Anomalous Diffusion of Major Histocompatibility Complex Class I Molecules on HeLa Cells Determined by Single Particle Tracking

Smith, Patricia R.; Morrison, Ian; Wilson, Keith; Fernández, Nelson; Cherry, Richard J.

doi:10.1016/s0006-3495(99)77486-2

Cited by 172 publications

(137 citation statements)

References 68 publications

(84 reference statements)

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“…1 also is not appropriate when the population contains different mobility fractions. Such heterogeneous populations can be analyzed much better and the mobility modes dissected to a certain degree by an analysis of jump-distance distributions (34,43,44). In this type of analysis, the probability p(r, t)dr that a particle starting at the origin will be encountered within a shell of radius r and a width dr at time t is considered.…”

Section: The Quantitative Analysis Of U1 Snrnp Trajectories Suggests mentioning

confidence: 99%

High intranuclear mobility and dynamic clustering of the splicing factor U1 snRNP observed by single particle tracking

Kues

Dickmanns

Lührmann

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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Uridine-rich small nuclear ribonucleoproteins (U snRNPs) are components of the splicing machinery that removes introns from precursor mRNA. Like other splicing factors, U snRNPs are diffusely distributed throughout the nucleus and, in addition, are concentrated in distinct nuclear substructures referred to as speckles. We have examined the intranuclear distribution and mobility of the splicing factor U1 snRNP on a single-molecule level. Isolated U1 snRNPs were fluorescently labeled and incubated with digitoninpermeabilized 3T3 cells in the presence of Xenopus egg extract. By confocal microscopy, U1 snRNPs were found to be imported into nuclei, yielding a speckled intranuclear distribution. Employing a laser video-microscope optimized for high sensitivity and high speed, single U1 snRNPs were visualized and tracked at a spatial precision of 35 nm and a time resolution of 30 ms. The singleparticle data revealed that U1 snRNPs occurred in small clusters that colocalized with speckles. In the clusters, U1 snRNPs resided for a mean decay time of 84 ms before leaving the optical slice in the direction of the optical axis, which corresponded to a mean effective diffusion coefficient of 1 m 2 ͞s. An analysis of the trajectories of single U1 snRNPs revealed that at least three kinetic classes of low, medium, and high mobility were present. Moreover, the mean square displacements of these fractions were virtually independent of time, suggesting arrays of binding sites. The results substantiate the view that nuclear speckles are not rigid structures but highly dynamic domains characterized by a rapid turnover of U1 snRNPs and other splicing factors.T he splicing of precursor mRNA in the nucleus is catalyzed by supramolecular assemblies designated as spliceosomes, which comprise more than 70 different proteins and five uridinerich small nuclear RNAs (snRNA; ref. 1). Most of these proteins and the snRNAs are organized in the Uridine-rich small nuclear ribonucleoproteins (U snRNPs), which are classified as U1, U2, U5, and U4͞U6, according to the snRNAs they contain. The snRNAs U1, U2, U4, and U5 are synthesized in the nucleus with a 5Ј-terminal monomethyl-guanosine (m 7 G)-cap structure, transiently exported into the cytoplasm, where a common set of seven core proteins (Sm proteins) bind to the snRNAs Sm site and form a ribonucleoprotein complex called ''Sm core'' (2). Stable association of all Sm proteins is necessary for hypermethylation of the m 7 G cap to the 2,2,7-trimethyl-guanosine (m 3 G)-cap structure (3, 4). Also, several proteins associate specifically with the individual U snRNPs; in the case of U1, those proteins are 70K, U1-A, and U1-C (5). After cap modification and 3Јend processing of the snRNAs (6), the mature snRNP particles are reimported into the nucleus by import receptors. The nuclear localization signal of U1 snRNPs is complex, with the m 3 G-cap structure representing one important signaling component (7,8). A second component is located at the Sm core but has not been defined precisely yet (9). Recent...

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Section: The Quantitative Analysis Of U1 Snrnp Trajectories Suggests mentioning

confidence: 99%

High intranuclear mobility and dynamic clustering of the splicing factor U1 snRNP observed by single particle tracking

Kues

Dickmanns

Lührmann

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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“…In particular, living cells provide striking examples for systems where subdiffusion has been repeatedly observed experimentally, either in the cytoplasm (6)(7)(8)(9), the nucleus (10,11), or the plasmic membrane (12)(13)(14). However, the microscopic origin of subdiffusion in cells is still debated, even if believed to be caused by crowding effects in a wide sense, as indicated by in vitro experiments (15)(16)(17)(18).…”

mentioning

confidence: 99%

Probing microscopic origins of confined subdiffusion by first-passage observables

Condamin

Tejedor

Voituriez

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

195

165

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Subdiffusive motion of tracer particles in complex crowded environments, such as biological cells, has been shown to be widespread. This deviation from Brownian motion is usually characterized by a sublinear time dependence of the mean square displacement (MSD). However, subdiffusive behavior can stem from different microscopic scenarios that cannot be identified solely by the MSD data. In this article we present a theoretical framework that permits the analytical calculation of first-passage observables (mean first-passage times, splitting probabilities, and occupation times distributions) in disordered media in any dimensions. This analysis is applied to two representative microscopic models of subdiffusion: continuous-time random walks with heavy tailed waiting times and diffusion on fractals. Our results show that first-passage observables provide tools to unambiguously discriminate between the two possible microscopic scenarios of subdiffusion. Moreover, we suggest experiments based on first-passage observables that could help in determining the origin of subdiffusion in complex media, such as living cells, and discuss the implications of anomalous transport to reaction kinetics in cells.anomalous diffusion ͉ cellular transport ͉ reaction kinetics ͉ random motion I n the past few years, subdiffusion has been observed in an increasing number of systems (1, 2), ranging from physics (3, 4) or geophysics (5) to biology (6, 7). In particular, living cells provide striking examples for systems where subdiffusion has been repeatedly observed experimentally, either in the cytoplasm (6-9), the nucleus (10, 11), or the plasmic membrane (12-14). However, the microscopic origin of subdiffusion in cells is still debated, even if believed to be caused by crowding effects in a wide sense, as indicated by in vitro experiments (15-18).The subdiffusive behavior significantly deviates from the usual Gaussian solution of the simple diffusion equation, and is usually characterized by a mean square displacement (MSD) (1) that scales as ͗⌬r 2 ͘ ϳ t ␤ with ␤ Ͻ 1. Such a scaling law can be obtained from a few models based on different underlying microscopic mechanisms. Here, we focus on two possibilities (a third classical model of subdiffusion is given by the fractional Brownian motion that concerns processes with long-range correlations): (i) The first class of models that we consider stems from continuous time random walks (CTRWs) (1, 19) and their continuous limit described by fractional diffusion equations (1, 20). The anomalous behavior in these models originates from a heavy-tailed distribution of waiting times (21): at each step the walker lands on a trap, where it can be trapped for extended periods of time. When dealing with a tracer particle, traps can be out-of-equilibrium chemical binding configurations (22, 23), and the waiting times are then the dissociation times; traps can also be realized by the free cages around the tracer in a hard sphere-like crowded environment, and the waiting times are the life times of the ...

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“…Studies using single particle tracking (SPT) showed mobile MHC I molecules following anomalous diffusion (i.e. nonlinear time dependence) over time scales of 100 ms to 300 s or transient confinements within domains of various sizes (13)(14)(15)(16). The lateral diffusion of MHC-I molecules in plasma membranes was increased upon truncation of their cytoplasmic tail or replacement of their transmembrane and intracellular portions with a glycosylphosphatidylinositol (GPI) anchor (12,16).…”

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confidence: 99%

Increased Mobility of Major Histocompatibility Complex I-Peptide Complexes Decreases the Sensitivity of Antigen Recognition

Segura

Guillaume

Mark

et al. 2008

Journal of Biological Chemistry

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Anomalous Diffusion of Major Histocompatibility Complex Class I Molecules on HeLa Cells Determined by Single Particle Tracking

Cited by 172 publications

References 68 publications

High intranuclear mobility and dynamic clustering of the splicing factor U1 snRNP observed by single particle tracking

High intranuclear mobility and dynamic clustering of the splicing factor U1 snRNP observed by single particle tracking

Probing microscopic origins of confined subdiffusion by first-passage observables

Increased Mobility of Major Histocompatibility Complex I-Peptide Complexes Decreases the Sensitivity of Antigen Recognition

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