Calcium signals and FGF-2 induced neurite growth in cultured parasympathetic neurons: spatial localization and mechanisms of activation

Abstract

The growth of neuritic processes in developing neurons is tightly controlled by a wide set of extracellular cues, that act by initiating downstream signalling cascades, where calcium signals play a major role. Here we analyze the calcium dependence of the neurite growth promoted by basic Fibroblast Growth Factor (bFGF, or FGF-2) in chick embryonic ciliary ganglion neurons, taking advantage of dissociated, organotypic and compartmentalized cultures. We report that signals at both the growth cone and the soma are involved in the promotion of neurite growth by the factor.Blocking calcium influx through L-and N-type voltage dependent calcium channels and TRPC channels reduces, while release from intracellular stores does not significantly affect, the growth of neuritic processes. Simultaneous recordings of calcium signals elicited by FGF-2 at the soma and at the growth cone show that the factor activates different patterns of responses in the two compartments: steady and sustained responses at the former, oscillations at the latter. At the soma, both voltage dependent channel and TRPC blockers strongly affect steady state levels. At the growth cone, the changes in the oscillatory pattern are more complex; therefore we used a tool based on wavelet analysis to obtain a quantitative evaluation of the effects of the two classes of blockers. We report that the oscillatory behaviour at the growth cone is dramatically affected by all the blockers, pointing to a role for calcium influx through the two classes of channels in the generation of signals at the leading edge of the elongating neurites.

Evidence for Fibroblast Growth Factor-2 as a Mediator of Amphetamine-Enhanced Motor Improvement following Stroke

“…8). These data are consistent with literature describing the neurite-promoting properties of FGF-2 [40]–[42].…”

Interplay between phosphoinositide lipids and calcium signals at the leading edge of chemotaxing ameboid cells

“…1) (Jin, 2013; Weiger and Parent, 2012; Cai and Devreotes, 2011; Hawkins et al, 2010; Swaney et al, 2010; Kolsch et al, 2008; Mortimer et al, 2008; von Philipsborn and Bastmeyer, 2007; Bourne and Weiner, 2002). In general, leading edge formation and maintenance requires the appearance of two localized second messenger signals: the signaling lipid phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P 3 ) (Jin, 2013; Weiger and Parent, 2012; Cai and Devreotes, 2011), and the signaling ion Ca 2+ (Collins and Meyer, 2009; Wei et al, 2012; Tsai and Meyer, 2012; Zamburlin et al, 2013; Henle et al, 2011; Tian et al, 2010; Wei et al, 2009; Evans and Falke, 2007). While the importance of PI(3,4,5)P 3 at the leading edge membrane has long been recognized, Ca 2+ has emerged as an essential leading edge signal more recently.…”

“…Contemporary leading edge models ignored Ca 2+ until local Ca 2+ signals at the leading edge were found to be essential for macrophage leading edge stability, dynamics and function (Evans and Falke, 2007), to play a role in directional control of migrating fibroblasts and endothelial cells (Wei et al, 2012; Tsai and Meyer, 2012; Wei et al, 2009), and to be involved in the guidance mechanism of neuronal growth (Zamburlin et al, 2013; Henle et al, 2011; Heckman and Plummer, 2013). Thus in recent years Ca 2+ has joined PI(3,4,5)P 3 as an essential second messenger in leading edge signaling (Collins and Meyer, 2009; Wei et al, 2012; Tsai and Meyer, 2012; Zamburlin et al, 2013; Henle et al, 2011; Tian et al, 2010; Wei et al, 2009; Evans and Falke, 2007; Heckman and Plummer, 2013; Schafer et al, 2012), with the possible exception of cells that lack constant external Ca 2+ levels such as Dictyostelium (Wessels et al, 2012; Traynor et al, 2000). Besides PI(3,4,5)P 3 and Ca 2+ , another second messenger – the signaling lipid diacylglycerol (DAG) and likely its phosphorylation product phosphatidic acid – is indirectly implicated at the leading edge (Tsai and Meyer, 2012; Abramovici et al, 2009).…”

“…The leading edge Ca 2+ signal has been linked to both influx through plasma membrane Ca 2+ channels and efflux from internal Ca 2+ stores, although certain cell types may employ only one of these mechanisms (Wei et al, 2012; Tsai and Meyer, 2012; Zamburlin et al, 2013; Henle et al, 2011; Tian et al, 2010; Wei et al, 2009; Evans and Falke, 2007; Heckman and Plummer, 2013; Schafer et al, 2012). Plasma membrane Ca 2+ channels including transient receptor potential (TRP) and Orai1 channels, and endoplasmic reticulum Ca 2+ channels including ryanodine and IP 3 receptors, are proposed to give rise to the leading edge Ca 2+ influxes and effluxes, respectively (Wei et al, 2012; Tsai and Meyer, 2012; Zamburlin et al, 2013; Henle et al, 2011; Tian et al, 2010; Wei et al, 2009; Heckman and Plummer, 2013; Schafer et al, 2012).…”

“…In addition, specific cell types possess specialized pathway elements that optimize performance for particular applications. Chemotactic cells in which the chemotaxis pathway has been investigated at the molecular level include leukocytes (Jin, 2013; Kolaczkowska and Kubes, 2013; Weiger and Parent, 2012; Cai and Devreotes, 2011; Hawkins et al, 2010; Collins and Meyer, 2009), fibroblasts (Wei et al, 2012), endothelial cells (Tsai and Meyer, 2012), neurons (Zamburlin et al, 2013; Henle et al, 2011; Waite and Eickholt, 2010), muscle cells (Trovati et al, 2013), mammary epithelial cells (Zhu and Nelson, 2013), cancer cells (Li et al, 2013; Vadas et al, 2011), and free-living amoeboid organisms such as Dictyostelium (Weiger and Parent, 2012; Cai and Devreotes, 2011). …”