Ca2+ waves in PC12 neurites: a bidirectional, receptor-oriented form of Ca2+ signaling.

Abstract

Abstract. Spatial and temporal aspects of Ca 2+ signaling were investigated in PC12 cells differentiated with nerve growth factor, the well known nerve cell model. Activation of receptors coupled to polyphosphoinositide hydrolysis gave rise in a high proportion of the cells to Ca :+ waves propagating non decrementally and at constant speed (2-4 #m/s at 18°C and ,,d0-fold faster at 37°C) along the neurites. These waves relied entirely on the release of Ca 2÷ from intracellular stores since they could be generated even when the cells were incubated in Ca2+-free medium. In contrast, when the cells were depolarized with high K + in Ca 2÷-containing medium, increases of cytosolic Ca 2÷ occurred in the neurites but failed to evolve into waves. Depending on the receptor agonist employed (bradykinin and carbachol versus ATP) the orientation of the waves could be opposite, from the neurite tip to the cell body or vice versa, suggesting different and specific distribution of the responsible surface receptors. Cytosolic Ca ~÷ imaging results, together with studies of inositol 1,4,5-trisphosphate generation in intact cells and inositol 1,4,5-trisphosphate-induced Ca :÷ release from microsomes, revealed the sustaining process of the waves to be discharge of Ca 2÷ from the inositol 1,4,5-trisphosphate-(and not the ryanodine-) sensitive stores distributed along the neurites. The activation of the cognate receptor appears to result from the coordinate action of the second messenger and Ca 2÷. Because of their properties and orientation, the waves could participate in the control of not only conventional cell activities, but also excitability and differential processing of inputs, and thus of electrochemical computation in nerve cells. VIDEO microscopy studies carried out on individual cells during the last several years have revealed that the changes of cytosolic Ca 2÷ concentration ([Ca2÷]~) in response to various stimuli do not develop always as a whole but can exhibit peculiar spatiotemporal aspects. In some cases, in fact, these responses have been shown to promote steep Ca 2÷ gradients between a discrete cytosolic area and the rest of the cell (Miiller and Connor, 1991;Guthrie et al., 1991;Silver et al., 1990); in others, to be composed by series of rhythmic [Ca2÷]i spikes, the oscillations (Berridge and Galione, 1988;Jacob, 1990b;Tsien and Tsien, 1990;Meyer and Stryer, 1991;Berridge, 1993), that are now believed to originate from an intracellular pacemaker or "trigger zone" (Rooney et al., 1990; D~ndrea et al., 1993;Kasai et al., 1993); in others, to consist of Ca 2÷ waves (Meyer, 1991;Amundson and Clapham, 1993;Berridge, 1993). Because of these processes, the host of functions that rely on [Ca2÷]~ for their regulation are believed to be affected to different extents or at different times depending on their localization within the stimulated cells. The present report concerns Ca 2÷ waves, i.e., intracellular events defined by their nondecremental propagation and distinct orientation, previously described in a number of ce...

Calcium and Fos Involvement in Brain‐Derived Ca2+‐Binding Protein (S100)‐Dependent Apoptosis in Rat Phaeochromocytoma Cells

“…3 for details). The spatial organisation of the [Ca¥]é transients occurring in 'slow responding' cells was studied using a cooled CCD camera, to reduce the signal-tonoise ratio and performing the S100 stimulation at low temperature (20°C), in order to slow down the process of the [Ca¥]é increase (Lorenzon et al 1995). We observed a nonhomogeneous [Ca¥]é increase that began peripherally and then propagated centripetally, invading the rest of the cytoplasm (Fig.…”

“…In order to study the spatial organisation of S100-induced responses (Fig. 4), a series of experiments was performed at 20°C (Lorenzon et al 1995) and, to improve the signal-to-noise ratio, we used a cooled CCD camera (Hamamatsu Photonics Fig. 4 (5 cells) in which different experimental conditions were used (low temperature and CCD pre-cooled) The buffers included in this kit were prepared according to a method already reported (Tsien & Pozzan, 1989) This method is based on the principle that when the concentrations of Ca¥ and EGTA are very close to each other, the only free Ca¥ available is that which is in equilibrium with EGTA.…”

Effects of prolactin on intracellular calcium concentration and cell proliferation in human glioma cells

“…Intracellular Ca 2ϩ waves had already been observed in several cell models (neurons, neuroblastoma cells, hepatocytes, prostatic cells, oocytes, etc.) in response to membrane potential variations (Perret et al, 1999), neurotransmitters, hormones, and growth factor stimulation (Nathanson et al, 1992;Kawanishi et al, 1995;Lorenzon et al, 1995;Wang and Thompson, 1995). Several hypotheses for the mechanisms of Ca 2ϩ waves have been proposed (Clapham and Sneyd, 1995 -free medium.…”

Actin-dependent anterograde movement of growth-cone-like structures along growing hippocampal axons: A novel form of axonal transport?

“…For example, since calcium may affect microfilament stability [Lankford and Letourneau, 1989] and increased concentrations of calcium have been shown to be associated with surface motility induced along axon shafts [Williams et al, 1995], waves might result from cytoskeletal rearrangements due to a propagated change in calcium concentration. While propagated calcium transients have been observed in the processes of PC-12 cells [Lorenzon et al, 1995], the rates of propagation (17-30 µm/sec) appear much too fast to have a plausible role in generating the growth-cone-like wave structures. Furthermore, the calcium hypothesis would not explain why cytochalasin reversibly inhibits wave advance.…”