Journal of Neuroscience, Vol 15, 3375-3389, Copyright © 1995 by Society for Neuroscience
Differential expression of protein phosphatase 1 isoforms in mammalian brain
EF da Cruz e Silva, CA Fox, CC Ouimet, E Gustafson, SJ Watson and P Greengard
Rockefeller University, New York, New York 10021, USA.
Rat cDNAs encoding neuronal isoforms of protein phosphatase 1 (PP1) were
isolated and their primary structures elucidated. The derived amino acid
sequences allowed us to design synthetic C-terminal peptides that were used
to raise antibodies. Isoform-specific anti-peptide antibodies against PP1
alpha and PP1 gamma 1 were used to investigate the tissue distribution of
PP1 isoforms by immunoblotting. Both isoforms were ubiquitously expressed
in mammalian tissues, with the highest levels being observed in brain. Of
all neuronal tissues examined, PP1 alpha and PP1 gamma 1 were found to be
most abundantly expressed in the striatum. Lesion experiments with kainic
acid indicated that both the alpha and the gamma 1 isoforms of protein
phosphatase 1 were relatively enriched in the medium-size spiny neurons of
the striatum. "In situ" hybridization to rat brain slices using highly
sensitive riboprobes also showed PP1 alpha, PP1 beta, and PP1 gamma 1 to be
widely expressed in mammalian brain. However, some interesting differences
were observed. For example, PP1 alpha and PP1 gamma 1 were found to be
expressed in the striatum, where DARPP-32 (dopamine- and cAMP-regulated
phosphoprotein, M(r) = 32,000 Da) is also known to be highly expressed. PP1
beta appeared to be relatively less abundant in the same cells, as judged
both by "in situ" hybridization and by the apparent absence of PP1 beta
clones from the striatal cDNA libraries used.