ADCY8

ADCY8 (AC8) is a Ca2+/calmodulin-stimulated transmembrane adenylyl cyclase that integrates local Ca2+ signals into compartmentalized cAMP synthesis at plasma-membrane microdomains (PMID:22494970, PMID:16258073). It is physically coupled to store-operated Ca2+ entry through a direct N-terminal interaction with the Orai1 channel pore, so that Ca2+ entering via Orai1 drives AC8-dependent cAMP production within a shared AC8-Orai1 microdomain (PMID:22494970). AC8 activity is shaped by a regulatory scaffold: AKAP79/150 binds AC8 and limits its sensitivity to intracellular Ca2+, and the AKAP-recruited PKA phosphorylates AC8 at Ser-112 on its N-terminus to provide negative feedback that slows cAMP production during Ca2+ oscillations (PMID:20410303, PMID:22976297). The same N-terminus binds a catalytically active PP2A core dimer in a manner antagonized by Ca2+/calmodulin, and the enzyme is processed with complex N-glycans and trafficked through lipid rafts via a dynamic caveolin-1 interaction that requires cytoskeletal integrity (PMID:16258073, PMID:30746562). A cryo-EM structure of AC8 bound to Gαs and forskolin, together with structural proteomics, defines the ordered domain architecture and the contact interfaces for CaM, Gαs, and Gβγ (PMID:38351373). Through cAMP-PKA signaling AC8 governs diverse physiological outputs: it mediates cAMP-PKA-dependent lipolysis in adipose tissue (PMID:40527393), shapes compartmentalized cardiac cAMP that selectively tunes sarcoplasmic reticulum Ca2+ uptake while shielding L-type Ca2+ channels (PMID:12890691, PMID:12206999), cooperates with AC1 to couple lysosomal NAADP-driven Ca2+ release to α-adrenergic chronotropic and inotropic responses in atrial myocytes [PMID:bio_10.1101_2024.11.25.625232], and is cell-autonomously required in retinal neurons for cAMP-dependent axonal midline crossing (PMID:20505109).

1. 2003 High

   Established that AC8-generated cAMP is spatially compartmentalized rather than diffuse, explaining how a single cyclase can selectively tune some Ca2+ handling pathways without causing global Ca2+ overload.

   Evidence Cardiac-directed AC8 transgenic mice with PDE isoform activity assays, patch-clamp L-type Ca2+ recordings and contractility measurements

   PMID:12206999 PMID:12890691

   Open questions at the time

   • Did not resolve the molecular scaffolds enforcing the cAMP compartment
   • PDE coupling specificity to AC8 not structurally defined
2. 2005 High

   Identified PP2A as a direct N-terminal AC8 partner antagonized by Ca2+/calmodulin, revealing a phosphatase arm in AC8 microdomain regulation and placing AC8 in lipid rafts.

   Evidence Yeast two-hybrid screen with GST pulldown from native forebrain membranes, phosphatase activity assay, and lipid raft fractionation

   PMID:16258073

   Open questions at the time

   • Substrates dephosphorylated by AC8-bound PP2A not identified
   • Functional consequence of CaM-PP2A competition on cAMP output not quantified
3. 2010 High

   Showed AKAP79/150 directly tunes down AC8's Ca2+ sensitivity, identifying a scaffold-based set-point control over Ca2+-to-cAMP coupling, validated in endogenous secretory and neuronal cells.

   Evidence Co-immunoprecipitation and live-cell imaging in HEK293 plus endogenous insulin-secreting and hippocampal neuron systems

   PMID:20410303

   Open questions at the time

   • Did not yet define the PKA phosphorylation event mediating feedback
   • Stoichiometry of the AKAP-AC8 complex unknown
4. 2010 Medium

   Demonstrated a cell-autonomous developmental role for ADCY8 in cAMP-dependent retinal axon guidance, extending its function beyond secretory and cardiac contexts.

   Evidence Morpholino knockdown in zebrafish with in vivo axon tracing and epistasis against slit/SDF1 signaling

   PMID:20505109

   Open questions at the time

   • Ortholog knockdown; mammalian requirement not tested
   • Direct biochemical link between AC8 cAMP and slit responsiveness not shown
5. 2012 High

   Resolved the direct AC8-Orai1 interaction, establishing the physical basis by which store-operated Ca2+ entry is converted into local cAMP.

   Evidence Co-IP, GST pulldown, and microdomain-targeted FRET biosensors with live-cell imaging

   PMID:22494970

   Open questions at the time

   • Stoichiometry of AC8-Orai1 in native cells not defined
   • Structural interface of the N-terminal interaction unresolved
6. 2012 High

   Pinpointed Ser-112 as the PKA phosphosite mediating AKAP79-dependent negative feedback, completing the local feedback loop that dampens cAMP during Ca2+ oscillations.

   Evidence Site-directed mutagenesis with imposed Ca2+ oscillations and live-cell cAMP biosensors plus Co-IP

   PMID:22976297

   Open questions at the time

   • Single lab; in vivo physiological role of Ser-112 phosphorylation untested
   • Kinetics of phosphorylation/dephosphorylation cycling not measured
7. 2012 Medium

   Showed AC8 expression is transcriptionally controlled, with Notch signaling restraining IL-1β-driven AC8 induction during vascular smooth muscle trans-differentiation.

   Evidence Notch pharmacological modulation and Hrt1/Hrt3 overexpression in VSMCs with an in vivo rat carotid balloon-injury model

   PMID:22613711

   Open questions at the time

   • Direct Notch-target binding at the ADCY8 locus not demonstrated
   • cAMP-dependent mechanism downstream of AC8 in VSMCs not defined
8. 2019 Medium

   Defined the trafficking and microdomain maintenance route of AC8, linking complex N-glycosylation, caveolin-1, and cytoskeletal integrity to AC8 plasma-membrane targeting and responsiveness.

   Evidence Site-directed mutagenesis, pharmacological disruption, biochemical fractionation and live-cell imaging

   PMID:30746562

   Open questions at the time

   • Single lab; caveolin-1 interaction interface not mapped
   • Whether trafficking defects alter Ca2+-cAMP coupling in vivo unknown
9. 2024 High

   Provided the first near-atomic AC8 architecture and mapped the regulatory contact surfaces for Gαs, CaM, and Gβγ, giving a structural framework for its allosteric control.

   Evidence 3.5 Å cryo-EM of bovine AC8 with Gαs and forskolin, integrated with LiP-MS and XL-MS structural proteomics

   PMID:38351373

   Open questions at the time

   • Captured state did not favour tight nucleotide binding, leaving the catalytic conformation undefined
   • Identity of the negatively charged extracellular pocket interactor unknown
   • N-terminal regulatory region not resolved
10. 2024 Medium

    Connected chronic AC8 activation to inflammatory remodeling, showing cardiac cAMP overdrive triggers cell-autonomous RelA/NF-κB and non-cell-autonomous proinflammatory signaling preceding fibrosis.

    Evidence Cardiac-specific TGAC8 transgenic mice with NF-κB assays, PKA inhibition, cell-type-specific analysis and cytokine measurement

    PMID:38499959

    Open questions at the time

    • Gain-of-function model; relevance to physiological AC8 levels unclear
    • Mechanism linking PKA to RelA activation not fully defined
11. 2024 Medium

    Linked lysosomal NAADP-driven Ca2+ release to AC8/AC1 activation in atrial α-adrenergic responses, expanding the Ca2+ sources that feed AC8.

    Evidence Adcy1/Adcy8 double-knockout mice with NAADP-pathway inhibitors, atrial cAMP biosensors and Ca2+ transient measurements (preprint)

    PMID:bio_10.1101_2024.11.25.625232

    Open questions at the time

    • Preprint, not peer-reviewed
    • Relative contributions of AC1 vs AC8 not separated
    • Direct AC8-lysosomal coupling mechanism unresolved
12. 2025 Medium

    Established AC8 as the obligate cyclase for cAMP-PKA-dependent adipose lipolysis using genetic loss-of-function with pharmacological rescue.

    Evidence Adcy8 knockout mice on normal and high-fat diet with cAMP measurement, lipolytic enzyme phosphorylation assays and forskolin stimulation

    PMID:40527393

    Open questions at the time

    • Single lab; upstream activator of adipose AC8 not defined
    • Tissue-autonomy versus systemic effects not fully dissected
13. 2025 Medium

    Revealed a transcriptional/metabolic function in cancer, where AC8 loss reprograms the mitochondrial proteome and shifts cells from glycolysis to oxidative phosphorylation.

    Evidence CRISPR-Cas9 knockout in U87MG glioma cells with quantitative proteomics, oxygen consumption and TCA/glycolytic flux analysis

    PMID:40669556

    Open questions at the time

    • Mechanism by which AC8 controls mitochondrial gene/protein expression not defined
    • Single cell line; generality across cancers untested
    • cAMP-dependence of the metabolic effect not demonstrated

• How the structurally defined AC8 catalytic and N-terminal regulatory architecture is dynamically organized within the Orai1/AKAP79/PP2A microdomain to control cAMP kinetics in native tissues remains unresolved.
• Catalytically competent AC8 conformation not captured
• Native-tissue stoichiometry of the AC8 signaling complex unknown
• Mechanism coupling AC8 to transcriptional/metabolic outputs undefined