FIG4 encodes a Sac1-domain polyphosphoinositide phosphatase (orthologue of mammalian FIG4/SAC3) that removes the 5-phosphate from phosphatidylinositol 3,5-bisphosphate, regenerating PI3P. Fig4 is a Mg2+-activated, PI(3,5)P2-selective enzyme that binds the HEAT-repeat scaffold Vac14 and, through it, joins the opposing PI3P 5-kinase Fab1, Vac7 and Atg18 in a single PI(3,5)P2 regulatory complex on the limiting membrane of the vacuole. Fig4 is the major enzyme for PI(3,5)P2 turnover after hyperosmotic shock, yet together with Vac14 it is also needed for normal Fab1 activation and PI(3,5)P2 synthesis, giving the complex a dual role in setting PI(3,5)P2 levels and vacuole size. fig4 deletion suppresses the enlarged-vacuole and PI(3,5)P2 defects of vac7 mutants. FIG4 was first identified as a pheromone-induced gene, and fig4 deletion mutants mate inefficiently because they polarize poorly and form misshapen mating projections in mating mixtures.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000329 fungal-type vacuole membrane | IDA PMID:14528018 Vacuole size control: regulation of PtdIns(3,5)P2 levels by ... | ACCEPT | Summary: Rudge et al. showed Fig4-GFP on the limiting membrane of the vacuole, dependent on Vac14. Supporting Evidence: PMID:14528018 Analysis of a Fig4-GFP fusion protein revealed that the Fig4 phosphatase is localized to the limiting membrane of the vacuole. |
| GO:0005515 protein binding | IPI PMID:12062051 Vac14 controls PtdIns(3,5)P(2) synthesis and Fab1-dependent ... | REMOVE | Summary: Dove et al. (focused study) report Vac14 interactions including Fig4. Real interaction within the PI(3,5)P2 regulatory complex, but bare protein binding is uninformative; captured by PAS complex. Removal does not dispute the interaction itself. Supporting Evidence: PMID:12062051 interacts with several proteins involved in clathrin-mediated membrane sorting and phosphoinositide metabolism |
| GO:0005515 protein binding | IPI PMID:14528018 Vacuole size control: regulation of PtdIns(3,5)P2 levels by ... | REMOVE | Summary: Rudge et al. show Fig4 physically associates with Vac14. Interaction is real and functionally important (Vac14 directs Fig4 localisation), but represented better by complex membership. Removal does not dispute the interaction itself. Supporting Evidence: PMID:14528018 we found that Fig4 physically associates with Vac14 in a common membrane-associated complex |
| GO:0005515 protein binding | IPI PMID:16429126 Proteome survey reveals modularity of the yeast cell machine... | REMOVE | Summary: Genome-wide TAP-MS complex survey (Gavin 2006) recovering Fig4-Vac14; uninformative bare binding from a large-scale screen, redundant with focused evidence. Supporting Evidence: PMID:16429126 Here we report the first genome-wide screen for complexes in an organism, budding yeast, using affinity purification and mass spectrometry. |
| GO:0005515 protein binding | IPI PMID:19037259 VAC14 nucleates a protein complex essential for the acute in... | REMOVE | Summary: Jin et al.: Fig4 co-precipitates with Fab1 within the Vac14-scaffolded complex (Fab1 and Fig4 do not interact directly by two-hybrid). Captured by PAS complex. Removal does not dispute the interaction itself. Supporting Evidence: PMID:19037259 Vac14 exerts an effect as a scaffold for the PI(3,5)P(2) regulatory complex by direct contact with the known regulators of PI(3,5)P(2): Fig4, Fab1, Vac7 and Atg18 |
| GO:0005515 protein binding | IPI PMID:19037259 VAC14 nucleates a protein complex essential for the acute in... | REMOVE | Summary: Jin et al.: Fig4 binds Vac14 directly at a site distinct from the Fab1/Vac7/Atg18-binding region. Captured by PAS complex. Removal does not dispute the interaction itself. Supporting Evidence: PMID:19037259 Vac14 exerts an effect as a scaffold for the PI(3,5)P(2) regulatory complex by direct contact with the known regulators of PI(3,5)P(2): Fig4, Fab1, Vac7 and Atg18 |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | REMOVE | Summary: Proteome-wide AE-MS interactome recovering Fig4-Vac14; bare protein binding from a large-scale map is uninformative. Supporting Evidence: PMID:37968396 The 4,159 pull-downs generated a highly structured network of 3,927 proteins connected by 31,004 interactions |
| GO:0005774 vacuolar membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt location (vacuole membrane, peripheral) mapped to GO; supported by Fig4-GFP imaging. Supporting Evidence: PMID:14528018 Analysis of a Fig4-GFP fusion protein revealed that the Fig4 phosphatase is localized to the limiting membrane of the vacuole. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | MODIFY | Summary: YeastPathways-to-GO-CAM default cytosol for PWY3O-242. Fig4 acts on PI(3,5)P2 on the vacuole limiting membrane within the Fab1-Vac14 complex; Vac14-Fig4 can associate in the cytosol but the ternary complex and activity are vacuolar. Proposed replacements: fungal-type vacuole membrane Supporting Evidence: PMID:14528018 Analysis of a Fig4-GFP fusion protein revealed that the Fig4 phosphatase is localized to the limiting membrane of the vacuole. |
| GO:0010511 regulation of phosphatidylinositol biosynthetic process | NAS PMID:24323921 Phosphatidylinositol 3,5-bisphosphate: low abundance, high s... | KEEP AS NON CORE | Summary: NAS from review. Besides hydrolysing PI(3,5)P2, Fig4 is paradoxically required (with Vac14) for full activation of Fab1 and PI(3,5)P2 synthesis, so a regulatory role in PIP synthesis is defensible; non-core relative to its phosphatase activity. Supporting Evidence: PMID:18653468 Vac14 and Fig4 serve a dual function: they are both implicated in the synthesis and turnover of PtdIns(3,5)P(2) PMID:24323921 A complex of proteins that includes Fab1/PIKfyve, Vac14, and Fig4/Sac3 mediates the biosynthesis of PI(3,5)P2 |
| GO:0016791 phosphatase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro IPR002013 (SAC domain) mapping to phosphatase activity; correct general parent of the PI(3,5)P2 5-phosphatase activity. Supporting Evidence: PMID:14528018 We demonstrate that Fig4 is a magnesium-activated PtdIns(3,5)P2-selective phosphoinositide phosphatase in vitro. |
| GO:0034399 nuclear periphery | IDA PMID:25817432 Cmr1/WDR76 defines a nuclear genotoxic stress body linking g... | KEEP AS NON CORE | Summary: High-throughput screen of proteins relocalising to the intranuclear quality control compartment (INQ) under genotoxic stress. Cannot be verified from cached text (not named in main text); likely a stress-induced sequestration rather than a functional location. Non-core. Supporting Evidence: PMID:25817432 define a novel intranuclear quality control compartment (INQ) that sequesters misfolded, ubiquitylated and sumoylated proteins in response to genotoxic stress |
| GO:0036092 phosphatidylinositol-3-phosphate biosynthetic process | IEA GO_REF:0000108 | MARK AS OVER ANNOTATED | Summary: Inter-ontology inference (GO_REF:0000108) from the PI(3,5)P2 5-phosphatase activity: the product is PI3P, so GO links the activity to PI3P biosynthesis. Physiologically Fig4 turns over PI(3,5)P2; bulk PI3P is made by Vps34 and Fig4 contributes trivially to it. The meaningful process is PI dephosphorylation / PI(3,5)P2 turnover. Supporting Evidence: PMID:11950935 turnover of PtdIns(3,5)P(2) is mediated in part by the Sac1 polyphosphoinositide phosphatase family member Fig4 |
| GO:0043813 phosphatidylinositol-3,5-bisphosphate 5-phosphatase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000127900 (Fig4/Sac3 clade) with Fig4 (SGD:S000005269) and human FIG4 (Q92562) as experimental descendants. Correct. Supporting Evidence: PMID:14528018 We demonstrate that Fig4 is a magnesium-activated PtdIns(3,5)P2-selective phosphoinositide phosphatase in vitro. |
| GO:0043813 phosphatidylinositol-3,5-bisphosphate 5-phosphatase activity | IDA PMID:14528018 Vacuole size control: regulation of PtdIns(3,5)P2 levels by ... | ACCEPT | Summary: Rudge et al. demonstrated Mg2+-activated, PI(3,5)P2-selective phosphatase activity of Fig4 in vitro. Core activity. Supporting Evidence: PMID:14528018 We demonstrate that Fig4 is a magnesium-activated PtdIns(3,5)P2-selective phosphoinositide phosphatase in vitro. |
| GO:0043813 phosphatidylinositol-3,5-bisphosphate 5-phosphatase activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA via RHEA:32955 and InterPro IPR043573 (Fig4 family). Correct. Supporting Evidence: PMID:14528018 We demonstrate that Fig4 is a magnesium-activated PtdIns(3,5)P2-selective phosphoinositide phosphatase in vitro. |
| GO:0043813 phosphatidylinositol-3,5-bisphosphate 5-phosphatase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways PWY3O-242 assigns Fig4 to PI(3,5)P2 -> PI3P; correct and experimentally supported. Supporting Evidence: PMID:14528018 We demonstrate that Fig4 is a magnesium-activated PtdIns(3,5)P2-selective phosphoinositide phosphatase in vitro. |
| GO:0046854 phosphatidylinositol phosphate biosynthetic process | RCA GO_REF:0000123 | MODIFY | Summary: YeastPathways places all enzymes of the PIP interconversion pathway under PIP biosynthesis. Fig4 removes the 5-phosphate from PI(3,5)P2; its process is phosphoinositide dephosphorylation (turnover), not PIP biosynthesis. Proposed replacements: phosphatidylinositol dephosphorylation Supporting Evidence: PMID:11950935 turnover of PtdIns(3,5)P(2) is mediated in part by the Sac1 polyphosphoinositide phosphatase family member Fig4 |
| GO:0046856 phosphatidylinositol dephosphorylation | IBA GO_REF:0000033 | ACCEPT | Summary: IBA (PTN000127900) for phosphatidylinositol dephosphorylation; correct for this PI(3,5)P2 5-phosphatase. Supporting Evidence: PMID:14528018 We demonstrate that Fig4 is a magnesium-activated PtdIns(3,5)P2-selective phosphoinositide phosphatase in vitro. |
| GO:0046856 phosphatidylinositol dephosphorylation | IDA PMID:14528018 Vacuole size control: regulation of PtdIns(3,5)P2 levels by ... | ACCEPT | Summary: Rudge et al.: Fig4 dephosphorylates PI(3,5)P2 in vitro. Supporting Evidence: PMID:14528018 We demonstrate that Fig4 is a magnesium-activated PtdIns(3,5)P2-selective phosphoinositide phosphatase in vitro. |
| GO:0046856 phosphatidylinositol dephosphorylation | IEA GO_REF:0000120 | ACCEPT | Summary: ARBA/InterPro mapping; correct. Supporting Evidence: PMID:14528018 We demonstrate that Fig4 is a magnesium-activated PtdIns(3,5)P2-selective phosphoinositide phosphatase in vitro. |
| GO:0046856 phosphatidylinositol dephosphorylation | IGI PMID:11950935 Regulation of Fab1 phosphatidylinositol 3-phosphate 5-kinase... | ACCEPT | Summary: Gary et al. genetic interaction with INP52 (SGD:S000005050): loss of FIG4 restores PI(3,5)P2 in vac7 cells, implicating Fig4 in PI(3,5)P2 turnover alongside other Sac-domain phosphatases. Supporting Evidence: PMID:11950935 Deletion of FIG4 in vac7Delta mutant cells suppresses the temperature sensitivity and vacuolar morphology defects, and dramatically restores PtdIns(3,5)P(2) levels. PMID:11950935 turnover of PtdIns(3,5)P(2) is mediated in part by the Sac1 polyphosphoinositide phosphatase family member Fig4 |
| GO:0046856 phosphatidylinositol dephosphorylation | IGI PMID:11950935 Regulation of Fab1 phosphatidylinositol 3-phosphate 5-kinase... | ACCEPT | Summary: Gary et al. genetic interaction with INP53 (SGD:S000005635); as above, supports Fig4 role in PI(3,5)P2 dephosphorylation. Supporting Evidence: PMID:11950935 turnover of PtdIns(3,5)P(2) is mediated in part by the Sac1 polyphosphoinositide phosphatase family member Fig4 |
| GO:0070772 PAS complex | IDA PMID:19037259 VAC14 nucleates a protein complex essential for the acute in... | ACCEPT | Summary: Jin et al.: Fig4 is a component of the Vac14-nucleated PI(3,5)P2 regulatory (PAS) complex with Fab1, Vac7 and Atg18 on the vacuole membrane. Supporting Evidence: PMID:19037259 Vac14 exerts an effect as a scaffold for the PI(3,5)P(2) regulatory complex by direct contact with the known regulators of PI(3,5)P(2): Fig4, Fab1, Vac7 and Atg18 PMID:19037259 Consistent with the yeast two-hybrid studies, Vac14p–mCherry colocalized on the vacuole membrane with GFP- or Venus-tagged Fab1p, Fig4p, Vac7p, and Atg18p |
| GO:0070772 PAS complex | IPI PMID:19037259 VAC14 nucleates a protein complex essential for the acute in... | ACCEPT | Summary: IPI with VAC14: Fig4 binds Vac14 directly within the complex. Supporting Evidence: PMID:19037259 Vac14 exerts an effect as a scaffold for the PI(3,5)P(2) regulatory complex by direct contact with the known regulators of PI(3,5)P(2): Fig4, Fab1, Vac7 and Atg18 |
| GO:0070772 PAS complex | NAS PMID:24323921 Phosphatidylinositol 3,5-bisphosphate: low abundance, high s... | ACCEPT | Summary: NAS from review; consistent with experimental data. Supporting Evidence: PMID:24323921 A complex of proteins that includes Fab1/PIKfyve, Vac14, and Fig4/Sac3 mediates the biosynthesis of PI(3,5)P2 |
| GO:1903100 1-phosphatidyl-1D-myo-inositol 3,5-bisphosphate metabolic process | NAS PMID:24323921 Phosphatidylinositol 3,5-bisphosphate: low abundance, high s... | ACCEPT | Summary: NAS from review. Fig4 participates in both turnover and (via Fab1 activation) synthesis of PI(3,5)P2, so the general PI(3,5)P2 metabolic process term fits. Supporting Evidence: PMID:18653468 Vac14 and Fig4 serve a dual function: they are both implicated in the synthesis and turnover of PtdIns(3,5)P(2) PMID:24323921 Fig4, a PI(3,5)P2 5-phosphatase, catalyzes the turnover of PI(3,5)P2 in yeast |
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Download this section (compressed HTML)Q: How is Fig4 phosphatase activity restrained within the Fab1-Vac14 complex so that Fig4 is simultaneously required for Fab1 activation, and is catalytic activity needed for that activating role?
Experiment: Express catalytically dead Fig4 (active-site Cys mutant) in fig4 cells and measure hyperosmotic PI(3,5)P2 elevation, Fab1-Vac14 co-IP and vacuole morphology.
Hypothesis: The Fig4 requirement for Fab1 activation is structural (complex assembly) rather than catalytic
Type: genetic / lipidomic
Phosphatidylinositol 3,5-bisphosphate (PtdIns[3,5]P2) phosphatase; required for efficient mating and response to osmotic shock; physically associates with and regulated by Vac14p; contains a SAC1-like domain; homologous to human FIG4, which is associated with CMT4J, a form of Charcot-Marie-Tooth disorder
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