GO:0004715 non-membrane spanning protein tyrosine kinase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004715 describes the catalytic activity of non-membrane spanning protein tyrosine kinases, which transfer a phosphate from ATP to tyrosine residues on protein substrates.
• This activity is defined by the absence of a transmembrane domain, distinguishing it from receptor tyrosine kinases.
• Focal adhesion kinase (FAK) is a classic example, phosphorylated in response to cell attachment to fibronectin.
• Janus kinase 2 (JAK2) and Src are regulated by heme, linking this activity to redox and metabolic signals.
• Dysregulation of non-membrane spanning tyrosine kinases is implicated in cancers and immune disorders.
• CRISPR-based knockout, point mutation, knock-in, and overexpression models are essential to dissect their specific functions.
Description
Non-membrane spanning protein tyrosine kinase activity (GO:0004715) is a fundamental molecular function that governs intracellular signal transduction. These enzymes catalyze the transfer of the gamma-phosphate of ATP to tyrosine residues on target proteins, a modification that creates docking sites for SH2 and PTB domain-containing proteins and alters enzymatic activity. Unlike receptor tyrosine kinases, they lack a transmembrane domain and are localized to the cytoplasm, nucleus, or associated with the inner leaflet of the plasma membrane. This activity is critical for processes such as cell adhesion, proliferation, differentiation, and immune responses. Researchers study this term to understand how aberrant tyrosine phosphorylation drives diseases like cancer and to develop targeted therapies.
non-membrane spanning protein tyrosine kinase activity At A Glance
| GO ID | GO:0004715 |
|---|---|
| GO term | non-membrane spanning protein tyrosine kinase activity |
| Ontology | molecular_function |
| Synonym | cytoplasmic protein tyrosine kinase activity; focal adhesion kinase activity; janus kinase 1 activity; janus kinase 2 activity; janus kinase 3 activity; Bruton's tyrosine kinase activity; p60c-src protein tyrosine kinase activity; ATP:protein-L-tyrosine O-phosphotransferase activity |
| Major function | Catalyzes phosphorylation of tyrosine residues on target proteins using ATP |
| Substrates | Proteins containing tyrosine residues, often other kinases, adaptors, or transcription factors |
| Cofactors | Magnesium or manganese ions (Mg2+/Mn2+) are typically required for ATP binding and catalysis |
| Localization | Cytoplasm, nucleus, focal adhesions, and other non-membrane compartments |
What Is GO:0004715?
According to the Gene Ontology, GO:0004715 is defined as the catalysis of the reaction: ATP + protein L-tyrosine = ADP + protein L-tyrosine phosphate by a non-membrane spanning protein. In other words, it is the enzymatic activity of kinases that phosphorylate tyrosine residues on proteins but do not contain a membrane-spanning region. This distinguishes them from receptor tyrosine kinases (GO:0004714) that have an extracellular ligand-binding domain, a transmembrane segment, and an intracellular kinase domain. The term encompasses many well-known kinases such as Src, JAK family members, FAK, and Bruton's tyrosine kinase (BTK), which are often referred to by their specific names but share this common catalytic function.
Why Is non-membrane spanning protein tyrosine kinase activity Important in Cell Biology?
Non-membrane spanning protein tyrosine kinase activity is central to intracellular signaling networks that control cell growth, survival, migration, and immune function. Dysregulation of these kinases, through mutation, overexpression, or aberrant activation, is a hallmark of many human diseases, especially cancers and inflammatory disorders. For example, FAK is phosphorylated upon cell attachment to fibronectin, influencing cell adhesion and migration. JAK2 and Src are regulated by heme, linking kinase activity to cellular redox state and metabolism. Understanding this activity at the molecular level is essential for developing targeted therapies and for interpreting genomic data in precision medicine.
• Drives key signaling pathways such as JAK-STAT, Src-family kinase, and focal adhesion signaling.
• Essential for immune cell activation and cytokine responses.
• Plays a critical role in cell adhesion and migration through FAK.
• Mutations and dysregulation are linked to leukemias, solid tumors, and immune deficiencies.
• Serves as a major class of drug targets for small molecule inhibitors (e.g., imatinib, ruxolitinib).
• Involved in heme-mediated regulation, connecting kinase activity to redox biology.
• Provides a model system for studying enzyme kinetics and substrate specificity.
• Enables research on post-translational modifications and signal integration.
• Facilitates the development of CRISPR-based disease models for drug discovery.
What Happens During non-membrane spanning protein tyrosine kinase activity?
Substrate recognition and binding
In simple terms: The kinase finds and grabs its target protein.
Non-membrane spanning tyrosine kinases recognize specific substrate proteins through interactions between their catalytic domain and short linear motifs surrounding the target tyrosine. For example, FAK is phosphorylated in response to cell attachment to fibronectin, indicating that substrate recognition can be regulated by extracellular matrix cues. The kinase domain typically has a conserved catalytic core that binds the substrate in a cleft, positioning the tyrosine residue for phosphoryl transfer.
ATP binding and catalysis
In simple terms: The kinase uses ATP to add a phosphate group to the target.
The catalytic mechanism involves the binding of ATP-Mg2+ complex in the kinase active site. The gamma-phosphate of ATP is transferred to the hydroxyl group of the tyrosine residue on the substrate protein, resulting in ADP and phosphorylated tyrosine. This reaction is highly conserved among protein tyrosine kinases. The presence of magnesium or manganese ions is required for neutralizing the negative charges of ATP phosphates and facilitating the transfer.
Regulation by cofactors and interacting proteins
In simple terms: Other molecules can turn the kinase on or off.
The activity of non-membrane spanning tyrosine kinases is tightly regulated by cofactors, interacting proteins, and post-translational modifications. For instance, heme has been shown to control the regulation of Jak2 and Src, suggesting that cellular heme levels can modulate kinase activity. Additionally, phosphorylation of the kinase itself or binding of regulatory subunits can alter catalytic efficiency and substrate specificity.
Downstream signaling and cellular responses
In simple terms: The phosphate tag triggers a chain reaction inside the cell.
Once a substrate is phosphorylated, it can recruit downstream signaling proteins containing SH2 or PTB domains, leading to activation of pathways such as MAPK, PI3K-AKT, and JAK-STAT. This ultimately affects gene expression, cell cycle progression, cytoskeletal reorganization, and cell survival. For example, FAK phosphorylation at focal adhesions promotes cell migration and survival signals.
Key Genes Involved in GO:0004715 non-membrane spanning protein tyrosine kinase activity
The following genes encode proteins that possess non-membrane spanning protein tyrosine kinase activity or are major substrates/regulators of this activity.
| Gene | Major Role | Research Relevance |
|---|---|---|
| FAK (PTK2) | Focal adhesion kinase, phosphorylated upon cell attachment to fibronectin | Cell adhesion, migration, cancer invasion |
| JAK2 | Janus kinase 2, mediates cytokine signaling; regulated by heme | Myeloproliferative neoplasms, immune disorders |
| SRC | Proto-oncogene tyrosine-protein kinase Src; regulated by heme | Cancer, cell proliferation, differentiation |
| JAK1 | Janus kinase 1, involved in cytokine receptor signaling | Inflammatory diseases, cancer |
| JAK3 | Janus kinase 3, primarily in immune cells | Severe combined immunodeficiency, leukemia |
| BTK | Bruton's tyrosine kinase, essential for B-cell development | X-linked agammaglobulinemia, B-cell malignancies |
| ABL1 | Abelson murine leukemia viral oncogene homolog 1 | Chronic myeloid leukemia |
| LYN | Src-family kinase involved in B-cell signaling | Autoimmunity, leukemia |
| FYN | Src-family kinase involved in T-cell signaling | Immune regulation, cancer |
| YES1 | Src-family kinase | Cancer, cell growth |
| HCK | Hematopoietic cell kinase | Myeloid leukemia |
| FGR | Gardner-Rasheed feline sarcoma viral oncogene homolog | Cancer, immune signaling |
| BLK | B-lymphoid tyrosine kinase | B-cell development, autoimmunity |
| CSK | C-terminal Src kinase, negative regulator of Src | Cancer, regulation of Src activity |
| TEC | Tyrosine-protein kinase Tec | T-cell signaling, cancer |
| SYK | Spleen tyrosine kinase | Immune receptor signaling, leukemia |
| ZAP70 | Zeta-chain-associated protein kinase 70 | T-cell signaling, immunodeficiency |
How Is non-membrane spanning protein tyrosine kinase activity Regulated?
The activity of non-membrane spanning protein tyrosine kinases is regulated at multiple levels. Intracellular heme levels can directly modulate the activity of JAK2 and Src, as demonstrated by Yao et al. (2010). Phosphorylation of conserved tyrosine residues within the kinase activation loop often leads to conformational changes that enhance catalytic activity. Additionally, protein-protein interactions, such as binding of regulatory subunits or adaptor proteins, can localize kinases to specific subcellular compartments and modulate substrate access. Dephosphorylation by protein tyrosine phosphatases provides a counterbalancing mechanism. Furthermore, ubiquitination and proteasomal degradation control the abundance of these kinases. These regulatory mechanisms ensure that tyrosine phosphorylation is transient and tightly controlled in response to extracellular and intracellular cues.
non-membrane spanning protein tyrosine kinase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| JAK2 | Myeloproliferative neoplasms, leukemia | Knock-in of JAK2 V617F mutation in cell lines |
| FAK | Cancer invasion and metastasis | Knockout of PTK2 in cancer cell lines |
| SRC | Colorectal cancer, breast cancer | Point mutation of Src activation loop |
| BTK | X-linked agammaglobulinemia, B-cell lymphoma | Knockout of BTK in B-cell lines |
| JAK3 | Severe combined immunodeficiency | Knock-in of patient-derived mutations |
Cancer
Dysregulated non-membrane spanning tyrosine kinase activity is a hallmark of many cancers. Activating mutations in JAK2 (e.g., V617F) lead to constitutive signaling and are found in myeloproliferative neoplasms. Overexpression or hyperactivation of Src and FAK promotes tumor growth, invasion, and metastasis. Targeting these kinases with small molecule inhibitors has proven effective in leukemia and solid tumors.
Immune disorders
Mutations in BTK cause X-linked agammaglobulinemia, characterized by a lack of mature B cells. JAK3 mutations result in severe combined immunodeficiency. These conditions highlight the essential role of non-membrane spanning tyrosine kinases in immune cell development and function.
Inflammatory diseases
JAK family kinases mediate signaling of pro-inflammatory cytokines. JAK inhibitors are used to treat rheumatoid arthritis and other inflammatory conditions. The regulation of these kinases by heme suggests a link between redox status and inflammation.
From non-membrane spanning protein tyrosine kinase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of FAK in cell adhesion? | FAK knockout cell lines via CRISPR |
| How does JAK2 V617F mutation affect signaling? | Knock-in of JAK2 V617F in hematopoietic cells |
| Does heme regulate Src activity? | Point mutation of heme-binding residues in Src |
| What are the substrates of BTK? | Overexpression of tagged BTK followed by phosphoproteomics |
| Can we screen for inhibitors of JAK2? | CRISPR library screening for resistance mutations |
| How does FAK localization affect function? | Knock-in of fluorescently tagged FAK |
How to Study the non-membrane spanning protein tyrosine kinase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Phosphoproteomics | Global tyrosine phosphorylation sites | Substrate identification |
| In vitro kinase assay | Catalytic activity and kinetics | Inhibitor screening |
| CRISPR knockout screen | Gene essentiality and resistance | Target discovery |
| FRET biosensor imaging | Real-time kinase activity | Live-cell signaling dynamics |
| Western blot with phospho-specific antibodies | Specific phosphorylation events | Validation of kinase activation |
| Immunoprecipitation | Protein-protein interactions | Complex composition |
| RNA-seq | Transcriptional changes | Downstream effects of kinase activity |
Phosphoproteomics
Mass spectrometry-based phosphoproteomics allows global identification of tyrosine phosphorylation sites and quantification of changes upon kinase activation or inhibition. This method is powerful for mapping substrates of non-membrane spanning tyrosine kinases.
Kinase activity assays
In vitro kinase assays using recombinant kinases and substrate peptides measure catalytic activity and kinetics. These assays are used to determine IC50 values for inhibitors and to study the effects of mutations.
CRISPR screening
Genome-wide CRISPR knockout or activation screens can identify genes that modulate sensitivity to kinase inhibitors or that regulate kinase activity. This approach is useful for discovering synthetic lethal interactions.
Imaging and FRET biosensors
Genetically encoded FRET biosensors can visualize tyrosine kinase activity in live cells with spatiotemporal resolution. This technique helps study the dynamics of kinase signaling at focal adhesions and other compartments.
How CRISPR Can Be Used to Study GO:0004715 non-membrane spanning protein tyrosine kinase activity
Knockout
CRISPR knockout of genes encoding non-membrane spanning tyrosine kinases (e.g., PTK2, JAK2, SRC) creates cell models to study loss-of-function phenotypes. These models are valuable for validating drug targets and understanding kinase-specific contributions to signaling.
Point Mutation
Introducing specific point mutations (e.g., kinase-dead or activation-loop mutations) via CRISPR base editing or HDR allows precise dissection of catalytic activity versus scaffolding functions. For example, mutating the ATP-binding lysine can abolish kinase activity.
Knock-in
Knock-in of disease-associated mutations (e.g., JAK2 V617F) or epitope tags (e.g., GFP, HA) enables studies of mutant kinase behavior and localization in a physiological context.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of wild-type or mutant kinases can model gain-of-function states observed in cancer. Overexpression combined with phosphoproteomics reveals downstream signaling networks.
How EDITGENE Supports non-membrane spanning protein tyrosine kinase activity Research
Researchers studying non-membrane spanning protein tyrosine kinase activity-related genes often need to determine whether a candidate gene is causally involved in a specific signaling pathway or disease phenotype. This requires precise genetic manipulation to avoid confounding effects from compensatory mechanisms or off-target activities.
Contact EDITGENE today to design your custom CRISPR model for non-membrane spanning protein tyrosine kinase activity research.
Frequently Asked Questions About non-membrane spanning protein tyrosine kinase activity
What is non-membrane spanning protein tyrosine kinase activity?
It is the enzymatic activity of kinases that phosphorylate tyrosine residues on proteins but lack a transmembrane domain, as defined by GO:0004715.
What genes are involved in non-membrane spanning protein tyrosine kinase activity?
Key genes include FAK (PTK2), JAK2, SRC, JAK1, JAK3, BTK, ABL1, and others listed in the key genes table.
How is this activity regulated?
It is regulated by phosphorylation, interacting proteins, heme levels, and subcellular localization.
What diseases are associated with dysregulated non-membrane spanning tyrosine kinases?
Cancers such as leukemia, myeloproliferative neoplasms, and immune disorders like X-linked agammaglobulinemia.
What methods are used to study this activity?
Phosphoproteomics, in vitro kinase assays, CRISPR screens, and FRET biosensors.
Can CRISPR be used to study non-membrane spanning tyrosine kinases?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used.
What is the difference between non-membrane spanning and receptor tyrosine kinases?
Non-membrane spanning kinases lack a transmembrane domain and are intracellular, while receptor tyrosine kinases have an extracellular ligand-binding domain and a transmembrane region.
Which kinase is phosphorylated in response to cell attachment to fibronectin?
Focal adhesion kinase (FAK) is phosphorylated upon cell attachment to fibronectin.
How does heme affect tyrosine kinases?
Heme controls the regulation of Jak2 and Src, influencing their activity.
What are the synonyms for GO:0004715?
Synonyms include cytoplasmic protein tyrosine kinase activity, focal adhesion kinase activity, janus kinase 1/2/3 activity, Bruton's tyrosine kinase activity, and p60c-src protein tyrosine kinase activity.
Conclusion
Non-membrane spanning protein tyrosine kinase activity (GO:0004715) is a cornerstone of intracellular signal transduction, with critical roles in cell growth, adhesion, and immunity. Its dysregulation underlies numerous diseases, making it a prime target for therapeutic intervention. Advances in CRISPR-based models and phosphoproteomics continue to unravel the complexities of these kinases, offering new opportunities for drug discovery and precision medicine.
References
- 1. Hanks SK et al.. 1992. Focal adhesion protein-tyrosine kinase phosphorylated in response to cell attachment to fibronectin.. Proc Natl Acad Sci U S A 89(18):8487-91 PMID: 1528852
- 2. Yao X et al.. 2010. Heme controls the regulation of protein tyrosine kinases Jak2 and Src.. Biochem Biophys Res Commun 403(1):30-5 PMID: 21036157
