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Media type:
E-Article
Title:
SPAR2, a novel SPAR‐related protein with GAP activity for Rap1 and Rap2
Contributor:
Spilker, Christina;
Acuña Sanhueza, Gustavo A.;
Böckers, Tobias M.;
Kreutz, Michael R.;
Gundelfinger, Eckart D.
imprint:
Wiley, 2008
Published in:Journal of Neurochemistry
Language:
English
DOI:
10.1111/j.1471-4159.2007.04991.x
ISSN:
0022-3042;
1471-4159
Origination:
Footnote:
Description:
<jats:title>Abstract</jats:title><jats:p>Spine‐associated RapGAP 2 (SPAR2) is a novel GTPase activating protein (GAP) for the small GTPase Rap that shows significant sequence homology to SPAR, a synaptic RapGAP that was reported to regulate spine morphology in hippocampal neurons. SPAR2, like SPAR, interacts with the recently described synaptic scaffolding protein ProSAP‐interacting protein (ProSAPiP), which in turn binds to the PDZ domain of ProSAP/Shank post‐synaptic density proteins. In subcellular fractionation experiments, SPAR2 is enriched in synaptosomes and post‐synaptic density fractions indicating that it is a synaptic protein. Furthermore, we could show using <jats:italic>in vitro</jats:italic> GAP assays that SPAR2 has GAP activity for Rap1 and Rap2. Expression in COS‐7 cells, however, revealed different actin‐binding properties of SPAR2 and SPAR. Additionally, over‐expression of SPAR2 in cultured hippocampal neurons did not affect spine morphology as it was reported for SPAR. <jats:italic>In situ</jats:italic> hybridization studies also revealed a differential tissue distribution of SPAR and SPAR2 with SPAR2 transcripts being mainly expressed in cerebellar and hippocampal granule cells. Moreover, in the cerebellum SPAR2 is developmentally regulated with a peak of expression around the period of synapse formation. Our results imply that SPAR2 is a new RapGAP with specific functions in cerebellar and hippocampal granule cells.</jats:p>