Dictyostelium extracellular cAMP relay / aggregation oscillator

The defining Dictyostelium discoideum aggregation system — a self-organising extracellular cAMP oscillator that propagates chemotactic waves so that starving amoebae stream together into a mound. Secreted cAMP is detected by the seven-transmembrane receptor cAR1 (carA), which couples through the heterotrimeric G protein Galpha2 (gpaB); receptor activation recruits the PH-domain adaptor CRAC (dagA) that is required to activate the aggregation adenylyl cyclase ACA (acaA), which synthesises cAMP. The newly made cAMP is secreted and activates cAR1 on neighbouring cells (the RELAY, a positive feedback), while the extracellular phosphodiesterase PdsA degrades secreted cAMP and the intracellular response-regulator phosphodiesterase RegA degrades internal cAMP — the negative feedback / adaptation that lets the system oscillate and produce propagating waves rather than saturate. This is the extracellular-cAMP CHEMOTACTIC oscillator, distinct from the generic intracellular GPCR->cAMP->PKA cassette. OUT OF SCOPE: the downstream PKA-driven developmental gene expression (cAMP effector; see the pkaC review and the SDF-2 relay module), the actin/PI3K chemotaxis motor, and the later adenylyl cyclases ACG/ACR. Phrased over functions and family selectors with D. discoideum representatives.

MODULE:dicty_extracellular_camp_relayDRAFTSignaling Pathwaymodules/dicty_extracellular_camp_relay.yaml
aggregation involved in sorocarp developmentGO:0031152
GO:0031152
aggregation involved in sorocarp development
The module's biological output is chemotactic aggregation (GO:0031152), driven by the relayed cAMP oscillator.
file:DICDI/carA/carA-ai-review.yaml
carA gene review (Dictyostelium discoideum)
cAMP receptor cAR1 grounding (UniProtKB:P13773, GO:0001646 cAMP receptor activity).
file:DICDI/gpaB/gpaB-ai-review.yaml
gpaB gene review (Dictyostelium discoideum)
Galpha2 grounding (UniProtKB:P16051, GO:0003925 G protein activity); couples cAR1 to downstream effectors.
file:DICDI/dagA/dagA-ai-review.yaml
dagA gene review (Dictyostelium discoideum)
CRAC adaptor grounding (UniProtKB:P35401, GO:0008047 enzyme activator activity); required to activate ACA.
file:DICDI/acaA/acaA-ai-review.yaml
acaA gene review (Dictyostelium discoideum)
Aggregation adenylyl cyclase ACA grounding (UniProtKB:Q03100, GO:0004016 adenylate cyclase activity); the cAMP source of the relay.
file:DICDI/pdsA/pdsA-ai-review.yaml
pdsA gene review (Dictyostelium discoideum)
Extracellular cAMP phosphodiesterase grounding (UniProtKB:P12019, GO:0004115); sharpens/resets the secreted cAMP wave.
file:DICDI/regA/regA-ai-review.yaml
regA gene review (Dictyostelium discoideum)
Intracellular cAMP phosphodiesterase grounding (UniProtKB:Q23917, GO:0004115); adaptation of the internal cAMP response.

Dictyostelium-specific extracellular-cAMP chemotactic oscillator grounded to cAR1 (P13773, GO:0001646), Galpha2 (P16051, GO:0003925), CRAC (P35401, GO:0008047), ACA (Q03100, GO:0004016), PdsA (P12019, GO:0004115) and RegA (Q23917, GO:0004115). GO molecular-function terms were taken from the completed DICDI reviews; nodes use PANTHER family selectors plus D. discoideum representative members. Explicitly named "extracellular_camp_relay" so it does not collide with the generic gpcr_camp_pka_signaling module: the discriminating feature is that the cAMP ligand is SECRETED and relayed between cells, driving chemotactic waves. PKA (the intracellular cAMP effector) is downstream and out of scope here.

4Nodes
3Parts
0Variant Sets
0Variants
6Annotons
4Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:dicty_extracellular_camp_relay deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Gene-review completeness (6/6 grounded genes reviewed)

3 complete review(s) · 0 with deep research · 0 missing review · 6 reviewed but lacking deep research

Gene Review Complete Deep research
acaA Q03100 ✓ ✓ ✗
carA P13773 ✓ ✓ ✗
dagA P35401 ✓ 36/38 ✗
gpaB P16051 ✓ 43/45 ✗
pdsA P12019 ✓ 28/29 ✗
regA Q23917 ✓ ✓ ✗

Details

Extracellular cAMP relay (cAR1/Galpha2 -> CRAC -> ACA -> secreted cAMP; PdsA/RegA reset)Signaling Pathwaydicty_extracellular_camp_relay
aggregation involved in sorocarp developmentGO:0031152

Connections

camp_reception -> aca_activation Positively Regulates
cAR1/Galpha2 activation recruits CRAC, which is required to activate ACA (the receptor-to-cyclase limb).
aca_activation -> camp_reception Provides Input For
The cAMP synthesised by ACA is secreted and activates cAR1 on neighbouring cells — the RELAY / positive-feedback that propagates the wave.
camp_degradation -> camp_reception Negatively Regulates
PdsA degrades secreted cAMP, terminating cAR1 stimulation between waves.
camp_degradation -> aca_activation Negatively Regulates
RegA degrades intracellular cAMP (adaptation), letting the oscillator reset rather than saturate.
Part 1: extracellular cAMP reception
cAR1 senses secreted cAMP and activates Galpha2Regulatory Stepcamp_reception

Annotons

cAR1 (carA): cAMP receptor GPCR
car1_activity
Participant: Family: cAMP receptor (cAR) GPCR family
Family:
cAMP receptor (cAR) GPCR familyPANTHER:PTHR23112
Representative Members: cAR1 (Dictyostelium discoideum)UniProtKB:P13773

Function

cAMP receptor activityGO:0001646

Locations

plasma membraneGO:0005886

Seven-transmembrane receptor that binds secreted cAMP and drives chemotaxis and the relay; first of the cAR1-4 series.

Galpha2 (gpaB): heterotrimeric G-protein alpha subunit
galpha2_activity
Participant: Family: Heterotrimeric G-protein alpha subunit family
Family:
Heterotrimeric G-protein alpha subunit familyPANTHER:PTHR10218
Representative Members: Galpha2 (Dictyostelium discoideum)UniProtKB:P16051

Function

G protein activityGO:0003925

Locations

plasma membraneGO:0005886

G-protein alpha subunit that transduces cAR1 activation to the adenylyl-cyclase-activation machinery.

Part 2: adenylyl cyclase activation (cAMP synthesis)
CRAC activates ACA to synthesise cAMPReactionaca_activation

Annotons

CRAC (dagA): PH-domain activator of ACA
crac_activity
Participant: Family: Tandem-PH-domain CRAC adaptor family
Family:
Tandem-PH-domain CRAC adaptor familyPANTHER:PTHR14336
Representative Members: CRAC (Dictyostelium discoideum)UniProtKB:P35401

Function

enzyme activator activityGO:0008047

Locations

plasma membraneGO:0005886

Pleckstrin-homology-domain adaptor that binds PIP3 at the membrane and is required for receptor/G-protein activation of ACA.

ACA (acaA): aggregation adenylyl cyclase
aca_activity
Participant: Family: Adenylyl cyclase class-4/guanylyl cyclase family (ACA)
Family:
Adenylyl cyclase class-4/guanylyl cyclase family (ACA)PANTHER:PTHR45627
Representative Members: ACA (Dictyostelium discoideum)UniProtKB:Q03100

Function

adenylate cyclase activityGO:0004016
Substrates: ATP
Products: 3',5'-cyclic AMP diphosphate

Locations

plasma membraneGO:0005886

Aggregation-stage adenylyl cyclase that makes the cAMP secreted to relay the chemotactic signal to neighbouring cells.

Part 3: cAMP degradation and adaptation (oscillator reset)
PdsA and RegA degrade extracellular and intracellular cAMPReactioncamp_degradation

Annotons

PdsA: extracellular cAMP phosphodiesterase
pdsa_activity
Participant: Family: Extracellular cyclic-nucleotide phosphodiesterase family (PdsA)
Family:
Extracellular cyclic-nucleotide phosphodiesterase family (PdsA)PANTHER:PTHR28283
Representative Members: PdsA (Dictyostelium discoideum)UniProtKB:P12019

Function

cAMP phosphodiesterase activityGO:0004115
Substrates: 3',5'-cyclic AMP (extracellular)
Products: AMP

Locations

extracellular regionGO:0005576

Secreted/cell-surface phosphodiesterase that degrades extracellular cAMP between waves, sharpening the chemotactic gradient.

RegA: intracellular cAMP phosphodiesterase (adaptation)
rega_activity_relay
Participant: Family: Response-regulator cyclic-nucleotide phosphodiesterase family (RegA)
Family:
Response-regulator cyclic-nucleotide phosphodiesterase family (RegA)PANTHER:PTHR11347
Representative Members: RegA (Dictyostelium discoideum)UniProtKB:Q23917

Function

cAMP phosphodiesterase activityGO:0004115
Substrates: 3',5'-cyclic AMP (intracellular)
Products: AMP

Locations

cytosolGO:0005829

Intracellular cAMP phosphodiesterase providing adaptation so the oscillator can reset and fire repetitively.