Plasma membrane oestrogen receptor mediates neuroprotection against β-amyloid toxicity through activation of Raf-1/MEK/ERK cascade in septal-derived cholinergic SN56 cells

Authors

  • Borja Guerra,

    1. Laboratory of Cellular Neurobiology, Department of Physiology
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  • Mario Díaz,

    1. Laboratory of Animal Physiology, Department of Animal Biology, Faculty of Biology, University of La Laguna, Santa Cruz de Tenerife, Spain
    2. Spanish Network for Neurological Disorders, La Laguna University, La Laguna, Spain
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  • Rafael Alonso,

    1. Laboratory of Cellular Neurobiology, Department of Physiology
    2. Spanish Network for Neurological Disorders, La Laguna University, La Laguna, Spain
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  • Raquel Marin

    1. Laboratory of Cellular Neurobiology, Department of Physiology
    2. Spanish Network for Neurological Disorders, La Laguna University, La Laguna, Spain
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Address correspondence and reprint requests to Dr Raquel Marin, Laboratory of Cellular Neurobiology, Department of Physiology, University of La Laguna, School of Medicine, 38071 Santa Cruz de Tenerife, Spain. E-mail: rmarin@ull.es

Abstract

Rapid oestrogen neuroprotection against β-amyloid peptide (Aβ)-induced toxicity, a main feature of Alzheimer's disease, may be partially initiated at the plasma membrane. However, the mechanism by which this oestrogen effect occurs is unknown. In a septal murine cell line (SN56), we observed that short exposures to either 17β-oestradiol (E2) or membrane impermeant E2 bound to horseradish peroxidase (E-HRP) induced a biphasic stimulation of extracellular-signal regulated protein kinase (ERK1/2) phosphorylation, with peak inductions detected around 4–8 min in the early phase and a second maximum around 8 h after treatment. ERK1/2 phosphorylation was abolished by ERK1/2 kinase (MEK) inhibitors PD98059 and U0126. Interestingly, PD98059 was also shown to block rapid E2-related prevention of death in cells exposed to Aβ fragment 1–40 (Aβ1−40) for 24 h. In contrast, no neuroprotective effects were obtained when MEK inhibitor was used to selectively abolish the late phosphorylation phase. Furthermore, both ERK1/2 activation and E2-associated protection were blocked by an inhibitor of Raf-1 kinase. Raf-1 may be involved in these effects because oestrogen caused the rapid serine 338 (Ser338) phosphorylation of this protein. In addition, the oestrogen receptor (ER) antagonist ICI 182 780 was also observed to block ERK1/2 phosphorylation. We propose a novel mechanism in SN56 cells by which rapid effects of oestrogen leading to neuroprotection are signalled through Raf-1/MEK/ERK1/2 pathway, possibly by activation of a membrane-related ER.

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