Partitioning of Dual-Lipidated Peptides into Membrane Microdomains:  Lipid Sorting vs Peptide Aggregation

Janosch, Sascha; Nicolini, Chiara; Ludolph, Björn; Peters, Carsten; Völkert, Martin; Hazlet, Theodore L; Gratton, Enrico; Waldmann, Herbert; Winter, Roland

doi:10.1021/ja049922i

Cited by 59 publications

(49 citation statements)

References 42 publications

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“…However, it is important to appreciate that the lipid anchor also has the capacity to modify its immediate lipid environment -for example, to facilitate or inhibit the chain and translational ordering of adjacent phospholipids. These phenomena have been clearly shown for lipidated peptides that interact with model membranes [33][34][35][36][37] 40 . It is also worth considering whether the plasma-membrane picket fence…”

Section: Determinants Of Raft Stabilitymentioning

confidence: 82%

Lipid rafts: contentious only from simplistic standpoints

Hancock

2006

Nat Rev Mol Cell Biol

749

716

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The hypothesis that lipid rafts exist in plasma membranes and have crucial biological functions remains controversial. The lateral heterogeneity of proteins in the plasma membrane is undisputed, but the contribution of cholesterol-dependent lipid assemblies to this complex, non-random organization promotes vigorous debate. In the light of recent studies with model membranes, computational modelling and innovative cell biology, I propose an updated model of lipid rafts that readily accommodates diverse views on plasma-membrane micro-organization.A widely accepted hypothesis in contemporary cell biology is that freely diffusing, stable, lateral assemblies of sphingolipids and cholesterol, which are termed lipid rafts 1-3 , constitute an important organizing principle for the plasma membrane. The basic concept is that lipid rafts can facilitate selective protein-protein interactions by selectively excluding or including proteins. This lipid-based sorting mechanism has been widely implicated in the assembly of transient signalling platforms and more permanent structures such as the immunological synapse, as well as in the sorting of proteins for entry into specific exocytic and endocytic trafficking pathways [1][2][3] . Despite the undoubted theoretical utility of lipid rafts to many cell biological processes, the basic hypothesis that stable lipid rafts exist at all in biological membranes is under intense scrutiny 4,5 . This is partly because lipid rafts, if they exist in resting cell membranes, are too small to be resolved by fluorescent microscopy and have no defined ultrastructure; therefore, proving their existence is problematic. This article will consider the biophysical properties of model membranes that underpin the lipid raft hypothesis, and the limitations of the biochemical approaches that have been used to study rafts in biological membranes that largely account for the current debate on the hypothesis mentioned above. After examining the challenges that are involved in correlating observations, which have been made in model and cellular membranes, I focus on synthesizing recent data on the size of lipid domains in model membranes with observations that have been obtained by imaging intact plasma membranes. These imaging approaches include single particle tracking (SPT), single fluorophore video tracking (SFVT), fluorescence resonance energy transfer (FRET), homo-FRET and electron microscopy (EM). On the one hand, these studies challenge the simplistic null hypothesis that lipid-based assemblies, such as lipid rafts, do not exist in biological membranes. On the other hand, it is timely to reconsider the raft hypothesis in the light of these new data because the consensus model that emerges is more complex than a simplistic notion of stable, freely diffusing lipid rafts. Some intriguing new questions aboutCompeting interests statement The author declares no competing financial interests. DATABASES

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Section: Determinants Of Raft Stabilitymentioning

confidence: 82%

Lipid rafts: contentious only from simplistic standpoints

Hancock

2006

Nat Rev Mol Cell Biol

749

716

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“…In a chemical biological approach to clarify some of these aspects for membraneembedded lipidated proteins, the effects of a fluorescent peptide on model membranes consisting of binary and ternary lipid mixtures were explored. [137] The peptide contained a farnesyl and a palmitoyl anchor, thus representing a membrane-recognition model system for N-Ras proteins. Specifically, the influence of the peptide on lipid lateral organization and concentration fluctuations as well as the possibility of molecular sorting of lipids by the embedded peptide was explored.…”

Section: Membrane Subdomain Bindingmentioning

confidence: 99%

Lipidated Ras and Rab Peptides and Proteins—Synthesis, Structure, and Function

et al. 2006

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Chemical biology can be defined as the study of biological phenomena from a chemical approach. Based on the analysis of relevant biological phenomena and their structural foundation, unsolved problems are identified and tackled through a combination of chemistry and biology. Thus, new synthetic methods and strategies are developed and employed for the construction of compounds that are used to investigate biological procedures. Solid-phase synthesis has emerged as the preferred method for the synthesis of lipidated peptides, which can be chemoselectively ligated to proteins of the Ras superfamily. The generated peptides and proteins have solved biological questions in the field of the Ras-superfamily GTPases that are not amendable to chemical or biological techniques alone.

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“…Ultimately this model will need to be refined with data on precisely how the C-terminal anchor of H-ras inserts into lipid bilayers and how GTP loading modulates this insertion. Recent studies investigating the structure and interaction of an N-ras C-terminal membrane anchor with model membranes are beginning to define the biophysical principles underlying the membrane attachment of prenylated and palmitoylated anchors (15,24,26). These studies show how the single palmitate of N-ras operating with the C-terminal prenylated, methylated cysteine inserts the C-terminal peptide sequence deep within the membrane bilayer.…”

mentioning

confidence: 99%

Individual Palmitoyl Residues Serve Distinct Roles in H-Ras Trafficking, Microlocalization, and Signaling

Roy

Plowman

Rotblat

et al. 2005

Molecular and Cellular Biology

197

257

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H-ras is anchored to the plasma membrane by two palmitoylated cysteine residues, Cys181 and Cys184, operating in concert with a C-terminal S-farnesyl cysteine carboxymethylester. Here we demonstrate that the two palmitates serve distinct biological roles. Monopalmitoylation of Cys181 is required and sufficient for efficient trafficking of H-ras to the plasma membrane, whereas monopalmitoylation of Cys184 does not permit efficient trafficking beyond the Golgi apparatus. However, once at the plasma membrane, monopalmitoylation of Cys184 supports correct GTP-regulated lateral segregation of H-ras between cholesterol-dependent and cholesterol-independent microdomains. In contrast, monopalmitoylation of Cys181 dramatically reverses Hras lateral segregation, driving GTP-loaded H-ras into cholesterol-dependent microdomains. Intriguingly, the Cys181 monopalmitoylated H-ras anchor emulates the GTP-regulated microdomain interactions of N-ras. These results identify N-ras as the Ras isoform that normally signals from lipid rafts but also reveal that spacing between palmitate and prenyl groups influences anchor interactions with the lipid bilayer. This concept is further supported by the different plasma membrane affinities of the monopalmitoylated anchors: Cys181-palmitate is equivalent to the dually palmitoylated wild-type anchor, whereas Cys184-palmitate is weaker. Thus, membrane affinity of a palmitoylated anchor is a function both of the hydrophobicity of the lipid moieties and their spatial organization. Finally we show that the plasma membrane affinity of monopalmitoylated anchors is absolutely dependent on cholesterol, identifying a new role for cholesterol in promoting interactions with the raft and nonraft plasma membrane.Ras GTPases operate as plasma membrane-localized molecular switches that regulate multiple signal transduction pathways. The three ubiquitously expressed Ras isoforms, H-, N-, and K-ras, are anchored to the inner surface of the plasma membrane by a C-terminal S-farnesyl cysteine carboxy methylester acting in concert with a second signal. The S-farnesyl cysteine carboxy methylester is generated by a triplet of post-

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Partitioning of Dual-Lipidated Peptides into Membrane Microdomains: Lipid Sorting vs Peptide Aggregation

Cited by 59 publications

References 42 publications

Lipid rafts: contentious only from simplistic standpoints

Lipid rafts: contentious only from simplistic standpoints

Lipidated Ras and Rab Peptides and Proteins—Synthesis, Structure, and Function

Individual Palmitoyl Residues Serve Distinct Roles in H-Ras Trafficking, Microlocalization, and Signaling

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