Pik1 is one of the two essential type III phosphatidylinositol 4-kinases of Saccharomyces cerevisiae (orthologous to mammalian PI4KIIIbeta/PI4KB). It phosphorylates phosphatidylinositol at the D-4 position to generate PtdIns4P (EC 2.7.1.67), the precursor of PtdIns(4,5)P2. Pik1 is a soluble protein that is recruited to trans-Golgi network cisternae by its calcium-binding regulatory subunit Frq1 (frequenin) and the clathrin adaptor Gga2, and it also shuttles into the nucleus (Kap95 import, Msn5 export). The Golgi pool of PtdIns4P made by Pik1 is required for exit of secretory cargo from the late Golgi, Golgi and vacuole membrane dynamics, clathrin adaptor progression at the TGN and Atg9 trafficking for autophagy; a nuclear pool is also required for viability. Pik1 and the plasma-membrane PI4K Stt4 together produce almost all cellular PtdIns4P but cannot substitute for each other.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004430 1-phosphatidylinositol 4-kinase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA transfer of PI 4-kinase activity from the PANTHER type III PI4K (PI4KB) clade. Pik1 is a well-characterised member of this clade with direct biochemical evidence, so the phylogenetic inference is sound. Supporting Evidence: PMID:8194527 PIK1 encodes a phosphatidylinositol 4-kinase (PI 4-kinase) essential for growth. file:yeast/PIK1/PIK1-uniprot.txt Type III PI4K |
| GO:0004430 1-phosphatidylinositol 4-kinase activity | IDA PMID:8194527 PIK1, an essential phosphatidylinositol 4-kinase associated ... | ACCEPT | Summary: Garcia-Bustos et al. cloned PIK1 and showed it encodes a PI 4-kinase whose activity is elevated on overexpression; direct evidence for the core catalytic activity. Supporting Evidence: PMID:8194527 PIK1 encodes a phosphatidylinositol 4-kinase (PI 4-kinase) essential for growth. PMID:8194527 overexpress PI 4-kinase activity exclusively in a nuclear fraction |
| GO:0004430 1-phosphatidylinositol 4-kinase activity | IDA PMID:8248783 Phosphatidylinositol 4-kinase: gene structure and requiremen... | ACCEPT | Summary: Flanagan et al. purified yeast PtdIns 4-kinase, cloned PIK1 from peptide sequence and showed that PIK1 overexpression raises PtdIns 4-kinase activity. Direct evidence for the core activity. Supporting Evidence: PMID:8248783 Expression of PIK1 from a multicopy plasmid elevated PtdIns 4-kinase activity |
| GO:0004430 1-phosphatidylinositol 4-kinase activity | IEA GO_REF:0000120 | ACCEPT | Summary: EC 2.7.1.67/RHEA:19877 mapping to 1-phosphatidylinositol 4-kinase activity; matches the experimentally established reaction for Pik1. Supporting Evidence: file:yeast/PIK1/PIK1-uniprot.txt EC=2.7.1.67; Evidence={ECO:0000269|PubMed:8194527, |
| GO:0004430 1-phosphatidylinositol 4-kinase activity | IMP PMID:10587649 The yeast phosphatidylinositol-4-OH kinase pik1 regulates se... | ACCEPT | Summary: Walch-Solimena and Novick (abstract not available in cache) used pik1 mutants to link Pik1 PI4K activity to Golgi secretion; the activity is independently established, so the curator's IMP is accepted. Supporting Evidence: PMID:10930462 Both gene products phosphorylate PtdIns at the D-4 position of the inositol ring to generate PtdIns(4)P |
| GO:0004430 1-phosphatidylinositol 4-kinase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways (PWY3O-242, phosphatidylinositol phosphate biosynthesis) places Pik1 on PI + ATP -> PI4P (EC 2.7.1.67). This is the correct step for Pik1. Supporting Evidence: PMID:10930462 Both gene products phosphorylate PtdIns at the D-4 position of the inositol ring to generate PtdIns(4)P file:yeast/PIK1/PIK1-uniprot.txt EC=2.7.1.67; Evidence={ECO:0000269|PubMed:8194527, |
| GO:0005515 protein binding | IPI PMID:18719252 High-quality binary protein interaction map of the yeast int... | REMOVE | Summary: Interaction with Frq1 (Q06389) from a high-throughput yeast two-hybrid study. Frq1 is the bona fide calcium-binding regulatory subunit that binds the Pik1 N-terminus and recruits it to the Golgi, so the interaction is real, but 'protein binding' conveys no functional information. Removal does not dispute the interaction; the informative content (Frq1-dependent Golgi recruitment) is captured by the TGN location and the description. Supporting Evidence: PMID:16365163 Frq1 (frequenin orthologue) also is essential for viability and binds near the NH2 terminus of Pik1. |
| GO:0005515 protein binding | IPI PMID:20489023 A global protein kinase and phosphatase interaction network ... | REMOVE | Summary: Interaction with Frq1 (Q06389) from a kinase/phosphatase interaction network AP-MS study. Frq1 is the bona fide calcium-binding regulatory subunit that binds the Pik1 N-terminus and recruits it to the Golgi, so the interaction is real, but 'protein binding' conveys no functional information. Removal does not dispute the interaction; the informative content (Frq1-dependent Golgi recruitment) is captured by the TGN location and the description. Supporting Evidence: PMID:16365163 Frq1 (frequenin orthologue) also is essential for viability and binds near the NH2 terminus of Pik1. |
| GO:0005515 protein binding | IPI PMID:22344030 Phosphoinositide-mediated clathrin adaptor progression at th... | REMOVE | Summary: Daboussi et al. showed the Gga2 VHS domain binds Pik1 directly and promotes Pik1 recruitment to the TGN. Genuine interaction, but bare 'protein binding' is uninformative. Removal does not dispute the interaction, which is reflected in the TGN location and description. Supporting Evidence: PMID:22344030 the Gga2p VHS domain bound directly to a recombinant Pik1p fragment |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | REMOVE | Summary: Interaction with Frq1 (Q06389) from a proteome-wide interactome study. Frq1 is the bona fide calcium-binding regulatory subunit that binds the Pik1 N-terminus and recruits it to the Golgi, so the interaction is real, but 'protein binding' conveys no functional information. Removal does not dispute the interaction; the informative content (Frq1-dependent Golgi recruitment) is captured by the TGN location and the description. Supporting Evidence: PMID:16365163 Frq1 (frequenin orthologue) also is essential for viability and binds near the NH2 terminus of Pik1. |
| GO:0005634 nucleus | IDA PMID:10587649 The yeast phosphatidylinositol-4-OH kinase pik1 regulates se... | ACCEPT | Summary: Nuclear localization of Pik1 reported by Walch-Solimena and Novick (abstract unavailable); consistent with the nuclear pool documented by Strahl et al., so accepted. Supporting Evidence: PMID:16365163 GFP-Pik1 localized to cytoplasmic puncta and the nucleus. The puncta colocalized with Sec7-DsRed, a marker of trans-Golgi cisternae. |
| GO:0005634 nucleus | IDA PMID:16365163 Yeast phosphatidylinositol 4-kinase, Pik1, has essential rol... | ACCEPT | Summary: Strahl et al. showed GFP-Pik1 in the nucleus with Kap95-dependent import and Msn5-dependent export, and that a nuclear pool of PtdIns4P is required for viability. Supporting Evidence: PMID:16365163 GFP-Pik1 localized to cytoplasmic puncta and the nucleus. The puncta colocalized with Sec7-DsRed, a marker of trans-Golgi cisternae. PMID:16365163 PtdIns4P must be generated both in the nucleus and at the Golgi for normal cell function |
| GO:0005634 nucleus | IDA PMID:8194527 PIK1, an essential phosphatidylinositol 4-kinase associated ... | ACCEPT | Summary: Original report that Pik1-dependent PI4K activity fractionates with nuclei. Supporting Evidence: PMID:8194527 overexpress PI 4-kinase activity exclusively in a nuclear fraction |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular location mapping (Nucleus); consistent with experimental data. Supporting Evidence: PMID:16365163 GFP-Pik1 localized to cytoplasmic puncta and the nucleus. The puncta colocalized with Sec7-DsRed, a marker of trans-Golgi cisternae. |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Broad IBA 'cytoplasm' for the PI3K/PI4K family node. Pik1 is soluble and partly cytoplasmic, but its functional sites are TGN membranes and the nucleus; uninformative. Supporting Evidence: PMID:16365163 GFP-Pik1 localized to cytoplasmic puncta and the nucleus. The puncta colocalized with Sec7-DsRed, a marker of trans-Golgi cisternae. |
| GO:0005794 Golgi apparatus | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt SubCell mapping to Golgi apparatus; correct but less specific than trans-Golgi network. Supporting Evidence: file:yeast/PIK1/PIK1-uniprot.txt Golgi apparatus, trans-Golgi network {ECO:0000269|PubMed:19898464}. |
| GO:0005802 trans-Golgi network | IDA PMID:10587649 The yeast phosphatidylinositol-4-OH kinase pik1 regulates se... | ACCEPT | Summary: Walch-Solimena and Novick localized Pik1 to the Golgi (abstract unavailable); consistent with later TGN localization. Supporting Evidence: PMID:16365163 GFP-Pik1 localized to cytoplasmic puncta and the nucleus. The puncta colocalized with Sec7-DsRed, a marker of trans-Golgi cisternae. |
| GO:0005802 trans-Golgi network | IDA PMID:16365163 Yeast phosphatidylinositol 4-kinase, Pik1, has essential rol... | ACCEPT | Summary: GFP-Pik1 puncta colocalize with Sec7, a trans-Golgi marker; Frq1-dependent Golgi recruitment. Supporting Evidence: PMID:16365163 GFP-Pik1 localized to cytoplasmic puncta and the nucleus. The puncta colocalized with Sec7-DsRed, a marker of trans-Golgi cisternae. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | MODIFY | Summary: YeastPathways RCA default places the PWY3O-242 reaction in cytosol. Pik1 is soluble but performs PI phosphorylation on TGN (and nuclear) membranes; the location of activity is the TGN. Proposed replacements: trans-Golgi network Supporting Evidence: PMID:16365163 GFP-Pik1 localized to cytoplasmic puncta and the nucleus. The puncta colocalized with Sec7-DsRed, a marker of trans-Golgi cisternae. |
| GO:0006897 endocytosis | IMP PMID:10930462 Distinct roles for the yeast phosphatidylinositol 4-kinases,... | KEEP AS NON CORE | Summary: Audhya et al. reported endocytic defects in pik1(ts) cells; a downstream consequence of loss of Golgi/endosomal PtdIns4P rather than a direct role of the kinase in endocytosis. Supporting Evidence: PMID:10930462 Pik1p is essential for normal secretion, Golgi and vacuole membrane dynamics, and endocytosis |
| GO:0006995 cellular response to nitrogen starvation | IMP PMID:32726584 Microautophagy in the yeast vacuole depends on the activitie... | KEEP AS NON CORE | Summary: Kurokawa et al. (2020) found reduced microautophagic vesicles in pik1 ts cells under nitrogen starvation; a phenotype-level process annotation, retained as non-core. Supporting Evidence: PMID:32726584 both Stt4p and Pik1p have important roles in the microautophagy of the vacuole in the stationary phase and under nitrogen starvation conditions |
| GO:0016020 membrane | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Generic 'membrane' from the family IBA; true (Pik1 acts on membranes) but uninformative. Supporting Evidence: PMID:16365163 GFP-Pik1 localized to cytoplasmic puncta and the nucleus. The puncta colocalized with Sec7-DsRed, a marker of trans-Golgi cisternae. |
| GO:0016301 kinase activity | IEA GO_REF:0000120 | MODIFY | Summary: ARBA/InterPro PI3/4-kinase domain mapping to generic 'kinase activity'. Correct but uninformative; the specific activity is 1-phosphatidylinositol 4-kinase activity. Proposed replacements: 1-phosphatidylinositol 4-kinase activity Supporting Evidence: PMID:8194527 PIK1 encodes a phosphatidylinositol 4-kinase (PI 4-kinase) essential for growth. |
| GO:0016773 phosphotransferase activity, alcohol group as acceptor | IEA GO_REF:0000117 | MODIFY | Summary: ARBA mapping to 'phosphotransferase activity, alcohol group as acceptor'; a high-level parent of the established PI 4-kinase activity. Proposed replacements: 1-phosphatidylinositol 4-kinase activity Supporting Evidence: PMID:8194527 PIK1 encodes a phosphatidylinositol 4-kinase (PI 4-kinase) essential for growth. |
| GO:0033554 cellular response to stress | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: ARBA rule mapping to 'cellular response to stress'. No specific stress-response role for Pik1 is documented; the term is vague and not supported for this protein. Supporting Evidence: PMID:10930462 Pik1p is essential for normal secretion, Golgi and vacuole membrane dynamics, and endocytosis |
| GO:0042998 positive regulation of Golgi to plasma membrane protein transport | IMP PMID:10930462 Distinct roles for the yeast phosphatidylinositol 4-kinases,... | ACCEPT | Summary: pik1(ts) cells show a rapid block in secretion of Golgi-modified cargo (Hsp150, invertase); Golgi PtdIns4P produced by Pik1 is required for post-Golgi exocytic traffic. This is the main physiological role of Pik1. Supporting Evidence: PMID:10930462 pik1(ts) cells exhibit a rapid defect in secretion of Golgi-modified secretory pathway cargos, Hsp150p and invertase |
| GO:0046854 phosphatidylinositol phosphate biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA for PIP biosynthesis from the PI3K/PI4K family node; correct for a PI 4-kinase. Pik1 directly catalyses PI -> PI4P, the entry step of phosphatidylinositol phosphate synthesis. Supporting Evidence: PMID:8194527 PIK1 encodes a phosphatidylinositol 4-kinase (PI 4-kinase) essential for growth. file:yeast/PIK1/PIK1-uniprot.txt Type III PI4K |
| GO:0046854 phosphatidylinositol phosphate biosynthetic process | IDA PMID:8194527 PIK1, an essential phosphatidylinositol 4-kinase associated ... | ACCEPT | Summary: PI4P production by Pik1 shown biochemically (Garcia-Bustos et al.). Pik1 directly catalyses PI -> PI4P, the entry step of phosphatidylinositol phosphate synthesis. Supporting Evidence: PMID:8194527 PIK1 encodes a phosphatidylinositol 4-kinase (PI 4-kinase) essential for growth. |
| GO:0046854 phosphatidylinositol phosphate biosynthetic process | IDA PMID:8248783 Phosphatidylinositol 4-kinase: gene structure and requiremen... | ACCEPT | Summary: PI4P production by Pik1 shown biochemically (Flanagan et al.). Pik1 directly catalyses PI -> PI4P, the entry step of phosphatidylinositol phosphate synthesis. Supporting Evidence: PMID:8248783 Expression of PIK1 from a multicopy plasmid elevated PtdIns 4-kinase activity |
| GO:0046854 phosphatidylinositol phosphate biosynthetic process | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro PI3/4-kinase catalytic domain mapping; correct for Pik1. Pik1 directly catalyses PI -> PI4P, the entry step of phosphatidylinositol phosphate synthesis. Supporting Evidence: file:yeast/PIK1/PIK1-uniprot.txt Type III PI4K |
| GO:0046854 phosphatidylinositol phosphate biosynthetic process | IMP PMID:10587649 The yeast phosphatidylinositol-4-OH kinase pik1 regulates se... | ACCEPT | Summary: Mutant analysis by Walch-Solimena and Novick (abstract unavailable); consistent with PI4P synthesis by Pik1. Pik1 directly catalyses PI -> PI4P, the entry step of phosphatidylinositol phosphate synthesis. Supporting Evidence: PMID:10930462 Both gene products phosphorylate PtdIns at the D-4 position of the inositol ring to generate PtdIns(4)P |
| GO:0046854 phosphatidylinositol phosphate biosynthetic process | IMP PMID:10930462 Distinct roles for the yeast phosphatidylinositol 4-kinases,... | ACCEPT | Summary: pik1(ts) reduces cellular PtdIns(4)P by ~50%; pik1 stt4 double mutants >10-fold. Pik1 directly catalyses PI -> PI4P, the entry step of phosphatidylinositol phosphate synthesis. Supporting Evidence: PMID:10930462 Both single mutants reduce PtdIns(4)P by approximately 50% |
| GO:0046854 phosphatidylinositol phosphate biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways PWY3O-242 RCA; correct pathway for the PI -> PI4P step. Pik1 directly catalyses PI -> PI4P, the entry step of phosphatidylinositol phosphate synthesis. Supporting Evidence: PMID:10930462 Both gene products phosphorylate PtdIns at the D-4 position of the inositol ring to generate PtdIns(4)P file:yeast/PIK1/PIK1-uniprot.txt EC=2.7.1.67; Evidence={ECO:0000269|PubMed:8194527, |
| GO:0048015 phosphatidylinositol-mediated signaling | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA 'phosphatidylinositol-mediated signaling' from the family node. PtdIns4P made by Pik1 acts as a signalling lipid recruiting Golgi effectors, but the term is broad and largely implied by the kinase activity. Supporting Evidence: PMID:16365163 PtdIns4P must be generated both in the nucleus and at the Golgi for normal cell function |
| GO:0050714 positive regulation of protein secretion | IMP PMID:10930462 Distinct roles for the yeast phosphatidylinositol 4-kinases,... | KEEP AS NON CORE | Summary: Same secretion phenotype as the Golgi-to-PM transport annotation; 'positive regulation of protein secretion' is a broader restatement. Retained as non-core. Supporting Evidence: PMID:10930462 pik1(ts) cells exhibit a rapid defect in secretion of Golgi-modified secretory pathway cargos, Hsp150p and invertase |
| GO:0140504 microlipophagy | IMP PMID:32726584 Microautophagy in the yeast vacuole depends on the activitie... | KEEP AS NON CORE | Summary: pik1 ts mutants have fewer microautophagic vesicles engulfing lipid droplets (microlipophagy). Phenotypic, downstream role of PtdIns4P; non-core. Supporting Evidence: PMID:32726584 both Stt4p and Pik1p have important roles in the microautophagy of the vacuole in the stationary phase and under nitrogen starvation conditions |
| GO:2000786 positive regulation of autophagosome assembly | IMP PMID:31125705 Essential and distinct roles of phosphatidylinositol 4-kinas... | KEEP AS NON CORE | Summary: Kurokawa et al. (2019) reported reduced autophagosome numbers in pik1 ts cells at restrictive temperature. A downstream PtdIns4P-dependent role, retained as non-core. Supporting Evidence: PMID:31125705 Pik1p and Stt4p play essential roles in autophagosome formation and autophagosome-vacuole fusion in yeast cells, respectively |
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Download this section (compressed HTML)Phosphatidylinositol 4-kinase; catalyzes the first step in the biosynthesis of phosphatidylinositol-4,5-biphosphate; may control cytokinesis through the actin cytoskeleton; required for autophagosome formation during autophagy and for lipophagy in both stationary phase cells and during nitrogen starvation; may control nonselective autophagy and mitophagy through trafficking of Atg9p; localizes to the nucleus and to the trans-Golgi network
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