apicomplexan dense granule

GO:0020026 · Membrane organelle · Membrane bounded organelle · Proposed

Electron-dense organelle with a granular internal matrix found in a apicomplexan parasite; contains proteins destined to be secreted into the parasitophorous vacuole following parasite invasion of a host cell. [GO:0020026]

Synonyms: dense body

Has part: apicomplexan dense granule membrane (GO:0030668)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Essential	Role
apicomplexan dense granule membrane	Lipid	part of	`GO:0030668`	ESSENTIAL	Lipid bilayer that bounds the dense granule and encloses its secretory cargo. `DOI:10.1111/jeu.12904` Griffith et al. 2022 review dense-granule biogenesis, secretion, and function in Toxoplasma gondii.
dense granule proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	UNKNOWN	Secretory cargo proteins stored in dense granules and released into the parasitophorous vacuole or host cell. `DOI:10.1111/jeu.12904` Griffith et al. 2022 review Toxoplasma dense granule proteins as secretory cargo. `DOI:10.1016/j.pt.2014.12.002` Mercier and Cesbron-Delauw 2015 review dense granules within the Toxoplasma secretory system.
GRA17/GRA23 PVM permeability factors	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	UNKNOWN	Toxoplasma dense-granule proteins that localize to the parasitophorous vacuole membrane and mediate small-molecule permeability. `DOI:10.1016/j.chom.2015.04.003` Gold et al. 2015 identified GRA17 and GRA23 as dense-granule proteins that mediate PVM permeability. `DOI:10.1016/j.parint.2013.04.003` Masatani et al. 2013 identified TgGRA23 as a Toxoplasma dense-granule protein associated with the PVM and intravacuolar network.
exported dense granule effectors	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	UNKNOWN	Dense-granule proteins exported beyond the parasitophorous vacuole membrane to alter host-cell pathways. `DOI:10.1016/j.chom.2013.03.002` Bougdour et al. 2013 identified GRA16 as an exported dense-granule protein that reaches the host nucleus.

Taxonomic distribution

NCBITaxon:2759 Eukaryota — RARE: Apicomplexan dense granules are specialized secretory organelles of microbial eukaryotes rather than conserved eukaryotic compartments. [DOI:10.1016/j.ijpara.2005.03.011]
NCBITaxon:5794 Apicomplexa — COMMON: Dense granules are secretory organelles found in apicomplexan parasites and defined by granular, electron-dense cargo. [DOI:10.1016/j.ijpara.2005.03.011]

Canonical examples

NCBITaxon:5811 Toxoplasma gondii — Apicomplexan model in which dense-granule GRA proteins, GRA16 export, and GRA17/GRA23-mediated PVM permeability have been experimentally studied. [DOI:10.1016/j.chom.2015.04.003]

Functions

dense granule protein secretion — Dense granules secrete GRA cargo proteins into the parasitophorous vacuole after host-cell invasion.
- PMID:9208224 Carruthers and Sibley 1997 showed that Toxoplasma dense-granule secretion follows microneme and rhoptry secretion during host-cell invasion.
- DOI:10.1111/jeu.12904 Griffith et al. 2022 review dense-granule secretion in Toxoplasma gondii.
parasitophorous vacuole membrane permeability — Dense-granule cargo proteins can localize to the PVM and mediate passive small-molecule movement between the host cell and parasitophorous vacuole.
- DOI:10.1016/j.chom.2015.04.003 Gold et al. 2015 linked the dense-granule proteins GRA17 and GRA23 to PVM permeability and nutrient access.
host cell effector delivery — Some dense-granule proteins cross the PVM and reach host-cell compartments where they modulate host gene expression and signaling.
- DOI:10.1016/j.chom.2013.03.002 Bougdour et al. 2013 showed that the exported dense-granule protein GRA16 reaches the host nucleus and alters host gene expression.

Mechanism graphs

Dense-granule GRA proteins remodel the parasitophorous vacuole (FUNCTION)

The dense-granule membrane encloses a secretory cargo compartment; after host-cell invasion, dense-granule exocytosis releases GRA proteins, including GRA17 and GRA23 PVM permeability factors, into the PV/PVM.

Subject	Predicate	Object	Evidence
apicomplexan dense granule membrane	bounds	apicomplexan dense granule	`DOI:10.1111/jeu.12904` Griffith et al. 2022 review dense-granule biogenesis in Toxoplasma.
dense granule lumen	is part of	apicomplexan dense granule	`DOI:10.1111/jeu.12904` Griffith et al. 2022 review dense granules as secretory organelles that store GRA cargo.
dense granule proteins	reside in	dense granule lumen	`DOI:10.1016/j.pt.2014.12.002` Mercier and Cesbron-Delauw 2015 review Toxoplasma GRA proteins as dense-granule cargo.
GRA17/GRA23 PVM permeability factors	are members of	dense granule proteins	`DOI:10.1016/j.chom.2015.04.003` Gold et al. 2015 identified GRA17 and GRA23 as Toxoplasma dense-granule proteins.
dense granule exocytosis	releases	dense granule proteins	`PMID:9208224` Carruthers and Sibley 1997 observed dense-granule secretion after host-cell invasion by Toxoplasma.
dense granule exocytosis	delivers	GRA17/GRA23 PVM permeability factors	`DOI:10.1016/j.chom.2015.04.003` Gold et al. 2015 studied GRA17 and GRA23 as dense-granule proteins that localize to the PVM.
GRA17/GRA23 PVM permeability factors	localize to	parasitophorous vacuole membrane	`DOI:10.1016/j.chom.2015.04.003` Gold et al. 2015 found that GRA17 localizes to the PVM and identified GRA23 as a related PVM permeability factor. `DOI:10.1016/j.parint.2013.04.003` Masatani et al. 2013 identified TgGRA23 as a Toxoplasma dense-granule protein associated with the PVM and intravacuolar network.
GRA17/GRA23 PVM permeability factors	mediate	PVM small-molecule permeability	`DOI:10.1016/j.chom.2015.04.003` Gold et al. 2015 connected GRA17 and GRA23 to PVM conductance and small-molecule permeability.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for dense granule proteins, GRA17/GRA23 PVM permeability factors, and exported dense-granule effectors. The first record uses functionally named GRA cargo cohorts because dense-granule cargo and exported effectors span multiple divergent families, and no exact cross-source CURIE was curated for each cohort.

Evidence

DOI:10.1111/jeu.12904 Griffith et al. 2022, Dense granule biogenesis, secretion, and function in Toxoplasma gondii, Journal of Eukaryotic Microbiology.
DOI:10.1016/j.pt.2014.12.002 Mercier and Cesbron-Delauw 2015, Toxoplasma secretory granules: one population or more?, Trends in Parasitology.
DOI:10.1016/j.ijpara.2005.03.011 Mercier et al. 2005, Dense granules: are they key organelles to help understand the parasitophorous vacuole of all apicomplexa parasites?, International Journal for Parasitology.
PMID:9208224 Carruthers and Sibley 1997, Sequential protein secretion from three distinct organelles of Toxoplasma gondii accompanies invasion of human fibroblasts, European Journal of Cell Biology.
DOI:10.1016/j.chom.2015.04.003 Gold et al. 2015, The Toxoplasma Dense Granule Proteins GRA17 and GRA23 Mediate the Movement of Small Molecules between the Host and the Parasitophorous Vacuole, Cell Host & Microbe.
DOI:10.1016/j.chom.2013.03.002 Bougdour et al. 2013, Host Cell Subversion by Toxoplasma GRA16, an Exported Dense Granule Protein that Targets the Host Cell Nucleus and Alters Gene Expression, Cell Host & Microbe.
DOI:10.1016/j.parint.2013.04.003 Masatani et al. 2013, TgGRA23, a novel Toxoplasma gondii dense granule protein associated with the parasitophorous vacuole membrane and intravacuolar network, Parasitology International.

Curation history

2026-09-10T05:11:00Z claude · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-10T05:11:59Z claude · EXPANDED_RECORD — Added the dense-granule membrane part, dense-granule protein cargo cohorts, rare eukaryotic and common Apicomplexa taxonomic scope, Toxoplasma gondii as a canonical example, secretion and parasitophorous-vacuole functions, a GRA17/GRA23 PVM permeability graph, and a grounding TODO for GRA cohorts.
2026-09-10T05:20:30Z claude · FIXED_EVIDENCE_SCOPE — Cited the Mercier et al. 2005 Apicomplexa dense-granule review on broad taxonomic distribution instead of relying on the GO identity alone.
2026-09-10T05:25:10Z claude · FIXED_EVIDENCE_SCOPE — Cited Masatani et al. 2013 on the GRA17/GRA23 component and PVM-localization edge to support TgGRA23 localization directly.

Source: data/structures/membrane_organelle/apicomplexan_dense_granule.yaml