Inhibition of cyclin-dependent kinase activity triggers neuronal differentiation of mouse neuroblastoma cells.

Abstract

Abstract. Studies on the molecular mechanisms underlying neuronal differentiation are frequently performed using cell lines established from neuroblastomas. In this study we have used mouse N1E-115 neuroblastoma cells that undergo neuronal differentiation in response to DMSO. During differentiation, cyclin-dependent kinase (cdk) activities decline and phosphorylation of the retinoblastoma gene product (pRb) is lost, leading to the appearance of a pRb-containing E2F DNA-binding complex. The loss of cdk2 activity is due to a decrease in cdk2 abundance whereas loss of cdk4 activity is caused by strong association with the cdk inhibitor (CKI) p27 KiP1 and concurrent loss of cdk4 phosphorylation. Moreover, neuronal differentiation can be induced by overexpression of p27 KIP1 or pRb, suggesting that inhibition of cdk activity leading to loss of pRb phosphorylation, is the major determinant for neuronal differentiation.

Rac1 and Rac3 have opposing functions in cell adhesion and differentiation of neuronal cells

“…In addition, we analyzed Rac3 expression in cells differentiated in other fashions, e.g. by dibutyryl cyclic AMP treatment (Abe et al, 2003) or by DMSO treatment (Kranenburg et al, 1995;Leeuwen et al, 1997). RT-PCR showed similar results to those of differentiation induced by serum starvation, namely a loss of Rac3 transcript in differentiated cells (not shown).…”

“…Various agents, including growth factors and kinase inhibitors, can also trigger this process (Leeuwen et al, 1997;van Horck et al, 2002). However, rounded Rac3-expressing cells were unable to spread or differentiate, regardless of whether differentiation was triggered by serum withdrawal, nerve growth factor (Estrach et al, 2002), dimethyl sulfoxide [DMSO (Kranenburg et al, 1995); 623/id (Leeuwen et al, 1997)], ROCK inhibitor or cyclic AMP (Abe et al, 2003) (Figs 2, 3, 5 and 6, and data not shown). We also found that coating the surface with laminin-1, collagen, poly-L-lysine or fibronectin did not stimulate spreading of Rac3-expressing cells when compared to an uncoated surface (data not shown).…”

The absence of p21Cip1/WAF1 alters keratinocyte growth and differentiation and promotes ras-tumor progression.

“…Unlike p21 cipl/wArl, expression of p27 Kip1 does not appear to be under p53 control, p27 Kip1 expression has also been shown to correlate with differentiation in vitro in certain cell types and in vivo in postmitotic neurons during mouse embryogenesis and in luteal cell differentiation (Kranenburg et al 1995;Kiyokawa et al 1996;Lee et al 1996). Like p21 knockouts, mice with a disruption of the p27 Kip1 gene develop normally, but they display hyperplasia of several organs, owing, at least in part, to increased cell proliferation (Fero et al 1996;Kiyokawa et al 1996;Nakayama et al 1996).…”

IL‐4 blocks M‐CSF‐dependent macrophage proliferation by inducing p21Waf1 in a STAT6‐dependent way

“…Cdk activity was analysed as described previously [65]. Briefly, 150 mg of total protein extracts was immunoprecipitated with the Cdk-2 and Cdk-4 pull-down experiments were performed in a similar way and then blotted for the desired protein.…”