title: How blebs and pseudopods cooperate during chemotaxis.
abstract: Two motors can drive extension of the leading edge of motile cells: actin polymerization and myosin-driven contraction of the cortex, producing fluid pressure and the formation of blebs. Dictyostelium cells can move with both blebs and actin-driven pseudopods at the same time, and blebs, like pseudopods, can be orientated by chemotactic gradients. Here we ask how bleb sites are selected and how the two forms of projection cooperate. We show that membrane curvature is an important, yet overlooked, factor. Dictyostelium cells were observed moving under agarose, which efficiently induces blebbing, and the dynamics of membrane deformations were analyzed. Blebs preferentially originate from negatively curved regions, generated on the flanks of either extending pseudopods or blebs themselves. This is true of cells at different developmental stages, chemotaxing to either folate or cyclic AMP and moving with both blebs and pseudopods or with blebs only. A physical model of blebbing suggests that detachment of the cell membrane is facilitated in concave areas of the cell, where membrane tension produces an outward directed force, as opposed to pulling inward in convex regions. Our findings assign a role to membrane tension in spatially coupling blebs and pseudopods, thus contributing to clustering protrusions to the cell front.
authors: Warwick Systems Biology Centre, University of Warwick, Coventry CV4 7AL, United Kingdom; and.
authors: Richard A
authors: RA
authors: Tyson
authors: Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors: Evgeny
authors: http://orcid.org/0000-0002-7847-5829
authors: E
authors: Zatulovskiy
authors: Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors: Robert R
authors: RR
authors: Kay
authors: Warwick Systems Biology Centre, University of Warwick, Coventry CV4 7AL, United Kingdom; and T.Bretschneider@warwick.ac.uk.
authors: Till
authors: T
authors: Bretschneider
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D055592:Biophysical Phenomena; D016764:Cell Polarity / Q000502:physiology; D022081:Cell Surface Extensions / Q000502:physiology*; D002633:Chemotaxis / Q000502:physiology*; D000242:Cyclic AMP / Q000378:metabolism; D004023:Dictyostelium / Q000502:physiology; D005492:Folic Acid / Q000378:metabolism; D023781:Fundulidae; D008954:Models, Biological; D015800:Protozoan Proteins / Q000378:metabolism; D011554:Pseudopodia / Q000502:physiology*
chemical_list: D000199:Actins; D015800:Protozoan Proteins; D005492:Folic Acid; D000242:Cyclic AMP