GUCY1B1

GUCY1B1 encodes the β1 subunit of soluble guanylyl cyclase (sGC), which heterodimerizes with the α1 subunit (GUCY1A1) to form the principal intracellular receptor for nitric oxide (NO) and catalyze the synthesis of cGMP from GTP (PMID:1980215, PMID:36442224). In the vasculature and gastrointestinal tract, sGC-derived cGMP signals through PKG to mediate smooth muscle relaxation, with cell-specific knockout studies demonstrating that both smooth muscle cells and interstitial cells of Cajal are jointly required for nitrergic GI relaxation (PMID:23528627). Transcription of GUCY1B1 in vascular smooth muscle is directly activated by FoxO4 binding at the promoter and by Notch/MAML2 signaling, and hypertension suppresses GUCY1B1 expression through impaired Notch activity (PMID:35089807, PMID:28465505). During cardiac development, Notch-driven induction of sGC subunits enables NO/cGMP-dependent endothelial-to-mesenchymal transition, while in cardiomyocytes GUCY1B1 confers protection against ischemia-reperfusion injury via PKCε/Akt signaling (PMID:21839921, PMID:30485489).

1. 1990 Medium

   Cloning of GUCY1B1 established that multiple soluble guanylyl cyclase β subunits exist with distinct tissue expression, resolving prior uncertainty about sGC heterogeneity.

   Evidence PCR cloning from human kidney/liver cDNA with sequence analysis and tissue mRNA distribution

   PMID:1980215

   Open questions at the time

   • No functional enzymatic characterization of the β2 isoform was performed
   • Whether this subunit forms active heterodimers with distinct α subunits was not tested
   • The isoprenylation motif identified at the C-terminus was not functionally validated
2. 2011 Medium

   Demonstration that Notch signaling directly induces GUCY1B3 transcription and that the resulting NO-sGC-cGMP axis is required for endothelial-to-mesenchymal transition placed sGC as a developmental effector downstream of Notch in cardiac valve formation.

   Evidence Notch gain-of-function and NO/cGMP pathway inhibition in embryonic atrioventricular canal development model

   PMID:21839921

   Open questions at the time

   • Direct Notch binding to the GUCY1B3 promoter was not shown by ChIP
   • Whether cGMP acts through PKG or other effectors in EndMT was not resolved
3. 2013 High

   Cell-specific knockouts revealed that nitrergic GI relaxation requires sGC in both smooth muscle cells and interstitial cells of Cajal acting in concert, resolving the long-standing question of which cell type mediates NO-dependent gut motility.

   Evidence Conditional Cre-lox deletion of Gucy1b3 from SMCs and/or ICCs with isometric force and gut transit measurements in mice

   PMID:23528627

   Open questions at the time

   • The relative cGMP output from each cell type was not quantified
   • Whether ICC-specific sGC contributes to relaxation in other GI regions was not tested
4. 2013 Medium

   Notch3-driven upregulation of GUCY1B3 and downstream PKG/VASP phosphorylation in ovarian epithelial cells extended the Notch–sGC axis beyond cardiac development to an epithelial/cancer context.

   Evidence Notch3 overexpression and DAPT inhibition in ovarian surface epithelial and OVCAR3 cancer cells with cGMP and pVASP readouts

   PMID:24041655

   Open questions at the time

   • Direct Notch3 binding to the GUCY1B3 promoter was not demonstrated
   • Functional consequences for cancer cell proliferation were shown with sGC inhibition but not with specific GUCY1B3 knockdown
5. 2017 Medium

   Identification of MAML2 and FRYL as Notch coactivators required for constitutive sGC expression in vascular smooth muscle, and demonstration that angiotensin II-induced hypertension represses sGC through the Notch pathway, established a disease-relevant transcriptional circuit controlling GUCY1B3.

   Evidence AngII hypertension mouse model, Notch gain/loss-of-function, motif analysis, western blot, and RNA-Seq in human coronary artery

   PMID:28465505

   Open questions at the time

   • Direct ChIP evidence for MAML2/Notch binding at the GUCY1B3 locus was not provided
   • Whether Notch-dependent sGC downregulation is reversible upon antihypertensive treatment is unknown
6. 2018 Medium

   Overexpression and silencing experiments established that GUCY1B3 protects cardiomyocytes from ischemia-reperfusion injury through PKCε/Akt signaling, identifying a cGMP-independent or cGMP-to-kinase cardioprotective branch downstream of sGC.

   Evidence sGC overexpression/siRNA in neonatal rat ventricular myocytes and in vivo mouse coronary ligation with pharmacological PKC/Akt inhibition

   PMID:30485489

   Open questions at the time

   • Whether the PKCε/Akt pathway is activated by cGMP/PKG or through a non-canonical mechanism was not determined
   • Single-lab finding without independent replication
7. 2022 High

   ChIP and promoter assays demonstrated that FoxO4 directly binds FoxO motifs in the GUCY1B3 promoter and is required for ~50% of basal sGC β expression and cGMP/PKG signaling in vascular smooth muscle, identifying the first transcription factor with validated direct binding at this locus.

   Evidence ChIP, luciferase promoter assay, shRNA knockdown in rat and human aortic SMCs with cGMP and PKG readouts

   PMID:35089807

   Open questions at the time

   • Interplay between FoxO4 and Notch at the GUCY1B3 promoter was not tested
   • Whether FoxO4 regulation is altered in hypertension is unknown
8. 2023 Medium

   Reconstitution of catalytically active sGC by co-expression of GUCY1A3 and GUCY1B3 in HEK293 cells provided direct biochemical proof that these two subunits are sufficient for heterodimer formation and cGMP production.

   Evidence Lentiviral co-overexpression in HEK293 cells with sGC activity and cGMP measurement

   PMID:36442224

   Open questions at the time

   • NO-stimulated versus basal activity was not characterized
   • Stoichiometry and heme incorporation were not assessed
9. 2025 Medium

   Localization of GUCY1B1 in retinal vascular and neuronal cells and demonstration that oxidative stress impairs sGC function—rescuable by pharmacological sGC activation—extended the functional role of the β1 subunit to neuroretinal protection in diabetic and ischemic retinopathy.

   Evidence Immunohistochemistry, oxidative stress assays, electroretinography, and optokinetic tracking in rat diabetic and ischemia-reperfusion models

   PMID:40249725

   Open questions at the time

   • Cell-type-specific genetic deletion in the retina was not performed
   • Whether oxidative stress acts by heme oxidation of sGC was not directly tested
10. 2026 Medium

    Identification of a ceRNA regulatory axis (LncRNA00178–miR-466b-3p–Gucy1b1) downstream of ASIC1a in acute lung injury revealed a post-transcriptional mechanism that degrades Gucy1b1 mRNA and promotes alveolar epithelial apoptosis.

    Evidence RNA-seq, dual-luciferase reporter assay validating miR-466b-3p targeting of Gucy1b1 3′UTR, gain/loss-of-function in LPS-stimulated rat alveolar epithelial cells

    PMID:41830717

    Open questions at the time

    • Single-lab finding in rat cells without in vivo validation of the ceRNA axis
    • Whether this regulatory mechanism operates in human lung injury is unknown
    • Downstream consequences of Gucy1b1 loss in this context were limited to apoptosis readouts

• Key unresolved questions include the structural basis for β1-specific functions versus other β isoforms, the integration of FoxO4 and Notch transcriptional inputs at the GUCY1B3 promoter, and whether sGC β1-specific knockout (distinct from pan-sGC disruption) produces unique phenotypes in the cardiovascular or nervous systems.
• No structural model of the full-length β1 subunit in complex with the α subunit exists from the primary literature surveyed
• Isoform-specific functions of β1 versus β2 remain largely undefined
• Cross-talk between transcriptional (Notch, FoxO4) and post-transcriptional (miRNA) regulation of GUCY1B1 has not been explored