ABHD15

ABHD15 is a PPARγ-induced α/β-hydrolase domain protein that functions in adipose tissue as a positive regulator of insulin's anti-lipolytic action and as a pro-survival, pro-adipogenic factor (PMID:29768196, PMID:24236098). Mechanistically, ABHD15 physically associates with and stabilizes phosphodiesterase 3B (PDE3B); loss of ABHD15 lowers PDE3B protein, leaving PKA activity elevated, increasing phosphorylation of HSL and Perilipin-1, and preventing insulin from suppressing fatty acid release — establishing ABHD15 as a required component upstream of insulin-mediated PKA suppression in the PDE3B–cAMP–PKA axis, with no role in insulin-stimulated glucose uptake in adipocytes (PMID:29768196, PMID:31105056). As a direct transcriptional target of PPARγ, ABHD15 is required for adipocyte differentiation, and its loss in preadipocytes triggers apoptosis (increased BAX, reduced BCL-2, elevated caspase 3/7) (PMID:24236098). Beyond these adipocyte roles, no biochemical detail of the ABHD15–PDE3B interaction interface or any catalytic hydrolase substrate has been characterized in the available corpus.

1. 2013 Medium

   Established ABHD15 as a downstream effector of the master adipogenic regulator PPARγ and as a survival factor, answering whether ABHD15 has a functional role in fat-cell development.

   Evidence Stable shRNA knockdown in 3T3-L1 cells with lipid staining, marker qPCR, apoptosis readouts, and PPARγ target validation

   PMID:24236098

   Open questions at the time

   • Molecular mechanism linking ABHD15 to apoptosis suppression not defined
   • No connection yet made to PDE3B or lipolysis
   • Single-lab cell-line data only
2. 2018 High

   Identified the molecular partner and mechanism — ABHD15 binds and stabilizes PDE3B — explaining how its loss elevates PKA activity and disrupts insulin suppression of fatty acid release.

   Evidence In vitro ABHD15–PDE3B co-association assay plus global and conditional Abhd15-KO mice with cAMP/PKA, HSL phosphorylation, and FA-release readouts

   PMID:29768196

   Open questions at the time

   • Interaction interface and stoichiometry not mapped
   • Whether ABHD15 has intrinsic hydrolase activity toward a substrate unresolved
   • Mechanism by which ABHD15 protects PDE3B from degradation unknown
3. 2019 High

   Placed ABHD15 causally upstream of PKA suppression by showing PKA substrate phosphorylation stays elevated without it, confirming its requirement for insulin's anti-lipolytic action while excluding a glucose-uptake role in adipocytes.

   Evidence ABHD15 knockdown/knockout adipocytes and fat explants with lipolysis assays, Perilipin-1 phosphorylation, glucose uptake, and whole-body lipid metabolism in ABHD15−/− mice

   PMID:31105056

   Open questions at the time

   • Does not address tissues outside adipose
   • Contribution of ABHD15 to systemic insulin resistance not fully resolved at molecular level
4. 2020 Low

   Extended ABHD15 function to cardiomyocytes under hypoxia, where overexpression promotes glucose uptake/glycolysis and inhibits apoptosis through insulin-receptor signaling branches.

   Evidence ABHD15 overexpression and siRNA in hypoxic cardiomyocytes with viability, glucose uptake, GLUT4 translocation, and inhibitor rescue experiments

   PMID:33257193

   Open questions at the time

   • Pathway placement inferred from inhibitor pharmacology only, with no direct binding or reconstitution data
   • Single-lab study not independently confirmed
   • Contradicts adipocyte finding of no glucose-uptake role — cell-type basis unexplained

• Whether ABHD15 possesses intrinsic enzymatic (hydrolase) activity and what its physiological substrate or catalytic role is remains unresolved.
• No catalytic substrate identified
• No structural model of ABHD15 or its complex with PDE3B
• Function outside adipose tissue and heart uncharacterized