Single Molecule Analysis of Chemotactic Signaling in Dictyostelium Cells

CHEMOATTRACTANT SIGNALING IN DICTYOSTELIUM DISCOIDEUM

“…Studies performed earlier on cAMP binding show that dissociation was multiphasic, which may be consistent with this finding (van Haastert 1983). In membranes, GTP increases the dissociation rate of Cy3-cAMP and this rate depends on G protein, which suggests that these proteins stabilize ligand binding (Ueda et al 2001), consistent with previous studies (Wu et al 1995).…”

CHEMOATTRACTANT SIGNALING IN DICTYOSTELIUM DISCOIDEUM

“…Studies performed earlier on cAMP binding show that dissociation was multiphasic, which may be consistent with this finding (van Haastert 1983). In membranes, GTP increases the dissociation rate of Cy3-cAMP and this rate depends on G protein, which suggests that these proteins stabilize ligand binding (Ueda et al 2001), consistent with previous studies (Wu et al 1995).…”

Mobility of G Proteins is Heterogeneous and Polarized During Chemotaxis

“…We and other groups have shown before that polarization in chemotaxing D. discoideum cells is present at the level of the GPCR (Ueda et al, 2001;de Keijzer et al, 2008). Here, we extended our model and show an F-actin-dependent, leading-edgespecific immobilization of the G heterodimer, which is an important mediator of chemotactic responses.…”

“…Despite extensive research, relocation of neither the receptor nor the G protein has ever been observed. Protein behavior and activation can be different at different locations owing to local variations in membrane curvature (Fischer et al, 2007), activated signaling cascades (Ueda et al, 2001) and the presence of signaling scaffolds (Pawson and Scott, 1997). Our experiments here show, as for the cAMP receptor, that cell polarization is reflected in a dynamic Fig.…”

Directional sensing and chemotaxis in eukaryotic cells - a quantitative study

“…If we add to these two properties the fact that the probability to have two binding events in a very small time interval should essentially be zero, we get the result that binding is a Poisson process. This has been confirmed experimentally by Ueda et al in [118]. In a uniform concentration C of cAMP, the number of occupied receptors R * is :…”

CHEMOATTRACTANT SIGNALING IN DICTYOSTELIUM DISCOIDEUM

“…Studies performed earlier on cAMP binding show that dissociation was multiphasic, which may be consistent with this finding (van Haastert 1983). In membranes, GTP increases the dissociation rate of Cy3-cAMP and this rate depends on G protein, which suggests that these proteins stabilize ligand binding (Ueda et al 2001), consistent with previous studies (Wu et al 1995).…”

Mobility of G Proteins is Heterogeneous and Polarized During Chemotaxis

“…We and other groups have shown before that polarization in chemotaxing D. discoideum cells is present at the level of the GPCR (Ueda et al, 2001;de Keijzer et al, 2008). Here, we extended our model and show an F-actin-dependent, leading-edgespecific immobilization of the G heterodimer, which is an important mediator of chemotactic responses.…”

“…Despite extensive research, relocation of neither the receptor nor the G protein has ever been observed. Protein behavior and activation can be different at different locations owing to local variations in membrane curvature (Fischer et al, 2007), activated signaling cascades (Ueda et al, 2001) and the presence of signaling scaffolds (Pawson and Scott, 1997). Our experiments here show, as for the cAMP receptor, that cell polarization is reflected in a dynamic Fig.…”

Directional sensing and chemotaxis in eukaryotic cells - a quantitative study

“…If we add to these two properties the fact that the probability to have two binding events in a very small time interval should essentially be zero, we get the result that binding is a Poisson process. This has been confirmed experimentally by Ueda et al in [118]. In a uniform concentration C of cAMP, the number of occupied receptors R * is :…”

CHEMOATTRACTANT SIGNALING IN DICTYOSTELIUM DISCOIDEUM

“…Studies performed earlier on cAMP binding show that dissociation was multiphasic, which may be consistent with this finding (van Haastert 1983). In membranes, GTP increases the dissociation rate of Cy3-cAMP and this rate depends on G protein, which suggests that these proteins stabilize ligand binding (Ueda et al 2001), consistent with previous studies (Wu et al 1995).…”

Mobility of G Proteins is Heterogeneous and Polarized During Chemotaxis

“…We and other groups have shown before that polarization in chemotaxing D. discoideum cells is present at the level of the GPCR (Ueda et al, 2001;de Keijzer et al, 2008). Here, we extended our model and show an F-actin-dependent, leading-edgespecific immobilization of the G heterodimer, which is an important mediator of chemotactic responses.…”

“…Despite extensive research, relocation of neither the receptor nor the G protein has ever been observed. Protein behavior and activation can be different at different locations owing to local variations in membrane curvature (Fischer et al, 2007), activated signaling cascades (Ueda et al, 2001) and the presence of signaling scaffolds (Pawson and Scott, 1997). Our experiments here show, as for the cAMP receptor, that cell polarization is reflected in a dynamic Fig.…”

Directional sensing and chemotaxis in eukaryotic cells - a quantitative study

“…If we add to these two properties the fact that the probability to have two binding events in a very small time interval should essentially be zero, we get the result that binding is a Poisson process. This has been confirmed experimentally by Ueda et al in [118]. In a uniform concentration C of cAMP, the number of occupied receptors R * is :…”