Protein processing and releases of neuregulin-1 are regulated in an activity-dependent manner

Authors

  • Miwako Ozaki,

    1. Laboratory for Memory and Learning
    2. Laboratory for Neural Architecture, Brain Science Institute, RIKEN (The Institute of Physical and Chemical Research), Saitama, Japan
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  • Kouich Itoh,

    1. Laboratory for Neural Architecture, Brain Science Institute, RIKEN (The Institute of Physical and Chemical Research), Saitama, Japan
    2. Department of Pharmacology, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan
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    • 1

      The present address of Kouich Itoh is Laboratory of Molecular Pharmacology, Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences at Kagawa Campus, Tokushima Bunri University, Sanuki-city, Kagawa, Japan.

  • Yukie Miyakawa,

    1. Laboratory for Neural Architecture, Brain Science Institute, RIKEN (The Institute of Physical and Chemical Research), Saitama, Japan
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  • Haruo Kishida,

    1. Laboratory for Neural Architecture, Brain Science Institute, RIKEN (The Institute of Physical and Chemical Research), Saitama, Japan
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  • Tsutomu Hashikawa

    1. Laboratory for Neural Architecture, Brain Science Institute, RIKEN (The Institute of Physical and Chemical Research), Saitama, Japan
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Address correspondence and reprint requests to Dr Miwako Ozaki, Laboratory for Memory and Learning, Brain Science Institute, RIKEN, Wako-shi, Saitama 351–0198, Japan. E-mail: mozaki@postman.riken.go.jp

Abstract

Identification of the key molecules that bridge presynaptic neuronal events and long-term modification of the postsynaptic process is an important challenge which will have to be met in order to further our understanding of the mechanisms for learning and memory. This study is focused on neuregulin-1 (NRG-1), a neurotrophic factor, that is known to regulate the development of various tissues and/or the life/death of cells through activation of the ErbB family receptor tyrosine kinases. It was discovered that the soluble form of NRG-1 (sNRG-1) is produced from the transmembrane form of NRG through proteolytic cleavage during electrical stimulation of either cultured cerebellar granule cells (GCs) or pontine nucleus neurons (PNs) that are presynaptic to GCs. sNRG-1 was assayed by measuring the phosphorylation of both the ErbB receptors and cyclic AMP-responsive element-binding protein (CREB), and by means of antibodies to sNRG-1. The cleavage and release of NRG-1 depended on the frequency of electrical stimulation; the peak effect was at 50 Hz in both GCs and PNs. Activation of protein kinase C (PKC) mimicked this effect. The culture apparatus provided along with the mass-electrical stimulation that was employed proved to be a powerful tool for combining neuronal electrical events and chemical events. We conclude from the results that, in mossy fibre (PN axon)-GC synapses, electrical activity controls the proteolytic processing of NRG-1 in a frequency-dependent fashion and involves PKC. Furthermore, cleaved sNRG-1 plays an important functional role in regulating transmission across these synapses.

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