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Single-molecule Super-resolution Imaging of Phosphatidylinositol 4,5-bisphosphate in the Plasma Membrane with Novel Fluorescent Probes
Published on: October 15, 2016
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PI(4,5)P2 diffuses freely in the plasma membrane even within high-density effector protein complexes.
Jonathan Pacheco1, Anna C Cassidy1, James P Zewe1
1Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA.
The Journal of Cell Biology
|November 23, 2022
Summary
Phosphatidyl-D-myo-inositol-4,5-bisphosphate [PI(4,5)P2] rapidly diffuses in the plasma membrane. PI(4,5)P2 mobility is only slowed by spectrin and septin cytoskeletons, not other effector protein complexes.
Area of Science:
- Cell biology
- Membrane biophysics
- Lipid signaling
Background:
- Phosphatidyl-D-myo-inositol-4,5-bisphosphate [PI(4,5)P2] is a key regulator of plasma membrane (PM) functions.
- PI(4,5)P2 effector proteins control transport, signaling, and cytoskeletal dynamics.
- The mechanism by which PI(4,5)P2 orchestrates diverse PM processes remains unclear.
Purpose of the Study:
- To investigate if spatially distinct PI(4,5)P2 pools associate with different PM complexes.
- To test the hypothesis that PI(4,5)P2 pools are segregated to regulate distinct cellular processes.
Main Methods:
- Utilized biosensors to measure PI(4,5)P2 mobility.
- Employed single-particle tracking techniques to analyze lipid diffusion dynamics.
- Quantified the impact of PI(4,5)P2-dependent complexes on PI(4,5)P2 lateral mobility.
Main Results:
- PM lipids, including PI(4,5)P2, exhibit rapid Brownian motion (∼0.3 µm2/s).
- PI(4,5)P2 molecules spend approximately one-third of their time diffusing more slowly.
- PI(4,5)P2 mobility was not significantly reduced by PI(4,5)P2-dependent complexes at clathrin-coated pits or focal adhesions.
- Only spectrin and septin cytoskeletons demonstrably reduced PI(4,5)P2 diffusion.
Conclusions:
- The lateral mobility of PI(4,5)P2 is largely independent of most effector protein complexes.
- Spectrin and septin cytoskeletons are key regulators of PI(4,5)P2 diffusion.
- The findings question the role of spatially segregated PI(4,5)P2 pools in organizing PM functions.
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