the actin binding domain of βi-spectrin regulates the morphological and functional dynamics of dendritic spines肌动蛋白结合域βi-spectrin调节树突棘的形态和功能动态.pdf

The Actin Binding Domain of bI-Spectrin Regulates the Morphological and Functional Dynamics of Dendritic Spines 1,2,3¤a 1 1¤b 1,2,3 1,2,3 Michael W. Nestor , Xiang Cai , Michele R. Stone , Robert J. Bloch , Scott M. Thompson * 1 Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America, 2 Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, United States of America, 3 Training Program in Integrative Membrane Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America Abstract Actin microfilaments regulate the size, shape and mobility of dendritic spines and are in turn regulated by actin binding proteins and small GTPases. The bI isoform of spectrin, a protein that links the actin cytoskeleton to membrane proteins, is present in spines. To understand its function, we expressed its actin-binding domain (ABD) in CA1 pyramidal neurons in hippocampal slice cultures. The ABD of bI-spectrin bundled actin in principal dendrites and was concentrated in dendritic spines, where it significantly increased the size of the spine head. These effects were not observed after expression of homologous ABDs of utrophin, dystrophin, and a-actinin. Treatment of slice cultures with latrunculin-B significantly decreased spine head size and decreased actin-GFP fluorescence in cells expressing the ABD of a-actinin, but not the ABD of bI-spectrin, suggesting that its presence inhibits actin depolymerization. We also observed an increase in the area of GFP- tagged PSD-95 in the spine head and an increase in the amplitude