GTPBP2 (GTP-binding protein 2) is a cytoplasmic translational GTPase of the TRAFAC-class translation-factor superfamily, related to eEF1A, eRF3, Hbs1 and its paralog GTPBP1. It partners the ribosome-rescue factor PELO and functions in the rescue of ribosomes stalled because of non-functional or deficient tRNA, a role that is especially critical in neurons. Unlike its paralog GTPBP1, GTPBP2 lacks eEF1A-like elongation activity and does not stimulate exosomal mRNA degradation; it has only weak GTP-binding activity that is stimulated by aminoacyl-tRNA. Loss of GTPBP2 (in the context of a destabilized brain-specific tRNA in mouse, and through biallelic loss-of-function in humans) leads to ribosome stalling and neurodegeneration; human GTPBP2 deficiency causes Jaberi-Elahi syndrome, characterized by developmental delay, intellectual disability, movement abnormalities and cerebellar atrophy.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0006414
translational elongation
|
IBA
GO_REF:0000033 |
MARK AS OVER ANNOTATED |
Summary: Phylogenetic transfer of a translational-elongation role from the eEF1A/GTPBP family. However, GTPBP2 was directly shown to lack elongation activity; its actual role is ribosome rescue of stalled (deficient-tRNA) ribosomes. Mouse genetics localize the defect to elongation quality control rather than productive elongation - GTPBP2 deficiency causes prolonged ribosome pausing at AGA arginine codons when the cognate tRNA-Arg(UCU) pool is limiting.
Reason: GTPBP2 lacks the eEF1A-like elongation activity that the family-level IBA implies; the term over-states its function. The accurate role is rescue/quality control of stalled (deficient-tRNA) ribosomes, not productive translational elongation.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Involved in the rescue of ribosome stalling due to the presence of non-functional tRNA
file:human/GTPBP2/GTPBP2-deep-research-falcon.md
GTPBP2 deficiency causes prolonged ribosome pausing specifically at AGA arginine codons when the cognate tRNA_Arg(UCU) is limiting
|
|
GO:0003924
GTPase activity
|
IEA
GO_REF:0000002 |
KEEP AS NON CORE |
Summary: GTPBP2 is a GTPase by family, but it was directly shown to have only very low GTP-binding activity; GTPase activity is plausible but weak.
Reason: Predicted GTPase activity is consistent with the GTPase fold, but experimentally GTPBP2's nucleotide handling is weak; retained as non-core rather than the defining function.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Has very low GTP-binding activity
|
|
GO:0005525
GTP binding
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: GTPBP2 binds GTP, though weakly; binding is stimulated by aminoacyl-tRNA.
Reason: GTP binding is directly observed (albeit weak) and is consistent with the GTPase fold.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Has very low GTP-binding activity
|
|
GO:1904678
alpha-aminoacyl-tRNA binding
|
IEA
GO_REF:0000117 |
ACCEPT |
Summary: GTPBP2 binds aminoacyl-tRNA; Phe-tRNA stimulates its GTP binding, indicating a functional aa-tRNA interaction.
Reason: Directly supported by the observation that aa-tRNA stimulates GTPBP2 GTP binding.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Has very low GTP-binding activity
|
|
GO:0005515
protein binding
|
IPI
PMID:23455924 A Y2H-seq approach defines the human protein methyltransfera... |
KEEP AS NON CORE |
Summary: Y2H interactome (protein methyltransferase network) capturing GTPBP2 interactions (e.g. PRMT5/PRMT6). Bare protein binding is uninformative and unrelated to the rescue function.
Reason: Records physical interactions but the generic term adds nothing to GTPBP2's ribosome-rescue function.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
O14744: PRMT5
|
|
GO:0005515
protein binding
|
IPI
PMID:32296183 A reference map of the human binary protein interactome. |
KEEP AS NON CORE |
Summary: Binary interactome capturing GTPBP2 interactions, including self-association. Bare protein binding.
Reason: Generic term; physical interactions recorded but uninformative for core function.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Q9BX10: GTPBP2
|
|
GO:0042802
identical protein binding
|
IPI
PMID:32296183 A reference map of the human binary protein interactome. |
KEEP AS NON CORE |
Summary: GTPBP2 self-association (homotypic interaction) detected in the binary interactome.
Reason: Records a homodimerization-type interaction; not established as functionally central to ribosome rescue.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Q9BX10: GTPBP2
|
|
GO:0003746
translation elongation factor activity
|
IDA
NOT
PMID:30108131 Functions of unconventional mammalian translational GTPases ... |
ACCEPT |
Summary: Directly demonstrated NEGATIVE result - GTPBP2 lacks eEF1A-like elongation activity, distinguishing it from its paralog GTPBP1. The negation is informative and consistent with GTPBP2 acting as a ribosome-rescue / quality-control GTPase rather than a productive elongation factor.
Reason: The negated annotation correctly records that GTPBP2 does NOT enable translation elongation factor activity, a key experimental finding. The codon-specific pausing phenotype reinforces that GTPBP2's role is elongation quality control, not canonical elongation.
Supporting Evidence:
PMID:30108131
GTPBP2 lacked elongation activity and did not stimulate exosomal degradation
file:human/GTPBP2/GTPBP2-deep-research-falcon.md
This codon-specific function indicates that GTPBP2 acts as a quality control GTPase rather than a canonical elongation factor or metabolic enzyme
|
|
GO:0005525
GTP binding
|
IDA
PMID:30108131 Functions of unconventional mammalian translational GTPases ... |
ACCEPT |
Summary: Direct demonstration that GTPBP2 binds GTP, albeit weakly, with binding stimulated by aa-tRNA.
Reason: Directly demonstrated (weak) GTP binding.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Has very low GTP-binding activity
|
|
GO:1904678
alpha-aminoacyl-tRNA binding
|
IDA
PMID:30108131 Functions of unconventional mammalian translational GTPases ... |
ACCEPT |
Summary: Direct evidence that aminoacyl-tRNA (Phe-tRNA) interacts with GTPBP2 and stimulates its GTP binding.
Reason: Directly demonstrated aa-tRNA binding.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Has very low GTP-binding activity
|
|
GO:0005576
extracellular region
|
TAS
Reactome:R-HSA-481007 |
KEEP AS NON CORE |
Summary: Reactome platelet-degranulation localization, reflecting detection of GTPBP2 in platelet alpha-granule releasate; not its functional compartment.
Reason: Specialized platelet-biology localization peripheral to GTPBP2's cytoplasmic ribosome-rescue function.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Involved in the rescue of ribosome stalling due to the presence of non-functional tRNA
|
|
GO:0031093
platelet alpha granule lumen
|
TAS
Reactome:R-HSA-481007 |
KEEP AS NON CORE |
Summary: Reactome platelet alpha-granule lumen localization from platelet proteomics; a specialized context distinct from GTPBP2's core function.
Reason: Specialized platelet-biology localization; peripheral and does not reflect GTPBP2's principal cytoplasmic role.
Supporting Evidence:
file:human/GTPBP2/GTPBP2-uniprot.txt
Involved in the rescue of ribosome stalling due to the presence of non-functional tRNA
|
Q: Does human GTPBP2, like its mouse ortholog, act with PELO specifically to rescue ribosomes stalled at deficient/hypomodified tRNAs, and is this the basis of Jaberi-Elahi syndrome neurodegeneration?
Q: Given its weak GTP binding and lack of elongation activity, what is GTPBP2's precise mechanistic contribution within the PELO-dependent rescue cycle relative to HBS1L?
Experiment: Reconstituted ribosome-rescue assays with PELO and ABCE1 comparing GTPBP2 and HBS1L on tRNA-deficient stalled ribosomes to define GTPBP2's specific activity.
Experiment: Ribosome profiling in GTPBP2-deficient human neurons (e.g. patient-derived or knockout iPSC neurons) to detect stalling at specific codons/tRNAs and link it to neurodegeneration.
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Gene Information: GTPBP2, UniProt Accession Q9BX10, Homo sapiens
Human GTPBP2 encodes GTP-binding protein 2, a translational GTPase that functions as a critical ribosome rescue factor during translation elongation. The protein resolves stalled ribosomes to maintain proteostasis and is essential for neuronal homeostasis. Recent human genetics studies (2024) have established that bi-allelic loss-of-function variants in GTPBP2 cause a severe neurodevelopmental syndrome, confirming its clinical importance (salpietro2024biallelicgeneticvariants pages 1-3).
Introduction and gene overview
Human GTPBP2 encodes GTP-binding protein 2 (UniProt Q9BX10), a member of the translational GTPase family related to factors that regulate elongation and ribosome rescue. Recent human genetics and translation-focused reviews consistently identify GTPBP2 as a factor involved in ribosomal homeostasis, mRNA translation quality control, and neuronal proteostasis, matching the supplied UniProt assignment for the human protein rather than another gene/protein with a similar name (salpietro2024biallelicgeneticvariants pages 1-3, anisimova2023humantissuesexhibit pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2). GTPBP2 is closely related to GTPBP1; the two proteins share substantial sequence similarity and are discussed together in the current literature as homologous translational GTPases with overlapping roles in ribosome-associated quality control and nervous-system maintenance (salpietro2024biallelicgeneticvariants pages 1-3). Recent work in humans established that bi-allelic loss-of-function variants in GTPBP2 cause a recognizable neurodevelopmental disorder, further confirming that the human protein has a conserved and clinically important role in translational homeostasis (salpietro2024biallelicgeneticvariants pages 1-3).
Primary molecular function
The best-supported current model is that GTPBP2 acts primarily as a ribosome rescue factor during translation elongation. Foundational mouse work showed that GTPBP2 deficiency causes prolonged ribosome pausing at AGA arginine codons when the cognate tRNA_Arg(UCU) pool is limiting, strongly indicating that GTPBP2 resolves elongation complexes stalled by codon-specific decoding problems rather than functioning as a canonical metabolic enzyme with a small-molecule substrate (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3). Reviews published in 2021β2025 describe GTPBP2 as a mammalian ribosome rescue factor that helps clear aberrantly stalled ribosomes and thereby limits accumulation of defective nascent chains and translational stress (yip2021detectingandrescuing pages 1-3, joazeiro2019mechanismsandfunctions pages 1-3, filbeck2022ribosomeassociatedqualitycontrolmechanisms pages 1-3, park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2, sitron2020detectionanddegradation pages 1-3).
GTPBP2 is a GTPase, but direct biochemical detail for human GTPBP2 remains limited compared with canonical elongation factors; accordingly, the strongest claim supported by the available literature is that GTP hydrolysis is coupled to ribosome rescue/recycling events rather than to a classical biosynthetic reaction. Its relevant βsubstrate specificityβ is therefore best understood at the level of stalled ribosomal complexes, especially those paused during elongation when decoding is impaired. The clearest experimentally demonstrated case is pausing at AGA codons under conditions of limited cognate tRNA availability, although review articles place GTPBP2 more broadly in the machinery that responds to translational stalls caused by aberrant mRNAs or problematic elongation states (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3, sitron2020detectionanddegradation pages 1-3).
Subcellular localization
Available evidence supports a primarily ribosome-associated cytoplasmic function for GTPBP2, because the key mechanistic and disease-linked studies concern stalled 80S cytosolic ribosomes during translation elongation in neurons and other cells (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, park2021thetrinityof pages 1-2, sitron2020detectionanddegradation pages 1-3). Reviews of ribosome rescue and RQC also situate GTPBP2 within the eukaryotic cytosolic surveillance machinery that detects and resolves problematic translating ribosomes (yip2021detectingandrescuing pages 1-3, joazeiro2019mechanismsandfunctions pages 1-3, filbeck2022ribosomeassociatedqualitycontrolmechanisms pages 1-3).
Some review literature discusses GTPBP2 in the broader context of mitochondrial proteostasis or mitochondrial-associated translation stress, but the strongest direct evidence in the retrieved sources supports cytosolic translation quality control rather than a definitively established autonomous mitochondrial localization for human GTPBP2 itself (nadler2022maintainingmitochondrialribosome pages 1-2, levi2019neurodegenerationwithbrain pages 1-3, mcgirr2025dysregulatedribosomequality pages 1-2). Therefore, the most evidence-based localization statement is that GTPBP2 acts on ribosomes in the cytoplasm, with disease consequences that intersect with mitochondrial and neuronal homeostasis indirectly through proteostasis failure and stress signaling (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2).
Biological processes and signaling pathways
GTPBP2 participates in ribosome-associated quality control (RQC) and closely related ribosome rescue pathways that maintain translational fidelity and proteostasis. Reviews describe collided or stalled ribosomes as central triggers for surveillance pathways that split ribosomes, degrade aberrant mRNAs, and dispose of incomplete nascent chains; GTPBP2 is repeatedly cited as one of the mammalian rescue factors acting upstream of or alongside these pathways (yip2021detectingandrescuing pages 1-3, joazeiro2019mechanismsandfunctions pages 1-3, filbeck2022ribosomeassociatedqualitycontrolmechanisms pages 1-3, park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2, sitron2020detectionanddegradation pages 1-3).
GTPBP2 deficiency also links elongation defects to the integrated stress response (ISR). In the mouse Gtpbp2 model, unresolved stalling caused increased eIF2Ξ± phosphorylation and activation of ATF4 target genes via GCN2, demonstrating that ribosome pausing can signal from elongation to initiation control. Importantly, this ISR response was observed before overt neurodegeneration and appeared to be at least partly protective in that model (ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3). A later study of the homologous GTPBP1 pathway likewise found GCN2-dependent ISR activation and reduced mTORC1 signaling during tRNA deficiency and ribosome pausing, reinforcing the idea that GTPBP-family rescue factors sit at the interface of translation elongation control, neuronal homeostasis, and stress signaling (terrey2020gtpbp1resolvespaused pages 1-2).
GTPBP2 is also discussed in relation to no-go decay (NGD) and broader mRNA surveillance. While the retrieved texts emphasize RQC more directly than NGD, reviews of stalled-ribosome surveillance place ribosome rescue factors such as GTPBP2 in the network that couples translational arrest to mRNA decay, ribosome splitting, and nascent-chain quality control (boopathy2023proteostasisregulationthrough pages 2-3, sitron2020detectionanddegradation pages 1-3). In neurons, these functions are especially important because codon-specific decoding stress and unresolved pauses can trigger selective vulnerability and cell death (terrey2020gtpbp1resolvespaused pages 1-2, burgess2023trnadysregulationin pages 1-3, park2021thetrinityof pages 1-2).
Molecular mechanism and cooperation with PELO/HBS1L
Mechanistically, GTPBP2 is most often discussed as cooperating with the conserved ribosome rescue factors PELO (Pelota) and HBS1L. Reviews of mammalian ribosome rescue describe PELOβHBS1L as the core machinery that recognizes stalled ribosomes and recruits ABCE1 to promote subunit dissociation; GTPBP2 is placed in this rescue framework as a mammalian factor required for efficient resolution of specific stalled elongation complexes, particularly internally stalled ribosomes caused by defective decoding (young2022rebirthofthe pages 1-3, park2021thetrinityof pages 1-2, sitron2020detectionanddegradation pages 1-3). Additional reviews explicitly note that GTPBP2 has been linked to the response to ribosome stalling caused by tRNA deficiency and discuss it together with HBS1L/PELO-type rescue mechanisms upstream of downstream RQC events (joazeiro2019mechanismsandfunctions pages 1-3, filbeck2022ribosomeassociatedqualitycontrolmechanisms pages 1-3).
Thus, the most conservative mechanistic synthesis is that GTPBP2 is a translational GTPase acting on stalled 80S ribosomes, functionally allied with PELO/HBS1L/ABCE1-mediated rescue, to enable ribosome splitting/recycling and prevent persistence of elongation-blocked complexes. The resulting release of stalled ribosomes protects cells from secondary collision-driven proteotoxicity and stress signaling (yip2021detectingandrescuing pages 1-3, young2022rebirthofthe pages 1-3, park2021thetrinityof pages 1-2, sitron2020detectionanddegradation pages 1-3).
Clinical significance
Human disease evidence for GTPBP2 has strengthened substantially. Earlier reports linked rare GTPBP2 variants to severe neurological disease, including neurodevelopmental and neurodegenerative phenotypes; more recent work consolidated these observations into a clearer syndrome concept (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, levi2019neurodegenerationwithbrain pages 1-3). In the largest recent study, 20 individuals from 16 families with bi-allelic variants in GTPBP1 or GTPBP2 were described, and the shared syndrome included microcephaly, profound neurodevelopmental impairment, characteristic craniofacial features, ectodermal defects, abnormal vision and/or hearing, progressive spasticity, choreoathetoid movements, refractory epilepsy, and brain atrophy (salpietro2024biallelicgeneticvariants pages 1-3). Functional studies in patient fibroblasts supported a loss-of-function mechanism, and reduced expression of the fly ortholog produced locomotor impairment, consistent with evolutionary conservation of the pathway (salpietro2024biallelicgeneticvariants pages 1-3).
Expert reviews interpret these findings within a broader framework in which failure of ribosome rescue/RQC preferentially harms neurons because of their dependence on long-lived proteostasis, precise translational control, and sensitivity to codon-tRNA imbalances. This interpretation is strongly supported by the tRNA-dysregulation literature, which highlights GTPBP2 as one of the key rescue factors whose loss converts altered tRNA supply into overt neurodegeneration (burgess2023trnadysregulationin pages 1-3, park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2).
Recent developments and current understanding (2023β2024 emphasis)
The most important recent advance is the 2024 human genetics study establishing that bi-allelic variants in GTPBP2 and its homolog GTPBP1 cause an identical, distinct neurodevelopmental syndrome, substantially refining the phenotype and moving GTPBP2 from a candidate neurological gene to a well-supported Mendelian disease gene (salpietro2024biallelicgeneticvariants pages 1-3). A 2023 survey of human translation machinery also highlighted GTPBP2 among translation-related factors relevant to tissue specialization, reinforcing the view that it belongs functionally within the translation-control apparatus rather than in unrelated signaling categories (anisimova2023humantissuesexhibit pages 1-2).
The 2023 review literature further sharpened the mechanistic context by emphasizing how deficits in tRNA biology, codon demand/supply imbalance, and stalled-ribosome surveillance converge in neurodevelopmental disease. In that framework, GTPBP2 is not merely an accessory factor but a critical failsafe for elongation stress, especially in neurons (burgess2023trnadysregulationin pages 1-3, boopathy2023proteostasisregulationthrough pages 2-3). Overall, the present consensus is that human GTPBP2 is a ribosome-associated translational GTPase whose primary job is to rescue stalled elongating ribosomes, limit proteotoxic translation products, and connect elongation surveillance to cell-wide stress adaptation and neuronal survival (salpietro2024biallelicgeneticvariants pages 1-3, yip2021detectingandrescuing pages 1-3, ishimura2016activationofgcn2 pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2).
Bottom line
Taken together, the available evidence supports a focused functional annotation for human GTPBP2: it is a cytosolic ribosome rescue GTPase acting in translation elongation quality control, with strongest evidence for resolving codon-specific ribosome pausing at AGA codons under limiting tRNA conditions; it functions in the broader RQC/NGD/ISR network, likely in concert with PELO/HBS1L/ABCE1, and its loss causes severe human neurodevelopmental disease because neurons are exceptionally vulnerable to unresolved translational stress (salpietro2024biallelicgeneticvariants pages 1-3, terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2, sitron2020detectionanddegradation pages 1-3).
Blockquote: This blockquoted artifact provides a citation-supported scientific report on human GTPBP2, summarizing its identity, molecular function in ribosome rescue, pathway context, localization, and disease relevance. It is useful as a compact evidence-backed narrative for final functional annotation.
GTPBP2 is a ribosome rescue factor that resolves elongation-stalled ribosomes. The most compelling evidence comes from foundational mouse genetics studies demonstrating that GTPBP2 deficiency causes prolonged ribosome pausing specifically at AGA arginine codons when the cognate tRNA_Arg(UCU) is limiting (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3). This codon-specific function indicates that GTPBP2 acts as a quality control GTPase rather than a canonical elongation factor or metabolic enzyme.
Substrate specificity: GTPBP2's "substrates" are best understood as stalled ribosomal complexes rather than small molecules. The protein demonstrates particular activity at:
- AGA codon-stalled ribosomes under tRNA limitation (experimentally validated) (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3)
- Internally stalled 80S ribosomes during elongation defects (yip2021detectingandrescuing pages 1-3, chang2026qualitycontroland pages 1-2, sitron2020detectionanddegradation pages 1-3)
- Collided ribosome complexes that form when trailing ribosomes encounter stalled ones (park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2)
GTPase activity: While direct biochemical characterization of human GTPBP2's GTPase activity remains limited in published literature, the protein is consistently classified as a translational GTPase related to the TRAFAC class translation factor GTPase superfamily (matching UniProt domain annotation) (salpietro2024biallelicgeneticvariants pages 1-3, anisimova2023humantissuesexhibit pages 1-2). The current mechanistic model proposes that GTP hydrolysis by GTPBP2 is coupled to ribosome rescue and recycling events, facilitating the resolution of stalled elongation complexes (filbeck2022ribosomeassociatedqualitycontrolmechanisms pages 1-3, sitron2020detectionanddegradation pages 1-3).
Recent structural work on the closely related homolog GTPBP1 (68% sequence similarity) demonstrates that these proteins deliver aminoacyl-tRNA to ribosomes in a GTP-dependent manner but exhibit slower elongation kinetics than canonical eEF1A, consistent with a quality control rather than productive elongation role (anisimova2023humantissuesexhibit pages 1-2).
GTPBP2 functions primarily in the cytoplasm, associated with cytosolic ribosomes. The strongest experimental evidence places GTPBP2 activity at stalled 80S cytosolic ribosomes during translation elongation in neurons and other mammalian cells (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, park2021thetrinityof pages 1-2, sitron2020detectionanddegradation pages 1-3).
Key localization findings:
- Ribosome-associated: GTPBP2 acts on ribosomal complexes, particularly the 60S large subunit after ribosome splitting (joazeiro2019mechanismsandfunctions pages 1-3, young2022rebirthofthe pages 1-3, filbeck2022ribosomeassociatedqualitycontrolmechanisms pages 1-3)
- Cytoplasmic translation machinery: The protein is positioned within the cytosolic ribosome quality control surveillance system (yip2021detectingandrescuing pages 1-3, filbeck2022ribosomeassociatedqualitycontrolmechanisms pages 1-3, mcgirr2025dysregulatedribosomequality pages 1-2)
- Potential mitochondrial connection: Some reviews mention GTPBP2 in the context of mitochondrial proteostasis and mitochondrial ribosome quality control, though direct evidence for autonomous mitochondrial localization is less definitive than for cytoplasmic function (nadler2022maintainingmitochondrialribosome pages 1-2, levi2019neurodegenerationwithbrain pages 1-3, mcgirr2025dysregulatedribosomequality pages 1-2)
The most evidence-supported statement is that GTPBP2 performs its primary function on cytosolic ribosomes, with downstream consequences for mitochondrial and neuronal homeostasis mediated indirectly through proteostasis maintenance and stress signaling (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2).
GTPBP2 participates in multiple interconnected quality control and stress response pathways:
A. Ribosome-Associated Quality Control (RQC)
GTPBP2 is a central component of the mammalian RQC pathway, which monitors translation elongation and eliminates defective nascent chains. Current models position GTPBP2 as acting upstream of or alongside core RQC factors to prevent accumulation of proteotoxic translation products (yip2021detectingandrescuing pages 1-3, joazeiro2019mechanismsandfunctions pages 1-3, filbeck2022ribosomeassociatedqualitycontrolmechanisms pages 1-3, park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2, sitron2020detectionanddegradation pages 1-3). The RQC pathway involves:
- Recognition of stalled/collided ribosomes
- Ribosome splitting into subunits
- Degradation of aberrant mRNAs
- Ubiquitination and proteasomal degradation of incomplete nascent chains
B. Integrated Stress Response (ISR)
Loss of GTPBP2 function activates the ISR through GCN2 kinase. In GTPBP2-deficient mouse models, unresolved ribosome stalling triggers:
- GCN2 activation (ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3)
- eIF2Ξ± phosphorylation at Ser51 (ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3)
- ATF4 transcription factor activation and induction of stress-responsive genes (ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3)
Notably, this ISR activation occurred before overt neurodegeneration and appeared to be neuroprotective in the mouse model, demonstrating that GTPBP2 deficiency links elongation defects to initiation control (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3). The ISR represents a critical adaptive response attempting to compensate for translational dysfunction.
C. mTORC1 Signaling
GTPBP2 deficiency also affects the mTORC1 pathway. Studies in GTPBP1-deficient mice (the closely related homolog) showed decreased mTORC1 signaling, which paradoxically increased neuronal death, contrasting with the protective effect of ISR activation (terrey2020gtpbp1resolvespaused pages 1-2). This demonstrates complex crosstalk between different translational signaling pathways in determining neuronal fate during elongation stress.
D. No-Go Decay (NGD) and mRNA Surveillance
GTPBP2 participates in the broader network coupling translational arrest to mRNA quality control. The NGD pathway recognizes stalled ribosomes and promotes:
- Endonucleolytic cleavage of problematic mRNAs
- Degradation of truncated mRNA products
- Prevention of continued translation of aberrant transcripts (boopathy2023proteostasisregulationthrough pages 2-3, sitron2020detectionanddegradation pages 1-3)
While RQC handles the protein products of stalled translation, NGD eliminates the causative mRNAs, and GTPBP2 functions at the interface of these complementary surveillance systems (yip2021detectingandrescuing pages 1-3, boopathy2023proteostasisregulationthrough pages 2-3, sitron2020detectionanddegradation pages 1-3).
E. Neuronal Homeostasis
In neurons specifically, GTPBP2 is essential for:
- Maintaining translational fidelity under codon-tRNA imbalances (terrey2020gtpbp1resolvespaused pages 1-2, burgess2023trnadysregulationin pages 1-3)
- Preventing accumulation of incomplete, potentially aggregation-prone proteins (park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2)
- Coordinating proteostasis with cellular stress adaptation (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2)
Neurons are particularly vulnerable to GTPBP2 loss because of their dependence on long-lived proteins, precise translational control, and sensitivity to proteotoxic stress (burgess2023trnadysregulationin pages 1-3, park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2).
GTPBP2 cooperates with the PELO/HBS1L ribosome rescue complex. The conserved machinery for mammalian ribosome rescue centers on:
- PELO (Pelota): Recognizes stalled ribosomes
- HBS1L: A GTPase that partners with PELO
- ABCE1: An ATPase that promotes ribosome subunit dissociation (young2022rebirthofthe pages 1-3, park2021thetrinityof pages 1-2, sitron2020detectionanddegradation pages 1-3)
Mechanistic model:
Current evidence supports the following sequence of events:
1. Ribosome stalling occurs due to tRNA limitation, aberrant mRNA, or other elongation defects
2. GTPBP2 recognizes stalled 80S complexes, particularly those with internal elongation blocks (yip2021detectingandrescuing pages 1-3, chang2026qualitycontroland pages 1-2, sitron2020detectionanddegradation pages 1-3)
3. PELO/HBS1L recruitment facilitates ribosome recognition and priming for splitting (young2022rebirthofthe pages 1-3, park2021thetrinityof pages 1-2)
4. ABCE1-mediated splitting separates the 80S into 60S and 40S subunits (young2022rebirthofthe pages 1-3, sitron2020detectionanddegradation pages 1-3)
5. Ribosome recycling returns the subunits to the free pool for new rounds of translation (young2022rebirthofthe pages 1-3)
GTPBP2 is positioned as a mammalian-specific factor required for efficient resolution of particular stalled elongation complexes, working within the PELO/HBS1L/ABCE1 framework (joazeiro2019mechanismsandfunctions pages 1-3, filbeck2022ribosomeassociatedqualitycontrolmechanisms pages 1-3, park2021thetrinityof pages 1-2, sitron2020detectionanddegradation pages 1-3). The most conservative mechanistic summary is that GTPBP2 is a translational GTPase acting on stalled 80S ribosomes to enable ribosome splitting, recycling, and protection from collision-driven proteotoxicity (yip2021detectingandrescuing pages 1-3, young2022rebirthofthe pages 1-3, park2021thetrinityof pages 1-2, sitron2020detectionanddegradation pages 1-3).
Bi-allelic GTPBP2 variants cause a severe neurodevelopmental syndrome. The most significant recent advance is the 2024 study by Salpietro et al. describing 20 individuals from 16 families with bi-allelic variants in either GTPBP1 or GTPBP2, demonstrating that these homologous proteins cause an identical, distinct neurodevelopmental syndrome (salpietro2024biallelicgeneticvariants pages 1-3).
Core clinical phenotype ("GTPBP1/2-Related Ectodermal Neurodevelopmental [GREND] Syndrome"):
- Microcephaly (salpietro2024biallelicgeneticvariants pages 1-3)
- Profound neurodevelopmental impairment (salpietro2024biallelicgeneticvariants pages 1-3)
- Pathognomonic craniofacial features (salpietro2024biallelicgeneticvariants pages 1-3)
- Ectodermal defects (salpietro2024biallelicgeneticvariants pages 1-3)
- Abnormal vision and/or hearing (salpietro2024biallelicgeneticvariants pages 1-3)
- Progressive spasticity (salpietro2024biallelicgeneticvariants pages 1-3)
- Choreoathetoid movements (salpietro2024biallelicgeneticvariants pages 1-3)
- Refractory epilepsy (salpietro2024biallelicgeneticvariants pages 1-3)
- Brain atrophy (salpietro2024biallelicgeneticvariants pages 1-3)
Molecular pathogenesis:
Functional studies in patient-derived fibroblasts confirmed a loss-of-function mechanism for disease-associated GTPBP2 variants (salpietro2024biallelicgeneticvariants pages 1-3). The phenotypic severity and multi-system involvement reflect the fundamental importance of ribosome rescue for:
- Neuronal development and survival (salpietro2024biallelicgeneticvariants pages 1-3, terrey2020gtpbp1resolvespaused pages 1-2, park2021thetrinityof pages 1-2)
- Proteostasis maintenance (park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2)
- Stress response coordination (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2)
Evolutionary conservation: Studies in Drosophila showed that reduced expression of CG2017 (the fly ortholog of GTPBP1/GTPBP2) produced locomotor impairment, confirming conservation of this pathway across species (salpietro2024biallelicgeneticvariants pages 1-3).
Prior disease associations: Earlier reports had linked rare GTPBP2 variants to:
- Neurodegeneration with brain iron accumulation (NBIA) (levi2019neurodegenerationwithbrain pages 1-3)
- Intellectual disability (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2)
- Cerebellar and retinal degeneration (ishimura2016activationofgcn2 pages 1-2, ishimura2016activationofgcn2 pages 2-3)
The 2024 study consolidated these observations into a clearer syndrome concept and moved GTPBP2 from a candidate to a well-supported Mendelian disease gene (salpietro2024biallelicgeneticvariants pages 1-3).
Pathophysiological interpretation: Expert reviews interpret GTPBP2-related disease within a framework where failure of ribosome rescue/RQC preferentially harms neurons due to their:
- Exceptional dependence on long-lived proteostasis (park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2)
- Requirement for precise translational control (terrey2020gtpbp1resolvespaused pages 1-2, burgess2023trnadysregulationin pages 1-3)
- Sensitivity to codon-tRNA imbalances and translational stress (burgess2023trnadysregulationin pages 1-3, park2021thetrinityof pages 1-2)
This makes neurons the "canary in the coal mine" for translational quality control defects (burgess2023trnadysregulationin pages 1-3, park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2).
2024: The landmark human genetics study established GTPBP2 as a definitive Mendelian disease gene and refined the clinical phenotype substantially (salpietro2024biallelicgeneticvariants pages 1-3). Published in The American Journal of Human Genetics, this work represents the most important recent advance in understanding GTPBP2 function and clinical relevance.
2023: Comprehensive surveys of human translation machinery highlighted GTPBP2 among translation-related factors with potential tissue-specific functions, reinforcing its classification within the translation control apparatus (anisimova2023humantissuesexhibit pages 1-2). Review literature from 2023 further sharpened the mechanistic context by emphasizing convergence of tRNA biology, ribosome surveillance, and neurodevelopmental disease (burgess2023trnadysregulationin pages 1-3).
2025-2026: Recent reviews continue to position GTPBP2 as a critical failsafe for elongation stress, particularly in neurons (chang2026qualitycontroland pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2, boopathy2023proteostasisregulationthrough pages 2-3). The emerging consensus is that GTPBP2 represents a specialized ribosome rescue factor whose dysfunction reveals the exceptional vulnerability of the nervous system to translation quality control failures.
Current consensus:
The available evidence supports a focused functional annotation for human GTPBP2:
Primary function: Cytosolic ribosome rescue GTPase acting in translation elongation quality control (salpietro2024biallelicgeneticvariants pages 1-3, terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2, sitron2020detectionanddegradation pages 1-3)
Mechanism: Resolves codon-specific ribosome pausing (especially at AGA codons under limiting tRNA conditions) through cooperation with PELO/HBS1L/ABCE1 (terrey2020gtpbp1resolvespaused pages 1-2, ishimura2016activationofgcn2 pages 1-2, young2022rebirthofthe pages 1-3, park2021thetrinityof pages 1-2, sitron2020detectionanddegradation pages 1-3)
Pathway context: Functions in the RQC/NGD/ISR network to maintain proteostasis and coordinate stress responses (yip2021detectingandrescuing pages 1-3, ishimura2016activationofgcn2 pages 1-2, park2021thetrinityof pages 1-2, mcgirr2025dysregulatedribosomequality pages 1-2, boopathy2023proteostasisregulationthrough pages 2-3)
Clinical importance: Loss of function causes severe human neurodevelopmental disease because neurons are exceptionally vulnerable to unresolved translational stress (salpietro2024biallelicgeneticvariants pages 1-3, terrey2020gtpbp1resolvespaused pages 1-2, burgess2023trnadysregulationin pages 1-3, park2021thetrinityof pages 1-2)
Remaining knowledge gaps:
GTPBP2 is a well-characterized translational GTPase that functions as a critical ribosome rescue factor in human cells. It resolves stalled ribosomes during translation elongation, particularly under conditions of tRNA limitation or other elongation stress. GTPBP2 operates within an interconnected network of quality control and stress response pathways, including RQC, ISR, and NGD, to maintain proteostasis and cellular homeostasis. The protein is essential for neuronal function, and bi-allelic loss-of-function variants cause a severe neurodevelopmental syndrome characterized by microcephaly, developmental impairment, and progressive neurological decline. Recent human genetics (2024) and mechanistic studies have firmly established GTPBP2 as a key player in translation quality control and a clinically important disease gene, with ongoing research continuing to elucidate the molecular details of its rescue mechanism and therapeutic potential.
Key Publications (Recent 2023-2024 Sources):
Salpietro et al. (2024). "Bi-allelic genetic variants in the translational GTPases GTPBP1 and GTPBP2 cause a distinct identical neurodevelopmental syndrome." The American Journal of Human Genetics 111:200-210. DOI: 10.1016/j.ajhg.2023.11.012 (salpietro2024biallelicgeneticvariants pages 1-3)
Anisimova et al. (2023). "Human Tissues Exhibit Diverse Composition of Translation Machinery." International Journal of Molecular Sciences 24:8361. DOI: 10.3390/ijms24098361 (anisimova2023humantissuesexhibit pages 1-2)
Burgess & Storkebaum (2023). "tRNA Dysregulation in Neurodevelopmental and Neurodegenerative Diseases." Annual Review of Cell and Developmental Biology 39:223-252. DOI: 10.1146/annurev-cellbio-021623-124009 (burgess2023trnadysregulationin pages 1-3)
References
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UniProt: Q9BX10. TRAFAC-class translation-factor GTPase, related to eEF1A/eRF3/Hbs1/GTPBP1.
GTPBP2 is a translational GTPase that partners PELO in ribosome rescue, particularly important
in neurons. The mouse Gtpbp2 / Pelo axis rescues ribosomes stalled at deficient tRNA; loss (with
the n-Tr20 tRNA mutation in the nmf205 mouse) causes ribosome stalling and neurodegeneration
(Ishimura et al. 2014, Science). In humans, GTPBP2 loss-of-function causes Jaberi-Elahi syndrome
(neurodegeneration with developmental delay, cerebellar atrophy).
Unlike GTPBP1, GTPBP2 lacks eEF1A-like elongation activity and did not stimulate exosomal
degradation; its GTP binding is weak though stimulated by Phe-tRNA.
- PMID:30108131
- The GOA has a NEGATED IDA annotation GO:0003746 translation elongation factor activity (PMID:30108131) β correct: GTPBP2 does NOT have elongation factor activity.
*-deep-research*.md file found in this gene directory.description/core_functions text, not as a proposed term).proposed_new_terms (or as a NEW annotation) [YAML]; consider adding Ishimura 2014 Science to references for the PELO-rescue/neurodegeneration evidence [REF].Translation|Cytosolic translation|Ribosome-associated QC|Ribosomal rescue ; PN-node mapping: type Ribosomal rescue=mappedβGO:0072344 rescue of stalled cytosolic ribosome (more_specific_than_existing_goa); group Ribosome-associated QC=mappedβGO:0006515 protein quality control (new_to_goa); class/branch=context_only (too broad).description/core_functions text, not as a proposed term).proposed_new_terms (or as a NEW annotation) [YAML]; consider adding Ishimura 2014 Science to references for the PELO-rescue/neurodegeneration evidence [REF].This file is generated from the current PROTEOSTASIS phase-1 dossier and local gene-review artifacts. Edit the source review, PN mapping, or dossier rather than this generated note when correcting the underlying curation.
id: Q9BX10
gene_symbol: GTPBP2
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:9606
label: Homo sapiens
description: GTPBP2 (GTP-binding protein 2) is a cytoplasmic translational GTPase of
the TRAFAC-class translation-factor superfamily, related to eEF1A, eRF3, Hbs1 and
its paralog GTPBP1. It partners the ribosome-rescue factor PELO and functions in
the rescue of ribosomes stalled because of non-functional or deficient tRNA, a role
that is especially critical in neurons. Unlike its paralog GTPBP1, GTPBP2 lacks eEF1A-like
elongation activity and does not stimulate exosomal mRNA degradation; it has only
weak GTP-binding activity that is stimulated by aminoacyl-tRNA. Loss of GTPBP2 (in
the context of a destabilized brain-specific tRNA in mouse, and through biallelic
loss-of-function in humans) leads to ribosome stalling and neurodegeneration; human
GTPBP2 deficiency causes Jaberi-Elahi syndrome, characterized by developmental delay,
intellectual disability, movement abnormalities and cerebellar atrophy.
alternative_products:
- name: 1 {ECO:0000269|PubMed:10833435}
id: Q9BX10-1
- name: 2 {ECO:0000269|PubMed:11054535}
id: Q9BX10-2
sequence_note: VSP_052154
- name: 3 {ECO:0000269|PubMed:14702039}
id: Q9BX10-3
sequence_note: VSP_052154, VSP_052156
- name: 4 {ECO:0000269|PubMed:14574404}
id: Q9BX10-4
sequence_note: VSP_052155
existing_annotations:
- term:
id: GO:0006414
label: translational elongation
evidence_type: IBA
original_reference_id: GO_REF:0000033
qualifier: involved_in
review:
summary: Phylogenetic transfer of a translational-elongation role from the eEF1A/GTPBP
family. However, GTPBP2 was directly shown to lack elongation activity; its actual
role is ribosome rescue of stalled (deficient-tRNA) ribosomes. Mouse genetics
localize the defect to elongation quality control rather than productive elongation
- GTPBP2 deficiency causes prolonged ribosome pausing at AGA arginine codons when
the cognate tRNA-Arg(UCU) pool is limiting.
action: MARK_AS_OVER_ANNOTATED
reason: GTPBP2 lacks the eEF1A-like elongation activity that the family-level IBA
implies; the term over-states its function. The accurate role is rescue/quality
control of stalled (deficient-tRNA) ribosomes, not productive translational
elongation.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Involved in the rescue of ribosome stalling due to the presence
of non-functional tRNA
- reference_id: file:human/GTPBP2/GTPBP2-deep-research-falcon.md
supporting_text: GTPBP2 deficiency causes prolonged ribosome pausing specifically
at AGA arginine codons when the cognate tRNA_Arg(UCU) is limiting
- term:
id: GO:0003924
label: GTPase activity
evidence_type: IEA
original_reference_id: GO_REF:0000002
qualifier: enables
review:
summary: GTPBP2 is a GTPase by family, but it was directly shown to have only very
low GTP-binding activity; GTPase activity is plausible but weak.
action: KEEP_AS_NON_CORE
reason: Predicted GTPase activity is consistent with the GTPase fold, but experimentally
GTPBP2's nucleotide handling is weak; retained as non-core rather than the defining
function.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Has very low GTP-binding activity
- term:
id: GO:0005525
label: GTP binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
qualifier: enables
review:
summary: GTPBP2 binds GTP, though weakly; binding is stimulated by aminoacyl-tRNA.
action: ACCEPT
reason: GTP binding is directly observed (albeit weak) and is consistent with the
GTPase fold.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Has very low GTP-binding activity
- term:
id: GO:1904678
label: alpha-aminoacyl-tRNA binding
evidence_type: IEA
original_reference_id: GO_REF:0000117
qualifier: enables
review:
summary: GTPBP2 binds aminoacyl-tRNA; Phe-tRNA stimulates its GTP binding, indicating
a functional aa-tRNA interaction.
action: ACCEPT
reason: Directly supported by the observation that aa-tRNA stimulates GTPBP2 GTP
binding.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Has very low GTP-binding activity
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:23455924
qualifier: enables
review:
summary: Y2H interactome (protein methyltransferase network) capturing GTPBP2 interactions
(e.g. PRMT5/PRMT6). Bare protein binding is uninformative and unrelated to the
rescue function.
action: KEEP_AS_NON_CORE
reason: Records physical interactions but the generic term adds nothing to GTPBP2's
ribosome-rescue function.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: 'O14744: PRMT5'
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:32296183
qualifier: enables
review:
summary: Binary interactome capturing GTPBP2 interactions, including self-association.
Bare protein binding.
action: KEEP_AS_NON_CORE
reason: Generic term; physical interactions recorded but uninformative for core
function.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: 'Q9BX10: GTPBP2'
- term:
id: GO:0042802
label: identical protein binding
evidence_type: IPI
original_reference_id: PMID:32296183
qualifier: enables
review:
summary: GTPBP2 self-association (homotypic interaction) detected in the binary
interactome.
action: KEEP_AS_NON_CORE
reason: Records a homodimerization-type interaction; not established as functionally
central to ribosome rescue.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: 'Q9BX10: GTPBP2'
- term:
id: GO:0003746
label: translation elongation factor activity
evidence_type: IDA
original_reference_id: PMID:30108131
qualifier: enables
negated: true
review:
summary: Directly demonstrated NEGATIVE result - GTPBP2 lacks eEF1A-like elongation
activity, distinguishing it from its paralog GTPBP1. The negation is informative
and consistent with GTPBP2 acting as a ribosome-rescue / quality-control GTPase
rather than a productive elongation factor.
action: ACCEPT
reason: The negated annotation correctly records that GTPBP2 does NOT enable translation
elongation factor activity, a key experimental finding. The codon-specific
pausing phenotype reinforces that GTPBP2's role is elongation quality control,
not canonical elongation.
supported_by:
- reference_id: PMID:30108131
supporting_text: GTPBP2 lacked elongation activity and did not stimulate exosomal
degradation
- reference_id: file:human/GTPBP2/GTPBP2-deep-research-falcon.md
supporting_text: This codon-specific function indicates that GTPBP2 acts as a
quality control GTPase rather than a canonical elongation factor or metabolic
enzyme
- term:
id: GO:0005525
label: GTP binding
evidence_type: IDA
original_reference_id: PMID:30108131
qualifier: enables
review:
summary: Direct demonstration that GTPBP2 binds GTP, albeit weakly, with binding
stimulated by aa-tRNA.
action: ACCEPT
reason: Directly demonstrated (weak) GTP binding.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Has very low GTP-binding activity
- term:
id: GO:1904678
label: alpha-aminoacyl-tRNA binding
evidence_type: IDA
original_reference_id: PMID:30108131
qualifier: enables
review:
summary: Direct evidence that aminoacyl-tRNA (Phe-tRNA) interacts with GTPBP2 and
stimulates its GTP binding.
action: ACCEPT
reason: Directly demonstrated aa-tRNA binding.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Has very low GTP-binding activity
- term:
id: GO:0005576
label: extracellular region
evidence_type: TAS
original_reference_id: Reactome:R-HSA-481007
qualifier: located_in
review:
summary: Reactome platelet-degranulation localization, reflecting detection of
GTPBP2 in platelet alpha-granule releasate; not its functional compartment.
action: KEEP_AS_NON_CORE
reason: Specialized platelet-biology localization peripheral to GTPBP2's cytoplasmic
ribosome-rescue function.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Involved in the rescue of ribosome stalling due to the presence
of non-functional tRNA
- term:
id: GO:0031093
label: platelet alpha granule lumen
evidence_type: TAS
original_reference_id: Reactome:R-HSA-481007
qualifier: located_in
review:
summary: Reactome platelet alpha-granule lumen localization from platelet proteomics;
a specialized context distinct from GTPBP2's core function.
action: KEEP_AS_NON_CORE
reason: Specialized platelet-biology localization; peripheral and does not reflect
GTPBP2's principal cytoplasmic role.
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Involved in the rescue of ribosome stalling due to the presence
of non-functional tRNA
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO
terms
findings: []
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings: []
- id: GO_REF:0000117
title: Electronic Gene Ontology annotations created by ARBA machine learning models
findings: []
- id: PMID:23455924
title: A Y2H-seq approach defines the human protein methyltransferase interactome.
findings: []
- id: PMID:30108131
title: Functions of unconventional mammalian translational GTPases GTPBP1 and GTPBP2.
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: "Cached publications/PMID_30108131.md frontmatter title matches the
YAML title; review establishes GTPBP2's translational-GTPase properties (weak
aa-tRNA-stimulated GTP binding, no eEF1A-like elongation activity), the basis
for the core GTP-binding / ribosome-rescue function."
findings:
- statement: GTPBP2 lacks eEF1A-like elongation activity and does not stimulate exosomal
degradation, distinguishing it from GTPBP1; its weak GTP binding is stimulated
by aminoacyl-tRNA.
reference_section_type: RESULTS
- id: PMID:32296183
title: A reference map of the human binary protein interactome.
findings: []
- id: Reactome:R-HSA-481007
title: Exocytosis of platelet alpha granule content
findings: []
- id: file:human/GTPBP2/GTPBP2-deep-research-falcon.md
title: Falcon deep research report for GTPBP2
reference_review:
relevance: MEDIUM
correctness: UNVERIFIED
review_notes: "LLM-synthesized (Edison Scientific Literature) deep research report.
GTPBP2-specific, primary-literature-anchored claims that are usable: the
ribosome-rescue / translation-elongation-quality-control role, cooperation with
the PELO/HBS1L/ABCE1 rescue machinery, cytosolic ribosome-associated localization,
and the codon-specific ribosome pausing at AGA arginine codons under limiting
tRNA-Arg(UCU) (from the Ackerman-lab mouse genetics, Ishimura 2016 / Terrey 2020).
CAUTION / not relied on here: the report repeatedly folds GTPBP2 together with its
paralog GTPBP1 (e.g. the Salpietro 2024 GTPBP1/GTPBP2 syndrome and the GTPBP1
structural / mTORC1 / aa-tRNA-delivery data are GTPBP1-centric and over-generalized
to GTPBP2), and it over-imputes canonical translation-factor GTPase mechanism
(GTP-hydrolysis-coupled splitting) that has not been directly demonstrated for human
GTPBP2, which has only weak GTP binding. Disease/RQC/ISR/NGD framing is review-level
and not used to change any molecular-function annotation. Citations are secondary
(this report), not the primary papers; correctness left UNVERIFIED for the synthesis."
findings:
- statement: GTPBP2 is a cytosolic ribosome rescue GTPase acting in translation
elongation quality control on stalled 80S ribosomes, functionally allied with the
PELO/HBS1L/ABCE1 rescue machinery; mouse genetics show GTPBP2 deficiency causes
prolonged ribosome pausing at AGA arginine codons when cognate tRNA-Arg(UCU) is
limiting.
reference_section_type: RESULTS
core_functions:
- description: Translational GTPase that partners the ribosome-rescue factor PELO to
rescue ribosomes stalled on non-functional or deficient tRNA, a function critical
for neuronal proteostasis; GTPBP2 binds aminoacyl-tRNA and GTP (weakly) but, unlike
GTPBP1, lacks elongation factor activity.
molecular_function:
id: GO:0005525
label: GTP binding
supported_by:
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Involved in the rescue of ribosome stalling due to the presence
of non-functional tRNA
- reference_id: file:human/GTPBP2/GTPBP2-uniprot.txt
supporting_text: Interacts with PELO
proposed_new_terms: []
suggested_questions:
- question: Does human GTPBP2, like its mouse ortholog, act with PELO specifically
to rescue ribosomes stalled at deficient/hypomodified tRNAs, and is this the basis
of Jaberi-Elahi syndrome neurodegeneration?
- question: Given its weak GTP binding and lack of elongation activity, what is GTPBP2's
precise mechanistic contribution within the PELO-dependent rescue cycle relative
to HBS1L?
suggested_experiments:
- description: Reconstituted ribosome-rescue assays with PELO and ABCE1 comparing GTPBP2
and HBS1L on tRNA-deficient stalled ribosomes to define GTPBP2's specific activity.
- description: Ribosome profiling in GTPBP2-deficient human neurons (e.g. patient-derived
or knockout iPSC neurons) to detect stalling at specific codons/tRNAs and link
it to neurodegeneration.