The formation of multiprotein complexes is a repeated theme in biology ranging from the regulation of the extracellular signal-regulated kinase and cAMP signaling pathways to the formation of ...postsynaptic density complexes or tight junctions. A-kinase anchoring proteins (AKAPs) are well known for their ability to scaffold protein kinase A and components upstream and downstream of cAMP production, including G protein-coupled receptors, cAMP-dependent Rap-exchange factors, and phosphodiesterases. Specific adenylyl cyclase (AC) isoforms have also been identified as components of AKAP complexes, namely AKAP79, Yotiao, and mAKAP. In this review, we summarize recent evidence for AC-AKAP complexes and requirements for compartmentalization of cAMP signaling. The ability of AKAPs to assemble intricate feedback loops to control spatiotemporal aspects of cAMP signaling adds yet another dimension to the classic cAMP pathway.
Adenylyl cyclases (ACs) generate the second messenger cAMP from ATP. Mammalian cells express nine transmembrane AC (mAC) isoforms (AC1-9) and a soluble AC (sAC, also referred to as AC10). This review ...will largely focus on mACs. mACs are activated by the G-protein G
and regulated by multiple mechanisms. mACs are differentially expressed in tissues and regulate numerous and diverse cell functions. mACs localize in distinct membrane compartments and form signaling complexes. sAC is activated by bicarbonate with physiologic roles first described in testis. Crystal structures of the catalytic core of a hybrid mAC and sAC are available. These structures provide detailed insights into the catalytic mechanism and constitute the basis for the development of isoform-selective activators and inhibitors. Although potent competitive and noncompetitive mAC inhibitors are available, it is challenging to obtain compounds with high isoform selectivity due to the conservation of the catalytic core. Accordingly, caution must be exerted with the interpretation of intact-cell studies. The development of isoform-selective activators, the plant diterpene forskolin being the starting compound, has been equally challenging. There is no known endogenous ligand for the forskolin binding site. Recently, development of selective sAC inhibitors was reported. An emerging field is the association of AC gene polymorphisms with human diseases. For example, mutations in the AC5 gene (
) cause hyperkinetic extrapyramidal motor disorders. Overall, in contrast to the guanylyl cyclase field, our understanding of the (patho)physiology of AC isoforms and the development of clinically useful drugs targeting ACs is still in its infancy.
Second messenger responses rely on where and when the enzymes that propagate these signals become active. Spatial and temporal organization of certain signaling enzymes is controlled in part by ...A-kinase anchoring proteins (AKAPs). This family of regulatory proteins was originally classified on the basis of their ability to compartmentalize the cyclic adenosine monophosphate (cAMP)-dependent protein kinase (also known as protein kinase A, or PKA). However, it is now recognized that AKAPs position G protein-coupled receptors, adenylyl cyclases, G proteins, and their effector proteins in relation to protein kinases and signal termination enzymes such as phosphodiesterases and protein phosphatases. This arrangement offers a simple and efficient means to limit the scope, duration, and directional flow of information to sites deep within the cell. This review focuses on the pros and cons of reagents that define the biological role of kinase anchoring inside cells and discusses recent advances in our understanding of anchored second messenger signaling in the cardiovascular and immune systems.
Cyclic AMP is a universal second messenger, produced by a family of adenylyl cyclase (AC) enzymes. The last three decades have brought a wealth of new information about the regulation of cyclic AMP ...production by ACs. Nine hormone-sensitive, membrane-bound AC isoforms have been identified in addition to a tenth isoform that lacks membrane spans and more closely resembles the cyanobacterial AC enzymes. New model systems for purifying and characterizing the catalytic domains of AC have led to the crystal structure of these domains and the mapping of numerous interaction sites. However, big hurdles remain in unraveling the roles of individual AC isoforms and their regulation in physiological systems. In this review we explore the latest on AC knockout and overexpression studies to better understand the roles of G protein regulation of ACs in the brain, olfactory bulb, and heart.
G protein-coupled receptors (GPCRs), G proteins and adenylyl cyclase (AC) comprise one of the most studied transmembrane cell signaling pathways. However, it is unknown whether the ligand-dependent ...interactions between these signaling molecules are based on random collisions or the rearrangement of pre-coupled elements in a macromolecular complex. Furthermore, it remains controversial whether a GPCR homodimer coupled to a single heterotrimeric G protein constitutes a common functional unit. Using a peptide-based approach, we here report evidence for the existence of functional pre-coupled complexes of heteromers of adenosine A
receptor and dopamine D
receptor homodimers coupled to their cognate Gs and Gi proteins and to subtype 5 AC. We also demonstrate that this macromolecular complex provides the necessary frame for the canonical Gs-Gi interactions at the AC level, sustaining the ability of a Gi-coupled GPCR to counteract AC activation mediated by a Gs-coupled GPCR.
Zinc is a transition metal that has a long history of use as an anti-inflammatory agent. It also soothes pain sensations in a number of animal models. However, the effects and mechanisms of zinc on ...chemotherapy-induced peripheral neuropathy remain unknown. Here we show that locally injected zinc markedly reduces neuropathic pain in male and female mice induced by paclitaxel, a chemotherapy drug, in a TRPV1-dependent manner. Extracellularly applied zinc also inhibits the function of TRPV1 expressed in HEK293 cells and mouse DRG neurons, which requires the presence of zinc-permeable TRPA1 to mediate entry of zinc into the cytoplasm. Moreover, TRPA1 is required for zinc-induced inhibition of TRPV1-mediated acute nociception. Unexpectedly, zinc transporters, but not TRPA1, are required for zinc-induced inhibition of TRPV1-dependent chronic neuropathic pain produced by paclitaxel. Together, our study demonstrates a novel mechanism underlying the analgesic effect of zinc on paclitaxel-induced neuropathic pain that relies on the function of TRPV1.
The chemotherapy-induced peripheral neuropathy is a major limiting factor affecting the chemotherapy patients. There is no effective treatment available currently. We demonstrate that zinc prevents paclitaxel-induced mechanical hypersensitivity via inhibiting the TRPV1 channel, which is involved in the sensitization of peripheral nociceptors in chemotherapy. Zinc transporters in DRG neurons are required for the entry of zinc into the intracellular side, where it inhibits TRPV1. Our study provides insight into the mechanism underlying the pain-soothing effect of zinc and suggests that zinc could be developed to therapeutics for the treatment of chemotherapy-induced peripheral neuropathy.
The scaffolding protein Yotiao is a member of a large family of protein A-kinase anchoring proteins with important roles in the organization of spatial and temporal signaling. In heart, Yotiao ...directly associates with the slow outward potassium ion current (IKs) and recruits both PKA and PP1 to regulate IKs phosphorylation and gating. Human mutations that disrupt IKs-Yotiao interaction result in reduced PKA-dependent phosphorylation of the IKs subunit KCNQ1 and inhibition of sympathetic stimulation of IKs, which can give rise to long-QT syndrome. We have previously identified a subset of adenylyl cyclase (AC) isoforms that interact with Yotiao, including AC1–3 and AC9, but surprisingly, this group did not include the major cardiac isoforms AC5 and AC6. We now show that either AC2 or AC9 can associate with KCNQ1 in a complex mediated by Yotiao. In transgenic mouse heart expressing KCNQ1-KCNE1, AC activity was specifically associated with the IKs-Yotiao complex and could be disrupted by addition of the AC9 N terminus. A survey of all AC isoforms by RT-PCR indicated expression of AC4–6 and AC9 in adult mouse cardiac myocytes. Of these, the only Yotiao-interacting isoform was AC9. Furthermore, the endogenous IKs-Yotiao complex from guinea pig also contained AC9. Finally, AC9 association with the KCNQ1-Yotiao complex sensitized PKA phosphorylation of KCNQ1 to β-adrenergic stimulation. Thus, in heart, Yotiao brings together PKA, PP1, PDE4D3, AC9, and the IKs channel to achieve localized temporal regulation of β-adrenergic stimulation.
Background: In heart, the A-kinase anchoring protein (AKAP) Yotiao anchors the KCNQ1 subunit of the slow outward potassium ion current (IKs).
Results: Adenylyl cyclase type 9 (AC9) is associated with the IKs complex and sensitizes PKA phosphorylation of KCNQ1 by isoproterenol.
Conclusion: Yotiao facilitates complex formation between AC9 and IKs in heart.
Significance: Sympathetic regulation of IKs is important for repolarization in heart.
Shining a light on GPCR complexes Dessauer, Carmen W.
The Journal of biological chemistry,
08/2017, Letnik:
292, Številka:
34
Journal Article
Recenzirano
Odprti dostop
The G protein–coupled receptor (GPCR) signaling pathways mediating information exchange across the cell membrane are central to a variety of biological processes and therapeutic strategies, but ...visualizing the molecular-level details of this exchange has been difficult for all but a few GPCR–G protein complexes. A study by Gao et al. now reports new strategies and tools to obtain receptor complexes in a near-native state, revealing insights into the gross conformational features of rhodopsin-transducin interactions and setting the stage for future studies.
Cyclic adenosine monophosphate (cAMP), synthesized by adenylyl cyclase (AC), is a universal second messenger that regulates various aspects of cardiac physiology from contraction rate to the ...initiation of cardioprotective stress response pathways. Local pools of cAMP are maintained by macromolecular complexes formed by A-kinase anchoring proteins (AKAPs). AKAPs facilitate control by bringing together regulators of the cAMP pathway including G-protein-coupled receptors, ACs, and downstream effectors of cAMP to finely tune signaling. This review will summarize the distinct roles of AC isoforms in cardiac function and how interactions with AKAPs facilitate AC function, highlighting newly appreciated roles for lesser abundant AC isoforms.
Adenylyl cyclases (ACs) catalyze the conversion of ATP to the ubiquitous second messenger cAMP. Mammals possess nine isoforms of transmembrane ACs, dubbed AC1-9, that serve as major effector enzymes ...of G protein-coupled receptors (GPCRs). The transmembrane ACs display varying expression patterns across tissues, giving the potential for them to have a wide array of physiological roles. Cells express multiple AC isoforms, implying that ACs have redundant functions. Furthermore, all transmembrane ACs are activated by Gα
, so it was long assumed that all ACs are activated by Gα
-coupled GPCRs. AC isoforms partition to different microdomains of the plasma membrane and form prearranged signaling complexes with specific GPCRs that contribute to cAMP signaling compartments. This compartmentation allows for a diversity of cellular and physiological responses by enabling unique signaling events to be triggered by different pools of cAMP. Isoform-specific pharmacological activators or inhibitors are lacking for most ACs, making knockdown and overexpression the primary tools for examining the physiological roles of a given isoform. Much progress has been made in understanding the physiological effects mediated through individual transmembrane ACs. GPCR-AC-cAMP signaling pathways play significant roles in regulating functions of every cell and tissue, so understanding each AC isoform's role holds potential for uncovering new approaches for treating a vast array of pathophysiological conditions.
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