ZDHHC21

ZDHHC21 is a plasma membrane palmitoyl acyltransferase (PAT) that S-acylates a defined set of substrates to control vascular, immune, metabolic, and neuronal signaling (PMID:27653213, PMID:34080635). Its catalytic activity is gated by Ca²⁺/calmodulin binding: disruption of the calmodulin-binding domain abolishes S-acylation of proximal T-cell receptor signaling proteins and blocks naïve CD4⁺ T-cell activation and Th1/Th2/Th17 differentiation without affecting thymic development (PMID:34080635, PMID:32789573). In the vasculature, ZDHHC21 palmitoylates PLCβ1 to drive inflammation-induced endothelial barrier hyperpermeability and ICAM-1 expression (PMID:27653213), and forms a complex with and palmitoylates the α1D-adrenoceptor to sustain α1-adrenergic vasoconstriction and downstream ERK activation, controlling vascular tone and renal perfusion (PMID:26715683, PMID:34045489). The same enzyme governs epithelial barrier integrity in response to TNF-α/IFN-γ (PMID:28838985). Through substrate-specific acylation it also regulates store-operated calcium entry by being recruited into Orai1/STIM1 puncta upon ER store depletion, where it binds and S-acylates STIM1 (PMID:41279060), promotes mitochondrial OXPHOS by palmitoylating adenylate kinase 2 (AK2) (PMID:37216691), and palmitoylates STING to drive pyroptosis (PMID:41460311). ZDHHC21 acylation activity is disease-linked: a gain-of-function p.T209S mutation in a familial Alzheimer's disease pedigree enhances palmitoylation of FYN and APP, causing NMDAR2B-mediated excitotoxicity and increased Aβ production, with palmitoyltransferase inhibitors reversing synaptic dysfunction in knock-in mice (PMID:37365538). In cancer, ZDHHC21 supports AML stemness via AK2/OXPHOS (PMID:37216691) and palmitoylates FASN at Cys1317 to destabilize it and suppress DLBCL proliferation (PMID:38195819).

1. 2015 High

   Established that ZDHHC21 acts on a G-protein-coupled receptor by palmitoylating the α1D-adrenoceptor, linking the enzyme to control of vascular tone in vivo.

   Evidence Biochemical palmitoylation and co-IP plus isolated vessel contractility and telemetry in F233Δ loss-of-function mice

   PMID:26715683

   Open questions at the time

   • Did not map the palmitoylated cysteine on the receptor
   • Did not establish whether Ca²⁺/calmodulin gates this particular reaction
2. 2016 High

   Identified PLCβ1 as a vascular substrate placing ZDHHC21 acylation upstream of inflammation-induced endothelial hyperpermeability.

   Evidence Zdhhc21dep/dep mice with overexpression rescue using wild-type vs catalytic-mutant constructs, palmitoylation and permeability assays in vitro and in vivo

   PMID:27653213

   Open questions at the time

   • Palmitoylation site on PLCβ1 not defined
   • Upstream signal coupling inflammation to enzyme activity not resolved
3. 2017 Medium

   Extended ZDHHC21's barrier role to gut epithelium under inflammatory stress, showing genetic and pharmacological loss attenuate hyperpermeability.

   Evidence ZDHHC21-deficient mice and 2-bromopalmitate inhibition with ECIS/FITC-dextran permeability, acyl-biotin exchange, histology and EM after thermal injury

   PMID:28838985

   Open questions at the time

   • Specific epithelial substrate not identified
   • 2-bromopalmitate is not ZDHHC21-selective
4. 2020 Medium

   First linked ZDHHC21 to immune signaling by showing it S-acylates proximal TCR signaling proteins required for T-cell activation.

   Evidence DHHC21 knockdown with S-acylation assays and T-cell activation/differentiation readouts

   PMID:32789573

   Open questions at the time

   • No rescue or structural validation
   • Individual TCR substrates and their acylation sites not fully resolved
5. 2021 High

   Defined ZDHHC21 as a Ca²⁺/calmodulin-dependent PAT, mechanistically coupling its catalytic activity to a regulatory domain and confirming its requirement for CD4⁺ T-cell lineage differentiation.

   Evidence Zdhhc21dep mice with calmodulin-binding domain disruption plus T-cell S-acylation, activation, and differentiation assays in vitro and in vivo

   PMID:34080635

   Open questions at the time

   • Structural basis of calmodulin-mediated activation not solved
   • Which TCR-pathway substrates are directly versus indirectly affected unclear
6. 2021 Medium

   Showed the α1-adrenergic axis controlled by ZDHHC21 operates during sepsis, coupling receptor palmitoylation to ERK activation and renal perfusion.

   Evidence Zdhhc21dep/dep mice in a CLP sepsis model with α1AR palmitoylation, ERK phosphorylation, renal blood flow, and vessel contractility measures

   PMID:34045489

   Open questions at the time

   • Single lab
   • Direct versus indirect contribution of receptor acylation to ERK output not separated
7. 2023 High

   Connected ZDHHC21 to mitochondrial metabolism in cancer by identifying AK2 as a substrate whose palmitoylation sustains OXPHOS and AML stemness.

   Evidence ZDHHC21 depletion/inhibition with AK2 palmitoylation, OXPHOS measurement, myeloid differentiation assays, and in vivo AML xenografts

   PMID:37216691

   Open questions at the time

   • AK2 palmitoylation site not mapped
   • How a plasma membrane PAT accesses a mitochondrial substrate not explained
8. 2023 High

   Provided direct disease causation by showing a gain-of-function ZDHHC21 mutation enhances FYN and APP palmitoylation to produce Alzheimer's pathology rescuable by PAT inhibitors.

   Evidence Exome sequencing of a familial AD pedigree plus CRISPR knock-in mice with FYN/APP palmitoylation assays, LTP recordings, behavior, Aβ ELISA, and pharmacological rescue

   PMID:37365538

   Open questions at the time

   • How p.T209S alters enzyme activity at the molecular level not defined
   • Relative contributions of FYN versus APP acylation to phenotype not dissected
9. 2024 High

   Showed substrate acylation can be destabilizing, with ZDHHC21 palmitoylating FASN at Cys1317 to reduce its stability and suppress lymphoma proliferation.

   Evidence Co-IP, palmitoylation assay, Cys1317 site-directed mutagenesis, and DLBCL proliferation assays in vitro and in vivo

   PMID:38195819

   Open questions at the time

   • Mechanism by which acylation destabilizes FASN not detailed
   • Context determining tumor-suppressive versus tumor-supportive ZDHHC21 roles unclear
10. 2025 High

    Resolved how Ca²⁺ gating is deployed spatially, showing store depletion recruits ZDHHC21 into Orai1/STIM1 puncta where it binds and S-acylates STIM1 to enable SOCE.

    Evidence Depilated mouse model with calmodulin-binding domain disruption plus STIM1 S-acylation, live-cell puncta imaging, co-IP, SOCE measurement, and immune phenotyping (preprint)

    PMID:41279060

    Open questions at the time

    • Preprint, not yet peer-reviewed
    • STIM1 acylation site and how acylation promotes SOCE not fully defined
11. 2025 Medium

    Placed ZDHHC21 in an AUF1–ETS2 transcriptional circuit and identified STING palmitoylation as a driver of epithelial pyroptosis in sepsis-induced lung injury.

    Evidence RIP, RNA pulldown, mRNA decay assays, ZDHHC21 knockdown/overexpression, STING palmitoylation and pyroptosis marker assays in CLP/LPS models

    PMID:41460311

    Open questions at the time

    • Single lab
    • STING palmitoylation site not mapped
    • Direct versus indirect effect on pyroptosis not separated

• A unifying structural and regulatory model explaining how Ca²⁺/calmodulin gating selects among diverse substrates across plasma membrane, ER-PM junctions, and mitochondria remains unresolved.
• No structure of ZDHHC21 or its calmodulin-bound active state
• Rules governing substrate selectivity unknown
• How a plasma-membrane PAT acts on mitochondrial substrates like AK2 is unexplained