Affinage

GNAI2

Guanine nucleotide-binding protein G(i) subunit alpha-2 · UniProt P04899

Length
355 aa
Mass
40.5 kDa
Annotated
2026-06-10
26 papers in source corpus 14 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GNAI2 encodes Gαi2, a heterotrimeric G protein α subunit that transduces chemoattractant-receptor signals to control lymphocyte trafficking and the architecture of secondary lymphoid organs (PMID:15780991, PMID:17579064). Gαi2 is non-redundantly required for B and T cell chemokine responses: Gnai2-deficient lymphocytes home poorly to lymph nodes, show defective chemokine-induced calcium mobilization and chemotaxis, and lose the amoeboid motility needed to navigate lymphoid compartments, defects that Gαi1 and Gαi3 cannot compensate for (PMID:15780991, PMID:17579064). Gαi2 dosage is itself a determinant of signaling output, controlling marginal zone B cell development and splenic architecture (PMID:20508603), and combined loss of Gαi2 and Gαi3 in B cells eliminates mucosal, marginal zone, and lymph node B cell compartments and produces a hyper-IgM-like syndrome (PMID:23977324). Gαi2 signaling is negatively constrained by RGS proteins acting as GTPase-activating factors: an RGS-insensitive G184S knock-in allele yields a pleiotropic multi-organ phenotype and, metabolically, protects against diet-induced obesity and insulin resistance while increasing energy expenditure (PMID:16943428, PMID:17928396). Downstream, Gαi2 couples receptors to discrete effector cascades — the cAMP-PKA axis controlling SREBP-1c maturation and hepatic lipogenesis downstream of GPR75 (PMID:41632920), and NF-κB/STAT3 signaling driving colitis-associated tumorigenesis in dendritic cells (PMID:30836096). Gαi2 expression is regulated by promoter sequence variation affecting Sp1/YY1 binding (PMID:16565233) and by direct 3'-UTR targeting by miR-138 (PMID:21079996).

Mechanistic history

Synthesis pass · year-by-year structured walk · 14 steps
  1. 2005 High

    Established that Gαi2 is non-redundantly required for B lymphocyte entry into and motility within lymph nodes, defining a specific physiological role for one Gαi isoform in immune cell trafficking.

    Evidence Intravital microscopy of adoptively transferred Gnai2-/- B cells with chemokine response assays

    PMID:15780991

    Open questions at the time
    • Did not identify the specific chemokine receptors coupling to Gαi2
    • Molecular basis of isoform non-redundancy not resolved
  2. 2006 High

    Demonstrated that RGS-mediated GTPase acceleration is essential to constrain Gαi2 signaling in vivo, showing the consequences of unrestrained Gαi2 activity across multiple organ systems.

    Evidence Genomic knock-in of the RGS-insensitive G184S Gnai2 allele with phenotypic characterization in two zygosity states

    PMID:16943428

    Open questions at the time
    • Did not assign individual RGS proteins to specific tissues
    • Did not connect organ phenotypes to specific receptor-effector circuits
  3. 2006 Medium

    Connected a GNAI2 promoter SNP to altered transcription factor binding and reduced expression, providing a mechanism for variation in Gαi2 levels linked to blood pressure.

    Evidence EMSA with Sp1/YY1 supershift and luciferase reporter assays in HEK293 cells

    PMID:16565233

    Open questions at the time
    • Causal link between expression change and blood pressure not established in vivo
    • Single-lab association
  4. 2007 High

    Extended the chemotaxis requirement to T cells, showing Gαi2 is essential for chemokine-induced calcium flux, motility, and paracortical positioning.

    Evidence Intravital imaging, calcium mobilization, chemotaxis, and homing assays in Gnai2-/- T cells

    PMID:17579064

    Open questions at the time
    • Did not map which downstream effectors mediate amoeboid movement
  5. 2007 High

    Revealed a metabolic role for RGS-Gαi2 signaling, showing that blocking RGS regulation of Gαi2 protects against diet-induced obesity and insulin resistance.

    Evidence G184S knock-in mice on high-fat diet with glucose/insulin tolerance and energy expenditure measurements

    PMID:17928396

    Open questions at the time
    • Tissue source of the metabolic phenotype not localized
    • Receptor and effector pathway in metabolism not defined
  6. 2010 Medium

    Showed that Gαi2 gene dosage quantitatively tunes chemokine signaling output and is required for proper splenic marginal zone organization.

    Evidence Allelic dosage series across Ccr7, Rgs1, Gnai2, and Gnai3 with chemotaxis and splenic histology

    PMID:20508603

    Open questions at the time
    • Single-lab study
    • Mechanism linking dosage to architectural changes not dissected
  7. 2010 Medium

    Identified post-transcriptional control of GNAI2 by miR-138 and linked its expression to proliferation and survival in carcinoma cells.

    Evidence Luciferase 3'-UTR reporter assays with miR-138 transfection/knockdown in tongue squamous cell carcinoma cells

    PMID:21079996

    Open questions at the time
    • Downstream Gαi2 effector mediating proliferation not identified
    • Single-lab study
  8. 2013 High

    Demonstrated combinatorial requirement of Gαi2 and Gαi3 in B cells for compartment formation and immunoglobulin homeostasis.

    Evidence B cell-specific conditional double knockout with chemokine stimulation, histology, flow cytometry, and immunoglobulin analysis

    PMID:23977324

    Open questions at the time
    • Did not separate Gαi2-specific from Gαi3-specific contributions in the double knockout
  9. 2019 High

    Placed Gαi2 in an IL6-driven NF-κB/STAT3 circuit in dendritic cells, showing it promotes colitis-associated tumorigenesis when GNAI1/3 are lost.

    Evidence Conditional knockout and double-knockout mice, immunoprecipitation, IL6 blockade, and flow cytometry

    PMID:30836096

    Open questions at the time
    • Direct biochemical coupling of Gαi2 to the JAK2/NF-κB/STAT3 machinery not fully resolved
  10. 2023 Medium

    Linked Gαi2 to the PKA/ERK/CREB axis in neurons, where miR-34b-5p suppression of Gαi2 contributes to apoptosis.

    Evidence Dual luciferase 3'-UTR assays with miR-34b-5p agomir/antagomir and pathway Western blots in neuronal models

    PMID:37186186

    Open questions at the time
    • Receptor upstream of Gαi2 in this context unknown
    • Single-lab study
  11. 2024 Medium

    Identified S100A4 as a physical partner that signals through Gαi2 to activate MAPK and drive endometrial epithelial proliferation.

    Evidence Co-IP/mass spectrometry plus overexpression/knockdown proliferation assays in sheep/mouse cells

    PMID:38872805

    Open questions at the time
    • Reciprocal validation of the S100A4-GNAI2 interaction limited
    • Mechanism of MAPK activation by the complex undefined
  12. 2024 Low

    Reported that Gαi2 promotes dermal papilla cell proliferation via Wnt/β-Catenin signaling and is repressed by miR-181a.

    Evidence Dual luciferase assays and proliferation/induction assays in ovine dermal papilla cells

    PMID:39063192

    Open questions at the time
    • Wnt activation inferred without direct mechanistic dissection
    • Non-canonical ovine model, single lab
  13. 2025 Medium

    Placed Gαi2 downstream of GPR75 in a cAMP-PKA pathway controlling SREBP-1c maturation and hepatic lipogenesis.

    Evidence Hepatocyte-specific Gpr75 knockout/overexpression in a diet-induced MASH model with signaling analysis

    PMID:41632920

    Open questions at the time
    • Direct GPR75-Gαi2 coupling not biochemically demonstrated
    • Single-lab, abstract-level detail
  14. 2025 Low

    Reported a PRDX1-GNAI2 complex whose disruption by TMEM100 dampens LPS-induced NF-κB activation in endothelial cells.

    Evidence Co-immunoprecipitation and TMEM100 overexpression in an LPS acute lung injury model (preprint)

    PMID:bio_10.1101_2025.10.24.684325

    Open questions at the time
    • Single Co-IP without reciprocal validation
    • Preprint, abstract-level detail only

Open questions

Synthesis pass · forward-looking unresolved questions
  • How Gαi2 selectively engages distinct effector cascades (cAMP/PKA, PI3K, MAPK, NF-κB/STAT3) depending on receptor and tissue context remains undefined.
  • No unifying model for context-dependent effector selection
  • Direct receptor-to-Gαi2 coupling biochemically established for few of the described pathways

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003924 GTPase activity 2 GO:0060089 molecular transducer activity 2
Localization
GO:0005886 plasma membrane 1
Pathway
R-HSA-168256 Immune System 4 R-HSA-162582 Signal Transduction 3 R-HSA-1430728 Metabolism 2
Partners
GPR75PRDX1RGS PROTEINSS100A4TMEM100
Complex memberships
PRDX1-GNAI2 complexheterotrimeric G protein (Gi)

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2005 GNAI2 (Gαi2) is required for B lymphocyte entry into lymph nodes via high endothelial venules and for normal motility within lymph node follicles. Gnai2-/- B cells enter lymph nodes poorly and move more slowly than wild-type B cells, and respond poorly to chemokines, demonstrating that Gαi1 and Gαi3 cannot compensate for loss of Gαi2 in this context. Intravital microscopy of adoptively transferred B cells from Gnai2-/- mice; chemokine response assays; genetic knockout with defined cellular phenotype Immunity High 15780991
2006 RGS proteins negatively regulate Gαi2 signaling in vivo. A G184S knock-in mutation in Gnai2 that blocks RGS protein binding produces a pleiotropic phenotype (enlarged spleen, elevated neutrophils, cardiac hypertrophy, shortened long bones, behavioral hyperactivity, reduced viability), demonstrating the essential role of RGS-mediated GTPase acceleration at Gαi2 across multiple organ systems. Genomic knock-in of RGS-insensitive G184S Gnai2 allele; phenotypic characterization of homozygous and heterozygous mice Molecular and cellular biology High 16943428
2007 GNAI2 (Gαi2) is essential for T lymphocyte chemokine receptor signaling. Gnai2-/- CD4 and CD8 T cells show profound defects in chemokine-induced intracellular calcium mobilization, chemotaxis, and lymph node homing. Intravital imaging showed Gnai2-/- CD4 T cells accumulate at the cortical ridge and fail to access the paracortex, lacking amoeboid movements and active membrane projections. Intravital imaging of Gnai2-/- T cells; chemotaxis assays; calcium mobilization assays; adoptive transfer homing assays Journal of immunology High 17579064
2007 RGS proteins and Gαi2 signaling regulate insulin sensitivity, glucose metabolism, and body weight. Homozygous Gαi2(G184S) knock-in mice are resistant to diet-induced obesity on a high-fat diet and are protected from insulin resistance, associated with increased energy expenditure. Both male and female G184S mice show enhanced insulin sensitivity and glucose tolerance. RGS-insensitive G184S Gnai2 knock-in mice on high-fat diet; body composition analysis; glucose/insulin tolerance tests; energy expenditure measurement Diabetes High 17928396
2010 The level of Gnai2 expression is a critical determinant of chemokine receptor signaling output and secondary lymphoid organ organization. Loss of a single Gnai2 allele reduces CCL19-triggered chemotaxis. Gnai2 is required for proper marginal zone B cell development, splenic architecture, lymphoid follicle size, germinal center morphology, and alignment of MOMA-1+ macrophages and MAdCAM-1+ endothelial cells along marginal zone sinuses. Mice with varying numbers of intact alleles of Ccr7, Rgs1, Gnai2, and Gnai3; chemotaxis assays; histological analysis of splenic architecture Genes and immunity Medium 20508603
2013 Combined loss of Gαi2 and Gαi3 in B cells eliminates B cell compartments at mucosal sites, splenic marginal zones, and lymph nodes, causes partial block in splenic follicular B cell development, disrupts lymphoid organ architecture, and produces a hyper-IgM-like syndrome. B cells lacking both subunits are refractory to chemokine stimulation and poorly responsive to antigen receptor engagement. B cell-specific conditional double knockout of Gnai2 and Gnai3; flow cytometry; histology; chemokine stimulation assays; immunoglobulin analysis PloS one High 23977324
2006 A -318 C>G SNP in the GNAI2 promoter impairs transcriptional activity by altering transcription factor binding specificity: the G allele binds Sp1 (confirmed by supershift with anti-Sp1 antibody), while the C allele binds YY1. The G allele has 2.5-fold reduced transcriptional activity in transfected HEK293 cells and is associated with higher systolic blood pressure. Electrophoretic mobility shift assay (EMSA) with competition; supershift with anti-Sp1 and anti-YY1 antibodies; luciferase reporter transfection in HEK293 cells Journal of the American Society of Nephrology Medium 16565233
2010 GNAI2 is a direct target of miR-138 in tongue squamous cell carcinoma cells. miR-138 directly binds two candidate sequences in the 3'-UTR of GNAI2 mRNA (confirmed by luciferase reporter assay). Knockdown of miR-138 increases GNAI2 at mRNA and protein levels; ectopic miR-138 reduces GNAI2 expression and leads to reduced proliferation, cell cycle arrest, and apoptosis. Luciferase reporter assay; qPCR; Western blot; genome-wide expression profiling; miR-138 transfection/knockdown in TSCC cells Human genetics Medium 21079996
2019 GNAI2 in CD11c+ dendritic cells promotes colitis-associated tumorigenesis. GNAI1 and GNAI3 suppress colonic tumor development by blocking IL6 signaling; their absence leads to increased GNAI2 expression. IL6 activates GNAI2 expression via JAK2-mediated NF-κB (through TRAF6-TAK1-CHUK/IKKβ) and STAT3 signaling pathways. Conditional disruption of Gnai2 in CD11c+ cells of GNAI1/3 double-knockout mice prevented NF-κB and STAT3 activation and normalized DC and MDSC numbers. Conditional knockout mice; immunoprecipitation; immunoblot; flow cytometry; IL6 antibody blockade; conditional Gnai2 disruption in CD11c+ cells; cytokine ELISA Gastroenterology High 30836096
2025 GPR75 signals through GNAI2 to regulate hepatic lipid metabolism. Depletion of hepatic Gpr75 activates the GNAI2-cAMP-PKA signaling pathway, reducing SREBP-1c maturation and de novo lipogenesis. GPR75 overexpression in hepatocytes exacerbates diet-induced MASH and liver fibrosis, while its deficiency is protective. Hepatocyte-specific Gpr75 knockout and overexpression in mice; diet-induced MASH model; signaling pathway analysis (cAMP-PKA, SREBP-1c) Hepatology Medium 41632920
2023 miR-34b-5p negatively targets Gnai2 by directly binding its 3'-UTR (validated by dual luciferase reporter assay). In fluorine-aluminum-induced neuronal apoptosis, decreased Gnai2 expression (caused by increased miR-34b-5p) suppresses the PKA/ERK/CREB signaling pathway, and inhibition of miR-34b-5p alleviates apoptosis by restoring Gnai2, PKA, ERK, and CREB expression. Dual luciferase reporter assay; miR-34b-5p agomir/antagomir transfection; Western blot; rat hippocampal neuron model and NG108-15 cell model Environmental science and pollution research international Medium 37186186
2024 S100A4 interacts with GNAI2 as a downstream binding partner (identified by co-immunoprecipitation and mass spectrometry), and S100A4 activates the MAPK signaling pathway to promote endometrial epithelial cell proliferation by targeting GNAI2. GnRH suppresses S100A4 expression, thereby inhibiting cell proliferation through the S100A4/GNAI2/MAPK pathway. Co-immunoprecipitation and mass spectrometry to identify GNAI2 as S100A4-interacting protein; overexpression/knockdown experiments; CCK-8 and EdU proliferation assays Frontiers in veterinary science Medium 38872805
2025 TMEM100 interacts with both PRDX1 and GNAI2, disrupting the PRDX1-GNAI2 protein complex. This disruption inhibits LPS-induced NF-κB activation in pulmonary vascular endothelial cells, contributing to anti-inflammatory effects in acute lung injury. Co-immunoprecipitation; overexpression of TMEM100; LPS-induced acute lung injury model; NF-κB activation assays bioRxivpreprint Low bio_10.1101_2025.10.24.684325
2024 GNAI2 is a direct target of miR-181a in ovine dermal papilla cells (confirmed by dual luciferase reporter assay). GNAI2 promotes proliferation and induction ability of dermal papilla cells and activates the Wnt/β-Catenin signaling pathway. miR-181a inhibits dermal papilla cell proliferation and induction ability by targeting GNAI2. Dual luciferase reporter assay; qRT-PCR; Western blot; CCK-8; EdU assay; flow cytometry; alkaline phosphatase staining International journal of molecular sciences Low 39063192

Source papers

Stage 0 corpus · 26 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 Rgs1 and Gnai2 regulate the entrance of B lymphocytes into lymph nodes and B cell motility within lymph node follicles. Immunity 144 15780991
2010 Identification and experimental validation of G protein alpha inhibiting activity polypeptide 2 (GNAI2) as a microRNA-138 target in tongue squamous cell carcinoma. Human genetics 85 21079996
2019 GNAI1 and GNAI3 Reduce Colitis-Associated Tumorigenesis in Mice by Blocking IL6 Signaling and Down-regulating Expression of GNAI2. Gastroenterology 80 30836096
2006 Pleiotropic phenotype of a genomic knock-in of an RGS-insensitive G184S Gnai2 allele. Molecular and cellular biology 67 16943428
2007 Impaired trafficking of Gnai2+/- and Gnai2-/- T lymphocytes: implications for T cell movement within lymph nodes. Journal of immunology (Baltimore, Md. : 1950) 44 17579064
2007 Resistance to diet-induced obesity and improved insulin sensitivity in mice with a regulator of G protein signaling-insensitive G184S Gnai2 allele. Diabetes 42 17928396
2013 The loss of Gnai2 and Gnai3 in B cells eliminates B lymphocyte compartments and leads to a hyper-IgM like syndrome. PloS one 26 23977324
2014 Suppression of GNAI2 message in ovarian cancer. Journal of ovarian research 20 24423449
1992 Regional localization of the human G protein alpha i2 (GNAI2) gene: assignment to 3p21 and a related sequence (GNAI2L) to 12p12-p13. Genomics 20 1733849
2010 Variations in Gnai2 and Rgs1 expression affect chemokine receptor signaling and the organization of secondary lymphoid organs. Genes and immunity 17 20508603
2006 The -318 C>G single-nucleotide polymorphism in GNAI2 gene promoter region impairs transcriptional activity through specific binding of Sp1 transcription factor and is associated with high blood pressure in Caucasians from Italy. Journal of the American Society of Nephrology : JASN 16 16565233
2021 GNAi2/gip2-Regulated Transcriptome and Its Therapeutic Significance in Ovarian Cancer. Biomolecules 14 34439877
2020 SNHG1 Inhibits ox-LDL-Induced Inflammatory Response and Apoptosis of HUVECs via Up-Regulating GNAI2 and PCBP1. Frontiers in pharmacology 13 32536864
2021 GNAI2 Promotes Proliferation and Decreases Apoptosis in Rabbit Melanocytes. Genes 12 34440304
2021 MiR-19 3b regulated the formation of coat colors by targeting WNT10A and GNAI2 in Cashmere goats. Animal biotechnology 10 34747678
2000 Absence of GNAI2 codon 179 oncogene mutations in inflammatory bowel disease. Inflammatory bowel diseases 8 10833069
2023 The miR-34b-5p-negative target Gnai2 aggravates fluorine combined with aluminum-induced apoptosis of rat offspring hippocampal neurons and NG108-15 cells. Environmental science and pollution research international 7 37186186
2023 MiR-30c-5p-Targeted Regulation of GNAI2 Improves Neural Function Injury and Inflammation in Cerebral Ischemia-Reperfusion Injury. Applied biochemistry and biotechnology 7 38153649
2022 GNAI2 Is a Risk Factor for Gastric Cancer: Study of Tumor Microenvironment (TME) and Establishment of Immune Risk Score (IRS). Oxidative medicine and cellular longevity 7 36275898
2024 GnRH-mediated suppression of S100A4 expression inhibits endometrial epithelial cell proliferation in sheep via GNAI2/MAPK signaling. Frontiers in veterinary science 4 38872805
2009 GNAI2 and regulators of G protein signaling as a potential Noonan syndrome mechanism. Medical hypotheses 2 19282110
2025 Plasma Exosomal-Derived SERPINA1 and GNAI2 Downregulation as Potential Diagnostic Biomarkers of Kawasaki Disease with Coronary Artery Aneurysms. International journal of molecular sciences 1 40141310
2024 MicroRNA-181a Targets GNAI2 and Affects the Proliferation and Induction Ability of Dermal Papilla Cells: The Potential Involvement of the Wnt/β-Catenin Signaling Pathway. International journal of molecular sciences 1 39063192
2024 Corrigendum: GnRH-mediated suppression of S100A4 expression inhibits endometrial epithelial cell proliferation in sheep via GNAI2/MAPK signaling. Frontiers in veterinary science 1 39229596
2026 Hepatic GPR75 exacerbates MASH through GNAI2-dependent signaling. Hepatology (Baltimore, Md.) 0 41632920
2025 MiR-4429 Serves as a Protective Regulator by Targeting GNAI2 in Coronary Artery Disease. International heart journal 0 40738708

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