The Journal of Neuroscience, April 15, 2000, 20(8):2860-2866
Calmodulin-Binding Peptide PEP-19 Modulates Activation of
Calmodulin Kinase II In Situ
Roy A.
Johanson1,
Henry
M.
Sarau2,
James J.
Foley2, and
J. Randall
Slemmon1
Departments of 1 Protein Biochemistry and
2 Pulmonary Pharmacology, SmithKline Beecham Research and
Development, King of Prussia, Pennsylvania 19406
PEP-19 is a 6 kDa polypeptide that is highly expressed in
select populations of neurons that sometimes demonstrate resistance to
degeneration. These include the granule cells of the hippocampus and
the Purkinje cells of the cerebellum. Its only identified activity to
date is that of binding apo-calmodulin. As a consequence, it has been
demonstrated to act as an inhibitor of calmodulin-dependent neuronal
nitric oxide synthase in vitro, although PEP-19
regulation of calmodulin-dependent enzymes has never been characterized
in intact cells. The activation of the calmodulin-dependent enzyme calmodulin kinase II (CaM kinase II) was studied in PC12 cells that had
been transfected so as to express physiological levels of PEP-19. The
expression of PEP-19 yielded a stable phenotype that failed to activate
CaM kinase II upon depolarization in high K+.
However, CaM kinase II could be fully activated when calcium influx was
achieved with ATP. The effect of PEP-19 on CaM kinase II activation was
not attributable to changes in the cellular expression of
calmodulin. The cellular permeability of the transfected cells to
calcium ions also appeared essentially unchanged. The results of this
study demonstrated that PEP-19 can regulate CaM kinase II in
situ in a manner that was dependent on the stimulus used to
mobilize calcium. The selective nature of the regulation by PEP-19
suggests that its function is not to globally suppress calmodulin
activity but rather change the manner in which different stimuli can
access this activity.
Key words:
PEP-19; calmodulin; calmodulin kinase II; calcium; regulation; enzyme assay; PC12; transfection
Copyright © 2000 Society for Neuroscience 0270-6474/00/2082860-07$05.00/0