A micromechanic study of cell polarity and plasma membrane cell body coupling in Dictyostelium

Citation
R. Merkel et al., A micromechanic study of cell polarity and plasma membrane cell body coupling in Dictyostelium, BIOPHYS J, 79(2), 2000, pp. 707-719
Citations number
47
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOPHYSICAL JOURNAL
ISSN journal
00063495 → ACNP
Volume
79
Issue
2
Year of publication
2000
Pages
707 - 719
Database
ISI
SICI code
0006-3495(200008)79:2<707:AMSOCP>2.0.ZU;2-0
Abstract
We used micropipettes to aspirate leading and trailing edges of wild-type a nd mutant cells of Dictyostelium discoideum. Mutants were lacking either my osin II or talin, or both proteins simultaneously. Talin is a plasma membra ne-associated protein important for the coupling between membrane and actin cortex, whereas myosin II is a cytoplasmic motor protein essential for the locomotion of Dictyostelium cells. Aspiration into the pipette occurred ab ove a threshold pressure only. For all cells containing talin this threshol d was significantly lower at the leading edge of an advancing cell as compa red to its rear end, whereas we found no such difference in cells lacking t alin. Wild-type and talin-deficient cells were able to retract from the pip ette against an applied suction pressure. In these cells, retraction was pr eceded by an accumulation of myosin II in the tip of the aspirated cell lob e. Mutants lacking myosin II could not retract, even if the suction pressur es were removed after aspiration. We interpreted the initial instability an d the subsequent plastic deformation of the cell surface during aspiration in terms of a fracture between the cell plasma membrane and the cell body, which may involve destruction of part of the cortex. Models are presented t hat characterize the coupling strength between membrane and cell body by a surface energy sigma. We find sigma approximate to 0.6(1.6) mJ/m(2) at the leading (trailing) edge of wild-type cells.