl cyclases (ACs) orchestrate dynamic interplay between Ca(2+) and cAMP that is a crucial feature of cellular homeostasis. Significantly, these ACs are highly selective for capacitative Ca(2+) entry (CCE) over other modes of Ca(2+) increase. To directly address the possibility that these ACs reside in discrete Ca(2+) microdomains, we tethered a Ca(2+) sensor, GCaMP2, to the N-terminus of Ca(2+)-stimulated AC8. GCaMP2-AC8 measurements were compared with global, plasma membrane (PM)-targeted or Ca(2+)-insensitive AC2-targeted GCaMP2. In intact cells, GCaMP2-AC8 responded rapidly to CCE, but was largely unresponsive to other types of Ca(2+) rise. The global GCaMP2, PM-targeted GCaMP2 and GCaMP2-AC2 sensors reported large Ca(2+) fluxes during Ca(2+) mobilization and non-specific Ca(2+) entry, but were less responsive to CCE than GCaMP2-AC8. Our data reveal that different AC isoforms localize to distinct Ca(2+)-microdomains within the plasma membrane. AC2, which is regulated via protein kinase C, resides in a microdomain that is exposed to a range of widespread Ca(2+) signals seen throughout the cytosol. By contrast, a unique Ca(2+) microdomain surrounds AC8 that promotes selectivity for Ca(2+) signals arising from CCE, and optimizes CCE-mediated cAMP synthesis. This direct demonstration of discrete compartmentalized Ca(2+) signals associated with specific signalling proteins provides a remarkable insight into the functional organization of signalling microdomains.
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Affiliation(s)
- Debbie Willoughby
- Department of Pharmacology, Tennis Court Road, University of Cambridge, CB2 1PD, UK
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21
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Is the lifetime of light-stimulated cGMP phosphodiesterase regulated by recoverin through its regulation of rhodopsin phosphorylation? Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00039522] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Masada N, Ciruela A, Macdougall DA, Cooper DMF. Distinct mechanisms of regulation by Ca2+/calmodulin of type 1 and 8 adenylyl cyclases support their different physiological roles. J Biol Chem 2008; 284:4451-63. [PMID: 19029295 DOI: 10.1074/jbc.m807359200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nine membrane-bound mammalian adenylyl cyclases (ACs) have been identified. Type 1 and 8 ACs (AC1 and AC8), which are both expressed in the brain and are stimulated by Ca(2+)/calmodulin (CaM), have discrete neuronal functions. Although the Ca(2+) sensitivity of AC1 is higher than that of AC8, precisely how these two ACs are regulated by Ca(2+)/CaM remains elusive, and the basis for their diverse physiological roles is quite unknown. Distinct localization of the CaM binding domains within the two enzymes may be essential to differential regulation of the ACs by Ca(2+)/CaM. In this study we compare in detail the regulation of AC1 and AC8 by Ca(2+)/CaM both in vivo and in vitro and explore the different role of each Ca(2+)-binding lobe of CaM in regulating the two enzymes. We also assess the relative dependence of AC1 and AC8 on capacitative Ca(2+) entry. Finally, in real-time fluorescence resonance energy transfer-based imaging experiments, we examine the effects of dynamic Ca(2+) events on the production of cAMP in cells expressing AC1 and AC8. Our data demonstrate distinct patterns of regulation and Ca(2+) dependence of AC1 and AC8, which seems to emanate from their mode of regulation by CaM. Such distinctive properties may contribute significantly to the divergent physiological roles in which these ACs have been implicated.
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Affiliation(s)
- Nanako Masada
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
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Willoughby D, Cooper DMF. Organization and Ca2+Regulation of Adenylyl Cyclases in cAMP Microdomains. Physiol Rev 2007; 87:965-1010. [PMID: 17615394 DOI: 10.1152/physrev.00049.2006] [Citation(s) in RCA: 327] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The adenylyl cyclases are variously regulated by G protein subunits, a number of serine/threonine and tyrosine protein kinases, and Ca2+. In some physiological situations, this regulation can be readily incorporated into a hormonal cascade, controlling processes such as cardiac contractility or neurotransmitter release. However, the significance of some modes of regulation is obscure and is likely only to be apparent in explicit cellular contexts (or stages of the cell cycle). The regulation of many of the ACs by the ubiquitous second messenger Ca2+provides an overarching mechanism for integrating the activities of these two major signaling systems. Elaborate devices have been evolved to ensure that this interaction occurs, to guarantee the fidelity of the interaction, and to insulate the microenvironment in which it occurs. Subcellular targeting, as well as a variety of scaffolding devices, is used to promote interaction of the ACs with specific signaling proteins and regulatory factors to generate privileged domains for cAMP signaling. A direct consequence of this organization is that cAMP will exhibit distinct kinetics in discrete cellular domains. A variety of means are now available to study cAMP in these domains and to dissect their components in real time in live cells. These topics are explored within the present review.
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Affiliation(s)
- Debbie Willoughby
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
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Gao X, Sadana R, Dessauer CW, Patel TB. Conditional stimulation of type V and VI adenylyl cyclases by G protein betagamma subunits. J Biol Chem 2006; 282:294-302. [PMID: 17110384 DOI: 10.1074/jbc.m607522200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In a yeast two-hybrid screen of mouse brain cDNA library, using the N-terminal region of human type V adenylyl cyclase (hACV) as bait, we identified G protein beta2 subunit as an interacting partner. Additional yeast two-hybrid assays showed that the Gbeta(1) subunit also interacts with the N-terminal segments of hACV and human type VI adenylyl cyclase (hACVI). In vitro adenylyl cyclase (AC) activity assays using membranes of Sf9 cells expressing hACV or hACVI showed that Gbetagamma subunits enhance the activity of these enzymes provided either Galpha(s) or forskolin is present. Deletion of residues 77-151, but not 1-76, in the N-terminal region of hACVI obliterated the ability of Gbetagamma subunits to conditionally stimulate the enzyme. Likewise, activities of the recombinant, engineered, soluble forms of ACV and ACVI, which lack the N termini, were not enhanced by Gbetagamma subunits. Transfection of the C terminus of G protein receptor kinase 2 to sequester endogenous Gbetagamma subunits attenuated the ability of isoproterenol to increase cAMP accumulation in COS-7 cells overexpressing hACVI even when G(i) was inactivated by pertussis toxin. Therefore, we conclude that the N termini of human hACV and hACVI are necessary for interactions with, and regulation by, Gbetagamma subunits both in vitro and in intact cells. Moreover, Gbetagamma subunits derived from a source(s) other than G(i) are necessary for the full activation of hACVI by isoproterenol in intact cells.
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Affiliation(s)
- Xianlong Gao
- Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois 60153, USA
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Cooper DMF, Crossthwaite AJ. Higher-order organization and regulation of adenylyl cyclases. Trends Pharmacol Sci 2006; 27:426-31. [PMID: 16820220 DOI: 10.1016/j.tips.2006.06.002] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2006] [Revised: 04/26/2006] [Accepted: 06/16/2006] [Indexed: 11/26/2022]
Abstract
There is increasing awareness of the compartmentalization of cAMP signalling--the means by which cAMP levels change in discrete domains of the cell with discrete local consequences. Current developments in understanding the organization of adenylyl cyclases in the plasma membrane are illuminating how the earliest part of cAMP compartmentalization could occur. This review focuses on recent findings regarding three levels of adenylyl cyclase organization--oligomerization, positioning to lipid rafts and participation in multiprotein signalling complexes. This organization, coupled with the role of scaffolding proteins in arranging the downstream effectors of cAMP, helps to identify complexes that greatly facilitate the translation of enzyme activation into local consequences.
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Affiliation(s)
- Dermot M F Cooper
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK.
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Diel S, Klass K, Wittig B, Kleuss C. Gbetagamma activation site in adenylyl cyclase type II. Adenylyl cyclase type III is inhibited by Gbetagamma. J Biol Chem 2005; 281:288-94. [PMID: 16275644 DOI: 10.1074/jbc.m511045200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Gbetagamma complex of heterotrimeric G proteins is the most outstanding example for the divergent regulation of mammalian adenylyl cyclases. The heterodimeric Gbetagamma complex inhibits some isoforms, e.g. ACI, and stimulates the isoforms ACII, -IV, and -VII. Although former studies identified the QEHA region located in the C2 domain of ACII as an important interaction site for Gbetagamma, the determinant of the stimulatory effect of Gbetagamma has not been detected. Here, we identified the C1b domain as the stimulatory region using full-length adenylyl cyclase. The relevant Gbetagamma signal transfer motif in IIC1b was determined as MTRYLESWGAAKPFAHL (amino acids 493-509). Amino acids of this PFAHL motif were absolutely necessary for ACII to be stimulated by Gbetagamma, whereas they were dispensable for Galpha(s) or forskolin stimulation. The PFAHL motif is present in all three adenylyl cyclase isoforms that are activated by Gbetagamma but is absent in other adenylyl cyclase isoforms as well as other known effectors of Gbetagamma. The emerging concept of two contact sites on different molecule halves for effective regulation of adenylyl cyclase is discussed.
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Affiliation(s)
- Susanne Diel
- Institut für Pharmakologie, Thielallee 67-73, Germany
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Abstract
The Ca2+/calmodulin-stimulated adenylyl cyclases, AC1 and AC8, play a critical role in several forms of neuroplasticity, including long-lasting long-term potentiation (L-LTP) and long-term memory (LTM). By coupling neuronal activity and Ca2+increases to the production of cAMP, AC1 and AC8 activate cAMP-dependent signal transduction and transcriptional pathways critical for L-LTP and LTM.
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Affiliation(s)
- Gregory D Ferguson
- Department of Pharmacology, University of Washington, Seattle, Washington 98195-7280, USA
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Litjens T, Harland ML, Roberts ML, Barritt GJ, Rychkov GY. Fast Ca(2+)-dependent inactivation of the store-operated Ca2+ current (ISOC) in liver cells: a role for calmodulin. J Physiol 2004; 558:85-97. [PMID: 15226409 PMCID: PMC1664903 DOI: 10.1113/jphysiol.2004.065870] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Store-operated Ca2+ channels (SOCs) provide a major pathway for Ca2+ entry in non-excitable cells. SOCs in immortalized liver cells are highly selective for Ca2+ over other cations and are similar to well-studied Ca2+ release activated Ca2+ (CRAC) channels in haematopoietic cell lines. In the present work, employing H4IIE liver cells, we investigated fast inactivation of SOC current (ISOC), which occurs at membrane potentials below -60 mV. This inactivation was significantly reduced when BAPTA, a faster Ca2+ buffer, was used instead of EGTA, and was completely abolished if Na+ was used as a charge carrier in the absence of divalent cations in the external medium. These results suggested that fast inactivation of SOCs in H4IIE cells was Ca2+ dependent and was similar to the fast inactivation of CRAC channels. Experiments showing that the fast inactivation of ISOC was not affected by the disruption of actin by latrunculin B indicate that the cytoskeleton is unlikely to be involved. To elucidate the mechanism of Ca2+ dependence, a possible role of calmodulin (CaM) in SOCs' fast inactivation was investigated. The CaM inhibitors Mas-7 and calmidazolium failed to affect ISOC fast inactivation, whereas over-expression of a CaM inhibitor peptide or a mutant CaM lacking functional EF hands significantly altered the inactivation of ISOC. Out of two exponential components normally required to approximate kinetics of ISOC fast inactivation, the faster component was reduced in amplitude by 30%, compared to the control. The results presented suggest that CaM is responsible for at least part of Ca(2+)-dependent fast inactivation of ISOC in liver cells. It is hypothesized that CaM is tethered to the channel itself and therefore protected from chemical inhibitors.
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Affiliation(s)
- Tom Litjens
- School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia 5005, Australia
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Leroy J, Pereverzev A, Vajna R, Qin N, Pfitzer G, Hescheler J, Malécot CO, Schneider T, Klöckner U. Ca2+-sensitive regulation of E-type Ca2+ channel activity depends on an arginine-rich region in the cytosolic II-III loop. Eur J Neurosci 2003; 18:841-55. [PMID: 12925010 DOI: 10.1046/j.1460-9568.2003.02819.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Ca2+-dependent regulation of L-type and P/Q-type Ca2+ channel activity is an important mechanism to control Ca2+ entry into excitable cells. Here we addressed the question whether the activity of E-type Ca2+ channels can also be controlled by Ca2+. Switching from Ba2+ to Ca2+ as charge carrier increased within 50 s, the density of currents observed in HEK-293 cells expressing a human Cav2.3d subunit and slowed down the inactivation kinetics. Furthermore, with Ca2+ as permeant ion, recovery from inactivation was accelerated, compared to the recovery process recorded under conditions where the accumulation of [Ca2+]i was prevented. In a Ba2+ containing bath solution the Ca2+-dependent changes of E-type channel activity could be induced by dialysing the cells with 1 micro m free [Ca2+]i suggesting that an elevation of [Ca2+]i is responsible for these effects. Deleting 19 amino acids in the intracellular II-III linker (exon 19) as part of an arginine-rich region, severely impairs the Ca2+ responsiveness of the expressed channels. Interestingly, deletion of an adjacent homologue arginine-rich region activates channel activity but now independently from [Ca2+]i. As a positive feedback-regulation of channel activity this novel activation mechanism might determine specific biological functions of E-type Ca2+ channels.
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Affiliation(s)
- Jérôme Leroy
- Institute of Neurophysiology, Institute of Vegetative Physiology, University of Cologne, Robert-Koch-Strasse 39, D-50931 Köln, Germany
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Haunsø A, Simpson J, Antoni FA. Small ligands modulating the activity of mammalian adenylyl cyclases: a novel mode of inhibition by calmidazolium. Mol Pharmacol 2003; 63:624-31. [PMID: 12606770 DOI: 10.1124/mol.63.3.624] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Molecular cloning of membrane-spanning mammalian adenylyl cyclases (ACs) has led to the discovery of nine different isotypes, making ACs potentially useful therapeutic targets. This study investigated the mechanism by which fungicidal nitroimidazole compounds modulate AC activity. Current evidence indicates that biological control of AC activity occurs through the cytosolic domains. Hence, full-length ACII, ACIX, and recombinant fusion proteins composed of the cytoplasmic loops of human ACIX or the first and second cytoplasmic loops of rat ACV and ACII, respectively, were expressed in human embryonic kidney 293 cells. The AC activities of the respective proteins were characterized, and their modulation by nitroimidazoles was investigated. Calmidazolium inhibited the activities of both full-length ACs and soluble fusion proteins (IC(50), approximately 10 microM). Inhibition of ACIX by calmidazolium was mediated by direct interaction with the catalytic core in a noncompetitive fashion. ACIX was essentially insensitive to 2'-deoxyadenosine 3'-monophosphate, a known blocker of AC activity. The ACV-ACII fusion protein was inhibited by calmidazolium (IC(50), approximately 20 microM) as well as by 2'-deoxyadenosine 3'-AMP (IC(50), approximately 2 microM), in a manner indicating independent mechanisms of action. Taken together, the data demonstrate that ACIX is insensitive to adenosine analogs and that calmidazolium inhibits AC activity by a novel, noncompetitive mechanism.
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Affiliation(s)
- Anders Haunsø
- Department of Neuroscience, University of Edinburgh, Edinburgh, Scotland, United Kingdom.
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Wang H, Storm DR. Calmodulin-regulated adenylyl cyclases: cross-talk and plasticity in the central nervous system. Mol Pharmacol 2003; 63:463-8. [PMID: 12606751 DOI: 10.1124/mol.63.3.463] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Gene disruption studies have shown that the Ca(2+)-stimulated adenylyl cyclases, AC1 and AC8, are critical for some forms of synaptic plasticity, including long-term potentiation as well as long-term memory formation (LTM). It is hypothesized that these enzymes are required for LTM to support the increased expression of a family of genes regulated through the cAMP/Ca(2+) response element-binding protein/cAMP response element transcriptional pathway. In contrast to AC1 and AC8, AC3 is a Ca(2+)-inhibited adenylyl cyclase that plays an essential role in olfactory signal transduction. Coupling of odorant receptors to AC3 stimulates cAMP transients that function as the major second messenger for olfactory signaling. These cAMP transients are caused, at least in part, by Ca(2+) inhibition of AC3, which is mediated through calmodulin-dependent protein kinase II. The unique structure and regulatory properties of these adenylyl cyclases make them attractive drug target sites for modulation of a number of physiological processes including memory formation and olfaction.
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Affiliation(s)
- Hongbing Wang
- Department of Pharmacology, University of Washington, Seattle, Washington 98195-7280, USA
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Nagakura A, Miyake-Takagi K, Takagi N, Fukui M, Takeo S. Impairment of adenylyl cyclase and of spatial memory function after microsphere embolism in rats. J Neurosci Res 2002; 68:363-72. [PMID: 12111867 DOI: 10.1002/jnr.10238] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The purpose of the present study was to characterize alterations in the adenylyl cyclase (AC), cyclic adenosine 3',5'-monophosphate (cAMP), and spatial memory function after sustained cerebral ischemia. Sustained cerebral ischemia was induced by injection of 900 microspheres (48 microm in diameter) into the right (ipsilateral) hemisphere of rats. Alterations in the AC and cAMP in the cerebral cortex and hippocampus were examined up to 7 days after the embolism. A decrease in the cAMP content was seen in the ipsilateral hemisphere throughout the experiment. Microsphere embolism (ME) decreased the activity of Ca(2+)/calmodulin (CaM)-sensitive AC in the ipsilateral hemisphere throughout the experiment, whereas the basal and 5'-guanylyl imidodiphosphate (Gpp(NH)p)-sensitive AC activities were not altered. Immunoblotting analysis of AC subtypes with specific antibodies showed a decrease in the immunoreactivity of AC-I in the ipsilateral hemisphere during these periods. No significant differences in the immunoreactivity of AC-V/VI and AC-VIII were observed after ME. The levels of GTP-binding proteins Galpha(s), Galpha(i), and Gbetawere unchanged. Furthermore, microsphere-embolized rats showed prolongation of the escape latency in the water maze task determined on the seventh to ninth day after the operation. These results suggest that sustained cerebral ischemia may induce the impairment of the AC, particularly a selective reduction in the AC-I level and activity, coupled with the decrease in cAMP content. This reduction may play an appreciable role in the disturbance in cAMP-mediated signal transduction system, possibly leading to learning and memory dysfunction.
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Affiliation(s)
- Akira Nagakura
- Department of Pharmacology, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo, Japan
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Patel TB, Wittpoth C, Barbier AJ, Yigzaw Y, Scholich K. Functional analyses of type V adenylyl cyclase. Methods Enzymol 2002; 345:160-87. [PMID: 11665603 DOI: 10.1016/s0076-6879(02)45015-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Affiliation(s)
- Tarun B Patel
- Department of Pharmacology and Vascular Biology Center, University of Tennessee, Health Science Center, Memphis, Tennessee 38163, USA
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Goldstein J, Silberstein C, Ibarra C. Adenylyl cyclase types I and VI but not II and V are selectively inhibited by nitric oxide. Braz J Med Biol Res 2002; 35:145-51. [PMID: 11847517 DOI: 10.1590/s0100-879x2002000200002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenylyl cyclase (AC) isoforms catalyze the synthesis of 3',5'-cyclic AMP from ATP. These isoforms are critically involved in the regulation of gene transcription, metabolism, and ion channel activity among others. Nitric oxide (NO) is a gaseous product whose synthesis from L-arginine is catalyzed by the enzyme NO synthase. It has been well established that NO activates the enzyme guanylyl cyclase, but little has been reported on the effects of NO on other important second messengers, such as AC. In the present study, the effects of sodium nitroprusside (SNP), a nitric oxide-releasing compound, on COS-7 cells transfected with plasmids containing AC types I, II, V and VI were evaluated. Total inhibition (approximately 98.5%) of cAMP production was observed in COS-7 cells transfected with the AC I isoform and previously treated with SNP (10 mM) for 30 min, when stimulated with ionomycin. A high inhibition (approximately 76%) of cAMP production was also observed in COS-7 cells transfected with the AC VI isoform and previously treated with SNP (10 mM) for 30 min, when stimulated with forskolin. No effect on cAMP production was observed in cells transfected with AC isoforms II and V.
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Affiliation(s)
- J Goldstein
- Laboratorio de Fisiopatogenia, Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
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Patel TB, Du Z, Pierre S, Cartin L, Scholich K. Molecular biological approaches to unravel adenylyl cyclase signaling and function. Gene 2001; 269:13-25. [PMID: 11376933 DOI: 10.1016/s0378-1119(01)00448-6] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Signal transduction through the cell membrane requires the participation of one or more plasma membrane proteins. For many transmembrane signaling events adenylyl cyclases (ACs) are the final effector enzymes which integrate and interpret divergent signals from different pathways. The enzymatic activity of adenylyl cyclases is stimulated or inhibited in response to the activation of a large number of receptors in virtually all cells of the human body. To date, ten different mammalian isoforms of adenylyl cyclase (AC) have been cloned and characterized. Each isoform has its own distinct tissue distribution and regulatory properties, providing possibilities for different cells to respond diversely to similar stimuli. The product of the enzymatic reaction catalyzed by ACs, cyclic AMP (cAMP) has been shown to play a crucial role for a variety of fundamental physiological cell functions ranging from cell growth and differentiation, to transcriptional regulation and apoptosis. In the past, investigations into the regulatory mechanisms of ACs were limited by difficulties associated with their purification and the availability of the proteins in any significant amount. Moreover, nearly every cell expresses several AC isoforms. Therefore, it was difficult to perform biochemical characterization of the different AC isoforms and nearly impossible to assess the physiological roles of the individual isoforms in intact cells, tissue or organisms. Recently, however, different molecular biological approaches have permitted several breakthroughs in the study of ACs. Recombinant technologies have allowed biochemical analysis of adenylyl cyclases in-vitro and the development of transgenic animals as well as knock-out mice have yielded new insights in the physiological role of some AC isoforms. In this review, we will focus mainly on the most novel approaches and concepts, which have delineated the mechanisms regulating AC and unravelled novel functions for this enzyme.
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Affiliation(s)
- T B Patel
- Department of Pharmacology and the Vascular Biology Center of Excellence, University of Tennessee, Memphis, 874 Union Avenue, Memphis, TN 38163, USA.
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Yan SZ, Beeler JA, Chen Y, Shelton RK, Tang WJ. The regulation of type 7 adenylyl cyclase by its C1b region and Escherichia coli peptidylprolyl isomerase, SlyD. J Biol Chem 2001; 276:8500-6. [PMID: 11113152 DOI: 10.1074/jbc.m010361200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Mammalian membrane-bound adenylyl cyclase consists of two highly conserved cytoplasmic domains (C1a and C2a) separated by a less conserved connecting region, C1b, and one of two transmembrane domains, M2. The C1a and C2a domains form a catalytic core that can be stimulated by forskolin and the stimulatory G protein subunit alpha (Galpha(s)). In this study, we analyzed the regulation of type 7 adenylyl cyclase (AC7) by C1b. The C1a, C1b, and C2a domains of AC7 were purified separately. Escherichia coli SlyD protein, a cis-trans peptidylprolyl isomerase (PPIase), copurifies with AC7 C1b (7C1b). SlyD protein can inhibit the Galpha(s)- and/or forskolin-activated activity of both soluble and membrane-bound AC7. Mutant forms of SlyD with reduced PPIase activity are less potent in the inhibition of AC7 activity. Interestingly, different isoforms of mammalian membrane-bound adenylyl cyclase can be either inhibited or stimulated by SlyD protein, raising the possibility that mammalian PPIase may regulate enzymatic activity of mammalian adenylyl cyclase. Purified 7C1b-SlyD complex has a greater inhibitory effect on AC7 activity than SlyD alone. This inhibition by 7C1b is abolished in a 7C1b mutant in which a conserved glutamic acid (amino acid residue 582) is changed to alanine. Inhibition of adenylyl cyclase activity by 7C1b is further confirmed by using 7C1b purified from an E. coli slyD-deficient strain. This inhibitory activity of AC7 is also observed with the 28-mer peptides derived from a region of C1b conserved in AC7 and AC2 but is not observed with a peptide derived from the corresponding region of AC6. This inhibitory activity exhibited by the C1b domain may result from the interaction of 7C1b with 7C1a and 7C2a and may serve to hold AC7 in the basal nonstimulated state.
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Affiliation(s)
- S Z Yan
- Department of Neurobiology, Pharmacology, and Physiology, The University of Chicago, Chicago, Illinois 60637, USA
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Kudlacek O, Mitterauer T, Nanoff C, Hohenegger M, Tang WJ, Freissmuth M, Kleuss C. Inhibition of adenylyl and guanylyl cyclase isoforms by the antiviral drug foscarnet. J Biol Chem 2001; 276:3010-6. [PMID: 11050094 DOI: 10.1074/jbc.m007910200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The pyrophosphate (PP(i)) analog foscarnet inhibits viral DNA-polymerases and is used to treat cytomegalovirus and human immunodeficiency vius infections. Nucleotide cyclases and DNA-polymerases catalyze analogous reactions, i.e. a phosphodiester bond formation, and have similar topologies in their active sites. Inhibition by foscarnet of adenylyl cyclase isoforms was therefore tested with (i) purified catalytic domains C1 and C2 of types I and VII (IC1 and VIIC1) and of type II (IIC2) and (ii) membrane-bound holoenzymes (from mammalian tissues and types I, II, and V heterologously expressed in Sf9 cell membranes). Foscarnet was more potent than PP(i) in suppressing forskolin-stimulated catalysis by both, IC1/IIC2 and VIIC1/IIC2. Stimulation of VIIC1/IIC2 by Galpha(s) relieved the inhibition by foscarnet but not that by PP(i). The IC(50) of foscarnet on membrane-bound adenylyl cyclases also depended on their mode of regulation. These findings predict that receptor-dependent cAMP formation is sensitive to inhibition by foscarnet in some, but not all, cells. This was verified with two cell lines; foscarnet blocked cAMP accumulation after A(2A)-adenosine receptor stimulation in PC12 but not in HEK-A(2A) cells. Foscarnet also inhibited soluble and, to a lesser extent, particulate guanylyl cylase. Thus, foscarnet interferes with the generation of cyclic nucleotides, an effect which may give rise to clinical side effects. The extent of inhibition varies with the enzyme isoform and with the regulatory input.
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Affiliation(s)
- O Kudlacek
- Institute of Pharmacology, University of Vienna, Währinger Str. 13a, A-1090 Vienna, Austria
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Yamamoto M, Götz ME, Ozawa H, Luckhaus C, Saito T, Rösler M, Riederer P. Hippocampal level of neural specific adenylyl cyclase type I is decreased in Alzheimer's disease. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1535:60-8. [PMID: 11113632 DOI: 10.1016/s0925-4439(00)00083-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previous studies reported disruption of adenylyl cyclase (AC)-cyclic AMP (cAMP) signal transduction in brain of Alzheimer's disease (AD). We also demonstrated that basal and stimulated AC activities in the presence of calcium and calmodulin (Ca(2+)/CaM) were significantly decreased in AD parietal cortex. In the present study, we examined the amounts of Ca(2+)/CaM-sensitive types I and VIII AC, and Ca(2+)/CaM-insensitive type VII AC in the postmortem hippocampi from AD patients and age-matched controls using immunoblotting. The specificities of the anti-type VII and VIII AC antibodies were confirmed by preabsorption with their specific blocking peptides. We observed a significant decrease in the level of type I AC and a tendency to decrease in the level of type VIII AC in AD hippocampus. On the other hand, the level of type VII AC showed no alteration between AD and controls. A body of evidence from the studies with invertebrates and vertebrates suggests that types I and VIII AC may play an essential role in learning and memory. Our finding thus firstly demonstrated that a specific disruption of the Ca(2+)/CaM-sensitive AC isoforms is likely involved in the pathophysiology in AD hippocampus.
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Affiliation(s)
- M Yamamoto
- Department of Psychiatry and Psychotherapy, University of Würzburg, Germany.
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Defer N, Best-Belpomme M, Hanoune J. Tissue specificity and physiological relevance of various isoforms of adenylyl cyclase. Am J Physiol Renal Physiol 2000; 279:F400-16. [PMID: 10966920 DOI: 10.1152/ajprenal.2000.279.3.f400] [Citation(s) in RCA: 273] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present review focuses on the potential physiological regulations involving different isoforms of adenylyl cyclase (AC), the enzymatic activity responsible for the synthesis of cAMP from ATP. Depending on the properties and the relative level of the isoforms expressed in a tissue or a cell type at a specific time, extracellular signals received by the G protein-coupled receptors can be differently integrated. We report here on various aspects of such regulations, emphasizing the role of Ca(2+)/calmodulin in activating AC1 and AC8 in the central nervous system, the potential inhibitory effect of Ca(2+) on AC5 and AC6, and the changes in the expression pattern of the isoforms during development. A particular emphasis is given to the role of cAMP during drug dependence. Present experimental limitations are also underlined (pitfalls in the interpretation of cellular transfection, scarcity of the invalidation models, and so on).
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Affiliation(s)
- N Defer
- Institut National de la Santé et de la Recherche Médicale U-99 Hôpital Henri Mondor, F-94010 Créteil, France
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Abstract
Several neuroendocrine control systems are prominently controlled by G-protein coupled receptors that activate the cAMP signal transduction pathway. The discovery of multiple genes that encode the molecular machinery of cAMP metabolism has revolutionized our knowledge of cAMP mediated processes. This perhaps all too familiar second messenger can be generated by nine different membrane enzymes in the context of varied levels of activation of G proteins as well as Ca(2+)- and protein kinase C-dependent processes. The amplitude, length and subcellular distribution of the cAMP signal are further modulated by over twenty functionally distinct isotypes of cAMP-degrading phosphodiesterases in a cell- and stimulus-specific manner. The present review summarizes the key properties of the molecular machinery that generates the cAMP signal and highlights how it is deployed in neuroendocrine systems.
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Affiliation(s)
- F A Antoni
- MRC Brain Metabolism Unit, University of Edinburgh, United Kingdom.
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Gu C, Cooper DM. Ca(2+), Sr(2+), and Ba(2+) identify distinct regulatory sites on adenylyl cyclase (AC) types VI and VIII and consolidate the apposition of capacitative cation entry channels and Ca(2+)-sensitive ACs. J Biol Chem 2000; 275:6980-6. [PMID: 10702261 DOI: 10.1074/jbc.275.10.6980] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+)-sensitive adenylyl cyclases may act as early integrators of the two major second messenger-signaling pathways mediated by Ca(2+) and cAMP. Ca(2+) stimulation of adenylyl cyclase type I (ACI) and adenylyl cyclase type VIII (ACVIII) is mediated by calmodulin and the site on these adenylyl cyclases that interacts with calmodulin has been defined. By contrast, the mechanism whereby Ca(2+) inhibits adenylyl cyclase type V (ACV) and adenylyl cyclase type VI (ACVI) is unknown. In this study, Ca(2+), Sr(2+), and Ba(2+) were compared to probe the involvement of E-F hand-like domains in both Ca(2+) stimulation and inhibition of ACVIII and ACVI, respectively. HEK 293 cells transfected with ACVIII cDNA and C6-2B glioma cells (where the endogenous adenylyl cyclases is predominantly ACVI) were used to compare the effects of these three cations in in vitro and in vivo measurements. The in vitro data identified two Ca(2+) regulatory sites for both ACVIII and ACVI. Strikingly different potency series for these cations at mediating high affinity stimulation and inhibition of ACVIII and ACVI, respectively, effectively rule out the possibility that calmodulin or proteins utilizing similar Ca(2+)-binding motifs mediate inhibition of ACVI. On the other hand, the low affinity inhibition that is common to both ACVIII and ACVI showed virtually identical potency profiles for the IIa cation series, indicating a common site of action. Remarkably, whereas Sr(2+) was rather ineffective at regulating these cyclases (particularly ACVI) in vitro, adequate concentrations accumulated in the vicinity of these enzymes as a consequence of capacitative cation entry to partially regulate both of these activities in vivo. This latter finding consolidates earlier observations that Ca(2+)-sensitive adenylyl cyclases detect and respond to capacitative cation entry rather than global cytosolic cation concentrations.
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Affiliation(s)
- C Gu
- Neuroscience Program, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Abstract
Ca(2+) regulates mammalian adenylyl cyclases in a type-specific manner. Stimulatory regulation is moderately well understood. By contrast, even the concentration range over which Ca(2+) inhibits adenylyl cyclases AC5 and AC6 is not unambiguously defined; even less so is the mechanism of inhibition. In the present study, we compared the regulation of Ca(2+)-stimulable and Ca(2+)-inhibitable adenylyl cyclases expressed in Sf9 cells with tissues that predominantly express these activities in the mouse brain. Soluble forms of AC5 containing either intact or truncated major cytosolic domains were also examined. All adenylyl cyclases, except AC2 and the soluble forms of AC5, displayed biphasic Ca(2+) responses, suggesting the presence of two Ca(2+) sites of high ( approximately 0.2 microM) and low affinity ( approximately 0.1 mM). With a high affinity, Ca(2+) (i) stimulated AC1 and cerebellar adenylyl cyclases, (ii) inhibited AC6 and striatal adenylyl cyclase, and (iii) was without effect on AC2. With a low affinity, Ca(2+) inhibited all adenylyl cyclases, including AC1, AC2, AC6, and both soluble forms of AC5. The mechanism of both high and low affinity inhibition was revealed to be competition for a stimulatory Mg(2+) site(s). A remarkable selectivity for Ca(2+) was displayed by the high affinity site, with a K(i) value of approximately 0.2 microM, in the face of a 5000-fold excess of Mg(2+). The present results show that high and low affinity inhibition by Ca(2+) can be clearly distinguished and that the inhibition occurs type-specifically in discrete adenylyl cyclases. Distinction between these sites is essential, or quite spurious inferences may be drawn on the nature or location of high affinity binding sites in the Ca(2+)-inhibitable adenylyl cyclases.
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Affiliation(s)
- J L Guillou
- Department of Pharmacology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Zimmermann G, Zhou D, Taussig R. Activating mutation of adenylyl cyclase reverses its inhibition by G proteins. Mol Pharmacol 1999; 56:895-901. [PMID: 10531392 DOI: 10.1124/mol.56.5.895] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have implemented a yeast genetic selection developed previously by our laboratory to identify mutant mammalian type V adenylyl cyclases insensitive to inhibition by G(ialpha.) One mutation isolated was localized to the first cytoplasmic domain at a Phe residue (position 400), which is conserved in all nine isoforms of membrane-bound mammalian adenylyl cyclase. Biochemical characterization of the F400Y mutant revealed a dramatic conversion of the G(ialpha) response from inhibitory to stimulatory. This mutation results in additional activating effects. The mutant exhibits an enhanced sensitivity toward activation by either G(salpha) or forskolin. Synergism between G(salpha) and forskolin is not observed for the F400Y mutant, presumably because the mutant already is in the sensitized state. Additionally, an enhancement of the basal unstimulated activity was observed. This mutation, which is the first demonstration of an activating point in a mammalian adenylyl cyclase, mimics a sensitized conformation of the wild-type enzyme that underlies the synergism between stimulatory inputs, and additionally, removes the inhibitory regulatory input provided by G(ialpha). Because sensitizing adenylyl cyclase toward its stimulators can have profound biological implications, this raises the possibility that naturally occurring mutations resembling those at the Phe400 residue may be associated with human disease states.
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Affiliation(s)
- G Zimmermann
- Department of Biological Chemistry, The University of Michigan Medical School, Ann Arbor, Michigan 48109-0636, USA
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Chabardès D, Imbert-Teboul M, Elalouf JM. Functional properties of Ca2+-inhibitable type 5 and type 6 adenylyl cyclases and role of Ca2+ increase in the inhibition of intracellular cAMP content. Cell Signal 1999; 11:651-63. [PMID: 10530873 DOI: 10.1016/s0898-6568(99)00031-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Among the different adenylyl cyclase (AC) isoforms, type 5 and type 6 constitute a subfamily which has the remarkable property of being inhibited by submicromolar Ca2+ concentrations in addition to Galphai-mediated processes. These independent and cumulative negative regulations are associated to a low basal enzymatic activity which can be strongly activated by Galphas-mediated interactions or forskolin. These properties ensure possible wide changes of cAMP synthesis. Regulation of cAMP synthesis by Ca2+ was studied in cultured or native cells which express naturally type 5 and/or type 6 AC, including well-defined renal epithelial cells. The results underline two characteristics of the inhibition due to agonist-elicited increase of intracellular Ca2+: i) Ca2+ rises achieved through capacitive Ca2+ entry or intracellular Ca2+ release can inhibit AC to a similar extent; and ii) in a same cell type, different agonists inducing similar overall Ca2+ rises elicit a variable inhibition of AC activity. The results suggest that a high efficiency of AC regulation by Ca2+ is linked to a requisite close localization of AC enzyme and Ca2+ rises.
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Affiliation(s)
- D Chabardès
- URA 1859 CNRS, Service de Biologie Cellulaire, Département de Biologie Cellulaire et Moléculaire, Gif sur Yvette, France.
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