Cell Shape-dependent Control of Ca2+ Influx and Cell Cycle Progression in Swiss 3T3 Fibroblasts

Abstract

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 m 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 Ca 2؉ 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 Ca 2؉ 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 Ca 2؉ concentration but failed to elicit the normal sustained influx of Ca 2؉ that follows Ca 2؉ 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 Ca 2؉ signaling is an essential component of mitogen responses, these findings implicate Ca 2؉ influx as a necessary component of cell shape-dependent control of the cell cycle.

Variations in Shape-Sensitive Restriction Points Mirror Differences in the Regeneration Capacities of Avian and Mammalian Ears

“…Other candidate mechanisms for shape control of proliferation include nuclear volume changes that promote chromatin decondensation [36], alterations in cytoplasmic and nuclear calcium concentrations [37], [38], activation of focal adhesion kinase [39], and regulation via Rho family GTPases [40], [41]. The PI3K-Akt-TOR and ERK/MAPK pathways have been implicated in the control of proliferation in vestibular supporting cells from mammals and birds and could act downstream of signals that originate through changes in shape [42], [43].…”

Long‐term exposure of 3T3 fibroblast cells to endocrine disruptors alters sensitivity to oxidative injury

“…We have examined whether long-term exposure to BPA or NP at lower concentrations induces alterations of cell survival or responses to oxidative injury in non-neuronal cells. Swiss 3T3 fibroblast cells were used, which are nontumor cells and widely used in pharmacological and toxicological studies (Vaziri and Faller, 1997;Shaw et al, 1998;Sinnett-Smith et al, 2004;Dekanty et al, 2006;Pennington et al, 2007).…”

Cell cycle dependent expression of the CCK2 receptor by gastrointestinal myofibroblasts: putative role in determining cell migration

“…In cells of fibroblastic lineages there is an association among cell shape, cell cycle progression, and calcium influx (Pennington et al. ). For the most part the focus of previous work in this area has been on progression from the checkpoint to S‐phase.…”

“…The GPCR agonists that are linked to increases in intracellular calcium are also mitogens for many different cell types where proliferative responses may reflect transactivation of the EGF receptor (Prenzel et al 1999;Varro et al 2002). In cells of fibroblastic lineages there is an association among cell shape, cell cycle progression, and calcium influx (Pennington et al 2007). For the most part the focus of previous work in this area has been on progression from the checkpoint to S-phase.…”