Journal Article

The Actin Binding Domain of betaI-Spectrin Regulates the Morphological and Functional Dynamics of Dendritic Spines

Nestor, Michael W, Cai, Xiang, Stone, Michele R, Bloch, Robert J, Thompson, Scott M

2011

Overview

Actin microfilaments regulate the size, shape and mobility of dendritic spines and are in turn regulated by actin binding proteins and small GTPases. The [beta]I 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 [beta]I-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 [alpha]-actinin. Treatment of slice cultures with latrunculin-B significantly decreased spine head size and decreased actin-GFP fluorescence in cells expressing the ABD of [alpha]-actinin, but not the ABD of [beta]I-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 of mEPSCs at spines expressing the ABD of [beta]I-spectrin. The effects of the [beta]I-spectrin ABD on spine size and mEPSC amplitude were mimicked by expressing wild-type Rac3, a small GTPase that co-immunoprecipitates specifically with [beta]I-spectrin in extracts of cultured cortical neurons. Spine size was normal in cells co-expressing a dominant negative Rac3 construct with the [beta]I-spectrin ABD. We suggest that [beta]I-spectrin is a synaptic protein that can modulate both the morphological and functional dynamics of dendritic spines, perhaps via interaction with actin and Rac3.

• Publisher: Public Library of Science
• Subject: Actin / Dystrophin / Fluorescence / G proteins / Neurons / Protein binding / Proteins / Utrophin