Activation of ERK1 and ERK2 is required for manganese-induced neurite outgrowth in rat pheochromocytoma (PC12) cells

Abstract

Mn(2+) treatment has been shown to promote neurite outgrowth in rat pheochromocytoma (PC12) cells in a time- and dose-dependent manner. This process is mediated through the interactions of extracellular matrix (ECM) proteins and integrin receptors. Studies were performed to determine whether the phosphorylation of the MAP kinases, ERK1 and 2, is required for Mn(2+)-induced neurite outgrowth. A time- and dose-dependent increase in phosphorylation of both ERK1 and 2 was observed upon treatment of PC12 cells with Mn(2+). Phosphorylation of the ERKs occurred as early as 2 hr after initiating treatment, with a maximum increase occurring at approximately 24 hr. Inhibition of MEK with the specific inhibitor, PD98059, blocked the phosphorylation of ERK1 and 2 and increased Mn(2+) toxicity. When cells were grown in serum-free defined medium, Mn(2+)-induced phosphorylation of ERK1 and ERK2 occurred in cells grown on surfaces treated with growth serum or fibronectin but not on surfaces treated with poly-L-lysine. In addition, the pentapeptide GRGDS, which blocks RGD-mediated interactions, inhibited Mn(2+)-induced phosphorylation of ERK1 and 2. The Mn(2+)-induced increase in phosphorylated ERK1 and 2 was not seen in a PC12 cell line that does not respond to Mn(2+). These data support the hypothesis that integrin-mediated activation of the MAPK signal transduction pathway leading to the activation of ERK1 and 2 is required for Mn(2+)-induced PC12 differentiation and neurite outgrowth.

Manganese-induced rat pheochromocytoma (PC12) cell death is independent of caspase activation

“…PC12 cells, a clonal cell line derived from a rat pheochromocytoma, have served as a model for studying the molecular mechanisms promoting neuronal differentiation and neurite outgrowth (Greene and Tischler, 1982) and have been proposed to serve as an effective in vitro model for studying the mechanisms of apoptosis and neurotoxicity (Shafer and Atchison, 1991). As noted previously, Mn can provoke integrin-dependent PC12 cell differentiation via phosphorylation of the MAP kinases, ERK1 and 2 (Walowitz and Roth, 1999). Activation of ERK1 and 2 has a neuroprotective effect because inhibition of the phosphorylation of both kinases potentiates Mn-induced toxicity in these cells.…”

“…Recent studies reveal that like NGF, Mn-induced neurite outgrowth requires the activation of the mitogen activated protein kinase (MAPK) signal transduction pathway via an integrin-dependent increase in the phosphorylation of both ERK1 and 2 (Walowitz and Roth, 1999). Inhibition of ERK1 and 2 phosphorylation by the MEK inhibitor, PD98059, prevents neurite outgrowth and promotes the cytotoxic actions of Mn.…”

Royal jelly-induced neurite outgrowth from rat pheochromocytoma PC12 cells requires integrin signal independent of activation of extracellular signalregulated kinases

“…Integrin signals activate the MAPK signaling pathway, which is required for Mn 2+ -induced neurite outgrowth of PC12 cells (34). TrkA signals evoked by NGF also cause MEK activation followed by ERK1/2 phosphorylation necessary for neurite outgrowth (26).…”

“…Furthermore, PC12 cells have been reported to respond to various molecules such as Mn 2+ (24,34), cAMP analogs (28), and fibroblast growth factor-2 (9) by extending neurites. As the signal transduction pathways are mutually different among these molecules, the activity of AMP N 1 -oxide may be influenced and/or modified by endogenous or exogenous active substances.…”

“…Various reagents were added to the cells 1 day after plating, and morphological changes were then assessed under a phase-contrast microscope. GRGDS, a pentapeptide including the RGD sequence common to extracellular matrix (ECM) components (Peptide Institute, Osaka, Japan), was used to block RGD-mediated interactions between ECM components and integrin receptors (34). Neurite-bearing cells were defined as those having neurites longer than the length of the cell body.…”