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this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.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.
CG6836 (UniProt Q9VVV2) is a poorly characterized Drosophila melanogaster protein whose strongest defensible annotation is “putative OST-alpha-family integral membrane protein.” The supplied UniProt record identifies it as an organic-solute-transporter-alpha-like protein/SLC51A homolog and assigns the Ostalpha/TMEM184C (IPR005178) and Solute_trans_a (PF03619) domains. These assignments are internally consistent with membership in the OST-alpha family. However, the literature search found no direct CG6836/Q9VVV2 transport assay, substrate identification, localization experiment, interacting-partner study, or loss-of-function phenotype, including no targeted 2023–2024 study.
Accordingly, it would be premature to annotate bile acids, steroid conjugates, or any other specific molecule as the CG6836 substrate. Those are experimentally established substrates of the vertebrate heteromeric OSTα–OSTβ transporter, not of fly CG6836. Comparative reviews specifically suggest that fly and worm OST-alpha homologs may retain an ancestral role involving non-bile-acid substrates, because bile acids have not been detected as normal invertebrate metabolites (dawson2010gettingthemost pages 4-5).
The research target was restricted to:
No literature was found that contradicts this supplied identifier mapping. The family and domain labels agree conceptually: vertebrate SLC51A/OSTα is the multipass, substrate-associated component of the OSTα–OSTβ organic-solute transporter (ticho2020intestinalabsorptionof pages 24-25, ballatori2013theheteromericorganic pages 1-2).
A superficially relevant paper entitled “Structural characterization and subcellular localization of Drosophila organic solute carrier partner 1” does not study CG6836. Its protein is dOSCP1 = CG13178, accession AFF58577.1, a 302-residue protein reported as 30% identical and 58% similar to human OSCP1 (huu2014structuralcharacterizationand pages 1-2, huu2014structuralcharacterizationand pages 9-10). Therefore, that paper’s localization to plasma membrane, ER, Golgi, mitochondria, and nucleus, and its reported oligomerization, must not be assigned to CG6836 (huu2014structuralcharacterizationand pages 5-9, huu2014structuralcharacterizationand pages 2-5).
This distinction is critical: OSCP1/CG13178 and OST-alpha-like CG6836 are different fly proteins.
| Annotation question | Best-supported conclusion | Evidence type/strength | Key caveat |
|---|---|---|---|
| Identity | CG6836 is the Drosophila melanogaster gene associated with UniProt Q9VVV2, described in the supplied UniProt record as an organic-solute-transporter-alpha-like/SLC51A-homolog protein. | Strong database-level identification from the specified UniProt record; literature searches using both identifiers found no contradictory identity. | No primary paper directly validating the Q9VVV2–CG6836 correspondence was found in the searched literature. |
| Family/domains | Q9VVV2 is assigned to the OST-alpha family and contains the supplied Ostalpha/TMEM184C (IPR005178) and Solute_trans_a (PF03619) annotations, consistent with an integral membrane OST-alpha-like protein. Vertebrate OSTα is a seven-transmembrane protein (ticho2020intestinalabsorptionof pages 24-25, ballatori2013theheteromericorganic pages 1-2, dawson2010gettingthemost pages 4-5). | Moderate-to-strong bioinformatic inference; agreement between the family and domain assignments supports the annotation. | Domain membership establishes evolutionary relatedness, not the transported substrate, membrane compartment, interaction partner, or physiological role in flies. |
| Molecular function | The safest annotation is putative organic-solute transporter or transporter component. No direct CG6836 transport assay was found. Vertebrate OSTα forms a transporter with OSTβ, but this heteromeric requirement has not been demonstrated for CG6836 (ballatori2013theheteromericorganic pages 2-5, dawson2010gettingthemost pages 5-6). | Moderate family-based inference; no direct CG6836 evidence. | It is unknown whether CG6836 transports solutes independently, requires a partner, or has a divergent membrane function. |
| Substrate | Unknown in D. melanogaster. Vertebrate OSTα/β transports bile acids, conjugated steroids, estrone-3-sulfate, DHEAS, digoxin, and prostaglandin E2 (dawson2010gettingthemost pages 8-9, ballatori2013theheteromericorganic pages 2-5, ballatori2009ostalphaostbeta pages 5-7). | No direct CG6836 evidence; strong vertebrate-family context only. | Bile acids have not been detected as normal invertebrate metabolites in the cited evolutionary analysis. Fly and worm OST-alpha homologs were therefore proposed to have ancestral non-bile-acid substrates (dawson2010gettingthemost pages 4-5). Assigning bile acids or steroids as CG6836 substrates would be unsupported. |
| Transport mechanism | If CG6836 retains canonical family activity, facilitated diffusion is plausible. Vertebrate OSTα/β transport is bidirectional and independent of ATP and imposed sodium, potassium, proton, chloride, or pH gradients (ticho2020intestinalabsorptionof pages 24-25, dawson2010gettingthemost pages 8-9, ballatori2013theheteromericorganic pages 2-5). | Mechanistically strong for vertebrate OSTα/β; weak inference for CG6836. | Directionality, coupling, kinetics, and even transport activity remain untested for the fly protein. |
| Cellular localization | CG6836 is most plausibly an integral cellular-membrane protein based on its OST-alpha-family and domain annotations. Its specific membrane and polarized distribution are unknown. | Moderate topology-level inference; no direct localization evidence. | Vertebrate OSTα/β occurs predominantly on basolateral epithelial membranes, but this localization cannot be transferred to CG6836 without imaging or fractionation evidence (ticho2020intestinalabsorptionof pages 24-25, ballatori2013theheteromericorganic pages 1-2, ballatori2009ostalphaostbeta pages 5-7). |
| Pathway | No specific Drosophila biochemical or signaling pathway can currently be assigned. Family membership suggests a possible role in small-organic-molecule homeostasis. Vertebrate OSTα/β participates in enterohepatic bile-acid recycling and FXR–FGF15/19 feedback (ticho2020intestinalabsorptionof pages 24-25, dawson2010gettingthemost pages 8-9). | No direct CG6836 pathway evidence; vertebrate comparative context only. | Drosophila does not possess the mammalian enterohepatic bile-acid pathway in the same physiological form, so this pathway must not be assigned to CG6836 by orthology alone. |
| Direct phenotype | No CG6836-specific loss-of-function, gain-of-function, rescue, or organismal phenotype was found. A fly bile-acid-toxicity study manipulated intestinal cncC/Nrf2, not CG6836; cncC knockdown increased bile-acid sensitivity (ferrebee2018organicsolutetransporter pages 41-45, ferrebee2018organicsolutetransporter pages 6-11). | Absence from the retrieved literature, not proof that unpublished or unindexed evidence does not exist. | Phenotypes from cncC/Nrf2 experiments cannot be attributed to CG6836. |
| Misleading near-match: dOSCP1 | The published Drosophila organic solute carrier partner 1 is dOSCP1 = CG13178, accession AFF58577.1, and is not CG6836/Q9VVV2 (huu2014structuralcharacterizationand pages 1-2, huu2014structuralcharacterizationand pages 9-10). | Strong identifier-level exclusion. | Its reported localization, oligomerization, expression, and proposed transport role concern CG13178 and must not be used to annotate CG6836 (huu2014structuralcharacterizationand pages 5-9, huu2014structuralcharacterizationand pages 2-5). |
Table: This table separates verified identity and domain information for CG6836/Q9VVV2 from vertebrate OSTα/β family context and unresolved fly-specific function. It also excludes the frequently confusable dOSCP1/CG13178 protein.
The most supportable description is:
Putative multipass membrane protein of the OST-alpha/SLC51A family, potentially involved in transmembrane movement or homeostasis of an unidentified organic solute.
This is a family/domain-based prediction, not a demonstrated activity. No CG6836 uptake, efflux, electrophysiology, vesicle-transport, metabolomics, or rescue assay was retrieved. It is also unknown whether the fly protein operates alone, as a homomer, or with another subunit.
In vertebrates, OSTα is not normally sufficient by itself. OSTα/SLC51A is approximately 340 amino acids with seven predicted transmembrane helices, whereas OSTβ/SLC51B is approximately 128 amino acids with one transmembrane segment. Coexpression promotes subunit stabilization, ER exit, Golgi maturation, and plasma-membrane delivery; either subunit alone gives no detectable transport in standard heterologous assays (ticho2020intestinalabsorptionof pages 24-25, ballatori2013theheteromericorganic pages 1-2, dawson2010gettingthemost pages 5-6). Whether these partner requirements apply to CG6836 is unknown. Evolutionary analysis suggests that OSTβ is less conserved and may have arisen later as a vertebrate cofactor, making simple transfer of the vertebrate architecture to insects unsafe (dawson2010gettingthemost pages 4-5).
CG6836 substrate: unknown.
For comparison only, vertebrate OSTα–OSTβ transports:
Skate OSTα/β transported taurocholate, estrone-3-sulfate, digoxin, and prostaglandin E2 but not p-aminohippurate or S-dinitrophenyl glutathione, demonstrating multispecificity without indiscriminate organic-anion transport (ballatori2013theheteromericorganic pages 2-5). None of these results establishes a substrate for CG6836.
The strongest evolutionary caution comes from Dawson and colleagues: fly and worm OSTα homologs were inferred to represent an ancestral transporter for non-bile-acid molecules, because bile acids have not been detected in invertebrates; vertebrate specialization for bile-acid handling may therefore be derived (dawson2010gettingthemost pages 4-5). Thus, “bile-acid transporter” should not be used as a definitive annotation for CG6836.
Vertebrate OSTα/β mediates bidirectional facilitated diffusion. Transport direction depends on the substrate electrochemical gradient and can support uptake or efflux. Activity in Xenopus oocytes is independent of ATP depletion and experimentally altered Na+, K+, H+, Cl−, and pH gradients; substrate trans-stimulation provides additional support for carrier-mediated exchange/facilitated diffusion (ticho2020intestinalabsorptionof pages 24-25, dawson2010gettingthemost pages 8-9, ballatori2013theheteromericorganic pages 2-5).
A similar passive-carrier mechanism is plausible for CG6836 if it retains canonical OST-family activity, but this remains untested. Transport coupling, directionality, kinetics, affinity, and inhibitor sensitivity cannot presently be assigned.
The OST-alpha-family and Solute_trans_a annotations support an integral cellular-membrane location, probably with multiple transmembrane helices. No CG6836-specific imaging, fractionation, surface biotinylation, proximity labeling, or polarized-epithelium analysis was found. Therefore, the exact compartment—plasma membrane, ER, another organelle, or multiple compartments—is unknown.
Vertebrate OSTα/β is predominantly located on basolateral epithelial membranes, including ileal enterocytes, renal proximal tubular cells, cholangiocytes, and under some conditions hepatocytes. In intestine it exports intracellular bile acids toward portal blood after apical uptake by ASBT (ticho2020intestinalabsorptionof pages 24-25, dawson2010gettingthemost pages 8-9, ballatori2013theheteromericorganic pages 1-2). Coexpression with OSTβ is important for OSTα maturation and surface trafficking (dawson2010gettingthemost pages 5-6).
These findings provide a testable localization hypothesis, not evidence that fly CG6836 is basolateral or intestinal. Polarized localization should be determined experimentally in Drosophila tissues.
No specific Drosophila signaling or biochemical pathway can currently be assigned with confidence. The conservative process-level prediction is small-organic-molecule transmembrane transport/homeostasis.
The mammalian pathway context is enterohepatic bile-acid recycling: ASBT mediates apical ileal uptake, and OSTα/β mediates basolateral return to portal circulation. Approximately 90–95% of intestinal bile acids are normally reabsorbed in this system (ballatori2013theheteromericorganic pages 2-5). Loss of mouse OSTα reduces the bile-acid pool by approximately 60%, impairs intestinal, renal, and biliary absorption, and promotes enterocyte bile-acid stress. Residual intracellular bile acid activates FXR–FGF15/19 signaling and suppresses hepatic bile-acid synthesis (ticho2020intestinalabsorptionof pages 24-25).
That mammalian FXR–FGF15/19 enterohepatic pathway should not be assigned to CG6836. Drosophila does not share the same bile-acid circulation physiology, and its OST-alpha homolog may transport a different endogenous metabolite.
A 2018 study exposed adult flies to chenodeoxycholic or deoxycholic acid and showed intestinal oxidative stress. The manipulated fly gene was cncC, the Nrf2 homolog—not CG6836. Enterocyte-specific cncC RNAi further reduced survival during bile-acid exposure (log-rank P < 0.0001; n = 50 per group); bile-acid-treated groups differed from sucrose controls at P < 0.001 with n = 30–44 (ferrebee2018organicsolutetransporter pages 41-45). These data demonstrate a fly intestinal antioxidant response to exogenous bile acids, but they provide no evidence that CG6836 transports those compounds.
Targeted searches did not retrieve a 2023 or 2024 primary study directly investigating CG6836 or Q9VVV2. This negative result is itself important for annotation: the record remains driven mainly by sequence/domain classification rather than recent experimental validation.
The field’s closest mechanistic progress available in the retrieved evidence concerns vertebrate OSTα/β structure–function relationships. A 2021 mutagenesis study identified OSTα residues Ser228, Thr229, Gln269, and Glu305 as affecting expression and/or taurocholate transport. Relative taurocholate uptake for S228K, T229S, Q269E, and Q269K was 0.76, 0.75, 0.79, and 0.13 of wild type; relative efflux for S228K, Q269K, and E305A was 0.86, 0.65, and 0.79, respectively (murphy2021identificationofkeya pages 1-8). These findings support OSTα as an important substrate-interacting component of the vertebrate complex, but residue-level transfer to CG6836 would require sequence alignment and experimental testing.
There is presently no demonstrated applied use of CG6836 itself. Potential value lies in its use as:
By contrast, mammalian OSTα/β already has real-world relevance to intestinal bile-acid reclamation, cholestasis, congenital diarrheal disease, drug disposition, and pharmacological transporter interactions. A human OSTβ frameshift has been linked to congenital diarrhea and cholestasis, while vertebrate OSTα/β transports or is inhibited by several drugs and xenobiotics (ticho2020intestinalabsorptionof pages 24-25, dawson2010gettingthemost pages 8-9, murphy2021identificationofkeya pages 1-8). These clinical associations should not be interpreted as CG6836 disease functions.
The most informative sequence of studies would be:
Recommended functional annotation:
CG6836 encodes a predicted multipass OST-alpha-family membrane protein. It is likely involved in organic-solute transport or homeostasis, but its endogenous substrate, transport mechanism, interaction partners, subcellular membrane, tissue of action, and physiological pathway in Drosophila melanogaster remain experimentally undetermined.
This formulation preserves the useful family-level inference while avoiding unsupported transfer of vertebrate bile-acid-transporter biology to the fly protein.
References
(dawson2010gettingthemost pages 4-5): Paul A. Dawson, Melissa L. Hubbert, and Anuradha Rao. Getting the most from ost: role of organic solute transporter, ostalpha-ostbeta, in bile acid and steroid metabolism. Biochimica et biophysica acta, 1801 9:994-1004, Sep 2010. URL: https://doi.org/10.1016/j.bbalip.2010.06.002, doi:10.1016/j.bbalip.2010.06.002. This article has 106 citations.
(ticho2020intestinalabsorptionof pages 24-25): Alexander L. Ticho, Pooja Malhotra, Pradeep K. Dudeja, Ravinder K. Gill, and Waddah A. Alrefai. Intestinal absorption of bile acids in health and disease. Comprehensive Physiology, 10 1:21-56, Dec 2020. URL: https://doi.org/10.1002/cphy.c190007, doi:10.1002/cphy.c190007. This article has 320 citations and is from a peer-reviewed journal.
(ballatori2013theheteromericorganic pages 1-2): Nazzareno Ballatori, Whitney V. Christian, Sadie G. Wheeler, and Christine L. Hammond. The heteromeric organic solute transporter, ostα-ostβ/slc51: a transporter for steroid-derived molecules. Molecular aspects of medicine, 34 2-3:683-92, Apr 2013. URL: https://doi.org/10.1016/j.mam.2012.11.005, doi:10.1016/j.mam.2012.11.005. This article has 97 citations and is from a highest quality peer-reviewed journal.
(huu2014structuralcharacterizationand pages 1-2): Nguyen Tho Huu, Hideki Yoshida, Takanari Umegawachi, Seiji Miyata, and Masamitsu Yamaguchi. Structural characterization and subcellular localization of drosophila organic solute carrier partner 1. BMC Biochemistry, 15:11-11, Jun 2014. URL: https://doi.org/10.1186/1471-2091-15-11, doi:10.1186/1471-2091-15-11. This article has 8 citations and is from a peer-reviewed journal.
(huu2014structuralcharacterizationand pages 9-10): Nguyen Tho Huu, Hideki Yoshida, Takanari Umegawachi, Seiji Miyata, and Masamitsu Yamaguchi. Structural characterization and subcellular localization of drosophila organic solute carrier partner 1. BMC Biochemistry, 15:11-11, Jun 2014. URL: https://doi.org/10.1186/1471-2091-15-11, doi:10.1186/1471-2091-15-11. This article has 8 citations and is from a peer-reviewed journal.
(huu2014structuralcharacterizationand pages 5-9): Nguyen Tho Huu, Hideki Yoshida, Takanari Umegawachi, Seiji Miyata, and Masamitsu Yamaguchi. Structural characterization and subcellular localization of drosophila organic solute carrier partner 1. BMC Biochemistry, 15:11-11, Jun 2014. URL: https://doi.org/10.1186/1471-2091-15-11, doi:10.1186/1471-2091-15-11. This article has 8 citations and is from a peer-reviewed journal.
(huu2014structuralcharacterizationand pages 2-5): Nguyen Tho Huu, Hideki Yoshida, Takanari Umegawachi, Seiji Miyata, and Masamitsu Yamaguchi. Structural characterization and subcellular localization of drosophila organic solute carrier partner 1. BMC Biochemistry, 15:11-11, Jun 2014. URL: https://doi.org/10.1186/1471-2091-15-11, doi:10.1186/1471-2091-15-11. This article has 8 citations and is from a peer-reviewed journal.
(ballatori2013theheteromericorganic pages 2-5): Nazzareno Ballatori, Whitney V. Christian, Sadie G. Wheeler, and Christine L. Hammond. The heteromeric organic solute transporter, ostα-ostβ/slc51: a transporter for steroid-derived molecules. Molecular aspects of medicine, 34 2-3:683-92, Apr 2013. URL: https://doi.org/10.1016/j.mam.2012.11.005, doi:10.1016/j.mam.2012.11.005. This article has 97 citations and is from a highest quality peer-reviewed journal.
(dawson2010gettingthemost pages 5-6): Paul A. Dawson, Melissa L. Hubbert, and Anuradha Rao. Getting the most from ost: role of organic solute transporter, ostalpha-ostbeta, in bile acid and steroid metabolism. Biochimica et biophysica acta, 1801 9:994-1004, Sep 2010. URL: https://doi.org/10.1016/j.bbalip.2010.06.002, doi:10.1016/j.bbalip.2010.06.002. This article has 106 citations.
(dawson2010gettingthemost pages 8-9): Paul A. Dawson, Melissa L. Hubbert, and Anuradha Rao. Getting the most from ost: role of organic solute transporter, ostalpha-ostbeta, in bile acid and steroid metabolism. Biochimica et biophysica acta, 1801 9:994-1004, Sep 2010. URL: https://doi.org/10.1016/j.bbalip.2010.06.002, doi:10.1016/j.bbalip.2010.06.002. This article has 106 citations.
(ballatori2009ostalphaostbeta pages 5-7): N. Ballatori, Na Li, Fang Fang, J. Boyer, W. V. Christian, and C. Hammond. Ost alpha-ost beta: a key membrane transporter of bile acids and conjugated steroids. Frontiers in bioscience, 14:2829-44, Jan 2009. URL: https://doi.org/10.2741/3416, doi:10.2741/3416. This article has 154 citations and is from a peer-reviewed journal.
(ferrebee2018organicsolutetransporter pages 41-45): Courtney B. Ferrebee, Jianing Li, Jamie Haywood, Kimberly Pachura, Brian S. Robinson, Benjamin H. Hinrichs, Rheinallt M. Jones, Anuradha Rao, and Paul A. Dawson. Organic solute transporter α-β protects ileal enterocytes from bile acid–induced injury. Cellular and Molecular Gastroenterology and Hepatology, 5:499-522, Jan 2018. URL: https://doi.org/10.1016/j.jcmgh.2018.01.006, doi:10.1016/j.jcmgh.2018.01.006. This article has 64 citations and is from a domain leading peer-reviewed journal.
(ferrebee2018organicsolutetransporter pages 6-11): Courtney B. Ferrebee, Jianing Li, Jamie Haywood, Kimberly Pachura, Brian S. Robinson, Benjamin H. Hinrichs, Rheinallt M. Jones, Anuradha Rao, and Paul A. Dawson. Organic solute transporter α-β protects ileal enterocytes from bile acid–induced injury. Cellular and Molecular Gastroenterology and Hepatology, 5:499-522, Jan 2018. URL: https://doi.org/10.1016/j.jcmgh.2018.01.006, doi:10.1016/j.jcmgh.2018.01.006. This article has 64 citations and is from a domain leading peer-reviewed journal.
(murphy2021identificationofkeya pages 1-8): WA Murphy, JJ Beaudoin, T Laitinen, and N Sjöstedt. Identification of key amino acids that impact organic solute transporter alpha/beta (ostα/ß). Unknown journal, 2021.