What is Phosphoinositides
Phosphoinositides (PIPs) are phosphorylated derivatives of phosphatidylinositols (PI) and serve as pivotal regulatory factors in fundamental physiological processes such as cell growth, proliferation, and motility (Cai T et al., 2015). PIPs are membrane-associated lipids that undergo dynamic phosphorylation and dephosphorylation at various positions on the inositol ring to generate a diverse array of phosphorylated derivatives, including PIP, PIP2, and PIP3, each characterized by distinct phosphate group positioning. Furthermore, individual PIPs can harbor different fatty acid chains, contributing to their structural complexity.
What Is The Function Of Phosphoinositides?
| Function | Description |
|---|---|
| Cell Signaling | Phosphoinositides serve as secondary messengers in cell signaling pathways. When cell membrane receptors are activated by external signals (e.g., hormones), enzymes modify phosphoinositides, relaying signals to the cell's interior. |
| Membrane Trafficking | Phosphoinositides regulate the movement of cellular vesicles, determining where they fuse with or bud from membranes. This process is essential for transporting molecules within cells. |
| Ion Channel Regulation | Phosphoinositides can modulate ion channel activity in cell membranes. They alter ion channel conformation, influencing ion flow in and out of cells and affecting electrical excitability. |
| Cytoskeletal Dynamics | Phosphoinositides play a role in regulating the cytoskeleton, the dynamic protein filament network that shapes cells and is involved in processes like cell division and motility. |
| Cell Growth and Differentiation | Certain phosphoinositides are involved in controlling cell growth and differentiation, influencing the balance between cell proliferation and cell death. |
| Membrane Composition | Phosphoinositides contribute to cell membrane properties, including fluidity and curvature, impacting overall membrane composition. |
| Specific Localization (e.g., PIP2, PIP3, etc.) | Different types of phosphoinositides are localized to distinct regions of the cell membrane, allowing precise regulation of cellular processes. Dysregulation can lead to various diseases. |
How Are Phosphoinositides Involved In Cell Signalling?
In mammalian cells, the most abundant phosphoinositide is phosphatidylinositol (PtdIns), which undergoes consecutive and reversible phosphorylation at the D-4 and D-5 positions by specific kinases. PtdIns is a small lipid molecule composed of an inositol ring and two fatty acid chains linked by a glycerol bond, which anchors PtdIns to the cytoplasmic surface of the cell membrane. PtdIns can be extensively phosphorylated at the 3, 4, and/or 5 hydroxyl positions of the inositol ring by various lipid kinases, resulting in a diverse array of phosphatidylinositol monophosphates (PI3P, PI4P, and PI5P), diphosphates [PI(3,4)P2, PI(3,5)P2, PI(4,5)P2], and triphosphates [PI(3,4,5)P3], collectively referred to as phosphoinositides. Site-specific lipid phosphatases can remove these phosphate groups, allowing for dynamic changes in lipid phosphorylation states.
Typically, phosphatidylinositol monophosphates are found in intracellular membranes (e.g., endocytic vesicles, Golgi apparatus, nucleus), while diphosphates and triphosphates are located in the plasma membrane. PtdIns (synthesized in the endoplasmic reticulum) and phosphoinositides shuttle between various subcellular compartments via intracellular vesicles, which associate with their corresponding modifying enzymes.
Phosphoinositides serve as universal signaling entities that regulate cellular activities either through direct interactions with membrane proteins (such as ion channels and GPCRs) or by recruiting cytoplasmic proteins. Cytoplasmic proteins contain structural domains that can directly bind to phosphoinositides, including Pleckstrin Homology (PH), FYVE, WD40 repeats, FERM, PTB, and PDZ domains, among others.
Among phosphoinositides, PI(3,4,5)P3 has been extensively studied. It is generated during the synthesis of PI(4,5)P2 through the action of class I PI3K and can be dephosphorylated by PTEN. Class I PI3K and PTEN are central mediators of receptor tyrosine kinase-induced Akt signaling and are frequently mutated in various forms of cancer. In addition to their roles in cell proliferation, survival, and metabolism associated with Akt signaling, phosphoinositide signaling induces changes in cell morphology and actin remodeling, mediates clathrin-mediated endocytosis, vesicle transport, membrane dynamics, autophagy, cell division/cytokinesis, cell migration, and responses to UV stress.
Targeted Phosphoinositides Analysis Service
The quantitative analysis of intracellular phosphoinositides is crucial for studying their roles in cellular function under both physiological and pathological conditions. At Creative Proteomics, we offer two quantitative approaches for PIPs detection. The first method is based on ion chromatography separation technology, allowing for precise quantification of the total levels of PIP, PIP2, and PIP3. The second method utilizes LC/MS technology, suitable for the quantification of PIP, PIP2, and PIP3 with specific fatty acid chain structural details.
Advantages of Our Targeted Phosphoinositides Analysis
- Rapid, simple, and sensitive workflow.
- Enables the imultaneous identification of PtdInsP3, PtdInsP2, PtdInsP.
- We were able to identify more than 90 phosphoinositides from different biological samples.
- Minimizes matrix effects or run-to-run differences that could potentially affect results.
- The remaining limitation to identify regioisomers of polyphosphoinositides could be resolved by combining our method with the appropriate phromatographic separation methods
Sample Requirement
- Normal Volume: 200 uL plasma, 20 mg tissue, 1e7 cells
- Minimal Volume: 50 uL, 5 mg tissue, 6e6 cells
Report
- A full report including all raw data, MS/MS instrument parameters and step-by-step calculations will be provided (Excel and PDF formats).
- Analytes are reported as uM, with CV's generally ~10%.
Ordering Procedure:
With integrated set of separation, characterization, identification and quantification systems featured with excellent robustness & reproducibility, high and ultra-sensitivity, Creative Proteomics provides reliable, rapid and cost-effective Phosphoinositides targeted lipidomics services.
References
- Cai T, Shu Q, Hou J, Liu P, Niu L, Guo X, et al. Profiling and relative quantitation of phosphoinositides by multiple precursor ion scanning based on phosphate methylation and isotopic labeling. Anal Chem. 2015; 87(1): 513-21.
- Kanehara K, Yu CY, Cho Y, Cheong WF, Torta F, Shui G, et al. Arabidopsis AtPLC2 Is a Primary Phosphoinositide-Specific Phospholipase C in Phosphoinositide Metabolism and the Endoplasmic Reticulum Stress Response. PLoS Genet. 2015; 11(9):e1005511.
- Clark J, Anderson KE, Juvin V, Smith TS, Karpe F, Wakelam MJ, et al. Quantification of PtdInsP3 molecular species in cells and tissues by mass spectrometry. Nature methods. 2011; 8(3): 267-72.