Affinage

PDE8A

High affinity cAMP-specific and IBMX-insensitive 3',5'-cyclic phosphodiesterase 8A · UniProt O60658

Length
829 aa
Mass
93.3 kDa
Annotated
2026-06-10
14 papers in source corpus 9 papers cited in narrative 9 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PDE8A is a high-affinity, cAMP-specific, IBMX-insensitive phosphodiesterase that degrades cAMP within discrete subcellular compartments to shape localized cAMP signaling (PMID:9618252). Beyond catalytic turnover, its principal mechanism is the formation of a direct protein-protein complex with Raf-1/C-Raf kinase, which establishes a low-cAMP microdomain that shields Raf-1 from PKA-mediated inhibitory phosphorylation on S259, thereby sustaining Raf-1 activation and downstream ERK signaling; disrupting this complex with cell-penetrating peptides raises inhibitory Raf-1 phosphorylation, reduces phospho-ERK, and impairs T effector cell adhesion and migration via LFA-1/ICAM-1, suppresses melanoma growth while countering B-Raf inhibitor-driven paradoxical ERK activation, and inhibits KRAS-mutant pancreatic cancer cell proliferation, adhesion, and migration (PMID:28851628, PMID:30909892, PMID:38637546). PDE8A activity is itself controlled by upstream inputs: focal adhesion kinase (FAK) directly phosphorylates PDE8A on tyrosine residues to activate it and suppress cAMP, coupling mechanical load to cAMP/PKA signaling in osteocytes (PMID:38979143). PDE8A also governs defined cAMP pools downstream of β-adrenergic receptor signaling, regulating excitation-contraction coupling in ventricular myocytes and operating within an AKAP12-PDE8 axis that controls cardiomyocyte contractility and calcium handling (PMID:20353794, PMID:38506047). PDE8A additionally acts as a host dependency factor for HIV-1 replication (PMID:21920574).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 1998 High

    Established the fundamental enzymatic identity of PDE8A, answering whether it was a distinct phosphodiesterase and defining its substrate, affinity, and pharmacology.

    Evidence Baculovirus expression of recombinant PDE8A C-terminal fragment with kinetic enzyme assays varying substrates, metals, and inhibitors

    PMID:9618252

    Open questions at the time
    • No subcellular compartmentalization or interacting partners defined
    • Full-length enzyme and regulatory N-terminal regions not characterized
    • No physiological substrate pool identified in cells
  2. 2009 Medium

    Tested whether coding and promoter variants alter PDE8A function and link it to ovarian androgen production, resolving that the examined variants are not functionally significant.

    Evidence Variant kinetic assays in cell-free systems, subcellular localization imaging, and transmission/disequilibrium testing in a PCOS cohort

    PMID:19482904

    Open questions at the time
    • Negative result for these specific variants only; other variants untested
    • Does not address PDE8A function in non-ovarian tissues
  3. 2010 High

    Defined a physiological role for PDE8A in heart, showing it controls a specific cAMP pool governing excitation-contraction coupling under β-adrenergic stimulation.

    Evidence PDE8A knockout mouse with patch-clamp ICa recordings, Ca2+ imaging, and Ca2+ spark measurements in ventricular myocytes

    PMID:20353794

    Open questions at the time
    • Molecular anchoring/targeting mechanism to the relevant cAMP pool not defined
    • Interacting partners localizing PDE8A to L-type channels/SR not identified
  4. 2011 Medium

    Identified PDE8A as a host factor for HIV-1, addressing whether its activity influences viral replication.

    Evidence PDE8A overexpression and siRNA knockdown in HEK293T cells with HIV-1 replication assay and SNP-mRNA association in monocyte-derived macrophages

    PMID:21920574

    Open questions at the time
    • Mechanism downstream of PDE8A linking cAMP control to replication unresolved
    • Single lab; direct effect in macrophages inferred from association
  5. 2017 Medium

    Revealed the central signaling mechanism: PDE8A directly complexes with Raf-1 to create a low-cAMP microdomain that protects Raf-1 from PKA-mediated inhibition, promoting ERK signaling and T cell adhesion.

    Evidence Cell-permeable PDE8A-Raf-1 disruptor peptide plus selective PDE8 inhibitor PF-04957325, flow-based T cell adhesion assays, and phospho-Raf-1/phospho-ERK western blots

    PMID:28851628

    Open questions at the time
    • Structural basis and binding interface of the complex not defined
    • Single lab; reciprocal endogenous co-IP not shown
    • Stoichiometry and dynamics of the microdomain not quantified
  6. 2019 Medium

    Extended the PDE8A-C-Raf mechanism to cancer, showing complex disruption counters paradoxical ERK activation and inhibits melanoma growth in vitro and in vivo.

    Evidence Cell-penetrating disruptor peptide PPL-008 in MM415 melanoma cells and xenografts, with phospho-Raf-S259/phospho-ERK blots and proliferation assays

    PMID:30909892

    Open questions at the time
    • No direct co-IP of the complex shown
    • Selectivity of the disruptor peptide for the PDE8A-C-Raf interface not fully established
  7. 2024 Medium

    Demonstrated upstream regulation of PDE8A by FAK, establishing direct tyrosine phosphorylation as a mechanosensory mechanism linking mechanical load to cAMP suppression in osteocytes.

    Evidence Tyrosine phospho-proteomics, in vitro FAK kinase assay with PDE8A as substrate, co-immunoprecipitation, and GloSensor cAMP biosensing with FAK and PDE8A inhibition in Ocy454 cells (preprint)

    PMID:38979143

    Open questions at the time
    • Preprint; single lab and not peer-reviewed
    • Specific phosphorylated tyrosine residues and their activating effect on catalysis not mapped
    • Generalizability beyond osteocytes untested
  8. 2024 Medium

    Placed PDE8A within an AKAP12-PDE8 axis controlling β2-adrenergic cAMP and showed disruption of c-RAF-PDE8A inhibits KRAS-mutant PDAC independently of ERK, broadening both physiological and oncogenic mechanism.

    Evidence GloSensor cAMP biosensing in AC16 cardiomyocytes with AKAP12 overexpression and PF-04957325, contractility/Ca2+ assays in AKAP12 OX mice; and DRx-170 disruptor peptide in PANC1 cells with proliferation/adhesion/migration assays

    PMID:38506047 PMID:38637546

    Open questions at the time
    • Direct physical PDE8A-AKAP12 binding not demonstrated
    • ERK-independent effector mechanism in PDAC not defined
    • Single-lab functional inference for the AKAP12-PDE8 axis

Open questions

Synthesis pass · forward-looking unresolved questions
  • The structural basis of the PDE8A-C-Raf interface and how it integrates upstream FAK phosphorylation and AKAP12-dependent scaffolding into a unified mechanism of compartmentalized cAMP control remains open.
  • No structure of PDE8A or its complexes available in the corpus
  • Map of which cAMP pools and PKA targets each PDE8A complex governs incomplete
  • Whether FAK phosphorylation modulates the Raf-1 complex is untested

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016787 hydrolase activity 1 GO:0140098 catalytic activity, acting on RNA 1
Pathway
R-HSA-162582 Signal Transduction 3
Partners
AKAP12PTK2RAF1

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1998 PDE8A encodes a high-affinity, cAMP-specific phosphodiesterase (Km ~55 nM for cAMP) that is IBMX-insensitive, requires Mn2+ or Mg2+ for maximal activity, has ~10-fold slower Vmax than PDE4, and is inhibited by dipyridamole (IC50 ~9 µM) but not by rolipram, zaprinast, vinpocetine, SKF-94120, or IBMX. Baculovirus expression of recombinant PDE8A C-terminal 545 aa followed by kinetic enzyme assays with varying substrates, metal ions, and inhibitors Biochemical and biophysical research communications High 9618252
2010 PDE8A controls a specific cAMP pool in ventricular myocytes that regulates excitation-contraction coupling; PDE8A-null cardiomyocytes show larger evoked Ca2+ transients, elevated L-type Ca2+ channel currents, and increased Ca2+ spark activity during beta-adrenergic receptor stimulation compared to wild-type. PDE8A knockout mouse model; patch-clamp electrophysiology (ICa), Ca2+ imaging, Ca2+ spark measurements in ventricular myocytes Journal of molecular and cellular cardiology High 20353794
2017 PDE8A forms a direct protein-protein complex with Raf-1 (C-Raf) kinase, creating a low-cAMP microdomain around Raf-1 that shields it from PKA-mediated inhibitory phosphorylation, thereby promoting Raf-1 activation; disruption of this complex with a cell-permeable disruptor peptide increases inhibitory Raf-1 phosphorylation, reduces ERK signaling, and inhibits CD4+ T effector cell adhesion and migration under flow via LFA-1/ICAM-1. Cell-permeable PDE8A-Raf-1 complex disruptor peptide; flow-based T cell adhesion assays; western blot for phospho-Raf-1 and phospho-ERK; selective PDE8 enzymatic inhibitor PF-04957325 Cellular signalling Medium 28851628
2019 PDE8A directly interacts with C-Raf; disruption of the PDE8A–C-Raf complex with cell-penetrating peptide PPL-008 increases inhibitory C-Raf-S259 phosphorylation, reduces phospho-ERK signaling, counters B-Raf inhibitor–driven paradoxical ERK activation, inhibits melanoma cell growth in vitro, and reduces phospho-ERK in MM415 xenograft tumors in vivo. Cell-penetrating disruptor peptide (PPL-008) in MM415 melanoma cells and xenograft mouse model; western blot for phospho-Raf-S259 and phospho-ERK; cell proliferation assays; in vivo tumor model BMC cancer Medium 30909892
2024 PDE8A is directly phosphorylated by focal adhesion kinase (FAK) on tyrosine residues; intracellular FAK-PDE8A association was demonstrated by immunoprecipitation. FAK inhibition or deletion increases intracellular cAMP levels in osteocytes, an effect mimicked by PDE8A inhibition, indicating FAK phosphorylates and activates PDE8A to suppress cAMP; this represents a mechanosensory pathway coupling mechanical load to cAMP/PKA-linked hormonal signaling. Tyrosine-focused phospho-proteomic profiling; in vitro FAK kinase assay with PDE8A as substrate; co-immunoprecipitation; real-time cAMP biosensor (GloSensor) in Ocy454 osteocyte-like cells; FAK inhibitor/KO with PDE8A inhibitor (PF-04957325) bioRxivpreprint Medium 38979143
2024 AKAP12 upregulation reduces intracellular cAMP downstream of β2-adrenergic receptor specifically through PDE8; PDE8 selective inhibitor PF-04957325 reversed AKAP12-overexpression-induced impairment of cardiomyocyte contractility and calcium handling, placing PDE8A within an AKAP12-PDE8 signaling axis that regulates cardiac function. GloSensor luciferase cAMP biosensor in AC16 cardiomyocytes overexpressing AKAP12; cardiomyocyte contractility and Ca2+ handling measurements in AKAP12 OX mice with PDE8 inhibitor PF-04957325; in vivo isoproterenol cardiac stress model Circulation research Medium 38506047
2024 Disruption of the c-RAF–PDE8A protein-protein interaction with cell-penetrating peptide DRx-170 promotes inactivation of c-RAF through an allosteric mechanism dependent on PKA inhibitory phosphorylation, and inhibits KRASMT PDAC cell proliferation, adhesion, and migration independently of ERK1/2 activity. Cell-penetrating peptide disruptor DRx-170 in PANC1 KRASMT PDAC cells; 2D and 3D cell proliferation, adhesion, migration assays; western blot for phospho-Raf and phospho-ERK; combination with afatinib Scientific reports Medium 38637546
2011 PDE8A overexpression in HEK293T cells increases HIV-1 replication, while PDE8A knockdown decreases it, establishing PDE8A as a host dependency factor required for HIV-1 replication in macrophages. PDE8A overexpression and siRNA knockdown in HEK293T cells with HIV-1 replication assay; SNP-mRNA level association in primary monocyte-derived macrophages Virology Medium 21920574
2009 PDE8A coding-sequence variants R136Q and N401S and two promoter SNPs did not show reduced enzymatic activity in cell-free assays or altered subcellular localization, and were not associated with PCOS or androgen levels, indicating these variants are not functionally significant for ovarian androgen production. Expressed variant kinetic assays in cell-free systems; subcellular localization imaging; transmission/disequilibrium test in PCOS cohort Molecular human reproduction Medium 19482904

Source papers

Stage 0 corpus · 14 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2018 Tumor-released exosomal circular RNA PDE8A promotes invasive growth via the miR-338/MACC1/MET pathway in pancreatic cancer. Cancer letters 289 29709702
1998 Isolation and characterization of PDE8A, a novel human cAMP-specific phosphodiesterase. Biochemical and biophysical research communications 198 9618252
2010 Phosphodiesterase 8A (PDE8A) regulates excitation-contraction coupling in ventricular myocytes. Journal of molecular and cellular cardiology 79 20353794
2016 Genomewide Association Study of African Children Identifies Association of SCHIP1 and PDE8A with Facial Size and Shape. PLoS genetics 70 27560698
2009 PDE8A genetic variation, polycystic ovary syndrome and androgen levels in women. Molecular human reproduction 21 19482904
2019 Brain region-specific alterations of RNA editing in PDE8A mRNA in suicide decedents. Translational psychiatry 18 30770787
2017 PDE8 controls CD4+ T cell motility through the PDE8A-Raf-1 kinase signaling complex. Cellular signalling 17 28851628
2019 Targeting B-Raf inhibitor resistant melanoma with novel cell penetrating peptide disrupters of PDE8A - C-Raf. BMC cancer 16 30909892
2024 AKAP12 Upregulation Associates With PDE8A to Accelerate Cardiac Dysfunction. Circulation research 10 38506047
2017 ERAP1 and PDE8A Are Downregulated in Cattle Protected against Bovine Tuberculosis. Journal of molecular microbiology and biotechnology 10 28903115
2011 Polymorphism in HIV-1 dependency factor PDE8A affects mRNA level and HIV-1 replication in primary macrophages. Virology 6 21920574
2024 Regulation of intracellular cAMP levels in osteocytes by mechano-sensitive focal adhesion kinase via PDE8A. bioRxiv : the preprint server for biology 2 38979143
2024 Disruption of the pro-oncogenic c-RAF-PDE8A complex represents a differentiated approach to treating KRAS-c-RAF dependent PDAC. Scientific reports 1 38637546
2019 Correction: Brain region-specific alterations of RNA editing in PDE8A mRNA in suicide decedents. Translational psychiatry 1 30872571

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