Protein phosphatase-1M and Rho-kinase affect exocytosis from cortical synaptosomes and influence neurotransmission at a glutamatergic giant synapse of the rat auditory system

Authors

  • Beáta Lontay,

    1. Department of Medical Chemistry and Cell Biology and Signaling Research Group of the Hungarian Academy of Sciences, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
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  • Balázs Pál,

    1. Department of Physiology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
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  • Zoltán Serfőző,

    1. Department of Experimental Zoology, Centre for Ecological Research, Balaton Limnological Institute, Hungarian Academy of Sciences, Tihany, Hungary
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  • Áron Kőszeghy,

    1. Department of Physiology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
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  • Géza Szücs,

    1. Department of Physiology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
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  • Zoltán Rusznák,

    1. Department of Physiology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
    2. Neuroscience Research Australia, Sydney, Australia
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  • Ferenc Erdődi

    1. Department of Medical Chemistry and Cell Biology and Signaling Research Group of the Hungarian Academy of Sciences, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
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Address correspondence and reprint requests to Dr. Ferenc Erdődi, Department of Medical Chemistry, Medical and Health Science Center, University of Debrecen, H-4032 Debrecen, Nagyerdei krt. 98. Hungary.
E-mail: erdodi@med.unideb.hu

Abstract

Protein phosphatase-1M (PP1M, myosin phosphatase) consists of a PP1 catalytic subunit (PP1c) and the myosin phosphatase target subunit-1 (MYPT1). RhoA-activated kinase (ROK) regulates PP1M via inhibitory phosphorylation of MYPT1. Using multidisciplinary approaches, we have studied the roles of PP1M and ROK in neurotransmission. Electron microscopy demonstrated the presence of MYPT1 and ROK in both pre- and post-synaptic terminals. Tautomycetin (TMC), a PP1-specific inhibitor, decreased the depolarization-induced exocytosis from cortical synaptosomes. trans-4-[(1R)-1-aminoethyl]-N-4-pyridinylcyclohexanecarboxamide dihydrochloride, a ROK-specific inhibitor, had the opposite effect. Mass spectrometry analysis identified several MYPT1-bound synaptosomal proteins, of which interactions of synapsin-I, syntaxin-1, calcineurin-A subunit, and Ca2+/calmodulin-dependent kinase II with MYPT1 were confirmed. In intact synaptosomes, TMC increased, whereas Y27632 decreased the phosphorylation levels of MYPT1Thr696, myosin-II light chainSer19, synapsin-ISer9, and syntaxin-1Ser14, indicating that PP1M and ROK influence their phosphorylation status. Confocal microscopy indicated that MYPT1 and ROK are present in the rat ventral cochlear nucleus both pre- and post-synaptically. Analysis of the neurotransmission in an auditory glutamatergic giant synapse demonstrated that PP1M and ROK affect neurotransmission via both pre- and post-synaptic mechanisms. Our data suggest that both PP1M and ROK influence synaptic transmission, but further studies are needed to give a full account of their mechanism of action.

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