Absence of clustering of phosphatidylinositol-(4,5)-bisphosphate in fluid phosphatidylcholine

Faébio Fernandes,Luiés M.S Loura,Alexander Fedorov,Manuel Prieto

doi:10.1194/jlr.m600121-jlr200

Abstract

Phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)] plays a key role in the modulation of actin polymerization and vesicle trafficking. These processes seem to depend on the enrichment of PI(4,5)P(2) in plasma membrane domains. Here, we show that PI(4,5)P(2) does not form domains when in a fluid phosphatidylcholine matrix in the pH range of 4.8-8.4. This finding is at variance with the spontaneous segregation of PI(4,5)P(2) to domains as a mechanism for the compartmentalization of PI(4,5)P(2) in the plasma membrane. Water/bilayer partition of PI(4,5)P(2) is also shown to be dependent on the protonation state of the lipid.

Highlights

Phosphatidylinositol-(4,5)-bisphosphate [PI[4,5] P2] plays a key role in the modulation of actin polymerization and vesicle trafficking
The Kp values obtained at pH 8.4, 7.1, and 4.8 for water/ POPC partition were (5.38 6 0.60) 3 104, (1.84 6 0.14) 3 104, and (2.18 6 0.18) 3 104, respectively, whereas for micelle/POPG partition, these were (1.84 6 0.33) 3 104, (2.29 6 0.38) 3 104, and (1.47 6 0.18) 3 103, respectively
The authors interpreted the decrease of energy transfer efficiencies at high pH [.Pka2 of PI[4,5]P2] as a demixing between PI[4,5]P2 and POPC

Summary

Introduction

Phosphatidylinositol-(4,5)-bisphosphate [PI[4,5] P2] plays a key role in the modulation of actin polymerization and vesicle trafficking. These processes seem to depend on the enrichment of PI[4,5]P2 in plasma membrane domains. We show that PI[4,5]P2 does not form domains when in a fluid phosphatidylcholine matrix in the pH range of 4.8–8.4 This finding is at variance with the spontaneous segregation of PI[4,5]P2 to domains as a mechanism for the compartmentalization of PI[4,5]P2 in the plasma membrane.

Methods

Results

Conclusion