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Developmental Changes in Calmodulin‐Kinase II Activity at Brain Synaptic Junctions: Alterations in Holoenzyme Composition
Author(s) -
Kelly Paul T.,
Shields Steven,
Conway Kathleen,
Yip Rick,
Burgin Karl
Publication year - 1987
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.1471-4159.1987.tb02456.x
Subject(s) - autophosphorylation , forebrain , biology , protein kinase a , microbiology and biotechnology , protein subunit , kinase , biochemistry , endocrinology , central nervous system , gene
Synaptic junctions (SJs) from rat forebrain were isolated at increasing postnatal ages and examined for endogenous protein kinase activities. Our studies focused on the postnatal maturation of the multifunctional protein kinase designated Ca 2+ /calmodulin‐dependent protein kinase II (CaM‐kinase II). This kinase is comprised of a major 50‐kilodalton (kDa) and a minor 60‐kDa subunit. Experiments examined the developmental properties of CaM kinase II associated with synaptic plasma membranes (SPMs) and synaptic junctions (SJs), as well as the holoenzyme purified from cytosolic extracts. Large developmental increases in CaM‐kinase II activity of SJ fractions were observed between postnatal days 6 and 20; developmental changes were examined for a number of properties including (a) autophosphorylation, (b) endogenous substrate phosphorylation, (c) exogenous substrate phosphorylation, and (d) immunoreactivity. Results demonstrated that fore brain CaM‐kinase II undergoes a striking age‐dependent change in subunit composition. In early postnatal forebrain the 60‐kDa subunit constitutes the major catalytic and immunoreactive subunit of the holoenzyme. The major peak of CaM‐kinase II activity in SJ fractions occurred at approximately postnatal day 20, a time near the end of the most active period of in vivo synapse formation. Following this developmental age, CaM‐kinase II continued to accumulate at SJs; however, its activity was not as highly activated by Ca 2+ plus calmodulin.