spongiome

GO:0062160 · Membrane organelle · Membrane bounded organelle · Proposed

A network of tubules and vesicles that is part of a contractile vacuole complex and participates in external water discharge during osmoregulation. [GO:0062160]

Synonyms: decorated spongiome

Part of: contractile vacuole complex (GO:0062159)

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

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
spongiome V-ATPase	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Proton-pumping complex on spongiome membranes that contributes to contractile-vacuole fluid segregation. `PMID:8294479` Nolta and Steck 1994 purified the Dictyostelium contractile-vacuole complex and distinguished V-H+-ATPase-rich spongiome membranes from the pump-poor bladder fraction. `DOI:10.1242/jcs.108.10.3163` Fok et al. 1995 localized V-ATPase antigenicity to the pegs on Paramecium decorated spongiome tubules. `DOI:10.1242/jeb.205.20.3261` Gronlien et al. 2002 linked V-ATPase on the Paramecium decorated spongiome to electrogenic fluid segregation in the contractile-vacuole complex.

Taxonomic distribution

NCBITaxon:44689 Dictyostelium discoideum — COMMON: Dictyostelium discoideum cells contain a bipartite contractile-vacuole complex with spongiome membranes surrounding the bladder. [PMID:8294479]
NCBITaxon:44030 Paramecium multimicronucleatum — COMMON: Paramecium multimicronucleatum cells have decorated spongiome regions in the radial arms of the contractile-vacuole complex. [DOI:10.1242/jeb.205.20.3261]

Canonical examples

NCBITaxon:44689 Dictyostelium discoideum — Amoebozoan model in which the contractile-vacuole complex was biochemically resolved into bladder and spongiome membranes. [PMID:8294479]
NCBITaxon:44030 Paramecium multimicronucleatum — Ciliate model in which microelectrode measurements and V-ATPase labeling tied decorated-spongiome radial arms to fluid segregation. [DOI:10.1242/jeb.205.20.3261]

Functions

contractile-vacuole fluid segregation — V-ATPase-bearing spongiome membranes participate in ion-driven water handling by the contractile-vacuole complex.
- PMID:8294479 Nolta and Steck 1994 interpreted the V-H+-ATPase-rich Dictyostelium spongiome as a candidate primary energy transducer for pumping water out of the cytoplasm.
- DOI:10.1242/jeb.205.20.3261 Gronlien et al. 2002 measured contractile-vacuole membrane potential in Paramecium and connected decorated-spongiome V-ATPase to fluid segregation.
- DOI:10.1016/B978-0-12-407695-2.00002-0 Docampo et al. 2013 review the contractile vacuole complex as an osmoregulatory organelle in protists.

Mechanism graphs

Spongiome V-ATPase supports contractile-vacuole fluid segregation (FUNCTION)

A V-ATPase-rich spongiome is the tubular or vesicular membrane subnetwork of the contractile-vacuole complex; in Paramecium, decorated-spongiome V-ATPase contributes to the electrogenic membrane potential needed for fluid segregation.

Subject	Predicate	Object	Evidence
spongiome	is part of	contractile vacuole complex	`GO:0062160` GO:0062160 defines the spongiome as part of the contractile vacuole complex. `PMID:8294479` Nolta and Steck 1994 purified a bipartite Dictyostelium contractile-vacuole complex with separable bladder and spongiome membranes.
spongiome V-ATPase	resides in	spongiome	`PMID:8294479` Nolta and Steck 1994 found a high density of catalytically active V-H+-ATPase projections on Dictyostelium spongiome membranes. `DOI:10.1242/jcs.108.10.3163` Fok et al. 1995 localized V-ATPase markers to decorated tubules of the Paramecium spongiome.
spongiome V-ATPase	contributes to	radial-arm membrane potential	`DOI:10.1242/jeb.205.20.3261` Gronlien et al. 2002 coupled V-ATPase labeling in radial arms to the measured contractile-vacuole membrane potential.
radial-arm membrane potential	supports	contractile-vacuole fluid segregation	`DOI:10.1242/jeb.205.20.3261` Gronlien et al. 2002 reported that V-ATPase inhibition decreased both contractile-vacuole membrane potential and fluid segregation.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for spongiome-localized V-ATPase complexes or subunit families. The cited organelle studies establish V-ATPase localization or activity at the spongiome, but this first record leaves the multisubunit complex ungrounded rather than choosing an unverified Complex Portal, GO, Pfam or InterPro CURIE for the exact spongiome-localized subset.

Evidence

GO:0062160 Gene Ontology cellular-component term for spongiome.
PMID:8294479 Nolta and Steck 1994, Isolation and initial characterization of the bipartite contractile vacuole complex from Dictyostelium discoideum, Journal of Biological Chemistry.
DOI:10.1242/jcs.108.10.3163 Fok et al. 1995, The pegs on the decorated tubules of the contractile vacuole complex of Paramecium are proton pumps, Journal of Cell Science.
DOI:10.1242/jeb.205.20.3261 Gronlien et al. 2002, Relationship between the membrane potential of the contractile vacuole complex and its osmoregulatory activity in Paramecium multimicronucleatum, Journal of Experimental Biology.
DOI:10.1016/B978-0-12-407695-2.00002-0 Docampo et al. 2013 review acidocalcisome and contractile-vacuole osmoregulation in protists and are cited by GO:0062160 for the spongiome definition.

Curation history

2026-09-12T10:35:12Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-12T10:36:04Z codex · EXPANDED_RECORD — Added contractile-vacuole-complex parthood, a decorated-spongiome synonym, spongiome V-ATPase as a reviewed-label-only constituent, Dictyostelium and Paramecium scope and examples, a fluid-segregation function, primary evidence, a nonmechanistic function graph and a V-ATPase grounding TODO.
2026-09-12T10:41:01Z codex · ADDRESSED_PR_REVIEW — Addressed PR #630 review issues #631 and #632 by narrowing species-scope notes to presence assertions and adding the Docampo 2013 GO-definition review to record-level evidence.

Source: data/structures/membrane_organelle/spongiome.yaml