Chemotaxis in multiple gradients Keith Erickson March 30

Chemotaxis in multiple gradients Keith Erickson March 30, 2005

• Single gradient • Multiple gradients Conflicting gradients Side gradients Interleukin-8, LTB 4: host regulatory signals Gradients in series C 5 a, f. MLP: end target signals

Key observations Foxman et al. JCB, 1997. • Conflicting gradients – Host/Host: • migrate to distant signal – f. MLP/Host • prioritize f. MLP • Side gradients – Host/Host: • migrate to vector sum – f. MLP/Host • prioritize f. MLP Consistent with vector sum model

Key observations Foxman et al. JCB, 1997. • Gradients in series Experiment # 1 saturation host 2 host 3 f. MLP 4 f. MLP Distance migrated Not consistent with vector sum model f. MLP or host

Hypotheses Richardson et al. JBC, 1995. 1. Heterologous desensitization- f. MLP promotes phosphorylation of IL-8 R

Hypotheses Heit et al. JCB, 2002. 2. Chemoattractants act on different pathways

Hypotheses 3. Null hypothesis- Weighted vector sum

Model and Assumptions constant in time vacuole Migration constant speed

Model and Assumptions • Define new states • Chain rule

Initial results • Receptor quantities and dissociation constants have an effect on signal prioritization

Experiments-mpipette assay • Easy to set up multiple mpipettes • Fluorescent tracer to measure concentrations • Reproducible?

Two mpipettes 2 - 10 m. M f. MLP 1 m. M and 10 m. M f. MLP

Show movies • • HL 60 upipette. avi Sampled 10 u. MFITC. avi Sampled 100 u. MFITC. avi 10 u. MC 5 a. avi phasecontrol. avi Sampled 1 u. M. avi

Image processing • Trace cell paths • Determine values – Persistence time – Chemotactic index • Relate to concentrations • Estimate model parameters

Future work • • Repeat experiments Get C 5 a to work Host chemoattractant- LTB 4 Inhibitors – LY 294002 (PI 3 K) – SKF 86002 (p 38 MAPK) • Fit model to results

Acknowledgements Martijn van Duijn Dan Fletcher Chris Rao Adam Arkin Af. CS The Whitaker Foundation