Affinage

ASB4

Ankyrin repeat and SOCS box protein 4 · UniProt Q9Y574

Length
426 aa
Mass
48.2 kDa
Annotated
2026-04-28
13 papers in source corpus 9 papers cited in narrative 10 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

ASB4 is a SOCS box-containing substrate-recognition subunit of an elongin B/C–cullin–Roc E3 ubiquitin ligase complex that targets specific proteins for proteasomal degradation in placental and hypothalamic contexts. ASB4 ubiquitinates ID2 in trophoblast cells to promote differentiation and proper vascular patterning—Asb4-null mice develop a preeclampsia-like phenotype exacerbated by hyperinsulinemia—and ubiquitinates IRS4 in hypothalamic POMC/NPY neurons to dampen insulin–AKT signaling (PMID:24586788, PMID:21955513, PMID:36768469). ASB4 activity is oxygen-regulated through FIH-mediated asparagine hydroxylation under normoxic conditions, and ASB4 additionally suppresses JNK signaling by reducing GPS1/CSN1 protein levels via its ankyrin repeat domain (PMID:17636018, PMID:17276034). In the hypothalamus, ASB4 acts downstream of AgRP to control satiety through calcitonin receptor expression and independently regulates glucose homeostasis in POMC neurons (PMID:35536884, PMID:19934378).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2000 Medium

    Identification of ASB4 as an ankyrin repeat/SOCS box protein established it as a candidate adaptor for elongin B/C-mediated ubiquitin-proteasome targeting, posing the question of what substrates it recognizes.

    Evidence Cloning and domain analysis of the ASB protein family

    PMID:11111040

    Open questions at the time
    • No substrates identified
    • No E3 ligase activity demonstrated
    • Expression pattern unknown
  2. 2007 High

    Demonstrating that FIH hydroxylates ASB4 in an oxygen-dependent manner and that ASB4 assembles an elongin B/C–cullin–Roc E3 complex resolved how ASB4 ligase activity is regulated and linked it to oxygen sensing, while showing that overexpression promotes vascular lineage differentiation in ES cells.

    Evidence Co-IP, hydroxylation assay, and oxygen-dependent differentiation assay in embryonic stem cells

    PMID:17636018

    Open questions at the time
    • Physiological substrates of the E3 complex not yet identified
    • In vivo relevance of oxygen-dependent regulation not tested
    • Hydroxylation site(s) not fully mapped to function
  3. 2007 High

    Discovery that ASB4 binds GPS1/CSN1 via its ankyrin repeats and suppresses JNK-mediated IRS-1 serine phosphorylation revealed a SOCS box-independent signaling function, establishing ASB4 as a bifunctional scaffold.

    Evidence Yeast two-hybrid screen confirmed by reciprocal Co-IP, JNK kinase assay, and SOCS box deletion mutant in HEK293 cells

    PMID:17276034

    Open questions at the time
    • Whether GPS1 itself is a ubiquitination substrate unclear
    • Physiological tissue context of JNK regulation not determined
    • Mechanism of GPS1 protein level reduction not resolved
  4. 2009 Medium

    Transgenic overexpression in POMC neurons showed that ASB4 increases food intake while reducing adiposity and raising metabolic rate, establishing it as a hypothalamic regulator of energy balance and placing it downstream of insulin and leptin signaling.

    Evidence POMC-Asb4 transgenic mice with metabolic phenotyping; intracerebroventricular insulin/leptin injection with in situ hybridization

    PMID:19934378

    Open questions at the time
    • Overexpression gain-of-function may not reflect endogenous stoichiometry
    • Hypothalamic substrates not identified at this stage
    • Single lab
  5. 2011 High

    Identification of IRS4 as a direct ubiquitination substrate of ASB4 in hypothalamic neurons explained how ASB4 attenuates insulin–AKT signaling in the brain, connecting its E3 ligase activity to the metabolic phenotype.

    Evidence Co-IP in HEK293 and rat hypothalamic extracts, ubiquitination assay, SOCS box deletion mutant, AKT phosphorylation readout

    PMID:21955513

    Open questions at the time
    • Whether IRS4 degradation fully accounts for metabolic phenotype unknown
    • Other hypothalamic substrates not excluded
    • No conditional loss-of-function for IRS4 in this context
  6. 2014 High

    Demonstration that ASB4 ubiquitinates ID2 in trophoblasts to promote differentiation and vascular patterning, with Asb4-null mice developing preeclampsia-like features, established a critical placental function and identified a second major substrate.

    Evidence Ubiquitination assay, degradation-resistant ID2 mutant rescue, Asb4-null mouse placental phenotype, endothelial tube formation assay

    PMID:24586788

    Open questions at the time
    • Precise ubiquitin chain type not characterized
    • Whether other E3 ligases compensate partially unknown
    • Human genetic association with preeclampsia not tested
  7. 2022 High

    Genetic epistasis and conditional knockout experiments placed ASB4 downstream of AgRP and upstream of calcitonin receptor expression in meal termination, and showed that ASB4 in POMC neurons independently controls glucose homeostasis, resolving the circuit-level position of ASB4 in hypothalamic feeding regulation.

    Evidence Asb4-null and AgRP-deficient epistasis mice, POMC-specific conditional KO, acute brain knockdown, calcitonin challenge, glucose tolerance tests

    PMID:35536884

    Open questions at the time
    • Direct ubiquitination substrate linking AgRP–ASB4–Calcr axis not identified
    • Mechanism of Calcr transcriptional regulation by ASB4 unknown
    • Whether ASB4 hydroxylation by FIH is relevant in hypothalamic neurons untested
  8. 2023 Medium

    Showing that insulin increases ID2 protein post-transcriptionally in ASB4-null placentas and human trophoblasts clarified how maternal hyperinsulinemia worsens preeclampsia by overwhelming the ASB4-dependent degradation pathway.

    Evidence ASB4-null mice on high-fat diet, ID2 quantification in placenta, HTR8/SVneo cell insulin versus leptin treatment

    PMID:36768469

    Open questions at the time
    • Mechanism by which insulin stabilizes ID2 independent of ASB4 not resolved
    • Single lab
    • Clinical relevance in human preeclampsia cohorts not established

Open questions

Synthesis pass · forward-looking unresolved questions
  • The direct ubiquitination substrate linking ASB4 to calcitonin receptor expression and AgRP-mediated feeding remains unidentified, and the structural basis and in vivo significance of FIH-mediated hydroxylation of ASB4 have not been determined.
  • No substrate identified for the AgRP–ASB4–Calcr axis
  • No structural model of ASB4 in complex with substrates or elongin B/C
  • Role of FIH hydroxylation in hypothalamic versus placental contexts unresolved

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 3
Localization
GO:0005829 cytosol 2
Pathway
R-HSA-162582 Signal Transduction 3 R-HSA-392499 Metabolism of proteins 3 R-HSA-1266738 Developmental Biology 1
Partners
ELOBELOCFIHGPS1ID2IRS4
Complex memberships
Elongin B/C–Cullin–Roc E3 ubiquitin ligase

Evidence

Reading pass · 10 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 ASB4 contains ankyrin repeat and SOCS box domains; the SOCS box couples ASB proteins and their binding partners to the elongin B/C complex, potentially targeting them for degradation. Cloning, sequence characterization, domain analysis Gene Medium 11111040
2007 ASB4 is a substrate for FIH (factor inhibiting HIF-1α)-mediated asparagine hydroxylation via an oxygen-dependent mechanism; ASB4 interacts with FIH and this interaction is oxygen-dependent. Co-immunoprecipitation, hydroxylation assay, overexpression in ES cells Molecular and cellular biology High 17636018
2007 ASB4 functions as the substrate recognition subunit of an elongin B/elongin C/cullin/Roc E3 ubiquitin ligase complex that mediates ubiquitination and proteasomal degradation of substrate proteins; overexpression of ASB4 in ES cells promotes vascular lineage differentiation in an oxygen-dependent manner. Overexpression in embryonic stem cells, oxygen-dependent differentiation assay, complex characterization Molecular and cellular biology High 17636018
2007 ASB4 interacts with GPS1 (CSN1) via its ankyrin repeat domain (independent of the SOCS box), reduces GPS1 protein levels, and thereby inhibits c-Jun NH2-terminal kinase (JNK) activity and IRS-1 serine 307 phosphorylation in response to insulin. Yeast two-hybrid screen, co-immunoprecipitation in vitro and in HEK293 cells, JNK activity assay, SOCS box deletion mutant Cellular signalling High 17276034
2011 ASB4 co-localizes with IRS4 in hypothalamic POMC and NPY neurons; ASB4 physically interacts with IRS4, ubiquitinates it via its SOCS box, and targets it for proteasomal degradation, thereby decreasing basal and insulin-stimulated AKT phosphorylation. In situ hybridization, co-immunoprecipitation (in vitro, HEK293, rat hypothalamic extracts), ubiquitination assay, SOCS box deletion mutant, AKT phosphorylation assay BMC neuroscience High 21955513
2009 Overexpression of ASB4 specifically in POMC neurons of the arcuate nucleus increases food intake, reduces fat mass, increases lean mass, raises metabolic rate, confers resistance to high-fat diet-induced obesity, and increases POMC mRNA expression; insulin injected into the third ventricle increases Asb4 mRNA in the paraventricular nucleus, and leptin increases it in both PVN and ARC. Transgenic mouse (POMC-Asb4), metabolic phenotyping, in situ hybridization, intracerebroventricular injection Endocrinology Medium 19934378
2014 ASB4 ubiquitinates and promotes proteasome-dependent degradation of ID2 (Inhibitor of DNA binding 2) in placental trophoblast cells; this activity requires the SOCS box; ASB4-mediated ID2 degradation promotes trophoblast differentiation and vascular patterning in the placenta, and ASB4-null mice develop a preeclampsia-like phenotype. Co-transfection in JAR cells, ubiquitination assay, proteasome inhibitor, degradation-resistant ID2 mutant rescue experiment, Asb4-null mouse model, endothelial co-culture tube formation assay PloS one High 24586788
2014 ASB4 knockdown in HCC cells inhibits cell migration and invasion, while ectopic ASB4 expression increases migration rate; ASB4 expression is negatively regulated post-transcriptionally by miR-200a binding to the 3′ UTR of ASB4 mRNA. siRNA knockdown, ectopic overexpression, migration/invasion assay, dual luciferase reporter assay, miRNA mimic/inhibitor Bioscience trends Medium 24815387
2022 ASB4 in hypothalamic neurons acts downstream of AgRP signaling to regulate satiety; Asb4 deficiency disrupts AgRP-induced feeding and impairs calcitonin-mediated meal termination associated with reduced Calcr (calcitonin receptor) expression; ASB4 specifically in POMC neurons controls glucose homeostasis independently of obesity. Asb4-null mice, acute brain-specific Asb4 knockdown, AgRP-deficient mouse epistasis, calcitonin administration, POMC-specific Asb4 conditional knockout, glucose tolerance test Science signaling High 35536884
2023 In ASB4-null placenta, insulin (elevated by high-fat diet-induced obesity) increases ID2 protein levels post-transcriptionally, worsening preeclampsia-like phenotypes; in human trophoblast HTR8/SVneo cells, insulin (but not leptin) increases ID2 protein, indicating that hyperinsulinemia disrupts ASB4-mediated ID2 removal. ASB4-null mice on high-fat diet, placental ID2 quantification, HTR8/SVneo cell insulin/leptin treatment International journal of molecular sciences Medium 36768469

Source papers

Stage 0 corpus · 13 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2002 Asb4, Ata3, and Dcn are novel imprinted genes identified by high-throughput screening using RIKEN cDNA microarray. Biochemical and biophysical research communications 116 11820791
2007 ASB4 is a hydroxylation substrate of FIH and promotes vascular differentiation via an oxygen-dependent mechanism. Molecular and cellular biology 83 17636018
2000 Cloning and characterization of the genes encoding the ankyrin repeat and SOCS box-containing proteins Asb-1, Asb-2, Asb-3 and Asb-4. Gene 48 11111040
2014 The ubiquitin ligase ASB4 promotes trophoblast differentiation through the degradation of ID2. PloS one 40 24586788
2018 The Antigen ASB4 on Cancer Stem Cells Serves as a Target for CTL Immunotherapy of Colorectal Cancer. Cancer immunology research 39 29371260
2011 Ankyrin repeat and SOCS box containing protein 4 (Asb-4) colocalizes with insulin receptor substrate 4 (IRS4) in the hypothalamic neurons and mediates IRS4 degradation. BMC neuroscience 24 21955513
2007 Ankyrin repeat and SOCS box containing protein 4 (Asb-4) interacts with GPS1 (CSN1) and inhibits c-Jun NH2-terminal kinase activity. Cellular signalling 24 17276034
2009 Expression of ankyrin repeat and suppressor of cytokine signaling box protein 4 (Asb-4) in proopiomelanocortin neurons of the arcuate nucleus of mice produces a hyperphagic, lean phenotype. Endocrinology 16 19934378
2014 Expression of ankyrin repeat and SOCS box containing 4 (ASB4) confers migration and invasion properties of hepatocellular carcinoma cells. Bioscience trends 15 24815387
2022 ASB4 modulates central melanocortinergic neurons and calcitonin signaling to control satiety and glucose homeostasis. Science signaling 11 35536884
2008 Stage-specific expression of ankyrin and SOCS box protein-4 (Asb-4) during spermatogenesis. Molecules and cells 8 18414003
2023 Insulin Elevates ID2 Expression in Trophoblasts and Aggravates Preeclampsia in Obese ASB4-Null Mice. International journal of molecular sciences 5 36768469
2024 The Roles of Obesity and ASB4 in Preeclampsia Pathogenesis. International journal of molecular sciences 3 39201703