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Activity dependent cleavage and protein phosphorylation regulate human glutamate decarboxylase GAD65 activity
Author(s) -
Buddhala Chandana,
Wei Jianning,
Wu Jang Yen
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1048.3
Subject(s) - phosphorylation , glutamate decarboxylase , glutamate receptor , biochemistry , protein phosphorylation , threonine , protein kinase c , chemistry , gene isoform , biology , microbiology and biotechnology , enzyme , protein kinase a , serine , receptor , gene
Brain L‐glutamate decarboxylase (GAD) is responsible for the synthesis of neurotransmitter GABA. There are two GAD isoforms, namely GAD65 and GAD67. The two are regulated differentially by protein phosphorylation. GAD65 is activated by phosphorylation mediated by PKC‐ε whereas GAD67 is inhibited by phosphorylation mediated by PKA. The phosphorylation site of GAD67 was identified as Threonine 91 based on MALDI‐TOF and site‐directed mutation analysis. (Biochemistry 43:6182–6189, 2004). Here we further report several lines of evidence on the regulation of GAD activity during neuronal activity with special focus on GAD65. Under stimulation condition, GAD65 activity is increased due to increase in phosphorylation through translocation of PKC‐ε to become membrane‐anchored. Several potential phosphorylation sites have been implicated in the regulation of GAD65 activity. In addition, cleavage of GAD65 by calpain also increased GAD65 activity. A model depicting activity‐dependent regulation of GAD65 by phosphorylation and proteolytic cleavage is proposed.