Nerve growth factor utilizes common signaling pathways to differentially regulate M4 muscarinic and adenosine A2A receptor mRNA

A precise description of the mechanisms by which estrogen receptor-α (ERα) exerts its influences on cellular growth and differentiation is still pending. Here, we report that the differentiation of PC12 cells is profoundly affected by ERα. Importantly, depending upon its binding to 17β-estradiol (17βE2), ERα is found to exert different effects on pathways involved in nerve growth factor (NGF) signaling. Indeed, upon its stable expression in PC12 cells, unliganded ERα is able to partially inhibit the neurite outgrowth induced by NGF. This process involves a repression of MAPK and phosphatidylinositol 3-kinase/Akt signaling pathways, which leads to a negative regulation of markers of neuronal differentiation such as VGF and NFLc. This repressive action of unliganded ERα is mediated by its D domain and does not involve its transactivation and DNA-binding domains, thereby suggesting that direct transcriptional activity of ERα is not required. In contrast with this repressive action occurring in the absence of 17βE2, the expression of ERα in PC12 cells allows 17βE2 to potentiate the NGF-induced neurite outgrowth. Importantly, 17βE2 has no impact on NGF-induced activity of MAPK and Akt signaling pathways. The mechanisms engaged by liganded ERα are thus unlikely to rely on an antagonism of the inhibition mediated by the unliganded ERα. Furthermore, 17βE2 enhances NGF-induced response of VGF and NFLc neuronal markers in PC12 clones expressing ERα. This stimulatory effect of 17βE2 requires the transactivation functions of ERα and its D domain, suggesting that an estrogen-responsive element-independent transcriptional mechanism is potentially relevant for the neuritogenic properties of 17βE2 in ERα-expressing PC12 cells. In the absence of its ligand, ERα partially inhibits the nerve growth factor-induced neurite outgrowth of PC12 cells, whereas, once liganded, it enhances differentiation.

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Nerve growth factor functions as a chemoattractant for mast cells through both mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling pathways

Blood ◽

10.1182/blood.v95.6.2052 ◽

2000 ◽

Vol 95 (6) ◽

pp. 2052-2058 ◽

Cited By ~ 94

Author(s):

Junko Sawada ◽

Atsuko Itakura ◽

Akane Tanaka ◽

Tohru Furusaka ◽

Hiroshi Matsuda

Keyword(s):

Nerve Growth Factor ◽

Growth Factor ◽

Mast Cells ◽

Protein Kinase ◽

Signaling Pathways ◽

Mitogen Activated Protein Kinase ◽

Phosphatidylinositol 3 Kinase ◽

Directional Migration ◽

Nerve Growth ◽

Mitogen Activated Protein

Abstract Despite being a well-characterized neurotrophic factor, nerve growth factor (NGF) influences survival, differentiation, and functions of mast cells. We investigated whether NGF was able to induce directional migration of rat peritoneal mast cells (PMCs). NGF clearly induced chemotactic movement of PMCs in a dose-dependent manner with the drastic morphological change and distribution of F-actin, which was completely blocked by pretreatment with Clostridium botulinumC2 toxin, an actin-polymerization inhibitor. Because PMCs constitutively express the NGF high-affinity receptor (TrkA) with a tyrosine kinase domain, we focused on downstream effectors in signaling cascades following the TrkA. NGF rapidly activated both mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K), and the addition of inhibitors specific for MAPK kinase and PI3K suppressed cell migration and these signals. In the coculture system with PMCs and fibroblasts, which produce biologically active NGF, directional migration of PMCs to fibroblasts was observed, and the addition of anti-NGF polyclonal antibodies significantly suppressed the migration of PMCs. These findings suggested that NGF initiated chemotactic movement of PMCs through both MAPK and PI3K signaling pathways following TrkA activation. Thus, locally produced NGF may play an important role in mast cell accumulation in allergic and nonallergic inflammatory conditions.

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