The Journal of Neuroscience, April 1, 2000, 20(7):2551-2557
Morphofunctional Plasticity in the Adult Hypothalamus Induces
Regulation of Polysialic Acid-Neural Cell Adhesion Molecule through
Changing Activity and Expression Levels of
Polysialyltransferases
Sylvia
Soares,
Ysander
von
Boxberg,
Michèle
Ravaille-Veron,
Jean-Didier
Vincent, and
Fatiha
Nothias
Institut Alfred Fessard, Centre National de la Recherche
Scientifique UPR 2212, Gif sur Yvette, 91198, France
Polysialic acid-neural cell adhesion molecule (PSA-NCAM)
expression in the adult nervous system is restricted to regions
retaining a capacity for morphological plasticity. For the female rat
hypothalamoneurohypophysial system (HNS), we have previously shown that
lactation induces a dramatic decrease in PSA-NCAM, while leaving the
level of total NCAM protein unchanged. Here, we wanted to elucidate the
molecular mechanisms leading to a downregulation of PSA, thereby
stabilizing newly established synapses and neurohemal contacts that
accompany the increased activity of oxytocinergic neurons.
First, we show that the overall specific activity of
polysialyltransferases present in tissue extracts from supraoptic
nuclei decreases by ~50% during lactation. So far, two
polysialyltransferase enzymes, STX and PST, have been
characterized for their capacity to transfer PSA onto NCAM in
vitro. Using a competitive RT-PCR on RNA extracts from the HNS,
we demonstrate furthermore a significant decrease in the expression
levels of both STX and PST mRNAs in lactating versus virgin animals.
Interestingly, this downregulation of NCAM polysialylation is not
correlated with the post-transcriptional regulation of variable
alternative spliced exon splicing, in contrast to neural development.
The control of polysialylation via a regulation of both enzyme activity
and expression underlines the important role of this post-translational
modification of NCAM in morphofunctional plasticity in adult brain.
Key words:
PSA-NCAM; PST; STX; competitive RT-PCR; enzymatic
activity; lactation
Copyright © 2000 Society for Neuroscience 0270-6474/00/2072551-07$05.00/0