Rapid WAVE dynamics in dendritic spines of cultured hippocampal neurons is mediated by actin polymerization

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Abstract
The Wiskott–Aldrich syndrome protein family Verprolin‐homologous protein (WAVE) complex has been proposed to link Rho GTPase activity with actin polymerization but its role in neuronal plasticity has never been documented. We now examined the presence, distribution and dynamics of WAVE3 in cultured hippocampal neurons. WAVE3 was localized to dendritic spines via its N‐terminal domain. Green fluorescent protein (GFP)‐tagged WAVE3 clusters demonstrate an F‐actin‐dependent high rate of local motility. Constitutive Rac activation translocates WAVE3 (via the N‐terminus), to the leading edge of lamellipodia. Also, spinogenesis is associated with actin‐based motility of the WAVE3 protein. Brain specific WAVE1 showed similar localization and effects on spine density. Cytoplasmic fragile X mental retardation protein interacting protein (CYFIP) and non‐catalytic region of tyrosine kinase adaptor protein 1 (NCK‐1), proteins that are assumed to complex with WAVE, have a somewhat similar cellular distribution and motility. We propose that the WAVE complex is a downstream effector of the Rac signaling cascade, localized to sites of novel synaptic contacts by means of its N‐terminal domain, to guide local actin polymerization needed for morphological plasticity of neurons.