The Journal of Neuroscience, July 15, 2002, 22(14):6092-6105
D1 Dopamine Receptor Regulation of Microtubule-Associated
Protein-2 Phosphorylation in Developing Cerebral Cortical Neurons
Z.-M.
Song1,
A. S.
Undie2,
P. O.
Koh1,
Y.-Y.
Fang3,
L.
Zhang1,
S.
Dracheva4,
S. C.
Sealfon4, and
M. S.
Lidow1
Departments of 1 Oral and Craniofacial Biological
Sciences, 2 Pharmaceutical Sciences, and
3 Neurology, University of Maryland, Baltimore, Maryland
21201, and 4 Department of Neurology and Dr. Arthur M. Fishberg Research Center for Neurobiology, Mount Sinai School of
Medicine, New York, New York 10029
This study addresses the hypothesis that the previously described
capacity of D1 dopamine receptors (D1Rs) to regulate dendritic growth
in developing cortical neurons may involve alterations in the
phosphorylation state of microtubule-associated protein-2 (MAP2). The
changes in phosphorylation of this protein are known to affect its
ability to stabilize the dendritic cytoskeleton. The study involved two
systems: primary cultures of mouse cortical neurons grown in the
presence of the D1R agonists, SKF82958 or A77636, and the cortex of
neonatal transgenic mice overexpressing the D1A subtype of D1R.
In both models, a decrease in dendritic extension corresponded
with an elevation in MAP2 phosphorylation. This phosphorylation
occurred on all three amino acid residues examined in this study:
serine, threonine, and tyrosine. In cultured cortical neurons, D1R
stimulation-induced increase in MAP2 phosphorylation was blocked by the
protein kinase A (PKA) inhibitor, H-89, and mimicked by the PKA
activator, Sp-cAMPS. This indicates that D1Rs modulate MAP2
phosphorylation through PKA-associated intracellular signaling
pathways. We also observed that the elevations in MAP2 phosphorylation
in neuronal cultures in the presence of D1R agonists (or
Sp-cAMPS) were maintained for a prolonged time (up to at
least 96 hr). Moreover, MAP2 phosphorylation underwent a substantial increase between 24 and 72 hr of exposure to these drugs. Our findings
are consistent with the idea that D1Rs can modulate growth and
maintenance of dendrites in developing cortical cells by regulating the
phosphorylation of MAP2. In addition, our observations suggest that
MAP2 phosphorylation by long-term activation of D1Rs (and PKA) can be
divided into two phases: the initial ~24-hr-long phase of a
relatively weak elevation in phosphorylation and the delayed phase of a
much more robust phosphorylation increase taking place during the next
~48 hr.
Key words:
D1 dopamine receptor; cerebral cortex; development; dendrites; MAP2; protein phosphorylation
Copyright © 2002 Society for Neuroscience 0270-6474/02/22146092-14$05.00/0