PHO86 encodes an endoplasmic-reticulum resident membrane chaperone required for ER exit of the high-affinity phosphate transporter Pho84. Pho86 is not itself the phosphate transporter; instead, it prevents aggregation or misfolding of its cognate polytopic client and enables Pho84 packaging into COPII vesicles. The defensible core curation is therefore ER-localized chaperone-mediated regulation of phosphate transport and ER-to-Golgi traffic, not direct phosphate ion transport or generic protein binding.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0006817
phosphate ion transport
|
IEA
GO_REF:0000043 |
MODIFY |
Summary: PHO86 affects phosphate uptake, but the direct transport activity belongs to Pho84 rather than Pho86.
Reason: Pho86 is required for Pho84 ER export and therefore regulates phosphate transport indirectly; the existing term overstates Pho86 as the transporter.
Proposed replacements:
regulation of phosphate transport
Supporting Evidence:
PMID:10655492
Pho84p is localized to the endoplasmic reticulum (ER) and fails to be targeted to the plasma membrane in the absence of Pho86p
|
|
GO:0016020
membrane
|
IEA
GO_REF:0000044 |
MODIFY |
Summary: Membrane localization is true but too broad for Pho86.
Reason: Direct evidence and functional context place Pho86 as an ER-resident membrane protein, making endoplasmic reticulum membrane more specific than the broad membrane term.
Proposed replacements:
endoplasmic reticulum membrane
Supporting Evidence:
PMID:10655492
Pho86p, an endoplasmic reticulum (ER) resident protein
|
|
GO:0005515
protein binding
|
IPI
PMID:16429126 Proteome survey reveals modularity of the yeast cell machine... |
MARK AS OVER ANNOTATED |
Summary: The high-throughput interaction annotation is too generic for PHO86 function.
Reason: Pho86's interpretable role is a client-specific ER chaperone for Pho84 export, not generic protein binding.
Supporting Evidence:
PMID:15623581
Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER
|
|
GO:0005515
protein binding
|
IPI
PMID:18467557 An in vivo map of the yeast protein interactome. |
MARK AS OVER ANNOTATED |
Summary: Interactome evidence does not provide a useful standalone molecular-function annotation.
Reason: Generic protein binding should not be accepted when the literature supports a more specific chaperone/export role.
Supporting Evidence:
PMID:10655492
Pho86p is required for packaging of Pho84p into COPII vesicles
|
|
GO:0005515
protein binding
|
IPI
PMID:27107014 An inter-species protein-protein interaction network across ... |
MARK AS OVER ANNOTATED |
Summary: Cross-species interaction data are too broad for accepting protein binding as PHO86's function.
Reason: The curated function should emphasize Pho84-specific ER chaperone activity and regulated phosphate transport.
Supporting Evidence:
file:yeast/PHO86/PHO86-deep-research-falcon.md
ER-resident membrane protein required for ER exit of the high-affinity phosphate transporter Pho84
|
|
GO:0005515
protein binding
|
IPI
PMID:37968396 The social and structural architecture of the yeast protein ... |
MARK AS OVER ANNOTATED |
Summary: Social-interactome protein binding is not informative enough for PHO86 curation.
Reason: Protein binding is a broad physical interaction bucket and should not obscure the direct ER chaperone/export phenotype.
Supporting Evidence:
PMID:15623581
prevent aggregation of polytopic proteins in the ER
|
|
GO:0005783
endoplasmic reticulum
|
HDA
PMID:26928762 One library to make them all: streamlining the creation of y... |
ACCEPT |
Summary: High-throughput ER localization is consistent with direct PHO86 evidence.
Reason: Pho86 is an ER-resident membrane protein required before Pho84 exits the ER.
Supporting Evidence:
PMID:10655492
endoplasmic reticulum (ER) resident protein
|
|
GO:0005783
endoplasmic reticulum
|
IDA
PMID:10655492 Pho86p, an endoplasmic reticulum (ER) resident protein in Sa... |
ACCEPT |
Summary: Direct ER localization is well supported and central to function.
Reason: Pho86 acts in the ER to permit Pho84 folding/export and does not travel with Pho84 to the plasma membrane.
Supporting Evidence:
PMID:10655492
Pho86p, an endoplasmic reticulum (ER) resident protein
|
|
GO:0006457
protein folding
|
IMP
PMID:15623581 Specialized membrane-localized chaperones prevent aggregatio... |
ACCEPT |
Summary: Protein folding is a defensible process annotation for Pho86's specialized ER chaperone role.
Reason: Pho86 prevents aggregation or misfolding of a cognate polytopic membrane client in the ER.
Supporting Evidence:
PMID:15623581
Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER
|
|
GO:0006888
endoplasmic reticulum to Golgi vesicle-mediated transport
|
IMP
PMID:10655492 Pho86p, an endoplasmic reticulum (ER) resident protein in Sa... |
ACCEPT |
Summary: Pho86 is required for ER exit of Pho84, so ER-to-Golgi vesicle-mediated transport is supported.
Reason: The phenotype specifically involves failure to package Pho84 into COPII vesicles.
Supporting Evidence:
PMID:10655492
Pho86p is required for packaging of Pho84p into COPII vesicles
|
|
GO:0010966
regulation of phosphate transport
|
IMP
PMID:10655492 Pho86p, an endoplasmic reticulum (ER) resident protein in Sa... |
ACCEPT |
Summary: Regulation of phosphate transport accurately captures the indirect transport phenotype.
Reason: Pho86 controls delivery of the high-affinity phosphate transporter Pho84, thereby regulating phosphate uptake capacity without being the transporter.
Supporting Evidence:
PMID:10655492
Pho84p is localized to the endoplasmic reticulum (ER) and fails to be targeted to the plasma membrane in the absence of Pho86p
|
|
GO:0051082
unfolded protein binding
|
IMP
PMID:15623581 Specialized membrane-localized chaperones prevent aggregatio... |
MODIFY |
Summary: The evidence supports a specialized ER chaperone role rather than generic unfolded protein binding.
Reason: Pho86 is one of the specialized membrane-localized chaperones that prevent aggregation of cognate polytopic membrane proteins in the ER; protein folding chaperone is the more informative term.
Proposed replacements:
protein folding chaperone
Supporting Evidence:
PMID:15623581
Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER
|
Q: What is the direct physical interface between Pho86 and Pho84, and which Pho84 folding state does Pho86 recognize?
Suggested experts: ER membrane-protein biogenesis experts, yeast phosphate-homeostasis researchers
Q: Does Pho86 act only on Pho84, or does it have a broader client range among phosphate- or nutrient-transporter family members?
Suggested experts: yeast transporter biologists
Experiment: Mutate conserved Pho86 transmembrane and loop residues, then assay Pho84 binding, Pho84 aggregation, and Pho84 ER export under phosphate starvation.
Hypothesis: A defined Pho86 membrane interface recognizes Pho84 and is required for transporter export without affecting general COPII function.
Type: site-directed mutagenesis and co-immunoprecipitation
Experiment: Reconstitute Pho84 packaging from ER membranes with wild-type or chaperone-defective Pho86 alleles and quantify Pho84 incorporation into COPII vesicles.
Hypothesis: Pho86 promotes a COPII-competent Pho84 state rather than acting downstream of vesicle formation.
Type: in vitro COPII budding assay
provider: falcon
model: Edison Scientific Literature
cached: false
start_time: '2026-05-04T10:46:59.426365'
end_time: '2026-05-04T10:56:38.380853'
duration_seconds: 578.95
template_file: templates/gene_research_go_focused.md
template_variables:
organism: yeast
gene_id: PHO86
gene_symbol: PHO86
uniprot_accession: P46956
protein_description: 'RecName: Full=Inorganic phosphate transporter PHO86;'
gene_info: Name=PHO86; OrderedLocusNames=YJL117W; ORFNames=J0744;
organism_full: Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
protein_family: Not specified in UniProt
protein_domains: Pho86. (IPR024297); Pho86 (PF11124)
provider_config:
timeout: 600
max_retries: 3
parameters:
allowed_domains: []
temperature: 0.1
citation_count: 15
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'PHO86' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene PHO86 (gene ID: PHO86, UniProt: P46956) in yeast.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'PHO86' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene PHO86 (gene ID: PHO86, UniProt: P46956) in yeast.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
All evidence below refers specifically to Saccharomyces cerevisiae (strain S288c) PHO86 / YJL117W, encoding Pho86p, an endoplasmic-reticulum (ER) resident membrane protein required for ER exit of the high-affinity inorganic phosphate transporter Pho84p (and not to any similarly named proteins in other organisms). Primary evidence explicitly names PHO86/YJL117W and experimentally tests Pho86p localization/function in budding yeast. (lau2000pho86panendoplasmic pages 1-2)
Pho86p is not a phosphate transporter. Instead, it is an ER-resident, cargo-specific trafficking/biogenesis factor that enables Pho84p (a polytopic plasma-membrane phosphate permease) to exit the ER and enter the secretory pathway. The canonical mechanistic description is that Pho86p functions as an ER “outfitter” or accessory factor that promotes COPII-dependent packaging of Pho84p into ER-derived vesicles. (lau2000pho86panendoplasmic pages 1-2, lau2000pho86panendoplasmic pages 4-5)
A useful operational definition supported by cell biology and proteostasis literature is that Pho86 belongs to a class of “specialized membrane-localized chaperones” that prevent aggregation/misfolding of particular polytopic membrane cargos during insertion/folding in the ER membrane, thereby allowing them to become export-competent. (kota2005specializedmembranelocalizedchaperones pages 1-2)
In budding yeast, phosphate starvation triggers a transcriptional program (the PHO pathway/PHO regulon) that induces high-affinity phosphate acquisition genes. PHO84 and PHO86 are among the genes highly induced upon phosphate starvation, and pho86 loss-of-function mutants phenocopy pho84 mutants in key readouts (defective phosphate uptake and PHO regulon derepression such as constitutive Pho5 acid phosphatase expression), consistent with Pho86 acting upstream by enabling functional Pho84 at the plasma membrane. (lau2000pho86panendoplasmic pages 1-2, howson2003systematicapproachesto pages 149-154)
Importantly, regulation of Pho84 protein localization (plasma membrane in low phosphate; internalization to vacuole after phosphate addition) is post-translational and was shown to be independent of canonical PHO signaling mutants tested in that work; thus Pho86’s core role is best framed as protein trafficking/quality control rather than phosphate sensing per se. (lau2000pho86panendoplasmic pages 3-4)
A functional Pho86p-GFP fusion (low-copy construct that complements pho86Δ phenotypes) localizes to a perinuclear compartment coincident with the ER marker Kar2/BiP, consistent with ER residence. Pho86p-GFP localization was observed in low-phosphate medium and also in high-phosphate medium, indicating Pho86 localization is not itself regulated by extracellular phosphate. (lau2000pho86panendoplasmic pages 3-4, lau2000pho86panendoplasmic media d64c6532)
Pho84p is dynamically regulated: it localizes to the plasma membrane under low-phosphate and is endocytosed and delivered to the vacuole after phosphate addition. In contrast, in pho86Δ cells, Pho84p-GFP is predominantly retained in the ER, co-localizing with Kar2p and other ER markers. This establishes Pho86 as necessary for Pho84 trafficking beyond the ER. (lau2000pho86panendoplasmic pages 1-2, lau2000pho86panendoplasmic pages 3-4, lau2000pho86panendoplasmic media 52ae20e9)
A key mechanistic experiment used an in vitro COPII vesicle budding assay from perforated spheroplasts:
Together, these experiments are strong evidence that Pho86 is a cargo-specific ER factor required for Pho84 incorporation into COPII vesicles. (lau2000pho86panendoplasmic pages 4-5, lau2000pho86panendoplasmic media 6beb61b8)
pho86Δ cells show normal localization of other plasma-membrane proteins assayed (e.g., Pma1p-HA and Gal2p-GFP), and exhibit normal growth across multiple conditions and normal mating, supporting a specialized role rather than global ER export failure. (lau2000pho86panendoplasmic pages 3-4)
The most directly supported functional relationship is that Pho84 requires Pho86 for ER exit and correct targeting; the requirement is described as specific to Pho84 relative to other hexose-transporter family members tested. (lau2000pho86panendoplasmic pages 1-2, lau2000pho86panendoplasmic pages 4-5)
Pho86 is grouped with other dedicated ER membrane chaperones (e.g., Shr3, Gsf2, Chs7) that prevent aggregation of their cognate multi-pass membrane cargos. In this model, loss of the dedicated factor causes aggregation and ER retention of the client cargo(s), thereby preventing ER export. This provides mechanistic interpretation for Pho86’s role in Pho84 maturation/export, even when direct binding interfaces are not mapped. (kota2005specializedmembranelocalizedchaperones pages 1-2)
A more recent stress-focused study notes that Pho86 was reported to interact with Fet3 in a large-scale screen of membrane protein interactors, raising the possibility that Pho86 overexpression influences iron uptake pathways under arsenate stress; however, this interaction is not presented as a direct, validated biochemical interaction within the retrieved evidence. (isik2022identificationofnovel pages 8-9)
Within the retrieved, accessible literature set, dedicated 2023–2024 primary mechanistic studies centered on PHO86 itself were not identified. The mechanistic foundation still rests primarily on the 2000–2005 cell biology/proteostasis work (ER localization, Pho84 dependence, COPII packaging, specialized chaperone model). (lau2000pho86panendoplasmic pages 4-5, kota2005specializedmembranelocalizedchaperones pages 1-2)
A notable recent experimental development is identification of PHO86 overexpression as an arsenate [As(V)] resistance determinant. Key reported findings include:
While this 2022 study is slightly outside the user’s preferred 2023–2024 window, it is among the most directly PHO86-relevant recent experimental papers found and provides quantitative assay context. (isik2022identificationofnovel pages 8-8, isik2022identificationofnovel pages 8-9)
Pho84 is a known import route for phosphate analogs such as arsenate; because Pho86 controls Pho84 abundance at the plasma membrane by enabling ER exit, PHO86 perturbation provides an actionable lever for modulating phosphate/arsenate uptake. In practical terms:
This axis can be relevant to (i) engineering yeast strains with altered metalloid uptake/toxicity profiles for screening or bioprocess robustness, and (ii) using yeast as a model to dissect membrane-proteostasis mechanisms for nutrient transporters under stress. (isik2022identificationofnovel pages 8-8, kota2005specializedmembranelocalizedchaperones pages 1-2)
High-affinity phosphate uptake and phosphate homeostasis influence central metabolism and stress responses; therefore, ensuring correct Pho84 biogenesis/trafficking—for which Pho86 is essential—can be a determinant of growth under phosphate limitation and could affect strain performance in phosphate-limited or fluctuating environments. The evidence base supporting this is mechanistic (Pho86→Pho84 trafficking) and physiological (pho86 phenocopies pho84 for phosphate uptake/PHO regulon readouts). (lau2000pho86panendoplasmic pages 1-2, persson2003regulationofphosphate pages 12-13)
Key quantitative points that can be extracted directly from the retrieved sources are:
The following table compiles the principal functional-annotation claims, evidence types, experimental details, and URLs.
| Claim/annotation | Evidence type (genetics/localization/biochemistry/omics/stress) | Key experimental details/quantitative data | Main conclusion | Source (authors, year, journal) | URL | Context citation ID |
|---|---|---|---|---|---|---|
| PHO86 encodes an ER-resident membrane protein rather than a plasma-membrane phosphate transporter | Localization, genetics | C-terminal PHO86-GFP low-copy construct complemented pho86Δ phenotypes; Pho86p-GFP localized to a perinuclear compartment coincident with Kar2/BiP and also colocalized with Ero1p-HA; localization unchanged in low- vs high-phosphate medium | Pho86 functions in the ER during Pho84 biogenesis/trafficking, not as the transporter itself | Lau et al., 2000, PNAS | https://doi.org/10.1073/pnas.97.3.1107 | (lau2000pho86panendoplasmic pages 3-4, lau2000pho86panendoplasmic pages 1-2) |
| PHO86 is required for proper localization of the high-affinity phosphate transporter Pho84 | Localization, genetics | In pho86Δ cells, genomically integrated Pho84-GFP was predominantly ER-localized and colocalized with Kar2p under low-phosphate conditions; wild-type Pho84 localizes to plasma membrane in low Pi and is internalized to vacuole after phosphate addition | Loss of Pho86 blocks ER exit of Pho84 and prevents normal plasma-membrane targeting | Lau et al., 2000, PNAS | https://doi.org/10.1073/pnas.97.3.1107 | (lau2000pho86panendoplasmic pages 3-4, lau2000pho86panendoplasmic pages 1-2) |
| Pho86 is specifically required for COPII packaging of Pho84 | Biochemistry, trafficking | In vitro COPII budding assay from perforated spheroplasts: Pho84p-HA packaged into COPII vesicles from wild-type membranes with ~20% efficiency; omission of Sar1p or any coat subunit reduced packaging by >3-fold; from pho86Δ membranes, Pho84 not detected above background in vesicle fraction | Pho86 is a cargo-specific ER export factor required for efficient incorporation of Pho84 into COPII vesicles | Lau et al., 2000, PNAS | https://doi.org/10.1073/pnas.97.3.1107 | (lau2000pho86panendoplasmic pages 4-5, lau2000pho86panendoplasmic media 6beb61b8) |
| Pho86 itself is not exported in COPII vesicles | Biochemistry, localization | In the same in vitro budding assay, Pho86p did not appear above background in vesicle fractions | Pho86 acts as an ER-resident “outfitter”/accessory factor rather than a co-transported cargo | Lau et al., 2000, PNAS | https://doi.org/10.1073/pnas.97.3.1107 | (lau2000pho86panendoplasmic pages 4-5, lau2000pho86panendoplasmic pages 1-2, lau2000pho86panendoplasmic media 6beb61b8) |
| Pho86 function is selective rather than a general requirement for secretion | Genetics, localization | pho86Δ cells showed normal localization of Gal2p-GFP and Pma1p-HA and retained normal growth on varied carbon sources and normal mating | Pho86 is specialized for Pho84/phosphate-transporter biogenesis rather than general ER export | Lau et al., 2000, PNAS | https://doi.org/10.1073/pnas.97.3.1107 | (lau2000pho86panendoplasmic pages 3-4, lau2000pho86panendoplasmic pages 4-5) |
| PHO86 mutations phenocopy PHO84 defects in phosphate homeostasis | Genetics, physiology | Historical genetic evidence summarized: pho86 mutants show phosphate uptake defects and constitutive acid phosphatase Pho5 expression; PHO84 and PHO86 are among genes most induced during phosphate starvation | Pho86 contributes to phosphate acquisition indirectly by enabling Pho84 function, thereby influencing PHO regulon outputs | Lau et al., 2000, PNAS | https://doi.org/10.1073/pnas.97.3.1107 | (lau2000pho86panendoplasmic pages 1-2, howson2003systematicapproachesto pages 149-154) |
| Pho86 is a 34-kDa, 311-aa membrane-associated protein with two N-terminal hydrophobic segments; transcript is present in both high- and low-Pi media but somewhat elevated in low Pi | Review synthesis from primary studies | Review summarizes prior work: PHO86 is transcribed under both phosphate-replete and phosphate-limited conditions, with slightly higher transcript in low Pi; disruption is not lethal but decreases Pi uptake activity | Pho86 is an accessory ER membrane factor under less stringent Pi transcriptional control than PHO84, yet functionally important for uptake | Persson et al., 2003, Current Genetics | https://doi.org/10.1007/s00294-003-0400-9 | (persson2003regulationofphosphate pages 12-13) |
| Current expert view places Pho86 in post-translational control of high-affinity phosphate uptake | Review/expert analysis | Review of S. cerevisiae phosphate transport: proper sorting of Pho84 lacking a signal peptide is mediated by Pho86; Pho84 induction under alkaline stress can increase ~12-fold after 25–45 min, but Pho86 mainly acts in targeting/export steps | Expert synthesis supports annotation of Pho86 as a trafficking factor in the phosphate-acquisition pathway rather than a transporter or sensor | Persson et al., 2003, Current Genetics | https://doi.org/10.1007/s00294-003-0400-9 | (persson2003regulationofphosphate pages 12-13) |
| Pho86 belongs to a class of specialized ER membrane-localized chaperones for polytopic proteins | Proteostasis, expert primary study | JCB study generalized from Shr3/Gsf2/Pho86/Chs7 systems: in cells lacking each dedicated factor, only cognate cargos aggregate and fail to exit the ER membrane | Pho86 prevents inappropriate interactions/aggregation of its cognate phosphate transporter cargo(s) during membrane insertion/folding in the ER | Kota & Ljungdahl, 2005, Journal of Cell Biology | https://doi.org/10.1083/jcb.200408106 | (kota2005specializedmembranelocalizedchaperones pages 1-2) |
| PHO86 overexpression confers arsenate [As(V)] resistance in yeast | Stress, genetics | Overexpression screen identified PHO86 as As(V)-resistance gene; phenotype observed in wild type and arsenic-sensitive GK4, but not for As(III) resistance | Elevated Pho86 can protect cells from arsenate stress, linking phosphate-transporter trafficking to metalloid response | Isik et al., 2022, MicrobiologyOpen | https://doi.org/10.1002/mbo3.1284 | (isik2022identificationofnovel pages 8-8) |
| PHO86-dependent arsenate phenotype requires Pho84 context and was assessed with quantitative uptake assays | Stress, genetics, quantitative assay | Intracellular arsenic measured after 1 mM As(V) for 1 h; averages from n=6; PHO86 overexpression did not provide extra As(V) resistance in pho84Δ and also not in pho87Δ/pho89Δ backgrounds, but did in pho90Δ/pho91Δ | The overexpression phenotype depends on phosphate/arsenate import circuitry, especially Pho84, supporting a mechanistic link through transporter trafficking | Isik et al., 2022, MicrobiologyOpen | https://doi.org/10.1002/mbo3.1284 | (isik2022identificationofnovel pages 8-8) |
| PHO86 overexpression raises intracellular arsenic yet limits proteotoxic damage | Stress, proteostasis, quantitative assay | Hsp104-GFP aggregation assay after 2 mM As(V); aggregates scored in 144–282 cells per strain/time point; n=3 biological replicates; PHO86-overexpressing cells did not show elevated protein aggregation despite higher intracellular arsenic | PHO86 overexpression appears to improve tolerance to intracellular arsenic burden without increasing detectable proteome damage | Isik et al., 2022, MicrobiologyOpen | https://doi.org/10.1002/mbo3.1284 | (isik2022identificationofnovel pages 9-9, isik2022identificationofnovel pages 8-9) |
Table: This table summarizes core experimental and review-supported evidence for the functional annotation of Saccharomyces cerevisiae Pho86/PHO86. It highlights ER localization, Pho84-specific trafficking, COPII export dependence, phosphate-homeostasis relevance, specialized chaperone/proteostasis roles, and recent stress-related findings.
Gene/protein: PHO86 / Pho86p (YJL117W; UniProt P46956)
Primary molecular function (experimentally supported): ER-resident membrane factor (“outfitter”/specialized membrane-localized chaperone) required for COPII-dependent ER export of Pho84 high-affinity inorganic phosphate permease; promotes Pho84 acquisition of an export-competent state and/or its selection for COPII packaging. (lau2000pho86panendoplasmic pages 4-5, kota2005specializedmembranelocalizedchaperones pages 1-2)
Biological process: High-affinity phosphate acquisition and phosphate homeostasis (indirectly), via enabling Pho84 delivery to the plasma membrane; impacts PHO regulon outputs (e.g., Pho5 acid phosphatase derepression) primarily through phosphate uptake capacity. (lau2000pho86panendoplasmic pages 1-2, persson2003regulationofphosphate pages 12-13)
Subcellular location: Endoplasmic reticulum (perinuclear ER), phosphate-independent localization. (lau2000pho86panendoplasmic pages 3-4, lau2000pho86panendoplasmic media d64c6532)
Key client cargo: Pho84p (high-affinity phosphate transporter). (lau2000pho86panendoplasmic pages 3-4, lau2000pho86panendoplasmic pages 4-5)
Recent/expanded phenotype space: PHO86 overexpression modulates arsenate [As(V)] stress phenotypes in a Pho84-dependent manner; quantitative assays include arsenic accumulation at 1 mM As(V) and proteotoxicity scoring at 2 mM As(V). (isik2022identificationofnovel pages 8-8, isik2022identificationofnovel pages 8-9)
References
(lau2000pho86panendoplasmic pages 1-2): W.-T. Walter Lau, Russell W. Howson, Per Malkus, Randy Schekman, and Erin K. O'Shea. Pho86p, an endoplasmic reticulum (er) resident protein in saccharomyces cerevisiae, is required for er exit of the high-affinity phosphate transporter pho84p. Proceedings of the National Academy of Sciences of the United States of America, 97 3:1107-12, Feb 2000. URL: https://doi.org/10.1073/pnas.97.3.1107, doi:10.1073/pnas.97.3.1107. This article has 117 citations and is from a highest quality peer-reviewed journal.
(lau2000pho86panendoplasmic pages 4-5): W.-T. Walter Lau, Russell W. Howson, Per Malkus, Randy Schekman, and Erin K. O'Shea. Pho86p, an endoplasmic reticulum (er) resident protein in saccharomyces cerevisiae, is required for er exit of the high-affinity phosphate transporter pho84p. Proceedings of the National Academy of Sciences of the United States of America, 97 3:1107-12, Feb 2000. URL: https://doi.org/10.1073/pnas.97.3.1107, doi:10.1073/pnas.97.3.1107. This article has 117 citations and is from a highest quality peer-reviewed journal.
(kota2005specializedmembranelocalizedchaperones pages 1-2): Jhansi Kota and Per O. Ljungdahl. Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the er. The Journal of Cell Biology, 168:79-88, Jan 2005. URL: https://doi.org/10.1083/jcb.200408106, doi:10.1083/jcb.200408106. This article has 134 citations.
(howson2003systematicapproachesto pages 149-154): RW Howson. Systematic approaches to identifying substrates of the budding yeast cyclin dependent kinase pho85. Unknown journal, 2003.
(lau2000pho86panendoplasmic pages 3-4): W.-T. Walter Lau, Russell W. Howson, Per Malkus, Randy Schekman, and Erin K. O'Shea. Pho86p, an endoplasmic reticulum (er) resident protein in saccharomyces cerevisiae, is required for er exit of the high-affinity phosphate transporter pho84p. Proceedings of the National Academy of Sciences of the United States of America, 97 3:1107-12, Feb 2000. URL: https://doi.org/10.1073/pnas.97.3.1107, doi:10.1073/pnas.97.3.1107. This article has 117 citations and is from a highest quality peer-reviewed journal.
(lau2000pho86panendoplasmic media d64c6532): W.-T. Walter Lau, Russell W. Howson, Per Malkus, Randy Schekman, and Erin K. O'Shea. Pho86p, an endoplasmic reticulum (er) resident protein in saccharomyces cerevisiae, is required for er exit of the high-affinity phosphate transporter pho84p. Proceedings of the National Academy of Sciences of the United States of America, 97 3:1107-12, Feb 2000. URL: https://doi.org/10.1073/pnas.97.3.1107, doi:10.1073/pnas.97.3.1107. This article has 117 citations and is from a highest quality peer-reviewed journal.
(lau2000pho86panendoplasmic media 52ae20e9): W.-T. Walter Lau, Russell W. Howson, Per Malkus, Randy Schekman, and Erin K. O'Shea. Pho86p, an endoplasmic reticulum (er) resident protein in saccharomyces cerevisiae, is required for er exit of the high-affinity phosphate transporter pho84p. Proceedings of the National Academy of Sciences of the United States of America, 97 3:1107-12, Feb 2000. URL: https://doi.org/10.1073/pnas.97.3.1107, doi:10.1073/pnas.97.3.1107. This article has 117 citations and is from a highest quality peer-reviewed journal.
(lau2000pho86panendoplasmic media 6beb61b8): W.-T. Walter Lau, Russell W. Howson, Per Malkus, Randy Schekman, and Erin K. O'Shea. Pho86p, an endoplasmic reticulum (er) resident protein in saccharomyces cerevisiae, is required for er exit of the high-affinity phosphate transporter pho84p. Proceedings of the National Academy of Sciences of the United States of America, 97 3:1107-12, Feb 2000. URL: https://doi.org/10.1073/pnas.97.3.1107, doi:10.1073/pnas.97.3.1107. This article has 117 citations and is from a highest quality peer-reviewed journal.
(isik2022identificationofnovel pages 8-9): Esin Isik, Çiğdem Balkan, Vivien Karl, Hüseyin Çağlar Karakaya, Sansan Hua, Sebastien Rauch, Markus J. Tamás, and Ahmet Koc. Identification of novel arsenic resistance genes in yeast. MicrobiologyOpen, Apr 2022. URL: https://doi.org/10.1002/mbo3.1284, doi:10.1002/mbo3.1284. This article has 5 citations and is from a peer-reviewed journal.
(isik2022identificationofnovel pages 8-8): Esin Isik, Çiğdem Balkan, Vivien Karl, Hüseyin Çağlar Karakaya, Sansan Hua, Sebastien Rauch, Markus J. Tamás, and Ahmet Koc. Identification of novel arsenic resistance genes in yeast. MicrobiologyOpen, Apr 2022. URL: https://doi.org/10.1002/mbo3.1284, doi:10.1002/mbo3.1284. This article has 5 citations and is from a peer-reviewed journal.
(persson2003regulationofphosphate pages 12-13): Bengt L. Persson, Jens O. Lagerstedt, James R. Pratt, Johanna Pattison-Granberg, Kent Lundh, Soheila Shokrollahzadeh, and Fredrik Lundh. Regulation of phosphate acquisition in saccharomyces cerevisiae. Current Genetics, 43:225-244, Jul 2003. URL: https://doi.org/10.1007/s00294-003-0400-9, doi:10.1007/s00294-003-0400-9. This article has 195 citations and is from a peer-reviewed journal.
(isik2022identificationofnovel pages 9-9): Esin Isik, Çiğdem Balkan, Vivien Karl, Hüseyin Çağlar Karakaya, Sansan Hua, Sebastien Rauch, Markus J. Tamás, and Ahmet Koc. Identification of novel arsenic resistance genes in yeast. MicrobiologyOpen, Apr 2022. URL: https://doi.org/10.1002/mbo3.1284, doi:10.1002/mbo3.1284. This article has 5 citations and is from a peer-reviewed journal.
id: P46956
gene_symbol: PHO86
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:559292
label: Saccharomyces cerevisiae
description: >-
PHO86 encodes an endoplasmic-reticulum resident membrane chaperone required
for ER exit of the high-affinity phosphate transporter Pho84. Pho86 is not
itself the phosphate transporter; instead, it prevents aggregation or
misfolding of its cognate polytopic client and enables Pho84 packaging into
COPII vesicles. The defensible core curation is therefore ER-localized
chaperone-mediated regulation of phosphate transport and ER-to-Golgi traffic,
not direct phosphate ion transport or generic protein binding.
references:
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
findings: []
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
findings: []
- id: PMID:10655492
title: Pho86p, an endoplasmic reticulum (ER) resident protein in Saccharomyces cerevisiae, is required for ER exit of the high-affinity phosphate transporter Pho84p.
findings:
- statement: Pho86 is an ER resident required for Pho84 ER exit and COPII packaging, while Pho84 is the phosphate transporter.
supporting_text: "Pho84p is retained in the ER in the absence of Pho86p, which appears to be involved in packaging of Pho84p into COPII vesicles."
- id: PMID:15623581
title: Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER.
findings:
- statement: Pho86 is one of the specialized ER membrane chaperones that prevents aggregation of cognate polytopic clients.
supporting_text: "Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER."
- id: PMID:16429126
title: Proteome survey reveals modularity of the yeast cell machinery.
findings:
- statement: High-throughput interaction evidence is not specific enough to define PHO86 molecular function.
supporting_text: "Proteome survey reveals modularity of the yeast cell machinery."
- id: PMID:18467557
title: An in vivo map of the yeast protein interactome.
findings:
- statement: Large-scale interactome evidence supports physical association context but not a standalone protein binding function.
supporting_text: "An in vivo map of the yeast protein interactome."
- id: PMID:26928762
title: 'One library to make them all: streamlining the creation of yeast libraries via a SWAp-Tag strategy.'
findings:
- statement: High-throughput localization data support ER localization.
supporting_text: "One library to make them all"
- id: PMID:27107014
title: An inter-species protein-protein interaction network across vast evolutionary distance.
findings:
- statement: Cross-species interaction data are too generic for accepting protein binding as a core PHO86 function.
supporting_text: "An inter-species protein-protein interaction network"
- id: PMID:37968396
title: The social and structural architecture of the yeast protein interactome.
findings:
- statement: Interactome data support broad association context but not a specific molecular-function annotation.
supporting_text: "The social and structural architecture of the yeast protein interactome."
- id: file:yeast/PHO86/PHO86-deep-research-falcon.md
title: Falcon deep research report on PHO86
findings:
- statement: Falcon synthesis identifies Pho86 as an ER-resident transporter-specific chaperone required for Pho84 ER exit.
supporting_text: "PHO86 encodes an ER-resident membrane protein required for ER exit of the high-affinity phosphate transporter Pho84."
existing_annotations:
- term:
id: GO:0006817
label: phosphate ion transport
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: PHO86 affects phosphate uptake, but the direct transport activity belongs to Pho84 rather than Pho86.
action: MODIFY
reason: Pho86 is required for Pho84 ER export and therefore regulates phosphate transport indirectly; the existing term overstates Pho86 as the transporter.
proposed_replacement_terms:
- id: GO:0010966
label: regulation of phosphate transport
supported_by:
- reference_id: PMID:10655492
supporting_text: "Pho84p is localized to the endoplasmic reticulum (ER) and fails to be targeted to the plasma membrane in the absence of Pho86p"
- term:
id: GO:0016020
label: membrane
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: Membrane localization is true but too broad for Pho86.
action: MODIFY
reason: Direct evidence and functional context place Pho86 as an ER-resident membrane protein, making endoplasmic reticulum membrane more specific than the broad membrane term.
proposed_replacement_terms:
- id: GO:0005789
label: endoplasmic reticulum membrane
supported_by:
- reference_id: PMID:10655492
supporting_text: "Pho86p, an endoplasmic reticulum (ER) resident protein"
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:16429126
review:
summary: The high-throughput interaction annotation is too generic for PHO86 function.
action: MARK_AS_OVER_ANNOTATED
reason: Pho86's interpretable role is a client-specific ER chaperone for Pho84 export, not generic protein binding.
supported_by:
- reference_id: PMID:15623581
supporting_text: "Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER"
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:18467557
review:
summary: Interactome evidence does not provide a useful standalone molecular-function annotation.
action: MARK_AS_OVER_ANNOTATED
reason: Generic protein binding should not be accepted when the literature supports a more specific chaperone/export role.
supported_by:
- reference_id: PMID:10655492
supporting_text: "Pho86p is required for packaging of Pho84p into COPII vesicles"
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:27107014
review:
summary: Cross-species interaction data are too broad for accepting protein binding as PHO86's function.
action: MARK_AS_OVER_ANNOTATED
reason: The curated function should emphasize Pho84-specific ER chaperone activity and regulated phosphate transport.
supported_by:
- reference_id: file:yeast/PHO86/PHO86-deep-research-falcon.md
supporting_text: "ER-resident membrane protein required for ER exit of the high-affinity phosphate transporter Pho84"
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:37968396
review:
summary: Social-interactome protein binding is not informative enough for PHO86 curation.
action: MARK_AS_OVER_ANNOTATED
reason: Protein binding is a broad physical interaction bucket and should not obscure the direct ER chaperone/export phenotype.
supported_by:
- reference_id: PMID:15623581
supporting_text: "prevent aggregation of polytopic proteins in the ER"
- term:
id: GO:0005783
label: endoplasmic reticulum
evidence_type: HDA
original_reference_id: PMID:26928762
review:
summary: High-throughput ER localization is consistent with direct PHO86 evidence.
action: ACCEPT
reason: Pho86 is an ER-resident membrane protein required before Pho84 exits the ER.
supported_by:
- reference_id: PMID:10655492
supporting_text: "endoplasmic reticulum (ER) resident protein"
- term:
id: GO:0005783
label: endoplasmic reticulum
evidence_type: IDA
original_reference_id: PMID:10655492
review:
summary: Direct ER localization is well supported and central to function.
action: ACCEPT
reason: Pho86 acts in the ER to permit Pho84 folding/export and does not travel with Pho84 to the plasma membrane.
supported_by:
- reference_id: PMID:10655492
supporting_text: "Pho86p, an endoplasmic reticulum (ER) resident protein"
- term:
id: GO:0006457
label: protein folding
evidence_type: IMP
original_reference_id: PMID:15623581
review:
summary: Protein folding is a defensible process annotation for Pho86's specialized ER chaperone role.
action: ACCEPT
reason: Pho86 prevents aggregation or misfolding of a cognate polytopic membrane client in the ER.
supported_by:
- reference_id: PMID:15623581
supporting_text: "Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER"
- term:
id: GO:0006888
label: endoplasmic reticulum to Golgi vesicle-mediated transport
evidence_type: IMP
original_reference_id: PMID:10655492
review:
summary: Pho86 is required for ER exit of Pho84, so ER-to-Golgi vesicle-mediated transport is supported.
action: ACCEPT
reason: The phenotype specifically involves failure to package Pho84 into COPII vesicles.
supported_by:
- reference_id: PMID:10655492
supporting_text: "Pho86p is required for packaging of Pho84p into COPII vesicles"
- term:
id: GO:0010966
label: regulation of phosphate transport
evidence_type: IMP
original_reference_id: PMID:10655492
review:
summary: Regulation of phosphate transport accurately captures the indirect transport phenotype.
action: ACCEPT
reason: Pho86 controls delivery of the high-affinity phosphate transporter Pho84, thereby regulating phosphate uptake capacity without being the transporter.
supported_by:
- reference_id: PMID:10655492
supporting_text: "Pho84p is localized to the endoplasmic reticulum (ER) and fails to be targeted to the plasma membrane in the absence of Pho86p"
- term:
id: GO:0051082
label: unfolded protein binding
evidence_type: IMP
original_reference_id: PMID:15623581
review:
summary: The evidence supports a specialized ER chaperone role rather than generic unfolded protein binding.
action: MODIFY
reason: Pho86 is one of the specialized membrane-localized chaperones that prevent aggregation of cognate polytopic membrane proteins in the ER; protein folding chaperone is the more informative term.
proposed_replacement_terms:
- id: GO:0044183
label: protein folding chaperone
supported_by:
- reference_id: PMID:15623581
supporting_text: "Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER"
core_functions:
- description: >-
Pho86 is an ER-resident, client-specific protein folding chaperone for the
high-affinity phosphate transporter Pho84. By enabling Pho84 folding or
anti-aggregation and packaging into COPII vesicles, Pho86 promotes ER-to-Golgi
transport of Pho84 and regulates phosphate transport capacity.
molecular_function:
id: GO:0044183
label: protein folding chaperone
directly_involved_in:
- id: GO:0006888
label: endoplasmic reticulum to Golgi vesicle-mediated transport
- id: GO:0010966
label: regulation of phosphate transport
locations:
- id: GO:0005789
label: endoplasmic reticulum membrane
supported_by:
- reference_id: PMID:10655492
supporting_text: "Pho84p is localized to the endoplasmic reticulum (ER) and fails to be targeted to the plasma membrane in the absence of Pho86p"
- reference_id: PMID:15623581
supporting_text: "Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER"
- reference_id: file:yeast/PHO86/PHO86-deep-research-falcon.md
supporting_text: "required for ER exit of the high-affinity phosphate transporter Pho84"
proposed_new_terms: []
suggested_questions:
- question: What is the direct physical interface between Pho86 and Pho84, and which Pho84 folding state does Pho86 recognize?
experts:
- ER membrane-protein biogenesis experts
- yeast phosphate-homeostasis researchers
- question: Does Pho86 act only on Pho84, or does it have a broader client range among phosphate- or nutrient-transporter family members?
experts:
- yeast transporter biologists
suggested_experiments:
- experiment_type: site-directed mutagenesis and co-immunoprecipitation
description: Mutate conserved Pho86 transmembrane and loop residues, then assay Pho84 binding, Pho84 aggregation, and Pho84 ER export under phosphate starvation.
hypothesis: A defined Pho86 membrane interface recognizes Pho84 and is required for transporter export without affecting general COPII function.
- experiment_type: in vitro COPII budding assay
description: Reconstitute Pho84 packaging from ER membranes with wild-type or chaperone-defective Pho86 alleles and quantify Pho84 incorporation into COPII vesicles.
hypothesis: Pho86 promotes a COPII-competent Pho84 state rather than acting downstream of vesicle formation.