C19orf12 is a small membrane-associated protein found at mitochondria, the endoplasmic reticulum and lipid droplets. In human adipocytes it accumulates during differentiation and localizes to lipid droplet–mitochondrial contact regions, where it associates with components of the mitochondrial protein-import machinery and supports lipid turnover and mitochondrial utilization of long-chain fatty acids. Its precise molecular activity is unresolved. Wild-type protein redistributes during oxidative stress, and cell studies link its abundance or disease-associated variants to autophagic responses, stress sensitivity and mitochondrial calcium homeostasis. Pathogenic variants cause mitochondrial membrane protein-associated neurodegeneration and a form of hereditary spastic paraplegia.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005739 mitochondrion | EXP PMID:21981780 Absence of an orphan mitochondrial protein, c19orf12, causes... | ACCEPT | Summary: C19orf12 localizes to mitochondria in human fibroblast models. Reason: PMID:21981780 reports mitochondrial colocalization of tagged C19orf12, antibody-based localization and subcellular fractionation. Human constructs and fibroblasts establish this location; the additional import experiment used mouse mitochondria and is not the sole basis for the human annotation. Supporting Evidence: PMID:21981780 protein localizes predominantly to mitochondria |
| GO:0005739 mitochondrion | EXP PMID:22508347 A new phenotype of brain iron accumulation with dystonia, op... | ACCEPT | Summary: Mitochondrial localization is independently supported despite limited access to this clinical paper. Reason: The normal cache for PMID:22508347 is abstract-only and does not expose its localization assay. Retain the experimental curator assertion because mitochondrial localization is independently demonstrated in PMID:21981780 and PMID:26136767 and curated in UniProt; do not claim that the original paper’s cellular localization data were inspected. Supporting Evidence: file:human/C19orf12/C19orf12-uniprot.txt |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | ACCEPT | Summary: The mitochondrial proteome annotation agrees with targeted C19orf12 localization studies. Reason: PMID:34800366 establishes the human MitoCoP proteomic framework. The preserved canonical body does not expose a C19orf12-specific table entry, so this review defers to the experimental curator for the target record. Independent targeted localization in PMID:21981780 and PMID:26136767 makes the cellular-component assertion well supported; a full-text flag is not treated as verification of the individual proteomic entry. |
| GO:0005739 mitochondrion | IDA PMID:23857908 Hereditary spastic paraplegia type 43 (SPG43) is caused by m... | ACCEPT | Summary: Wild-type recombinant C19orf12 occupies mitochondria as well as ER in cultured cells. Reason: The inspected primary Results in PMID:23857908 distinguish the variable ER/mitochondrial distribution of wild-type tagged C19orf12 from the more generalized cytoplasmic distribution of pathogenic variants. Preserve the mitochondrial annotation without transferring mutant mislocalization to wild type or claiming an exclusive mitochondrial location. Supporting Evidence: |
| GO:0005739 mitochondrion | IDA PMID:26136767 Mutations of C19orf12, coding for a transmembrane glycine zi... | ACCEPT | Summary: Wild-type C19orf12 is detected in mitochondrial fractions and by colocalization. Reason: PMID:26136767 reports both tagged-protein experiments and fractionation of endogenous protein in HEK293 cells, with compartment controls. The wild-type signal in mitochondria supports this location independently of mutant effects or predicted transporter homology. Supporting Evidence: PMID:26136767 present in both mitochondria and ER |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | ACCEPT | Summary: The UniProt subcellular-location mapping to mitochondrion is supported. Reason: The electronic mapping reproduces a curated UniProt location supported by multiple experimental studies. It is consistent with the independently inspected human localization experiments and does not imply a specific mitochondrial subcompartment. |
| GO:0005783 endoplasmic reticulum | EXP PMID:22508347 A new phenotype of brain iron accumulation with dystonia, op... | ACCEPT | Summary: ER localization is supported by independent wild-type localization experiments. Reason: PMID:22508347 is available only as a clinical abstract, so its original localization assay is uninspected. Retain the experimental assertion with curator deference and independent corroboration from the explicit wild-type ER localization in PMID:23857908 and endogenous fractionation in PMID:26136767; the clinical abstract alone is not treated as ER evidence. ORGANELLES check (2026-11-05, ER batch 2): the ER claim holds on the inspected papers; the ER-membrane sub-compartment is added as a separate NEW GO:0005789 row and this root row is unchanged. Supporting Evidence: file:human/C19orf12/C19orf12-uniprot.txt |
| GO:0005783 endoplasmic reticulum | IDA PMID:23857908 Hereditary spastic paraplegia type 43 (SPG43) is caused by m... | ACCEPT | Summary: Wild-type C19orf12 can show prominent ER localization in cultured cells. Reason: PMID:23857908 reports colocalization with calreticulin and comparable localization effects with N-terminal HA and C-terminal Myc tagging. The authors distinguish wild-type localization from pathogenic-variant redistribution and explicitly leave endogenous localization for further study. ORGANELLES check (2026-11-05, ER batch 2): tagged overexpressed protein with an ER marker is weaker than endogenous staining, but the endogenous fractionation in PMID:26136767 independently places a native pool in the ER, so the row stands; the membrane sub-compartment is added as a separate NEW GO:0005789 row. Supporting Evidence: PMID:23857908 primarily the ER but also the mitochondria |
| GO:0005783 endoplasmic reticulum | IDA PMID:26136767 Mutations of C19orf12, coding for a transmembrane glycine zi... | ACCEPT | Summary: Endogenous and recombinant C19orf12 are detected at the ER. Reason: PMID:26136767 reports endogenous HEK293 fractionation with ER, mitochondrial and mitochondria-associated membrane controls, and tagged wild-type colocalization in HeLa cells. These observations support the ER location without establishing a particular ER molecular activity. ORGANELLES check (2026-11-05, ER batch 2): this is the strongest ER row, endogenous protein in an IP3R-marked ER fraction; a fraction cannot by itself resolve membrane from lumen, so the sub-compartment is recorded in a separate NEW GO:0005789 row that combines it with topology. Supporting Evidence: |
| GO:0005783 endoplasmic reticulum | IEA GO_REF:0000044 | ACCEPT | Summary: The curated UniProt ER-location mapping is experimentally corroborated. Reason: The electronic assertion agrees with independently inspected wild-type ER localization in PMID:23857908 and PMID:26136767. Preserve the machine mapping; the evidence supports an ER pool rather than exclusive localization. ORGANELLES check (2026-11-05, ER batch 2): the SL-0095 keyword rests on UniProt text tagged ECO:0000269 to PMID:22508347, and the claim is independently confirmed by PMID:23857908 and PMID:26136767. UniProt gives no ER sub-location (its Mitochondrion membrane statement does not extend to the ER pool), which is why the mapping stops at the root; the membrane is added as a NEW GO:0005789 row. |
| GO:0005789 endoplasmic reticulum membrane | IC PMID:26136767 Mutations of C19orf12, coding for a transmembrane glycine zi... | NEW | Summary: Proposed sub-compartment. The ER pool of C19orf12 is a membrane pool, held by its single predicted TM segment; the existing ER annotations stop at the organelle. Reason: ORGANELLES rule 4 (2026-11-05, ER batch 2). Lines that agree on the membrane rather than the lumen. (1) Topology - UniProt records one predicted helical TM segment (40-60) and a single-pass membrane protein, with no signal peptide, so the protein cannot be released into the ER lumen and any ER pool is membrane-inserted. (2) Direct assay on the endogenous protein - naive HEK293 C19orf12 is in the ER fraction, controlled with IP3R (ER), VDAC (mitochondria) and Sigma-1R (MAM) markers (PMID:26136767). (3) Supportive - tagged wild-type protein co-localizes with calreticulin in many cells (PMID:23857908). The pool is endogenous and marker-controlled, so it is not a transit or overexpression artefact. IC because the TM is predicted and no carbonate extraction or protease protection of the ER pool was done. The same paper detects a small endogenous fraction in the MAM; with only that one line a MAM (GO:0044233) row is not added. The ER pool is not the core location, so core_functions are unchanged. Supporting Evidence: file:human/C19orf12/C19orf12-uniprot.txt FT TRANSMEM 40..60 FT /note="Helical" PMID:26136767 the wild-type protein was present in both mitochondria and ER PMID:26136767 Anti-IP3R, VDAC, and Sigma-1R were used as ER, mitochondria and MAM markers respectively |
| GO:0005811 lipid droplet | IDA PMID:38565923 A spatiotemporal proteomic map of human adipogenesis. | ACCEPT | Summary: C19orf12 localizes around adipocyte lipid droplets and at adjacent mitochondrial contact regions. Reason: PMID:38565923 reports immunofluorescence in human SGBS and hAPC adipocytes, consistent with the organellar proteomic profile. The inspected Results and Methods support lipid-droplet localization; TOM-component coassociation adds context but does not make C19orf12 a TOM pore or establish a molecular tethering activity. Supporting Evidence: PMID:38565923 C19orf12 immunostaining around the LDs |
| GO:0005811 lipid droplet | IEA GO_REF:0000044 | ACCEPT | Summary: The UniProt lipid-droplet mapping reflects direct human adipocyte observations. Reason: The curated location is supported by the targeted immunostaining and organellar proteomics in PMID:38565923. Retain the lipid-droplet assertion while keeping the adipocyte context explicit. |
| GO:0005829 cytosol | IDA GO_REF:0000052 | KEEP AS NON CORE | Summary: A cytosolic C19orf12 pool is compatible with independent fractionation and stress-response observations. Reason: The original GO_REF:0000052 immunofluorescence curation is retained with curator deference; its individual Human Protein Atlas image was not inspected. PMID:26136767 independently detects a wild-type cytosolic pool and stress-induced redistribution. Keep this contextual location outside the core lipid-droplet/mitochondrial synthesis and distinguish it from mutant mislocalization. |
| GO:0005829 cytosol | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: The UniProt cytosol mapping represents a supported, context-dependent pool. Reason: PMID:26136767 and the curated UniProt record support cytosolic detection and redistribution during oxidative stress. This is a genuine location, but it is not sufficient to define an independent cytosolic molecular activity or the main adipocyte function. |
| GO:0006629 lipid metabolic process | IMP PMID:38565923 A spatiotemporal proteomic map of human adipogenesis. | ACCEPT | Summary: C19orf12 supports lipid turnover and mitochondrial fatty-acid utilization in human adipocytes. Reason: PMID:38565923 combines targeted lipid-droplet/mitochondrial localization and TOM-component coassociation with early and late siRNA depletion. Late depletion reduces lipid turnover and fatty-acid-dependent respiratory capacity; palmitate and etomoxir experiments distinguish impaired fatty-acid utilization from a general loss of respiration. GO:0019216 regulation of lipid metabolic process was considered. Retain the existing experimental curator assertion to the broad lipid metabolic process because the evidence places C19orf12 at the relevant interface and functionally links it to lipid utilization, while neither an exclusively regulatory step nor a direct lipid-handling reaction is resolved. This is conservative retention of a curated process role, not a claim that depletion alone proves catalysis or transport. The corresponding core records this broad role with molecular function omitted; lipase, fatty-acid transporter, lipid-transfer and tether activities remain unassigned. Supporting Evidence: PMID:38565923 capability of mitochondria to metabolize long-chain fatty acids |
| GO:0006914 autophagy | IMP PMID:26136767 Mutations of C19orf12, coding for a transmembrane glycine zi... | MODIFY | Summary: Wild-type C19orf12 overexpression increases basal autophagic activity in HeLa cells. Reason: PMID:26136767 reports increased LC3 puncta and LC3 conversion together with reduced p62 after wild-type C19orf12 overexpression; the NH4Cl comparison argues against accumulation caused solely by blocked degradation. The positive-regulation term captures the observed increase in autophagic activity more precisely than the undifferentiated autophagy assertion. G58S and Q96P constructs do not reproduce the wild-type effect, and hydrogen peroxide changes the response. The inference is bounded to these overexpression experiments: it does not establish the endogenous regulatory step, autophagosome structural membership or selective mitophagy. Regulatory participation does not require C19orf12 itself to catalyse degradation. Proposed replacements: positive regulation of autophagy Supporting Evidence: PMID:26136767 indicating the elevation of basal autophagic levels |
| GO:0006915 apoptotic process | IMP PMID:26136767 Mutations of C19orf12, coding for a transmembrane glycine zi... | MARK AS OVER ANNOTATED | Summary: G58S patient fibroblasts show greater peroxide-induced cell death, but a specific apoptotic-process role is not established. Reason: PMID:26136767 compares one G58S patient-derived fibroblast line with two controls after hydrogen peroxide exposure and reports increased cell death using automated nuclear counts. This establishes a stress-sensitivity phenotype in that model, but does not isolate a C19orf12-dependent apoptotic execution or regulatory step; no rescue or isogenic comparison is reported for this death experiment. The authors propose a protective relationship between autophagy and apoptosis, but the patient-line result alone cannot distinguish specific negative regulation of apoptosis (GO:0043066) from broader cellular stress susceptibility. Mark the existing apoptotic-process claim as over-annotated at this evidential resolution, while retaining the separately reviewed oxidative-stress and calcium-homeostasis observations. This judgment is not based on the absence of catalytic activity or on an assumption that apoptotic-process annotations must be pro-apoptotic. Supporting Evidence: |
| GO:0006979 response to oxidative stress | IMP PMID:26136767 Mutations of C19orf12, coding for a transmembrane glycine zi... | KEEP AS NON CORE | Summary: Wild-type C19orf12 redistributes in response to oxidative stress. Reason: Live imaging in PMID:26136767 follows tagged wild-type and mutant constructs after hydrogen peroxide treatment. Wild-type redistribution and the altered responses of pathogenic variants support the response process. The experiment does not establish antioxidant enzymatic activity or identify a redox-sensing reaction. Supporting Evidence: PMID:26136767 changed its localization pattern from reticular to cytosolic |
| GO:0031966 mitochondrial membrane | EXP PMID:21981780 Absence of an orphan mitochondrial protein, c19orf12, causes... | ACCEPT | Summary: A mitochondrial membrane-associated C19orf12 pool is experimentally supported. Reason: PMID:21981780 combines mitochondrial colocalization and fractionation, and identifies the protein as membrane associated; independent fractionation in PMID:26136767 corroborates mitochondrial membrane localization. Keep this broad membrane term without asserting inner- versus outer-membrane residence, topology, or that every isoform shares the same distribution. |
| GO:0031966 mitochondrial membrane | IDA PMID:26136767 Mutations of C19orf12, coding for a transmembrane glycine zi... | ACCEPT | Summary: Wild-type C19orf12 is present in mitochondrial membrane fractions. Reason: The inspected PMID:26136767 Results and Figure 1 caption distinguish mitochondrial membranes from matrix and cytosolic fractions using markers. Matrix detection of the G58S mutant is not treated as a wild-type matrix annotation. Retain the experimental mitochondrial-membrane location. Supporting Evidence: |
| GO:0031966 mitochondrial membrane | IEA GO_REF:0000044 | ACCEPT | Summary: The UniProt mitochondrial-membrane mapping is consistent with primary fractionation data. Reason: The curated membrane-location statement is supported by PMID:21981780 and PMID:26136767. The electronic assertion does not establish an inner/outer membrane subdivision or a channel function. |
| GO:0051560 mitochondrial calcium ion homeostasis | IMP PMID:26136767 Mutations of C19orf12, coding for a transmembrane glycine zi... | KEEP AS NON CORE | Summary: C19orf12 dysfunction perturbs mitochondrial calcium handling in patient fibroblasts. Reason: PMID:26136767 uses mitochondrially targeted aequorin and ATP-triggered calcium release to show larger mitochondrial calcium responses in G58S patient fibroblasts than controls. Retain the existing homeostasis assertion as a non-core cellular effect, without claiming direct calcium transport, a calcium-binding activity or the speculative MgtE-like regulatory mechanism. Supporting Evidence: |
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Download this section (compressed HTML)Q: What molecular activity couples C19orf12 at lipid droplet–mitochondrial contact regions to fatty-acid utilization: regulation of mitochondrial protein composition, direct lipid handling, contact organization, or another mechanism? TOM coassociation and depletion phenotypes do not yet distinguish these models.
Q: How do the four named products differ in expression, membrane topology and function? Historical long/short construct names and numbered variants need sequence-level mapping before they can be assigned to the current UniProt product accessions.
Q: Do endogenous C19orf12 perturbations and rescue establish direct roles in autophagic regulation, calcium homeostasis and neuronal survival beyond the currently inspected overexpression and patient-fibroblast phenotypes?
Q: Which specific cellular-component term best represents C19orf12 at lipid droplet–mitochondrial contact regions? The observed contact-region localization can be distinguished from an experimentally demonstrated bridging or lipid-transfer activity; a verified lipid droplet–mitochondrion term and the appropriate annotation scope remain to be established.
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