Affinage

GNAI1

Guanine nucleotide-binding protein G(i) subunit alpha-1 · UniProt P63096

Round 2 corrected
Length
354 aa
Mass
40.4 kDa
Annotated
2026-04-28
51 papers in source corpus 13 papers cited in narrative 13 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GNAI1 encodes Gαi1, an inhibitory heterotrimeric G protein α-subunit that cycles between GDP-bound (inactive) and GTP-bound (active) states to transduce signals from Gi-coupled GPCRs, principally by inhibiting adenylyl cyclase and thereby lowering intracellular cAMP (PMID:8521505, PMID:35678269). In its GDP-bound form, Gαi1 assembles with Gβ1γ2 into a heterotrimer; GTP binding triggers switch II rearrangement and βγ dissociation, while RGS proteins such as RGS10 accelerate GTP hydrolysis to terminate signaling (PMID:8521505, PMID:8774883). Beyond classical GPCR transduction, Gαi1 participates in mitotic spindle positioning through the LGN–NuMA cortical complex (PMID:15537540), suppresses colitis-associated tumorigenesis by restraining JAK2/STAT3 and NF-κB signaling (PMID:30836096), and is required for ciliogenesis, with disease-associated missense variants disrupting GTP exchange, GTP hydrolysis, D2 receptor coupling, and ciliary localization, defining a neurodevelopmental GNAI1 syndrome (PMID:41329793, PMID:41052774, PMID:34685729).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 1995 High

    Resolution of the Gαi1·GDP–Gβ1γ2 heterotrimer crystal structure established the atomic basis for subunit assembly and revealed how GTP-induced switch II rearrangement drives subunit dissociation, providing the structural framework for all subsequent functional studies.

    Evidence X-ray crystallography at 2.3 Å resolution

    PMID:8521505

    Open questions at the time
    • Structure captured the GDP-bound state; the active GTP-bound Gαi1 conformation with effectors was not resolved
    • No effector or GPCR complexes in the crystal
  2. 1996 High

    Identification of RGS10 as a selective GAP for Gαi-family members demonstrated that signal termination is actively regulated and subfamily-specific, not merely a function of intrinsic GTP hydrolysis rates.

    Evidence Co-immunoprecipitation with activated Gα subunits plus in vitro GTPase assays with purified proteins

    PMID:8774883

    Open questions at the time
    • RGS10 selectivity was shown primarily for Gαi3, Gαz, and Gαo; direct GAP activity on Gαi1 specifically was not the focus
    • Cellular context for RGS10–Gαi1 regulation was not established
  3. 2004 High

    Discovery that Gαi1 binds the GoLoco domain of LGN to release NuMA and drive cortical spindle positioning revealed a GPCR-independent, cell-division-related function of Gαi1.

    Evidence Co-immunoprecipitation, FRET biosensor, and overexpression phenotypic analysis (spindle oscillations) in mammalian cells

    PMID:15537540

    Open questions at the time
    • Whether endogenous Gαi1 versus other Gαi paralogs is the primary spindle-positioning subunit in vivo was not resolved
    • Upstream regulators of Gαi1-GDP loading at the cortex were not identified
  4. 2012 Medium

    Demonstration that GNAI1 suppresses hepatocellular carcinoma cell migration and is post-transcriptionally repressed by miR-320a/c/d linked Gαi1 loss to tumor invasiveness.

    Evidence Lentiviral overexpression, siRNA knockdown, miRNA mimic transfection, Transwell assays in HCC cell lines

    PMID:23691483

    Open questions at the time
    • Direct miRNA–3′UTR binding validation (e.g., luciferase reporter) was not shown
    • In vivo metastasis data were lacking
    • Downstream effectors mediating migration suppression were not defined
  5. 2015 Medium

    Valproic acid–induced miR-124 was shown to repress GNAI1, relieving adenylyl cyclase inhibition and elevating cAMP/Bdnf, connecting Gαi1 to neurotrophin regulation via miRNA control.

    Evidence miRNA microarray, iTRAQ proteomics, miR-124 mimic/inhibitor transfection with Western blot and RT-qPCR readouts

    PMID:26519098

    Open questions at the time
    • No direct miR-124 binding assay for GNAI1 3′UTR
    • Functional consequence on neuronal phenotype (beyond Bdnf mRNA) not tested
  6. 2019 High

    Genetic deletion of Gnai1 and Gnai3 in mice revealed that these subunits suppress colitis-associated tumorigenesis by restraining JAK2-mediated NF-κB and STAT3 activation downstream of IL-6, establishing Gαi1 as a tumor suppressor in inflammatory colon cancer.

    Evidence Double-knockout mouse model (DSS/AOM), co-IP, immunoblot, conditional Gnai2 rescue

    PMID:30836096

    Open questions at the time
    • Individual contributions of Gnai1 versus Gnai3 were not fully separable
    • Direct physical interaction between Gαi1 and JAK2 was suggested by co-IP but structural details are absent
  7. 2021 High

    Biochemical characterization of the Gln52Pro disease variant showed abolished GTP binding and hydrolysis and mislocalization away from the plasma membrane, providing the first molecular explanation for how a GNAI1 syndrome mutation disrupts G protein cycling.

    Evidence GTPase/GTP-binding assays, co-IP with partner proteins, subcellular localization imaging in transfected cells

    PMID:34685729

    Open questions at the time
    • Only one variant characterized in detail; spectrum of other syndrome variants not addressed
    • No structural data explaining why Q52P blocks nucleotide binding
  8. 2022 Medium

    Identification of puerarin as a direct Gαi1-binding ligand that relieves adenylyl cyclase inhibition in podocytes demonstrated pharmacological targeting of Gαi1 to increase cAMP/PKA/CREB signaling and protect against high-glucose-induced apoptosis.

    Evidence DARTS-mass spectrometry for direct binding; cAMP ELISA; CREB phosphorylation immunoblot; PKA inhibitor rescue

    PMID:35678269

    Open questions at the time
    • Binding site on Gαi1 not mapped
    • Specificity of puerarin for Gαi1 versus other Gαi paralogs not determined
    • Single lab, awaits independent confirmation
  9. 2024 Medium

    Exosomal miR-320d from colorectal cancer cells was shown to target GNAI1 in endothelial cells, activating JAK2/STAT3 and VEGFA to promote angiogenesis, extending the GNAI1–JAK2/STAT3 axis to the tumor microenvironment.

    Evidence Exosome transfer, miRNA mimic/inhibitor, GNAI1 knockdown/overexpression, in vivo mouse tumor model

    PMID:39695099

    Open questions at the time
    • Mechanism by which GNAI1 restrains JAK2 in endothelial cells (direct interaction vs. indirect) not resolved
    • Single lab study
  10. 2025 High

    Comprehensive functional profiling of GNAI1 syndrome variants revealed gain-of-function D2R signaling, disrupted GTP exchange/hydrolysis kinetics, and impaired ciliogenesis, unifying GPCR-transduction and ciliogenic defects as co-pathogenic mechanisms in the neurodevelopmental syndrome.

    Evidence Xenopus oocyte GIRK channel electrophysiology, GTPγS binding/hydrolysis assays, CRISPR knock-in C. elegans cilia phenotyping, human ciliated cell fluorescence microscopy

    PMID:41052774 PMID:41329793

    Open questions at the time
    • Neuronal-specific consequences of ciliary and D2R signaling defects in mammalian brain not tested
    • How variant-specific biochemical defects map onto clinical severity is unknown
    • Therapeutic rescue strategies not explored

Open questions

Synthesis pass · forward-looking unresolved questions
  • Major open questions include which effector complexes Gαi1 engages in its GTP-bound form at atomic resolution, the paralog-specific contributions of Gαi1 versus Gαi2/Gαi3 in vivo, and whether pharmacological modulation of Gαi1 can ameliorate GNAI1 syndrome phenotypes.
  • No high-resolution structure of GTP-Gαi1 bound to an effector
  • Paralog-specific knockout phenotypes in the nervous system not fully characterized
  • No therapeutic intervention data for GNAI1 syndrome

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003924 GTPase activity 4 GO:0098772 molecular function regulator activity 3 GO:0060089 molecular transducer activity 2
Localization
GO:0005886 plasma membrane 3 GO:0005829 cytosol 1 GO:0005929 cilium 1
Pathway
R-HSA-162582 Signal Transduction 6 R-HSA-1643685 Disease 3 R-HSA-1640170 Cell Cycle 1 R-HSA-168256 Immune System 1
Partners
GNB1GNG2GPSM2JAK2NGBNUMA1RGS10
Complex memberships
Gαi1–Gβ1γ2 heterotrimerLGN–NuMA spindle-positioning complex

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1995 Crystal structure of the Gαi1(GDP)β1γ2 heterotrimer resolved at 2.3 Å, revealing two non-overlapping contact regions between α and β subunits, an extended β/γ interface covering nearly all of γ, limited α/γ interaction, GTP-induced rearrangement of switch II causing subunit dissociation, and a circularized sevenfold β-propeller formed by WD repeats in the β subunit. X-ray crystallography (2.3 Å resolution) Cell High 8521505
2004 Mammalian LGN (mPins) binds Gαi1 through its C-terminal GoLoco/GPR domain; Gαi1 binding displaces the intramolecular LGN interaction, acting as a conformational switch that recruits NuMA to the cell cortex during mitosis. Overexpression of Gαi1 or LGN causes pronounced metaphase spindle oscillations, establishing a Gαi1–LGN–NuMA axis in mitotic spindle positioning. Co-immunoprecipitation, FRET biosensor, overexpression phenotypic analysis in mammalian cells Cell High 15537540
1996 RGS10 associates specifically with activated forms of Gαi-family members and acts as a GTPase-activating protein (GAP), potently and selectively increasing GTP hydrolytic activity of Gαi3, Gαz, and Gαo; it does not interact with Gαs, demonstrating selectivity within the Gαi subfamily. Co-immunoprecipitation with activated Gα subunits; in vitro GTPase assay with purified proteins Nature High 8774883
2021 Disease-associated Gln52Pro substitution in Gαi1 (and the analogous Gln52Pro/Gln52Arg in Gαo) abolishes GTP binding and GTP hydrolysis, disrupts interaction with partner proteins that recognize GDP- or GTP-loaded Gα, and markedly reduces plasma membrane localization of the mutant protein, shifting it away from the plasma membrane toward intracellular compartments. Biochemical GTPase/GTP-binding assays, co-immunoprecipitation with partner proteins, subcellular localization imaging in transfected cells Cells High 34685729
2025 Four GNAI1 syndrome missense variants (T48K, T48I, C224Y, V332E) show increased dopamine potency at the D2 receptor and elevated constitutive Gαi1 activity (gain-of-function on D2R signaling) in Xenopus oocyte assays, while the G40C variant is unresponsive to D2R activation. All variants display reduced GTP-γ-S binding rates and undetectable GTP hydrolysis except T48I, which shows accelerated binding and hydrolysis, indicating that GNAI1 syndrome variants collectively disrupt GTP exchange. Xenopus laevis oocyte electrophysiology (GIRK channel assay for D2R/Gαi1 coupling), GTP-γ-S binding assay, GTP hydrolysis assay Science Signaling High 41329793
2025 GNAI1 is required for ciliogenesis in human ciliated cells. C. elegans orthologous GNAI1 variants T48I, K272R, A328P, and V334E disrupt cilia assembly and chemosensory function in AWC neurons; D175V exerts neuron-specific effects on cilia-dependent behaviors; M88V and I321T have no detectable impact. Human D173V, K270R, and A326P variants disrupt ciliary localization of Gαi1 in human ciliated cell lines, validating conserved ciliogenic roles. CRISPR-Cas9 knock-in in C. elegans; cilia morphology imaging; chemotaxis behavioral assay; ciliary localization by fluorescence microscopy in human ciliated cell lines Genetics High 41052774
2019 GNAI1 and GNAI3 suppress colitis-associated tumorigenesis by blocking IL6 signaling; their absence leads to activation of NF-κB (via JAK2-TRAF6-TAK1-CHUK/IKKβ) and STAT3 (via JAK2), increased GNAI2 expression, IL6, and nitric oxide synthase 2 levels, and expansion of MDSCs. Immunoprecipitation and immunoblot analyses of colon tumor tissues and MEFs confirmed interactions of GNAI1 and GNAI3 with proteins in the IL6 signaling pathway. Double-knockout mouse model (DSS/AOM CAC model); immunoprecipitation; immunoblot; flow cytometry; conditional Gnai2 knockout rescue experiment Gastroenterology High 30836096
2012 GNAI1 suppresses migration and invasion of hepatocellular carcinoma (HCC) cells; it is post-transcriptionally repressed by miR-320a/c/d, which directly target GNAI1 and promote HCC cell migratory and invasive capacity in vitro. Lentiviral GNAI1 overexpression; siRNA knockdown; miRNA mimic transfection; Transwell migration/invasion assays; Western blot Cancer Biology & Medicine Medium 23691483
2022 Puerarin directly binds Gαi1 (Gnai1) in podocytes, identified by drug affinity responsive target stability (DARTS) combined with mass spectrometry. By binding and inhibiting Gnai1, puerarin relieves inhibition of adenylyl cyclase, increasing cAMP production and activating PKA/CREB signaling to protect against high-glucose-induced podocyte apoptosis. DARTS-mass spectrometry (direct binding identification); cAMP ELISA; CREB phosphorylation immunoblot; PKA inhibitor (Rp-cAMP) rescue; CREB overexpression apoptosis assay Journal of Cellular and Molecular Medicine Medium 35678269
2015 Valproic acid induces miR-124, which represses GNAI1 protein expression; reduced GNAI1 relieves inhibition of adenylyl cyclase, elevating cAMP and increasing Bdnf mRNA expression. GNAI1 protein and Bdnf mRNA levels can be bidirectionally manipulated by miR-124 mimic or inhibitor. miRNA microarray; iTRAQ proteomics; miR-124 mimic/inhibitor transfection; Western blot; RT-qPCR Neurochemistry International Medium 26519098
2023 Neuroglobin (NGB) physically interacts with GNAI1 and reduces GNAI1 and p-EGFR expression, thereby inhibiting EGFR/AKT/ERK signaling and suppressing pancreatic cancer cell proliferation, migration, invasion, and EMT. Co-immunoprecipitation; Western blot; in vitro proliferation, migration, invasion assays; in vivo xenograft; RT-PCR Biochemical and Biophysical Research Communications Medium 37141638
2024 Exosomal miR-320d from colorectal cancer cells is transferred to vascular endothelial cells where it directly targets GNAI1, reducing its expression and thereby increasing JAK2/STAT3 activation and VEGFA production, promoting endothelial cell migration and angiogenesis. Exosome transfer experiments; miRNA mimic/inhibitor; GNAI1 knockdown/overexpression; JAK2/STAT3 pathway immunoblot; in vivo mouse tumor model Cell Death & Disease Medium 39695099
2022 In Ostm1-null mice, transcriptomic analysis of early DN1 T cell precursors identified a Foxo1-Klf2-S1pr1-Gnai1-Rac1 signaling axis regulated by Ostm1, placing Gnai1 within a T lymphopoiesis regulatory network; transgenic restoration of Ostm1 in DN1 cells rescued T cell subpopulations from ETP onwards. Transcriptome profiling of DN1 cells from Ostm1-null mice; transgenic rescue (cell-autonomous Ostm1 expression); flow cytometry of T cell subpopulations iScience Low 35434560

Source papers

Stage 0 corpus · 51 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2002 Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences. Proceedings of the National Academy of Sciences of the United States of America 1479 12477932
2003 Functional characterization of human receptors for short chain fatty acids and their role in polymorphonuclear cell activation. The Journal of biological chemistry 1291 12711604
2003 Free fatty acids regulate insulin secretion from pancreatic beta cells through GPR40. Nature 1255 12629551
2001 Identification of the platelet ADP receptor targeted by antithrombotic drugs. Nature 1139 11196645
2015 The BioPlex Network: A Systematic Exploration of the Human Interactome. Cell 1118 26186194
2017 Architecture of the human interactome defines protein communities and disease networks. Nature 1085 28514442
2015 A human interactome in three quantitative dimensions organized by stoichiometries and abundances. Cell 1015 26496610
1995 The structure of the G protein heterotrimer Gi alpha 1 beta 1 gamma 2. Cell 1011 8521505
2014 A proteome-scale map of the human interactome network. Cell 977 25416956
2002 The orphan G protein-coupled receptor GPR40 is activated by medium and long chain fatty acids. The Journal of biological chemistry 908 12496284
2020 A reference map of the human binary protein interactome. Nature 849 32296183
2000 DNA cloning using in vitro site-specific recombination. Genome research 815 11076863
2001 Integrin-associated protein (CD47) and its ligands. Trends in cell biology 719 11306274
2021 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. Cell 705 33961781
2012 A census of human soluble protein complexes. Cell 689 22939629
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
2008 Large-scale proteomics and phosphoproteomics of urinary exosomes. Journal of the American Society of Nephrology : JASN 607 19056867
2018 Structure of the µ-opioid receptor-Gi protein complex. Nature 553 29899455
1994 Structural determinants for activation of the alpha-subunit of a heterotrimeric G protein. Nature 517 8208289
2011 Mapping the NPHP-JBTS-MKS protein network reveals ciliopathy disease genes and pathways. Cell 507 21565611
2000 Molecular cloning and characterization of a novel type of histamine receptor preferentially expressed in leukocytes. The Journal of biological chemistry 481 10973974
2008 Lactate inhibits lipolysis in fat cells through activation of an orphan G-protein-coupled receptor, GPR81. The Journal of biological chemistry 470 19047060
2004 The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome research 438 15489334
2010 Systematic analysis of human protein complexes identifies chromosome segregation proteins. Science (New York, N.Y.) 421 20360068
1999 The chemokine SDF-1alpha triggers CXCR4 receptor dimerization and activates the JAK/STAT pathway. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 415 10506573
2015 Panorama of ancient metazoan macromolecular complexes. Nature 407 26344197
2001 Multiplicity of mechanisms of serotonin receptor signal transduction. Pharmacology & therapeutics 361 11916537
2011 Acetylation regulates gluconeogenesis by promoting PEPCK1 degradation via recruiting the UBR5 ubiquitin ligase. Molecular cell 337 21726808
2004 Mammalian Pins is a conformational switch that links NuMA to heterotrimeric G proteins. Cell 321 15537540
1996 RGS10 is a selective activator of G alpha i GTPase activity. Nature 321 8774883
2019 GNAI1 and GNAI3 Reduce Colitis-Associated Tumorigenesis in Mice by Blocking IL6 Signaling and Down-regulating Expression of GNAI2. Gastroenterology 80 30836096
2012 GNAI1 Suppresses Tumor Cell Migration and Invasion and is Post-Transcriptionally Regulated by Mir-320a/c/d in Hepatocellular Carcinoma. Cancer biology & medicine 66 23691483
2021 Variants in GNAI1 cause a syndrome associated with variable features including developmental delay, seizures, and hypotonia. Genetics in medicine : official journal of the American College of Medical Genetics 30 33473207
2021 Pediatric Encephalopathy: Clinical, Biochemical and Cellular Insights into the Role of Gln52 of GNAO1 and GNAI1 for the Dominant Disease. Cells 27 34685729
2022 Puerarin attenuates diabetic kidney injury through interaction with Guanidine nucleotide-binding protein Gi subunit alpha-1 (Gnai1) subunit. Journal of cellular and molecular medicine 23 35678269
2024 Exosomal miR-320d promotes angiogenesis and colorectal cancer metastasis via targeting GNAI1 to affect the JAK2/STAT3 signaling pathway. Cell death & disease 18 39695099
2023 Neuroglobin inhibits pancreatic cancer proliferation and metastasis by targeting the GNAI1/EGFR/AKT/ERK signaling axis. Biochemical and biophysical research communications 14 37141638
2015 Variants in SELL, MRPS36P2, TP63, DDB2, CACNA1H, ADAM19, GNAI1, CDH13 and GABRG2 interact to confer risk of acne in Chinese population. The Journal of dermatology 10 25573302
2015 Valproic acid mediates miR-124 to down-regulate a novel protein target, GNAI1. Neurochemistry international 8 26519098
2016 Integrated analysis of omics data using microRNA-target mRNA network and PPI network reveals regulation of Gnai1 function in the spinal cord of Ews/Ewsr1 KO mice. BMC medical genomics 6 27534535
2021 Novel de novo pathogenic variant in the GNAI1 gene as a cause of severe disorders of intellectual development. Journal of human genetics 5 34819662
2022 A Foxo1-Klf2-S1pr1-Gnai1-Rac1 signaling axis is a critical mediator of Ostm1 regulatory network in T lymphopoiesis. iScience 2 35434560
2025 miRNA-200a suppresses GNAI1 and PLCB4 to modulate skin pigmentation in cashmere goats. Scientific reports 1 40394057
2025 Identification and functional analysis of GNAI1 as a biomarker associated with immune-related genes in pediatric acute myeloid leukemia. Translational cancer research 1 40530109
2025 Functional classification of GNAI1 disorder variants in Caenorhabditis elegans uncovers conserved and cell-specific mechanisms of dysfunction. Genetics 1 41052774
2026 The protective role of FLI-1 in cardiac hypertrophy: Modulation of the IGF-1R/GNAI1/PLCG1 pathway. Histology and histopathology 0 41797647
2025 Dysregulation of G protein subunits in autism: decreased GNAO1 and elevated GNAI1 levels in ASD. Frontiers in psychiatry 0 40873676
2025 Functional classification of GNAI1 disorder variants in C. elegans uncovers conserved and cell-specific mechanisms of dysfunction. bioRxiv : the preprint server for biology 0 40894620
2025 SOGA1 drives ovarian cancer progression via regulation of GNAI1 and activation of the TNF/NF-κB pathway. Gene 0 41022165
2025 A GNAI1 Pathogenic Variant Mimicking Cerebral Palsy: Expanding the Phenotypic Spectrum of GNAI1-Associated Neurodevelopmental Disorder. Clinical case reports 0 41235373
2025 GNAI1 missense mutations associated with a neurodevelopmental syndrome modify Gαi1 function. Science signaling 0 41329793