Domains of E1A that bind p105Rb, p130, and p300 are required to block nerve growth factor-induced neurite growth in PC12 cells.

Abstract

Nerve growth factor (NGF) causes PC12 cells to cease division and undergo sympathetic neuron-like differentiation, including neurite outgrowth. We have tested whether differentiation and division share overlapping control mechanisms in these cells. To do this, we have perturbed the activity of proteins known to participate in cell-cycle regulation by introducing the E1A oncogene or its mutant forms via microinjection into PC12 cells. The E1A protein binds to several putative cell cycle control proteins, including p105Rb (the product of the retinoblastoma susceptibility gene), as well as others of unknown function such as p130, p107, and p300. Similar to previous results, we find that wild-type E1A abrogates NGF-induced neurite extension. However, NGF does cause neurite outgrowth in the presence of E1A mutants known to have greatly reduced binding to either p105Rb and p130 or p300. Our experiments suggest that p105Rb, p130, and p300 may participate either in E1A-mediated inhibition of differentiation or in the NGF signal transduction pathway. We also report here that NGF affects phosphorylation of p105Rb, suggesting that Rb mediates at least some of NGF's effects. Our results raise the possibility that putative cell-cycle control proteins may participate not only in NGF-induced cessation of division but also in differentiation.

The retinoblastoma-related Rb2/p130 gene is an effector downstream of AP-2 during neural differentiation

“…In this model, during NGF-induced di erentiation, neurite outgrowth is inhibited by those domains of the viral oncoprotein E1A that bind to and inactivate pRb, pRb2/p130 and p300 (Kalman et al, 1993), con®rming a relevant role in neural di erentiation program for these regulators. NGF induces p21 and cyclin D1 transcription in PC12 cells (Yan and Zi , 1997), but ectopic p21 overexpression, while causing a permanent cell-cycle arrest, thus accelerating NGF-dependent di erentiation, is not su cient per se to establish a di erentiation program (Van Grunsven et al, 1996;Erhardt and Pittman, 1998).…”

Transcriptional down-regulation of the retinoblastoma protein is associated with differentiation and apoptosis in human colorectal epithelial cells

“…Additionally, in vitro experiments have shown that hypophosphorylation of the Rb protein may play a role in the differentiation of some cell types, e.g. human haematopoietic cells (Furukawa et al, 1990), leukaemia cell lines (Chen et al, 1989), PC12 neuronal cells (Kalman et al, 1993;Li et al, 1996) and myoblast cell lines (Gu et al, 1993). Interestingly, while differentiation in erythroleukaemia cells (Coppola et al, 1990;Richon et al, 1992), myocytes (Coppola et al, 1990;Endo and Goto, 1992), and embryonal carcinoma cells (Slack et al, 1993) is associated with an accumulation of RB-1 mRNA, the other pocket proteins do not appear to play such a crucial role in differentiation.…”

E1A-mediated inhibition of myogenesis correlates with a direct physical interaction of E1A12S and basic helix-loop-helix proteins.

“…Thus, the region of ElA which represses both muscle and nonmuscle enhancer activity resides outside the most highly conserved domains but within the amino terminus of the molecule. (2,9,22,27). However, several of these studies have also demonstrated a requirement for the amino terminus of ElA in repression of cellular differentiation (9,27), implying that ElA may mediate repression through both CR1/CR2-depen-VOL.…”

“…(2,9,22,27). However, several of these studies have also demonstrated a requirement for the amino terminus of ElA in repression of cellular differentiation (9,27), implying that ElA may mediate repression through both CR1/CR2-depen-VOL. 13,1993 4723 (Fig.…”