The Journal of Neuroscience, September 1, 1999, 19(17):7415-7425
Regulated Expression and Subcellular Localization of Syndecan
Heparan Sulfate Proteoglycans and the Syndecan-Binding Protein
CASK/LIN-2 during Rat Brain Development
Yi-Ping
Hsueh and
Morgan
Sheng
Howard Hughes Medical Institute and Department of Neurobiology,
Massachusetts General Hospital and Harvard Medical School, Boston,
Massachusetts 02114
The syndecan family of cell surface heparan sulfate
proteoglycans interacts via their cytoplasmic C-terminal tail
with the PDZ domain of CASK/LIN-2, a
membrane-associated guanylate kinase homolog. The syndecan-CASK
interaction may be involved in intercellular signaling and/or cell
adhesion. Here we show that syndecan-1 to syndecan-4 have distinctive
mRNA distributions in adult rat brain by in situ
hybridization, with syndecan-2 and -3 being the major syndecans
expressed in neurons of the forebrain. At the protein level, syndecan-2
and -3 are differentially localized within neurons; syndecan-3 is
concentrated in axons, whereas syndecan-2 is localized in synapses. The
synaptic accumulation of syndecan-2 occurs late in synapse development.
CASK is a cytoplasmic-binding partner for syndecans, and its
subcellular distribution changes strikingly during development,
shifting from a primarily axonal distribution in the first 2 postnatal
weeks to a somatodendritic distribution in adult brain. This change in
CASK distribution correlates temporally and spatially with the
expression patterns of syndecan-3 and -2, consistent with the
association of both of these syndecans with CASK in
vivo. In support of this, we were able to coimmunoprecipitate a
complex of CASK and syndecan-3 from brain extracts. Our results indicate that specific syndecans are differentially expressed in
various cell types of the brain and are targeted to distinct subcellular compartments in neurons, where they may serve specialized functions. Moreover, CASK is appropriately expressed and localized to
interact with both syndecan-2 and -3 in different compartments of the
neuron throughout postnatal development.
Key words:
syndecan; CASK/LIN-2; heparan sulfate proteoglycan; MAGUK; subcellular targeting; axon
Copyright © 1999 Society for Neuroscience 0270-6474/99/19177415-11$05.00/0