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Does PtdIns(4,5) P 2 concentrate so it can multitask?
Author(s) -
Hammond Gerald,
Balla Tamas
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.568.22
Subject(s) - biosensor , chemistry , resolution (logic) , lipid bilayer , membrane , biophysics , molecule , nanotechnology , diffusion , materials science , biochemistry , biology , physics , computer science , organic chemistry , artificial intelligence , thermodynamics
PtdIns(4,5) P 2 drives many plasma membrane (PM) functions which can be summarized as the delivery of materials and information into, out of and across the membrane, as well as the assembly of structural components. How does the lipid execute so many disparate functions involving a vast array of different protein complexes? A leading hypothesis is that the PM organizes into nanoscopic PtdIns(4,5) P 2 ‐rich platforms that associate with specific molecular complexes. Here, we have employed single molecule, super‐resolution techniques to test this hypothesis. Imaging fixed cells expressing PtdIns(4,5) P 2 biosensors (< 40 nm resolution) reveals no evidence for discrete domains. Experiments where the dynamics of biosensor molecules are tracked in living cells reveals rapid diffusion of biosensor/PtdIns(4,5) P 2 in the PM, indicating that biosensor:lipid complexes may be released from pre‐existing PtdIns(4,5) P 2 ‐rich platforms. On the other hand, diffusion of biosensor/lipid complexes shows clear signs of anomalous diffusion. To circumvent potential occlusion of PtdIns(4,5) P 2 ‐rich platforms by an expressed biosensor, we have interrogated isolated plasma membrane sheets with exogenous PtdIns(4,5) P 2 probes. Again, these results reveal no evidence for PtdIns(4,5) P 2 ‐rich platforms at a resolution levels of < 40 nm. Given the rapid diffusion of the free lipid molecules across such small distances as this, our results are inconsistent with pre‐existing PtdIns(4,5) P 2 ‐rich platforms that recruit protein complexes. Rather, it seems more likely that protein complexes recruit the lipid into functionally dedicated complexes in the PM.