Although it is easy to lose one's way when interpreting the many biophysical approaches of analyzing the existence of lipid rafts, few conclusions could be drawn without significant dissent. Model membrane studies are vital in understanding lipid-lipid and lipid-protein interaction, but there is still a long way to go in understanding multicomponent complex biological membranes. This could be analogous to the "three-body problem" where the gravitational interaction of three masses is surprisingly difficult to solve. In the light of information that small transition energies could bring about remarkable structural changes, there may be serious problems in extending model membrane studies to biological membranes. This includes all model membrane studies which support the concept of "detergent-insoluble" complexes to describe lipid rafts. Although diffusion-based studies provide valuable live cell data, they have several drawbacks. It is not easy to interpret results from diffusion data due to a poor understanding of: (1) the diffusion of molecules in complex biological membranes; (2) the ultrastructure of biological membranes; and (3) interaction of the cytoskeleton with biological membranes. Diffusion data might provide a valuable time-kinetics, though it is difficult to deduce structural information from diffusion data with current theoretical understanding. Although homo-FRET-based studies provide an excellent source of structural information on proximity relationships derived by lipidic interactions, the relatively longer time scales of measurement mask the temporal information. In the absence of any ideal "sub-resolution ultra-fast imaging" technique, it is desirable to study chosen model raft components in a model cellular system with available biophysical techniques, and appropriate functional consequences.



anchored protein


cholera toxin B


detergent-insoluble glycolipid




dilauroyl phosphatidylcholine


dipalmitoyl phosphatidylcholine


detergent-resistant membrane


electron microscopy


endoplasmic reticulum


fluorescence correlation spectroscopy






fluorescein phosphatidylethanolamine


fluorescence recovery after photobleaching


Foerster's resonance energy transfer




giant unilamellar vesicle




human coronary artery smooth muscle


lactase-phlorizin hydrolase


methyl- b-cyclodextrin


Madin-Darby canine kidney


neural cell adhesion molecule


nuclear magnetic resonance




polyacrylamide gel electrophoresis




placental alkaline phosphatase


rat basophilic leukemia




single-particle tracking


surface scanning resistance


transient confinement zone


transferrin receptor


trans-Golgi network


yellow fluorescent protein


1 Singer, S.J. and G. L. Nicolson. The fluid mosaic model of the structure of cell membranes. Science 1972; 175(23): 720-731.

2 Jain, M.K. and H.B. White, III. Longrange order in biomembranes. Adv. Lipid Res. 1977; 15: 1-60.

3 Klausner, R. D., et al. Lipid domains in membranes. Evidence derived from structural perturbations induced by free fatty acids and lifetime heterogeneity analysis. J. Biol. Chem. 1980; 255(4): 1286-1295.

4 Simons, K. and G. van Meer. Lipid sorting in epithelial cells. Biochemistry 1988; 27(17): 6197-6202.

5 Simons, K. and E. Ikonen. Functional rafts in cell membranes. Nature 1997; 387(6633): 569-572.

6 Simons, K. and D. Toomre. Lipid rafts and signal transduction. Nat. Rev. Mol. Cell. Biol. 2000; 1(1): 31-39.

7 Chatterjee, S. and S. Mayor. The GPI-an-chor and protein sorting. Cell. Mol. Life Sci. 2001; 58(14): 1969-1987.

8 Udenfriend, S. and K. Kodukula. How gly-cosylphosphatidylinositol-anchored membrane proteins are made. Annu. Rev. Bio-chem. 1995; 64: 563-591.

9 Mayor, S. and H. Riezman. Sorting GPI-anchored proteins. Nat. Rev. Mol. Cell. Biol. 2004; 5(2): 110-120.

10 Robinson, P.J. Signal transduction via GPI-anchored membrane proteins. Adv. Exp. Med. Biol. 1997; 419: 365-370.

11 Tsui-Pierchala, B.A., et al. Lipid rafts in neuronal signaling and function. Trends Neurosci. 2002; 25(8): 412-417.

12 Horejsi, V., et al. GPI-microdomains: a role in signalling via immunoreceptors. Immunol. Today 1999; 20(8): 356-361.

13 Parton, R.G. and J.F. Hancock. Lipid rafts and plasma membrane microorganization: insights from Ras. Trends Cell Biol. 2004; 14(3): 141-147.

14 Gonen, A., P. Weisman-Shomer, and M. Fry. Cell adhesion and acquisition of detergent resistance by the cytoskeleton of cultured chick fibroblasts. Biochim. Biophys. Acta 1979; 552(2): 307-321.

15 Streuli, C.H., B. Patel, and D.R. Critchley. The cholera toxin receptor ganglioside GM remains associated with Triton X-100 cy-toskeletons of BALB/c-3T3 cells. Exp. Cell Res. 1981; 136(2): 247-254.

16 Helenius, A. and K. Simons. Solubilization of membranes by detergents. Biochim. Bio-phys. Acta 1975; 415(1): 29-79.

17 Simons, K., A. Helenius, and H. Garoff. Solubilization of the membrane proteins from Semliki Forest virus with Triton X-100. J. Mol. Biol. 1973; 80(1): 119-133.

18 Becker, R., A. Helenius, and K. Simons. Solubilization of the Semliki Forest virus membrane with sodium dodecyl sulfate. Biochemistry 1975; 14(9): 1835-1841.

19 Helenius, A., et al. Solubilization of the Semliki Forest virus membrane with sodium deoxycholate. Biochim. Biophys. Acta 1976; 436(2): 319-334.

20 Brown, D. A. and J.K. Rose. Sorting of GPI-anchored proteins to glycolipid-en-riched membrane subdomains during transport to the apical cell surface. Cell 1992; 68(3): 533-544.

21 Brown, D. A. Interactions between GPI-an-chored proteins and membrane lipids. Trends Cell Biol. 1992; 2(11): 338-343.

22 Yeagle, P. The Membranes of Cells. 2nd edn. San Diego, CA: Academic Press, 1993.

23 Lamaze, C., et al. Interleukin 2 receptors and detergent-resistant membrane domains define a clathrin-independent endo-cytic pathway. Mol. Cell 2001; 7(3): 661-671.

24 Brown, D. A. and E. London. Functions of lipid rafts in biological membranes. Annu. Rev. Cell Dev. Biol. 1998; 14: 111-136.

25 London, E. and D.A. Brown. Insolubility of lipids in Triton X-100: physical origin and relationship to sphingolipid/choles-terol membrane domains (rafts). Biochim. Biophys. Acta 2000; 1508(1-2): 182-195.

26 Shaw, A. R. and L. Li. Exploration of the functional proteome: lessons from lipid rafts. Curr. Opin. Mol. Ther. 2003; 5(3): 294-301.

27 Foster, L.J., C.L. De Hoog, and M. Mann. Unbiased quantitative proteomics of lipid rafts reveals high specificity for signaling factors. Proc. Natl. Acad. Sci. USA 2003; 100(10): 5813-5818.

28 Heerklotz, H. Triton promotes domain formation in lipid raft mixtures. Biophys. J. 2002; 83(5): 2693-2701.

29 Heerklotz, H., et al. The sensitivity of lipid domains to small perturbations demonstrated by the effect of Triton. J. Mol. Biol. 2003; 329(4): 793-799.

30 Mayor, S. and M. Rao. Rafts: scale-dependent, active lipid organization at the cell surface. Traffic 2004; 5(4): 231-240.

31 Mayor, S., K.G. Rothberg, and F.R. Max-field. Sequestration of GPI-anchored proteins in caveolae triggered by cross-linking. Science 1994; 264(5167): 1948-1951.

32 Mayor, S. and F. R. Maxfield. Insolubility and redistribution of GPI-anchored proteins at the cell surface after detergent treatment. Mol. Biol. Cell 1995; 6(7): 929-944.

33 Parton, R.G., B. Joggerst, and K. Simons. Regulated internalization of caveolae. J. Cell Biol. 1994; 127(5): 1199-1215.

34 Maunsbach, A. Immunolabeling and staining of ultrathin sections in biological electron microscopy. In: Celis, J. (Ed.). Cell Biology: A Laboratory Handbook. Academic Press: San Diego, CA, 1998.

35 Sheets, E. D., R. Simson, and K. Jacobson. New insights into membrane dynamics from the analysis of cell surface interactions by physical methods. Curr. Opin. Cell Biol. 1995; 7(5): 707-714.

36 Sheets, E. D., et al. Transient confinement of a glycosylphosphatidylinositol-anchored protein in the plasma membrane. Biochemistry 1997; 36(41): 12449-12458.

37 Dietrich, C., et al. Relationship of lipid rafts to transient confinement zones detected by single particle tracking. Biophys. J. 2002; 82(1 Pt 1): 274-284.

38 Simson, R., et al. Structural mosaicism on the submicron scale in the plasma membrane. Biophys. J. 1998; 74(1): 297-308.

39 Schutz, G.J., et al. Properties of lipid microdomains in a muscle cell membrane visualized by single molecule microscopy. EMBO J. 2000; 19(5): 892-901.

40 Pralle, A., et al. Sphingolipid-cholesterol rafts diffuse as small entities in the plasma membrane of mammalian cells. J. Cell Biol. 2000; 148(5): 997-1008.

41 Saffman, P.G. and M. Delbruck. Brownian motion in biological membranes. Proc. Natl. Acad. Sci. USA 1975; 72(8): 3111-3113.

42 Kusumi, A., I. Koyama-Honda, and K. Suzuki. Molecular dynamics and interactions for creation of stimulation-induced stabilized rafts from small unstable steady-state rafts. Traffic 2004; 5(4): 213-230.

43 Kusumi, A., et al. Paradigm shift of the plasma membrane concept from the two-dimensional continuum fluid to the partitioned fluid: high-speed single-molecules tracking of membrane molecules. Annu. Rev. Biophys. Biomol. Struct. 2005; 34: 351-378.

44 Suzuki, K., R.E. Sterba, and M.P. Sheetz. Outer membrane monolayer domains from two-dimensional surface scanning resistance measurements. Biophys. J. 2000; 79(1): 448-459.

45 Suzuki, K. and M.P. Sheetz. Binding of cross-linked glycosylphosphatidylinositol-an-chored proteins to discrete actin-associated sites and cholesterol-dependent domains. Biophys. J. 2001; 81(4): 2181-2189.

46 Ritchie, K. and A. Kusumi. Single-particle tracking image microscopy. Methods Enzy-mol. 2003; 360: 618-634.

47 Edidin, M. In: Damjanovich, S., Edidin, M., Szollosi, J., Tron, L. (Eds.). Mobility and Proximity in Biological Membranes. CRC: Boca Raton, Florida, 1994: 109-135.

48 Reits, E.A. and J.J. Neefjes. From fixed to FRAP: measuring protein mobility and activity in living cells. Nat. Cell. Biol. 2001; 3(6): E145-E147.

49 Houtsmuller, A. B. and W. Vermeulen. Macromolecular dynamics in living cell nuclei revealed by fluorescence redistribution after photobleaching. Histochem. Cell. Biol. 2001; 115(1): 13-21.

50 Lippincott-Schwartz, J. and G.H. Patterson. Development and use of fluorescent protein markers in living cells. Science 2003; 300(5616): 87-91.

51 Lippincott-Schwartz, J., N. Altan-Bonnet, and G. H. Patterson. Photobleaching and photoactivation: following protein dynamics in living cells. Nat. Cell. Biol. 2003; Suppl: S7-S14.

52 Ishihara, A., Y. Hou, and K. Jacobson. The Thy-1 antigen exhibits rapid lateral diffusion in the plasma membrane of rodent lymphoid cells and fibroblasts. Proc. Natl. Acad. Sci. USA 1987; 84(5): 1290-1293.

53 Hannan, L.A., et al. Correctly sorted molecules of a GPI-anchored protein are clustered and immobile when they arrive at the apical surface of MDCK cells. J. Cell Biol. 1993; 120(2): 353-358.

54 Oliferenko, S., et al. Analysis of CD44-con-taining lipid rafts: recruitment of annexin II and stabilization by the actin cytoskele-ton. J. Cell Biol. 1999; 146(4): 843-854.

55 Edidin, M. Patches, posts and fences: proteins and plasma membrane domains. Trends Cell Biol. 1992; 2(12): 376-380.

56 Shvartsman, D. E., et al. Differently anchored influenza hemagglutinin mutants display distinct interaction dynamics with mutual rafts. J. Cell Biol. 2003; 163(4): 879-888.

57 Niv, H., et al. Activated K-Ras and H-Ras display different interactions with saturable nonraft sites at the surface of live cells. J. Cell Biol. 2002; 157(5): 865-872.

58 Niv, H., et al. Membrane interactions of a constitutively active GFP-Ki-Ras 4B and their role in signaling. Evidence from lateral mobility studies. J. Biol. Chem. 1999; 274(3): 1606-1613.

59 Prior, I.A., et al. GTP-dependent segregation of H-ras from lipid rafts is required for biological activity. Nat. Cell. Biol. 2001; 3(4): 368-375.

60 Bulseco, D.A. and D.E. Wolf. Fluorescence correlation spectroscopy: molecular complexing in solution and in living cells. Methods Cell Biol. 2003; 72: 465498.

61 Berland, K.M. Fluorescence correlation spectroscopy: a new tool for quantification of molecular interactions. Methods Mol. Biol. 2004; 261: 383-398.

62 Haupts, U., et al. Dynamics of fluorescence fluctuations in green fluorescent protein observed by fluorescence correlation spectroscopy. Proc. Natl. Acad. Sci. USA 1998; 95(23): 13573-13578.

63 Koppel, D. E., et al. Dynamics of fluorescence marker concentration as a probe of mobility. Biophys. J. 1976; 16(11): 1315-1329.

64 Schwille, P., J. Korlach, and W.W. Webb. Fluorescence correlation spectroscopy with single-molecule sensitivity on cell and model membranes. Cytometry 1999; 36(3): 176-182.

65 Rigler, R. Fluorescence correlations, single molecule detection and large number screening. Applications in biotechnology. J. Biotechnol. 1995; 41(2-3): 177-186.

66 Korlach, J., et al. Characterization of lipid bilayer phases by confocal microscopy and fluorescence correlation spectroscopy. Proc. Natl. Acad. Sci. USA 1999; 96(15): 8461-8466.

67 Kahya, N., et al. Probing lipid mobility of raft-exhibiting model membranes by fluorescence correlation spectroscopy. J. Biol. Chem. 2003; 278(30): 28109-28115.

68 Bacia, K., et al. Fluorescence correlation spectroscopy relates rafts in model and na tive membranes. Biophys. J. 2004; 87(2): 1034-1043.

69 Lang, T., et al. SNAREs are concentrated in cholesterol-dependent clusters that define docking and fusion sites for exocyto-sis. EMBO J. 2001; 20(9): 2202-2213.

70 Chamberlain, L. H., R. D. Burgoyne, and G.W. Gould. SNARE proteins are highly enriched in lipid rafts in PC12 cells: implications for the spatial control of exocytosis. Proc. Natl. Acad. Sci. USA 2001; 98(10): 5619-5624.

71 Xia, F., et al. Disruption of pancreatic beta-cell lipid rafts modifies Kv2.1 channel gating and insulin exocytosis. J. Biol. Chem. 2004; 279(23): 24685-24691.

72 Bacia, K., P. Schwille, and T. Kurzchalia. Sterol structure determines the separation of phases and the curvature of the liquid-ordered phase in model membranes. Proc. Natl. Acad. Sci. USA 2005; 102(9): 3272-3277.

73 Hac, A. E., et al. Diffusion in two-component lipid membranes - a fluorescence correlation spectroscopy and Monte Carlo simulation study. Biophys. J. 2005; 88(1): 317-333.

74 Lakowicz, J.R. Principles of Fluorescence Spectroscopy. 2nd edn. Kluwer Academic/ Plenum Publishers, 1999.

75 Krishnan, R. V., R. Varma, and S. Mayor. Fluorescence methods to probe nanometer-scale organization of molecules in living cell membranes. J. Fluorescence 2001; 11(3): 211-226.

76 Varma, R. and S. Mayor. GPI-anchored proteins are organized in submicron domains at the cell surface. Nature 1998; 394(6695): 798-801.

77 Zacharias, D.A., et al. Partitioning of lipid-modified monomeric GFPs into membrane microdomains of live cells. Science 2002; 296(5569): 913-916.

78 Sharma, P., et al. Nanoscale organization of multiple GPI-anchored proteins in living cell membranes. Cell 2004; 116(4): 577-589.

79 Fivaz, M., et al. Differential sorting and fate of endocytosed GPI-anchored proteins. EMBO J. 2002; 21(15): 3989-4000.

80 Kenworthy, A. K. and M. Edidin. Distribution of a glycosylphosphatidylinositol-an-chored protein at the apical surface of

MDCK cells examined at a resolution of <100 A using imaging fluorescence resonance energy transfer. J. Cell Biol. 1998; 142(1): 69-84.

81 Kenworthy, A. K., N. Petranova, and M. Edidin. High-resolution FRET microscopy of cholera toxin B-subunit and GPI- anchored proteins in cell plasma membranes. Mol. Biol. Cell 2000; 11(5): 1645-1655.

82 Hatanaka, M., et al. Cellular distribution of a GPI-anchored complement regulatory protein CD59: homodimerization on the surface of HeLa and CD59-transfected CHO cells. J. Biochem. (Tokyo) 1998; 123(4): 579-586.

83 Anderson, R. G. and K. Jacobson. A role for lipid shells in targeting proteins to cav-eolae, rafts, and other lipid domains. Science 2002; 296(5574): 1821-1825.

84 Maxfield, F. R. Plasma membrane microdomains. Curr. Opin. Cell Biol. 2002; 14(4): 483-487.

85 Subczynski, W. K. and A. Kusumi. Dynamics of raft molecules in the cell and artificial membranes: approaches by pulse EPR spin labeling and single molecule optical microscopy. Biochim. Biophys. Acta 2003; 1610(2): 231-243.

86 Jacobson, K., and Dietrich. Looking at Lipid rafts? Trends Cell Biol. 1999; 9 (3): 87-91.

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