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D Lauffenburger

Publications and source records attributed to D Lauffenburger.

11 recordsLinked to original sources
PubMed2006

Decreased internalisation of erbB1 mutants in lung cancer is linked with a mechanism conferring sensitivity to gefitinib.

A majority of gefitinib (IRESSA)-responsive tumours in non-small cell lung cancer have been found to carry mutations in ErbB1. Previously, it has been observed that internalisation-deficient ErbB1 receptors are strong drivers of oncogenesis. Using a computational model of ErbB1 trafficking and signalling, it is found that a deficiency in ErbB1 internalisation is sufficient to explain the observed signalling phenotype of these gefitinib-responsive ErbB1 mutants in lung cancer cell lines. Experimental tests confirm that gefitinib-sensitive cell lines with and without ErbB1 mutations exhibit markedly slower internalisation rates than gefitinib-insensitive cell lines. Moreover, the computational model demonstrates that reduced ErbB1 internalisation rates are mechanistically linked to upregulated AKT signalling. Experimentally it is confirmed that impaired internalisation of ErbB1 is associated with increased AKT activity, which can be blocked by gefitinib. On the basis of these experimental and computational results, it is surmised that gefitinib sensitivity is a marker of a reliance on AKT signalling for cell survival that may be brought about by impaired ErbB1 internalisation.

Antineoplastic Agents↗
PubMed1993

pH sensitivity of epidermal growth factor receptor complexes.

The association/dissociation binding kinetics of 125I-labeled mouse epidermal growth factor (EGF) to receptors on human fibroblast cells in monolayer culture have been measured at 4 degrees C as a function of extracellular pH from pH 5-9. At pH 8, steady-state total binding is maximal. As pH is lowered to 6.5, total binding monotonically decreases dramatically. It changes further only slightly between pH 6.5 and 5 to about 20% of the maximum binding value. Scatchard binding plots at pH 7.5 and above show the commonly observed concave-upward, non-linear curve; as pH is lowered, this plot becomes much more linear, indicating that the "high affinity" bound receptor population is greatly diminished. Application of our ternary complex binding model [Mayo et al., J Biol Chem 264:17838-17844, 1989], which hypothesizes complexation of the EGF-bound receptor with a cell surface interaction molecule, indicates that pH may have some direct effects on ternary complex formation, but the major effect is on EGF-receptor dissociation.

ErbB Receptors↗
PubMed1989

Epidermal growth factor receptor binding is not a simple one-step process.

The binding kinetics of 125I-labeled mouse epidermal growth factor (EGF) to receptors on human fibroblast cells in monolayer culture were measured at 4 degrees C. Initial binding rates as a function of hormone concentration allowed estimation of simple two-state on-off rate constants of 1.2 x 10(6) M-1 s-1 and 4.9 x 10(-3) s-1, respectively. These two-state parameters gave inadequate computer fits to long term kinetic and equilibrium-binding data, suggesting that an additional process(es) was occurring. Nonlinear equilibrium Scatchard plots and transient "pseudo-Scatchard" plots taken at pre-equilibrium times support the idea that at least one other process is occurring during receptor binding. 125I-EGF-receptor dissociation kinetic plots were biphasic, yielding rate constants of 1.5 x 10(-2) s-1 and 5.6 x 10(-5) s-1 with the ratio of the two components changing with the time of initial incubation with 125I-EGF. Application of a ternary complex model which assumed complexation of the bound receptor with a cell surface interaction molecule gave satisfactory fits to all data.

Animals↗
PubMed1983

Analysis of the linear under-agarose leukocyte chemotaxis assay.

Random and chemotactic movement of leukocytes appear to be key processes in the host inflammatory response. Abnormalities in leukocyte motility and chemosensory behavior have been implicated in a large number of pathological conditions, but there is no adequate quantitative understanding of these properties. In this paper we present an approach for determination of phenomenological cell motility and chemotaxis parameters, by analysis of a common leukocyte migration assay. Using data from a set of cell migration experiments reported in the literature, we show how to determine the value of the random motility coefficient and its dependence upon concentration of a tripeptide chemotactic attractant, as well as the value of the chemotaxis coefficient, assumed here to be independent of attractant concentration. These parameters can be used to improve quantitative understanding of the relationship between leukocyte motility and chemosensory behavior and effective functioning of the host inflammatory response.

Biomedical Engineering↗
PubMed1983

Measurement of leukocyte motility and chemotaxis parameters with a linear under-agarose migration assay.

The interpretation of quantitative assays for leukocyte chemotactic migration is usually made in terms of measurements such as leading front distance, total migrating cells, and leukotactic index. These quantities allow comparison of cellular migration behavior under specified conditions. They are not useful; however, for comparisons between systems or for correlation with in vivo performance, because they depend upon specific physical aspects of the assay system, such as the geometry, chemoattractant concentration and diffusivity, and observation time. It would be more helpful to measure intrinsic properties of cell movement that could be used for comparison between systems, for correlation with in vivo studies, and to increase our understanding of the cell physiology. In this paper we demonstrate a means of quantitating leukocyte random motility, chemokinesis, and chemotaxis in terms of parameters that do characterize intrinsic cell properties. These parameters are the random motility coefficient and the chemotaxis coefficient, which appear in theoretical models of cell migration. We examine how well such a model describes the leukocyte density profile data observed in a modified under-agarose assay having a linear geometry. Furthermore, we obtain values for the random motility coefficient (and its dependence upon the concentration of the attractant peptide FNLLP) and for the chemotaxis coefficient for leukocytes responding to FNLLP.

Agar↗
PubMed1982

Effects of cell motility and chemotaxis on microbial population growth.

A mathematical model is developed to elucidate the effects of biophysical transport processes (nutrient diffusion, cell motility, and chemotaxis) along with biochemical reaction processes (cell growth and death, nutrient uptake) upon steady-state bacterial population growth in a finite one-dimensional region. The particular situation considered is that of growth limitation by a nutrient diffusing from an adjacent phase not accessible to the bacteria. It is demonstrated that the cell motility and chemotaxis properties can have great influence on steady-state population size. In fact, motility effects can be as significant as growth kinetic effects, in a manner analogous to diffusion- and reaction-limited regimes in chemically reacting systems. In particular, the following conclusions can be drawn from our analysis for bacterial populations growing at steady-state in a confined, unmixed region: (a) Random motility may lead to decreased population density; (b) chemotaxis can allow increased population density if the chemotactic response is large enough; (c) a species with superior motility properties can outgrow a species with superior growth kinetic properties; (d) motility effects become greater as the size of the confined growth region increases; and (e) motility effects are diminished by significant mass-transfer limitation of the nutrient from the adjacent source phase. The relationships of these results for populations to previous conclusions for individual cells is discussed, and implications for microbial competition are suggested.

Bacterial Physiological Phenomena↗