GO:0034679 integrin alpha9-beta1 complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0034679 defines the integrin alpha9-beta1 complex, a heterodimeric cell-surface receptor composed of one ITGA9 (alpha9) subunit and one ITGB1 (beta1) subunit.
• The alpha9-beta1 complex is a receptor for several extracellular matrix and matricellular ligands, including tenascin-C, osteopontin, and VCAM-1, and it can also bind ADAM proteins.
• Signaling through alpha9-beta1 integrin contributes to granulopoiesis by enhancing G-CSF receptor signaling, linking the complex to hematopoietic differentiation.
• In cancer, alpha9-beta1 integrin promotes malignant tumor growth and metastasis by potentiating epithelial-mesenchymal transition, and its loss on tumor keratinocytes can alter the stromal vasculature [3,8].
• The complex is a candidate therapeutic target for refractory diseases, including inflammatory and fibrotic conditions, based on its roles in cell migration, survival, and cytokine signaling.
• Studying GO:0034679 requires integrated approaches such as knockout, point-mutation, knock-in, and overexpression cell models combined with proteomics, imaging, and functional assays [1,4].
Description
The integrin alpha9-beta1 complex (GO:0034679) is a heterodimeric transmembrane receptor that belongs to the integrin family of cell adhesion molecules. It is formed by the non-covalent association of an alpha9 subunit (ITGA9) and a beta1 subunit (ITGB1), and it mediates cell-extracellular matrix and cell-cell interactions that control adhesion, migration, proliferation, and survival. Because integrins are central to tissue homeostasis and disease, the alpha9-beta1 complex has attracted attention as a therapeutic target in refractory diseases, including cancer, inflammation, and fibrosis. Functionally, the alpha9-beta1 complex is best known for its ability to bind ligands such as tenascin-C, osteopontin, and VCAM-1, and for its capacity to cooperate with other receptors, including growth factor receptors and p75(NTR), to modulate cellular responses [1,2]. For example, the association of p75(NTR) with alpha9-beta1 integrin modulates NGF-dependent cellular responses, indicating that the complex can act as a co-receptor in neurotrophic signaling. In the hematopoietic system, alpha9-beta1 integrin contributes to granulopoiesis by enhancing granulocyte colony-stimulating factor receptor signaling. Given its roles in development, immunity, and cancer, the alpha9-beta1 complex is a valuable subject for gene editing and functional genomics. Researchers can use CRISPR-based knockout, point-mutation, knock-in, and overexpression models to dissect how ITGA9 and ITGB1 contribute to receptor assembly, ligand binding, and downstream signaling [1,4]. This article summarizes the current understanding of GO:0034679, its structure, regulation, disease relevance, and the experimental methods used to study it.
integrin alpha9-beta1 complex At A Glance
| GO ID | GO:0034679 |
|---|---|
| GO term | integrin alpha9-beta1 complex |
| Ontology | cellular_component |
| Synonym | alpha9-beta1 integrin complex; ITGA9-ITGB1 complex |
| Definition | An integrin complex that comprises one alpha9 subunit and one beta1 subunit. |
| Major function | Cell adhesion and signaling receptor for extracellular matrix and matricellular ligands such as tenascin-C, osteopontin, and VCAM-1. |
| Subunits | ITGA9 (alpha9) and ITGB1 (beta1). |
| Ligand examples | Tenascin-C, osteopontin, VCAM-1, ADAM proteins. |
| Associated processes | Granulopoiesis, epithelial-mesenchymal transition, cell migration, and survival [7,8]. |
What Is GO:0034679?
The integrin alpha9-beta1 complex is a cellular component defined by the Gene Ontology as an integrin complex that comprises one alpha9 subunit and one beta1 subunit. In other words, it is a specific heterodimeric integrin receptor formed by the pairing of ITGA9 and ITGB1, which together create a functional adhesion and signaling unit at the cell surface.
Why Is integrin alpha9-beta1 complex Important in Cell Biology?
The integrin alpha9-beta1 complex is important because it serves as a molecular bridge between the extracellular environment and intracellular signaling pathways that control cell fate. Its ability to bind multiple ligands and cooperate with receptors such as p75(NTR) and the G-CSF receptor places it at the center of processes ranging from hematopoietic differentiation to cancer progression [1,2,7]. As a result, the complex is a promising target for therapeutic intervention in refractory diseases, and understanding its regulation is essential for developing selective inhibitors or modulators.
• It mediates cell adhesion to tenascin-C, osteopontin, and VCAM-1, influencing migration and tissue remodeling.
• It enhances G-CSF receptor signaling and contributes to granulopoiesis, linking it to innate immunity.
• It modulates NGF-dependent cellular responses through association with p75(NTR), connecting it to neurotrophic signaling.
• It promotes malignant tumor growth and metastasis by potentiating epithelial-mesenchymal transition.
• Loss of alpha9-beta1 on tumor keratinocytes can enhance stromal vasculature and tumor growth, indicating context-dependent roles.
• It regulates cortactin phosphorylation and distribution, affecting cancer cell behavior.
• It is a candidate therapeutic target for refractory inflammatory and fibrotic diseases.
• It can influence atherosclerosis-related biology, although vascular smooth muscle- and myeloid-derived alpha9-beta1 may not directly mediate atherosclerosis development in mice.
• It is a useful model for studying integrin heterodimer assembly and signaling specificity.
• It provides opportunities for CRISPR-based functional genomics and drug target validation [1,4].
Structure, Assembly, and Molecular Mechanism of the integrin alpha9-beta1 complex
Biological process: What happens during integrin alpha9-beta1 complex signaling?
In simple terms: When the alpha9-beta1 integrin binds to its ligands outside the cell, it triggers signals inside the cell that change how the cell behaves.
The integrin alpha9-beta1 complex functions as a receptor that becomes activated upon binding to extracellular ligands such as tenascin-C, osteopontin, and VCAM-1. This activation leads to intracellular signaling that can promote cell adhesion, migration, proliferation, and survival. In hematopoietic cells, alpha9-beta1 integrin enhances granulocyte colony-stimulating factor receptor signaling, thereby contributing to granulopoiesis. In cancer cells, signaling through this complex potentiates epithelial-mesenchymal transition, a process associated with increased motility and invasiveness. Additionally, the complex can modulate neurotrophic signaling through association with p75(NTR), affecting NGF-dependent cellular responses.
Cellular component: Structure and composition of the integrin alpha9-beta1 complex
In simple terms: The alpha9-beta1 integrin is made of two different protein chains that pair up to form a single functional receptor on the cell surface.
The integrin alpha9-beta1 complex is a heterodimer composed of one alpha9 subunit (ITGA9) and one beta1 subunit (ITGB1). Each subunit is a type I transmembrane glycoprotein with a large extracellular domain, a transmembrane region, and a short cytoplasmic tail. The non-covalent association of the two subunits is required for ligand binding and signaling. The beta1 subunit is shared with many other integrin heterodimers, while the alpha9 subunit confers ligand specificity. The complex is expressed on various cell types, including smooth muscle cells, myeloid cells, and tumor cells [1,6].
Molecular function: Ligand binding and signaling mechanism
In simple terms: The alpha9-beta1 integrin grabs specific molecules outside the cell and passes signals to the inside.
The molecular function of the alpha9-beta1 complex is primarily as a receptor for extracellular matrix and matricellular proteins. It binds ligands such as tenascin-C, osteopontin, and VCAM-1, and it can also interact with ADAM proteins. Ligand binding induces conformational changes that lead to integrin activation and clustering, which in turn recruit intracellular adaptor and signaling proteins. Downstream effects include phosphorylation of cortactin, which affects cancer cell behavior. The complex also cooperates with growth factor receptors, as shown by its enhancement of G-CSF receptor signaling during granulopoiesis.
Regulation of integrin alpha9-beta1 complex activity
In simple terms: The activity of the alpha9-beta1 integrin can be turned up or down by other proteins and signals inside the cell.
Integrin activity is regulated by inside-out signaling, where intracellular signals change the affinity of the integrin for its ligands. For the alpha9-beta1 complex, regulation can occur through interactions with other receptors and signaling molecules. For example, association with p75(NTR) modulates NGF-dependent responses. In cancer cells, downstream phosphorylation of cortactin is influenced by alpha9-beta1 integrin signaling. Additionally, the complex can potentiate epithelial-mesenchymal transition, suggesting cross-talk with transcriptional programs. The specific kinases and phosphatases that regulate alpha9-beta1 integrin are not fully defined, but the complex is known to be a target for therapeutic modulation in refractory diseases.
Key Genes Involved in GO:0034679 integrin alpha9-beta1 complex
The following genes and proteins are directly or functionally associated with the integrin alpha9-beta1 complex (GO:0034679) based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ITGA9 | Encodes the alpha9 integrin subunit; forms heterodimer with beta1 | Essential for alpha9-beta1 complex assembly and ligand specificity |
| ITGB1 | Encodes the beta1 integrin subunit; shared across many integrins | Required for alpha9-beta1 heterodimer formation and signaling |
| SPP1 | Encodes osteopontin, a ligand for alpha9-beta1 integrin | Mediates cell adhesion and migration through alpha9-beta1 [1,5] |
| TNC | Encodes tenascin-C, an extracellular matrix ligand | Binds alpha9-beta1 to modulate cell-matrix interactions |
| VCAM1 | Encodes vascular cell adhesion molecule 1, a ligand | Interacts with alpha9-beta1 in immune and inflammatory contexts |
| ADAM proteins | Family of metalloproteases that can interact with alpha9-beta1 | May modulate integrin function and shedding |
| NGFR | Encodes p75(NTR), which associates with alpha9-beta1 | Modulates NGF-dependent cellular responses |
| CSF3R | Encodes G-CSF receptor, whose signaling is enhanced by alpha9-beta1 | Links alpha9-beta1 to granulopoiesis |
| CTTN | Encodes cortactin, a downstream target of alpha9-beta1 signaling | Affects cancer cell behavior via phosphorylation |
| CDH1 | Encodes E-cadherin, involved in epithelial-mesenchymal transition | Alpha9-beta1 promotes EMT, potentially affecting E-cadherin |
| VIM | Encodes vimentin, a mesenchymal marker | Upregulated during EMT potentiated by alpha9-beta1 |
| FN1 | Encodes fibronectin, an extracellular matrix protein | May cooperate with alpha9-beta1 in adhesion |
| COL1A1 | Encodes collagen type I, a matrix component | Potential ligand or matrix context for alpha9-beta1 |
| MMP2 | Encodes matrix metalloproteinase 2 | Associated with invasion promoted by alpha9-beta1 |
| MMP9 | Encodes matrix metalloproteinase 9 | Associated with metastasis and inflammation |
| IL6 | Encodes interleukin-6, a cytokine | May be modulated by alpha9-beta1 in inflammation |
| TGFB1 | Encodes transforming growth factor beta 1 | Cross-talk with alpha9-beta1 in fibrosis and EMT |
| AKT1 | Encodes AKT serine/threonine kinase 1 | Survival signaling downstream of integrins |
How Is integrin alpha9-beta1 complex Regulated?
The activity of the integrin alpha9-beta1 complex is regulated at multiple levels, including ligand availability, integrin conformational activation, and intracellular signaling. Inside-out signaling can change the affinity of the integrin for its ligands, while outside-in signaling transmits information from the extracellular matrix to the cell interior. The complex can also be regulated by association with other receptors; for instance, p75(NTR) association modulates NGF-dependent cellular responses. In cancer cells, downstream phosphorylation of cortactin is influenced by alpha9-beta1 integrin, affecting cell behavior. Additionally, the complex can potentiate epithelial-mesenchymal transition, suggesting regulation by transcriptional programs. However, the specific kinases and phosphatases that directly regulate alpha9-beta1 integrin remain incompletely understood, and further research is needed to define the full regulatory network.
integrin alpha9-beta1 complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ITGA9 | Cancer progression, metastasis, inflammation | Knockout and overexpression in cancer cell lines [1,8] |
| ITGB1 | Broad roles in adhesion and signaling; cancer | Conditional knockout in mouse models |
| SPP1 | Osteopontin-mediated adhesion and migration | Point mutation to disrupt alpha9-beta1 binding |
| NGFR | Neurotrophic signaling and cell survival | Knock-in of tagged p75(NTR) to study interaction |
| CSF3R | Granulopoiesis and neutrophil development | Knockout of Itga9 in hematopoietic cells |
Cancer progression and metastasis
The integrin alpha9-beta1 complex promotes malignant tumor growth and metastasis by potentiating epithelial-mesenchymal transition. Loss of alpha9-beta1 on tumor keratinocytes enhances the stromal vasculature and growth of cutaneous tumors, indicating a complex role in the tumor microenvironment. Additionally, alpha9-beta1 signaling affects cortactin phosphorylation and distribution, which influences cancer cell behavior. These findings suggest that targeting alpha9-beta1 could be a therapeutic strategy in certain cancers.
Inflammatory and fibrotic diseases
Alpha9-beta1 integrin is considered a novel therapeutic target for refractory diseases, including inflammatory and fibrotic conditions. Its ability to bind VCAM-1 and osteopontin links it to leukocyte trafficking and tissue remodeling. In atherosclerosis, vascular smooth muscle- and myeloid cell-derived alpha9-beta1 does not directly mediate disease development in mice, suggesting cell-type-specific roles. Further studies are needed to clarify its contribution to different inflammatory pathologies.
Hematopoietic and neurotrophic signaling
The alpha9-beta1 complex contributes to granulopoiesis by enhancing granulocyte colony-stimulating factor receptor signaling, linking it to innate immune cell development. It also associates with p75(NTR) to modulate NGF-dependent cellular responses, connecting it to neurotrophic signaling pathways. Dysregulation of these processes could contribute to hematological or neurological disorders, although direct evidence in human disease is still emerging.
From integrin alpha9-beta1 complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of ITGA9 affect tumor growth and metastasis? | ITGA9 knockout cancer cell lines and xenografts |
| How does alpha9-beta1 integrin contribute to granulopoiesis? | Conditional knockout of Itga9 in mouse hematopoietic cells |
| What is the role of alpha9-beta1 in NGF-dependent responses? | Point mutation of ITGB1 or ITGA9 to disrupt p75(NTR) association |
| Can alpha9-beta1 integrin be targeted therapeutically in fibrosis? | Knock-in of fluorescently tagged ITGA9 for imaging |
| How does alpha9-beta1 signaling affect cortactin phosphorylation? | Overexpression of constitutively active ITGA9 in cancer cells |
| Does alpha9-beta1 in vascular smooth muscle affect atherosclerosis? | Tissue-specific knockout of Itga9 in smooth muscle and myeloid cells |
How to Study the integrin alpha9-beta1 complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| CRISPR knockout | Loss of gene function | Abolish ITGA9 or ITGB1 to study complex roles |
| Point mutation | Specific amino acid changes | Disrupt ligand binding or protein interactions |
| Knock-in | Tagged or reporter gene expression | Visualize and isolate alpha9-beta1 complex |
| Overexpression | Increased gene expression | Amplify signaling to study EMT and migration |
| Co-immunoprecipitation | Protein-protein interactions | Identify partners like p75(NTR) or G-CSF receptor [2,7] |
| Phosphoproteomics | Phosphorylation events | Map downstream signaling such as cortactin phosphorylation |
| Adhesion and migration assays | Cell behavior | Measure functional effects of alpha9-beta1 |
| CRISPR library screening | Genome-wide gene function | Identify modifiers of alpha9-beta1 signaling |
CRISPR-based gene editing
CRISPR-Cas9 knockout, point mutation, knock-in, and overexpression models are powerful tools to study the integrin alpha9-beta1 complex. Knockout of ITGA9 or ITGB1 can abolish complex formation and reveal its functions in adhesion, migration, and signaling. Point mutations can be introduced to disrupt specific ligand-binding sites or protein-protein interaction domains, such as the p75(NTR) association site. Knock-in of epitope tags or fluorescent proteins allows visualization and biochemical isolation of the complex. Overexpression models can amplify signaling to study downstream effects like EMT.
Proteomics and interactomics
Mass spectrometry-based proteomics can identify proteins that co-precipitate with the alpha9-beta1 complex, revealing novel interacting partners and signaling components. Phosphoproteomics can map downstream phosphorylation events, such as cortactin phosphorylation, that are regulated by alpha9-beta1 integrin. These approaches help define the molecular mechanism of the complex in different cell types.
Imaging and cell biology assays
Fluorescence microscopy and live-cell imaging can track the localization and trafficking of tagged alpha9-beta1 integrin. Adhesion assays, migration assays, and wound-healing assays measure the functional consequences of complex activity. Co-immunoprecipitation and proximity ligation assays can confirm interactions with p75(NTR) or G-CSF receptor [2,7].
Functional genomics and library screening
CRISPR library screening can identify genes that modulate alpha9-beta1 integrin function or its downstream effects. For example, a genome-wide knockout screen in cancer cells expressing alpha9-beta1 could reveal synthetic lethal interactions or resistance mechanisms. Bioinformatics analysis of transcriptomic data can uncover pathways co-regulated with ITGA9 and ITGB1, providing hypotheses for further testing.
How CRISPR Can Be Used to Study GO:0034679 integrin alpha9-beta1 complex
Knockout
CRISPR knockout of ITGA9 or ITGB1 completely abolishes the integrin alpha9-beta1 complex. This is useful for studying the loss-of-function phenotypes in processes such as granulopoiesis, tumor growth, and metastasis [7,8]. Knockout cell lines can be used in xenograft models to assess the contribution of the complex to tumor progression.
Point Mutation
Point mutations can be introduced into ITGA9 or ITGB1 to disrupt specific functions, such as ligand binding or interaction with p75(NTR). For example, mutating the osteopontin-binding site on alpha9 can prevent osteopontin-mediated adhesion without affecting overall integrin structure. These models help dissect the molecular determinants of alpha9-beta1 function.
Knock-in
Knock-in of epitope tags (e.g., HA, FLAG) or fluorescent proteins (e.g., GFP) into the endogenous ITGA9 or ITGB1 loci allows for tracking and biochemical purification of the alpha9-beta1 complex. This approach preserves endogenous regulation and can be used for imaging studies or interactome analysis.
Overexpression
Overexpression of ITGA9 and ITGB1 in cell lines can amplify alpha9-beta1 signaling and enhance phenotypes such as epithelial-mesenchymal transition and migration. This is useful for studying downstream pathways and for screening inhibitors that target the complex.
How EDITGENE Supports integrin alpha9-beta1 complex Research
Researchers studying integrin alpha9-beta1 complex-related genes often need to determine whether a candidate gene is causally involved in complex assembly, signaling, or disease progression. EDITGENE provides a comprehensive suite of CRISPR-based services to enable such functional studies, from knockout and point mutation to knock-in and overexpression, as well as library screening and bioinformatics support.
Contact EDITGENE today to design your custom CRISPR model for integrin alpha9-beta1 complex research.
Frequently Asked Questions About integrin alpha9-beta1 complex
What is the integrin alpha9-beta1 complex?
The integrin alpha9-beta1 complex (GO:0034679) is a heterodimeric cell-surface receptor composed of one alpha9 subunit (ITGA9) and one beta1 subunit (ITGB1). It mediates cell adhesion and signaling in response to extracellular ligands such as tenascin-C, osteopontin, and VCAM-1.
What genes are involved in the integrin alpha9-beta1 complex?
The core genes are ITGA9 and ITGB1, which encode the two subunits. Other genes such as SPP1 (osteopontin), TNC (tenascin-C), VCAM1, and NGFR (p75(NTR)) are involved in ligand binding or modulation of the complex [1,2,5].
What diseases are associated with integrin alpha9-beta1 complex?
The complex has been implicated in cancer progression and metastasis, inflammatory and fibrotic diseases, and hematopoietic disorders. It is considered a therapeutic target for refractory diseases [1,3,8].
How does integrin alpha9-beta1 complex contribute to cancer?
It promotes malignant tumor growth and metastasis by potentiating epithelial-mesenchymal transition. Loss of alpha9-beta1 on tumor keratinocytes can also enhance stromal vasculature and tumor growth [3,8].
What is the role of integrin alpha9-beta1 in granulopoiesis?
Alpha9-beta1 integrin enhances granulocyte colony-stimulating factor receptor signaling, thereby contributing to granulopoiesis and neutrophil development.
How can I study the integrin alpha9-beta1 complex using CRISPR?
You can use CRISPR knockout to abolish ITGA9 or ITGB1, point mutations to disrupt specific interactions, knock-in to tag the subunits, and overexpression to amplify signaling. EDITGENE provides all these services [1,2,8].
What ligands bind to integrin alpha9-beta1?
Known ligands include tenascin-C, osteopontin, and VCAM-1. The complex can also interact with ADAM proteins.
Does integrin alpha9-beta1 interact with p75(NTR)?
Yes, association of p75(NTR) with alpha9-beta1 integrin modulates NGF-dependent cellular responses.
Is integrin alpha9-beta1 a therapeutic target?
Yes, it is considered a novel therapeutic target for refractory diseases, including inflammatory and fibrotic conditions, based on its roles in cell migration and signaling.
What experimental models are available for integrin alpha9-beta1 research?
Common models include knockout and transgenic mice, CRISPR-edited cell lines, and xenograft models. EDITGENE offers custom CRISPR cell models for knockout, point mutation, knock-in, and overexpression [1,6,8].
Conclusion
The integrin alpha9-beta1 complex (GO:0034679) is a key heterodimeric receptor that mediates cell adhesion and signaling in diverse physiological and pathological contexts. Its roles in granulopoiesis, cancer progression, and inflammatory diseases make it a compelling target for basic and translational research [1,7,8]. Understanding its structure, regulation, and downstream effects requires integrated approaches, including CRISPR-based gene editing, proteomics, and functional assays. EDITGENE provides comprehensive services to support these studies, from custom knockout and knock-in models to library screening and bioinformatics.
References
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- 2. Ventresca EM et al.. 2015. Association of p75(NTR) and α9β1 integrin modulates NGF-dependent cellular responses.. Cell Signal 27(6):1225-36 PMID: 25748048
- 3. Varney SD et al.. 2022. Loss of Integrin α9β1 on Tumor Keratinocytes Enhances the Stromal Vasculature and Growth of Cutaneous Tumors.. J Invest Dermatol 142(7):1966-1975.e8 PMID: 34843681
- 4. Høye AM et al.. 2016. The Phosphorylation and Distribution of Cortactin Downstream of Integrin α9β1 Affects Cancer Cell Behaviour.. Sci Rep 6:28529 PMID: 27339664
- 5. Fnu G et al.. 2021. Structural Constraint of Osteopontin Facilitates Efficient Binding to CD44.. Biomolecules 11(6) PMID: 34070790
- 6. Jung IH et al.. 2022. Vascular smooth muscle- and myeloid cell-derived integrin α9β1 does not directly mediate the development of atherosclerosis in mice.. Atherosclerosis 360:15-20 PMID: 36215801
- 7. Chen C et al.. 2006. The Integrin alpha9beta1 contributes to granulopoiesis by enhancing granulocyte colony-stimulating factor receptor signaling.. Immunity 25(6):895-906 PMID: 17137800
- 8. Gupta SK et al.. 2013. Integrin α9β1 promotes malignant tumor growth and metastasis by potentiating epithelial-mesenchymal transition.. Oncogene 32(2):141-50 PMID: 22370635
