Role of L‐type Ca²⁺ channels in neural stem/progenitor cell differentiation

Abstract

Ca(2+) influx through voltage-gated Ca(2+) channels, especially the L-type (Ca(v)1), activates downstream signaling to the nucleus that affects gene expression and, consequently, cell fate. We hypothesized that these Ca(2+) signals may also influence the neuronal differentiation of neural stem/progenitor cells (NSCs) derived from the brain cortex of postnatal mice. We first studied Ca(2+) transients induced by membrane depolarization in Fluo 4-AM-loaded NSCs using confocal microscopy. Undifferentiated cells (nestin(+)) exhibited no detectable Ca(2+) signals whereas, during 12 days of fetal bovine serum-induced differentiation, neurons (beta-III-tubulin(+)/MAP2(+)) displayed time-dependent increases in intracellular Ca(2+) transients, with DeltaF/F ratios ranging from 0.4 on day 3 to 3.3 on day 12. Patch-clamp experiments revealed similar correlation between NSC differentiation and macroscopic Ba(2+) current density. These currents were markedly reduced (-77%) by Ca(v)1 channel blockade with 5 microm nifedipine. To determine the influence of Ca(v)1-mediated Ca(2+) influx on NSC differentiation, cells were cultured in differentiative medium with either nifedipine (5 microm) or the L-channel activator Bay K 8644 (10 microm). The latter treatment significantly increased the percentage of beta-III-tubulin(+)/MAP2(+) cells whereas nifedipine produced opposite effects. Pretreatment with nifedipine also inhibited the functional maturation of neurons, which responded to membrane depolarization with weak Ca(2+) signals. Conversely, Bay K 8644 pretreatment significantly enhanced the percentage of responsive cells and the amplitudes of Ca(2+) transients. These data suggest that NSC differentiation is strongly correlated with the expression of voltage-gated Ca(2+) channels, especially the Ca(v)1, and that Ca(2+) influx through these channels plays a key role in promoting neuronal differentiation.

Sumoylation dynamics during keratinocyte differentiation

“…Ca 2+ signaling stimulates expression of the sumoylation system leading to changes in the sumoylation state of target proteins and allowing proper keratinocyte differentiation. Ca 2+ signaling is also an important mediator of lymphocyte activation and differentiation (Freedman, 2006), oesteoblastic activity and bone formation (Henriksen et al, 2006), neuronal stem cell development (D'Ascenzo et al, 2006) and smooth muscle formation (Wamhoff et al, 2006). Although the intermediate signals are largely unknown for these processes, our work suggests that sumoylation may be modulated in each of these systems through Ca 2+ -responsive transcription factors.…”

Ion channels in postnatal neurogenesis

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Moreover, the sequence diversity of ion channels, even within channel families, as well as their often multi-subunit complex three-dimensional structures provide the potential for the development of drugs that are highly selective for specific channel isoforms expressed at discrete stages of neurogenesis. This approach may be advantageous over infusion of growth factors or other bioactive peptides that are likely to have more widespread, pleiotropic effects across neuronal development.…”

Characterization of Ionic Currents in Human Neural Stem Cells

“…Piper et al also observed Ca 2+ inward currents, but they did not present the raw data. As Ca 2+ channels are reported to play a key role in promoting neural stem/progenitor cell differentiation in mice (D'Ascenzo et al, 2006) and we observed a nicardipine-sensitive Ca 2+ current in neuronal cells derived from human mesenchymal stem cells (unpublished observation), we expected to observe a Ca 2+ current rather than a Na + current, when we initiated our experiments. However, we failed to observe an inward Ca 2+ current.…”