Cell shape-dependent Control of Ca2+ influx and cell cycle progression in Swiss 3T3 fibroblasts.
The ability of adherent cells such as fibroblasts to enter the cell cycle and progress to S phase is strictly dependent on the extent to which individual cells can attach to and spread on a substratum. Here we have used microengineered adhesive islands of 22 and 45 mum diameter surrounded by a nonadhesive substratum of polyhydroxyl methacrylate to accurately control the extent to which individual Swiss 3T3 fibroblasts may spread. The effect of cell shape on mitogen-evoked Ca2+ signaling events that accompany entry into the cell cycle was investigated. In unrestricted cells, the mitogens bombesin and fetal calf serum evoked a typical biphasic change in the cytoplasmic free Ca2+ concentration. However, when the spreading of individual cells was restricted, such that progression to S phase was substantially reduced, both bombesin and fetal calf serum caused a rapid transient rise in the cytoplasmic free Ca2+ concentration but failed to elicit the normal sustained influx of Ca2+ that follows Ca2+ release. As expected, restricting cell spreading led to the loss of actin stress fibers and the formation of a ring of cortical actin. Restricting cell shape did not appear to influence mitogen-receptor interactions, nor did it influence the presence of focal adhesions. Because Ca2+ signaling is an essential component of mitogen responses, these findings implicate Ca2+ influx as a necessary component of cell shape-dependent control of the cell cycle.
Pennington
Stephen R
SR
Department of Human Anatomy and Cell Biology, School of Biomedical Sciences, University of Liverpool, Sherrington Buildings, Ashton Street, Liverpool L69 3GE, United Kingdom.
Foster
Brian J
BJ
Hawley
Shaun R
SR
Jenkins
Rosalind E
RE
Zolle
Olga
O
White
Michael R H
MR
McNamee
Christine J
CJ
Sheterline
Peter
P
Simpson
Alec W M
AW
D016475:3T3 Cells; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002453:Cell Cycle; D048430:Cell Shape; D003599:Cytoskeleton / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D016196:S Phase; D015398:Signal Transduction
D002118:Calcium