Lipid rafts are membrane domains enriched in cholesterol and sphingolipids and their importance is constantly increasing: they are involved in membrane organization and internal signaling since different membrane receptors also engages lipid rafts during signaling (i.e.TCR and H-Ras) . After reading different papers, many aspects of lipid rafts biophysics are now clear to me but one is still obscure: why only particular protein receptors are associated to rafts? what are the factors that determine this specificity?
Hi Giulio.
Since you've read around in the literature you'll be aware that rafts are a diverse collection of membrane platforms that differ in both composition (both protein and lipid) and stability. The current evidence favours a combination of factors that influence targeting to and dwell-time in such platforms that include acylation, amino acid sequence adjacent to acylation, membrane penetrating or spanning sequences, and protein-interaction domains. In other words, there isn´t a simple answer to your question.
I've talked to a number of membrane biophysicists who deny that the canonical "lipid rafts" even exist in biological membranes at physiological temperatures, except in the trivial sense that such membranes are inhomogeneous. And certainly the relationship between such membrane domains and the experimental cold detergent-resistant fractions is much questioned.
Nat Commun. 2015 Apr 21;6:6969. doi: 10.1038/ncomms7969.
GPI-anchored proteins do not reside in ordered domains in the live cell plasma membrane.
Sevcsik E1, Brameshuber M1, Fölser M1, Weghuber J2, Honigmann A3, Schütz GJ1.
I am not an expert in lipid rafts but perhaps you might find the above mentioned article interesting.
I only have a very general answer... Rafts represent a phase with a rather high degree of molecular order. Incorporation of molecules into rafts is basically determined by thermodynamics of the system. So the ability of lipid and protein molecules to join rafts will depend on how well they fit into this phase without disturbing its orderliness. On the other hand, raft edges can be considered as a specific molecular surface, and association of other molecules with it should obey the general principles of molecular interactions.
Hi Giulio.
Since you've read around in the literature you'll be aware that rafts are a diverse collection of membrane platforms that differ in both composition (both protein and lipid) and stability. The current evidence favours a combination of factors that influence targeting to and dwell-time in such platforms that include acylation, amino acid sequence adjacent to acylation, membrane penetrating or spanning sequences, and protein-interaction domains. In other words, there isn´t a simple answer to your question.
I've talked to a number of membrane biophysicists who deny that the canonical "lipid rafts" even exist in biological membranes at physiological temperatures, except in the trivial sense that such membranes are inhomogeneous. And certainly the relationship between such membrane domains and the experimental cold detergent-resistant fractions is much questioned.
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