Potential role of synaptopodin in spine motility by coupling actin to the spine apparatus

Dendritic spines are dynamic structures that rapidly remodel their shape an d size. These morphological adaptations are regulated by changes in synapti c activity, and result from rearrangements of the postsynaptic cytoskeleton . A cytoskeletal molecule preferentially found in mature spines is the acti n-associated protein synaptopodin. It is strongly expressed by spine-bearin g neurons in the olfactory bulb, striatum, cerebral cortex, and hippocampus . In the hippocampus, principal cells express synaptopodin mRNA and sort th e protein to the spine compartment. Within the spine microdomain, synaptopo din is preferentially located in the spine neck and is closely associated w ith the spine apparatus. On the basis of these data we hypothesize that syn aptopodin could affect spine motility by bundling actin filaments in the sp ine neck. In addition, it could link the actin cytoskeleton of spines to in tracellular calcium stores, i.e., the spine apparatus and the smooth endopl asmic reticulum. Hippocampus 2000;10:569-581. (C) 2000 Wiley-Liss, Inc.