PDE4B (phosphodiesterase 4B; HGNC:8781, NCBI Gene ID 5142) is a human locus mapped to chromosome band 1p31.3 that encodes cAMP-specific 3-prime,5-prime-cyclic phosphodiesterase 4B isoforms PDE4B1–PDE4B5 (736 aa long isoform; EC 3.1.4.53). PDE4B acts in hydrolysis of cAMP in striatal D1/D2 medium spiny neurons, DISC1 synaptic complexes & TLR4-stimulated microglia/neutrophils/monocytes, together with PDE4 Pharmacology & Inhibitor Registry, PDE4A (Prefrontal & Airway Paralog Gene), and PDE4C (Ciliary & Lung Paralog Gene). Encodes cAMP-specific phosphodiesterase 4B, the DISC1-binding synaptic enzyme and primary innate-immune PDE4 isoform driving TNF-alpha production in monocytes and microglia.
Approved Symbol
PDE4B
Chromosomal Locus
1p31.3
Encoded Product
cAMP-specific 3-prime,5-prime-cyclic phosphodiesterase 4B isoforms PDE4B1–PDE4B5 (736 aa long isoform; EC 3.1.4.53)
Primary Pathway
Hydrolysis of cAMP in striatal D1/D2 medium spiny neurons, DISC1 synaptic complexes & TLR4-stimulated microglia/neutrophils/monocytes
Clinical / Therapeutic Role
Balanced t(1;16) translocation in schizophrenia (DISC1 partner); predominant pro-inflammatory PDE4 in TNF-alpha release; target of nerandomilast (BI 1015550) in IPF
Gene Structure & Expression
Genomic Organization & Cytogenetic Locus: 19-exon gene spanning ~580 kb on chromosome 1p31.3 generating long (PDE4B1, PDE4B3), short (PDE4B2), and super-short (PDE4B5) splice isoforms via distinct internal promoters; the short PDE4B2 promoter is rapidly induced by Toll-like receptor 4 (LPS) and TNF-alpha NF-kappaB signaling in myeloid cells.
Cellular & Tissue Expression Profile: Abundantly expressed in striatal medium spiny neurons, amygdala, hypothalamus, and white matter oligodendrocytes/microglia, and serves as the predominant inducible PDE4 isoform in circulating human monocytes, macrophages, and neutrophils.
Molecular Function & Pathways
Biochemical & Physiological Mechanism: In innate immune cells (monocytes, macrophages, microglia), TLR engagement induces PDE4B2 to degrade intracellular cAMP; because cAMP-PKA normally inhibits NF-kappaB and activates CREB1-IL-10, PDE4B activity is strictly required for lipopolysaccharide-induced TNF-alpha (TNF) secretion; in the brain, long PDE4B1 binds the scaffolding protein Disrupted-in-Schizophrenia 1 (DISC1) and gates dopamine D1/D2 receptor (DRD2) cAMP-PKA-DARPP-32 signaling.
Clinical & Therapeutic Significance
Human Genetic Variants & Disease Phenotypes: First linked to major psychiatric disease when a balanced chromosomal translocation t(1;16)(p31.2;q21) directly disrupting PDE4B co-segregated with schizophrenia and psychotic illness in a Scottish kindred, and PDE4B physically complexes with DISC1; Pde4b-knockout macrophages fail to produce TNF-alpha upon endotoxemia, and mice carrying a catalytically hypomorphic Pde4b-Tyr358Cys mutation display enhanced neurogenesis, anxiolysis, and superior spatial memory without emetic side effects.
Therapeutic & Clinical Pharmacology: Because emesis (nausea/vomiting) from classical pan-PDE4 inhibitors is driven primarily by PDE4D in the brainstem area postrema, selective PDE4B inhibitors—led by nerandomilast (BI 1015550, which showed positive Phase 3 efficacy in idiopathic pulmonary fibrosis and progressive pulmonary fibrosis) and brain-penetrant PDE4B inhibitors (A33)—achieve potent anti-fibrotic and anti-inflammatory efficacy with markedly improved gastrointestinal tolerability.