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Characterization of Neuronal Protein Phosphatases in Aplysia californica
Author(s) -
Endo Shogo,
Shenolikar Shirish,
Eskin Arnold,
Zwartjes Ray E.,
Byrne John H.
Publication year - 1992
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1992.tb09351.x
Subject(s) - okadaic acid , aplysia , dephosphorylation , phosphatase , biology , biochemistry , protein phosphatase 1 , protein subunit , phosphorylation , cytosol , kinase , protein kinase a , microbiology and biotechnology , enzyme , neuroscience , gene
Biochemical properties of neuronal protein phos‐phatases from Aplysia californica were characterized. Dephosphorylation of phosphorylase a by extracts of abdominal ganglia and clusters of sensory neurons from pleural ganglia was demonstrated. Type‐1 protein phosphatase (PrP‐1) was identified in these extracts by the dephosphorylation of the β‐subunit of phosphorylase kinase and its inhibition by the protein, inhibitor‐2. Type‐2A protein phosphatase (PrP‐2A) was demonstrated by the dephosphorylation of the α‐subunit of phosphorylase kinase, which was insensitive to inhibitor‐2. As in vertebrate tissues, only four enzymes, PrP‐1 (47%), PrP‐2A (42%), PrP‐2B (11%), and PrP‐2C (<1%), accounted for all the cellular protein phosphatase activity dephosphor‐ylating phosphorylase kinase. Aplysia PrP‐1 and PrP‐2A were potently inhibited by okadaic acid, with PrP‐1 being approximately 20‐fold more sensitive than PrP‐2A. By comparison, purified PrP‐2A from rabbit skeletal muscle was 15‐ to 20‐fold more sensitive to okadaic acid than PrP‐1 from the same source. Only PrP‐1 was associated with the particulate fractions from Aplysia neurons, whereas PrP‐1 and PrP‐2A, ‐2B, and ‐2C were all present in the cytosol. Extraction of the particulate PrP‐1 decreased its sensitivity to okadaic acid by sixfold, suggesting that cellular factors) affect its sensitivity to this inhibitor. In most respects, protein phosphatases from Aplysia neurons resemble their mammalian counterparts, and their biochemical characterization sets the stage for examining the role of these enzymes in neuronal plasticity, and in learning and memory.