Receptor occupancy on an ellipsoidal cell exposed to diffusion from a point source of chemoattractant

Igor Weber

Ruđer Bošković Institute, Department of Molecular Biology, Bijenička 54, HR-10000 Zagreb, Croatia

Chemotactic eukaryotic cells can respond to small differences in chemoattractant concentration between the front and the back of the cell. To sense such weak gradients, cells must compare differences in receptor occupancy along their length and convert this signal into a localized response. Diffusion of a chemoattractant from a micropipette is routinely used to examine different aspects of cell’s chemotactic response. For quantitative analysis of this response cells are usually considered to be spherical bodies, which is not appropriate for elongated cells like neutrophils and especially for amoeboid Dictyostelium cells. In order to quantify the effect of cell elongation on chemotactic sensitivity in the micropipette assay, chemoattractant concentration at the cell plasma membrane was determined by solving the equation for diffusion from a point source in the presence of a prolate ellipsoid. The results show that cell elongation can significantly increase the difference in receptor occupancy between near and far cell ends and thereby enhance sensitivity of chemotactic cells to shallow chemoattractant gradients.

Email: iweber@irb.hr

Address: Dr. Igor Weber, Institut