CLEC7A (Dectin-1) is a type II transmembrane C-type lectin receptor (CLR) expressed primarily on microglia and other myeloid cells. Dectin-1 is the defining surface marker of disease-associated microglia (DAM) — a protective microglial activation state discovered in Alzheimer's disease that is dependent on TREM2 signaling. CLEC7A activates SYK kinase-dependent phagocytic and inflammatory programs through its hemITAM signaling motif.
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| Protein Name | C-type Lectin Domain Family 7 Member A (Dectin-1) |
| Gene | [CLEC7A](/genes/clec7a) |
| UniProt ID | [Q9BXN2](https://www.uniprot.org/uniprot/Q9BXN2) |
| Molecular Weight | ~28 kDa |
| Subcellular Localization | Plasma membrane (type II orientation) |
| Protein Family | C-type lectin receptors (CLRs), Group V NK cell receptors |
| Associated Diseases | [Alzheimer's disease](/diseases/alzheimers-disease), [Multiple Sclerosis](/diseases/multiple-sclerosis), [ALS](/diseases/amyotrophic-lateral-sclerosis) |
CLEC7A is a 247 amino acid type II transmembrane glycoprotein:
¶ Domain Architecture
- Cytoplasmic tail (aa 1–44): Contains a hemITAM motif (YxxxL) at Tyr-15 that recruits SYK kinase upon phosphorylation. Unlike classical ITAM motifs (which have two YxxL sequences), the hemITAM is sufficient for SYK recruitment through receptor dimerization
- Transmembrane domain (aa 45–66): Single-pass type II orientation (N-terminus intracellular, C-terminus extracellular)
- Stalk region (aa 67–117): Flexible linker; contains an N-linked glycosylation site. The stalk enables dimerization, which is required for full signaling capacity
- C-type lectin-like domain (CTLD) (aa 118–247): Binds beta-1,3-glucan ligands. Despite being classified as a C-type lectin, Dectin-1 binds ligands in a calcium-independent manner. The CTLD adopts a compact fold with two alpha-helices, two antiparallel beta-sheets, and a ligand-binding groove
Dectin-1 forms homodimers on the cell surface through its stalk region and CTLD. Dimerization brings two hemITAM motifs into proximity, enabling productive SYK recruitment (SYK has tandem SH2 domains that bridge two phospho-hemITAMs).
Two major isoforms exist:
- Isoform A (full-length): Contains the stalk region; forms higher-order oligomers
- Isoform B (Δ stalk): Lacks the stalk; remains monomeric but retains ligand binding and some signaling capacity
In the periphery, Dectin-1 is the primary receptor for beta-1,3-glucans on fungal cell walls, mediating antifungal innate immunity. In the CNS, Dectin-1 recognizes endogenous ligands:
- Damage-associated molecular patterns (DAMPs): Released from dying neurons, including oxidized lipids and carbohydrates
- Myelin debris: During demyelination, exposed carbohydrate structures on damaged myelin are recognized by Dectin-1
- Amyloid-associated lipids: Modified lipoproteins in the plaque microenvironment
Ligand binding triggers:
- Src family kinase phosphorylation of the hemITAM Tyr-15
- SYK kinase recruitment and activation
- Downstream activation of:
- CARD9/BCL10/MALT1 → NF-κB → pro-inflammatory cytokines (IL-1β, TNF, IL-6)
- PLCγ2 (PLCG2) → NFAT → immune gene transcription
- PI3K/AKT → cell survival and metabolic reprogramming
- Raf-1 → noncanonical NF-κB → anti-inflammatory cytokine production (IL-10)
- NADPH oxidase (NOX2) → ROS production for pathogen killing
Dectin-1 directly triggers phagocytic cup formation through SYK-dependent actin remodeling. In microglia, this mediates:
- Amyloid-beta plaque phagocytosis
- Myelin debris clearance for remyelination
- Apoptotic neuron engulfment
- Synaptic pruning (complement-dependent and independent)
CLEC7A is one of the most robustly upregulated genes in DAM:
- Single-cell RNA-seq of 5xFAD mouse brains identified CLEC7A as a top Stage 2 DAM marker
- CLEC7A+ microglia form a physical barrier around amyloid plaques, compacting them and limiting neuritic dystrophy
- TREM2 loss-of-function (e.g., R47H variant) prevents CLEC7A upregulation, locking microglia in a dysfunctional intermediate state
- Human AD brain single-nucleus RNA-seq confirms CLEC7A as a conserved DAM marker
- CLEC7A expression correlates with Braak stage and plaque density
Dectin-1 has dual roles in demyelinating disease:
- Protective: Promotes myelin debris phagocytosis, enabling remyelination by oligodendrocyte precursors
- Pathogenic: Excessive Dectin-1 signaling can amplify inflammatory demyelination through IL-17 and GM-CSF production
¶ ALS and Aging
CLEC7A marks activated microglia in the spinal cord of SOD1 mice and in aging white matter (white matter-associated microglia, WAM). These populations share the DAM transcriptional signature.
- Systemic administration of particulate beta-glucan (curdlan, whole glucan particles) in AD mouse models enhances amyloid phagocytosis and improves cognition
- Trained immunity: Beta-glucan epigenetically reprograms myeloid cells for enhanced responsiveness, potentially providing long-lasting benefit
TREM2 agonist antibodies (AL002/latozinemab) in AD clinical trials promote CLEC7A upregulation by facilitating the Stage 1 → Stage 2 DAM transition.