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(poly) Phosphoinositide phosphorylation is a marker for plasma membrane in Friend erythroleukaemic cells
Abstract:
Upon subcellular fractionation of (murine) Friend erythroleukaemic cells (FELCs), purified plasma membranes were identified by their high enrichment in specific marker enzymes and typical plasma membrane lipids. When FELCs were incubated for short periods with 32Pi before cell fractionation, the lipid-bound radioactivity was almost exclusively present in phosphatidylinositol-4-phosphate (DPI) and phosphatidylinositol-4,5-bisphosphate (TPI), and its distribution closely matched that of the plasma membrane markers. In addition, purified plasma membranes actively incorporated 32P from [gamma-32P]ATP into polyphosphoinositides, and the specific activities of the involved kinases were again mostly enriched in the plasma membrane fraction.
Insights
Researchers found that phosphatidylinositol phosphates (PIPs) are concentrated in the plasma membranes of murine Friend erythroleukaemic cells (FELCs). These membranes also actively synthesize PIPs, indicating their crucial role in cell function.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Friend erythroleukaemic cells (FELCs) are a model system for studying erythroid differentiation.
- Plasma membranes play critical roles in cellular communication and transport.
- Polyphosphoinositides (PIPs) are key signaling lipids involved in various cellular processes.
Purpose of the Study:
- To investigate the localization and synthesis of polyphosphoinositides (PIPs) in murine Friend erythroleukaemic cells (FELCs).
- To determine if PIPs are enriched in the plasma membrane fraction of FELCs.
- To examine the activity of PIP-synthesizing kinases in purified plasma membranes.
Main Methods:
- Subcellular fractionation of murine Friend erythroleukaemic cells (FELCs).
- Enzymatic assays to identify plasma membrane markers.
- Radioactive labeling with 32P to trace lipid incorporation.
- Analysis of lipid-bound radioactivity and kinase activity in isolated fractions.
Main Results:
- Purified plasma membranes from FELCs showed enrichment in specific marker enzymes and lipids.
- Radioactivity from 32P was predominantly found in phosphatidylinositol-4-phosphate (PI(4)P) and phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) within the plasma membrane fraction.
- Isolated plasma membranes actively incorporated 32P into PIPs from [gamma-32P]ATP.
- Kinases responsible for PIP synthesis were significantly enriched in the plasma membrane fraction.
Conclusions:
- Polyphosphoinositides (PIPs), specifically PI(4)P and PI(4,5)P2, are localized to the plasma membrane of FELCs.
- The plasma membrane of FELCs is an active site for PIP synthesis.
- These findings highlight the importance of plasma membrane-associated PIPs in FELC biology.