[Abstract Title]. - Society for Neuroscience

Support: Grant-in-Aid for Scientific research (B)
Title: Vezatin is a possible downstream effector of ADP-rybosilation factor 6 that regulates
dendritic formation
Authors: *M. SANDA 1,2 , K. FUKUNAGA 2 , H. SAKAGAMI 1 ;
1 Anat., Kitasato Univ., sagamihara, Japan; 2 Pharmacol., Tohoku Univ. Grad. Sch. of Pharmaceut.
Sci., Sendai, Japan
Abstract: ADP-ribosylation factor 6 (ARF6) belongs to the ARF family of Ras-related small
GTPases and mediates various neuronal functions through the regulation of actin cytoskeleton
and membrane trafficking. Although ARF6 has recently been shown to regulate the dendritic
formation, the detailed mechanisms by which ARF6 regulates the dendritic formation are poorly
understood. To address this issue, it is crucial to identify interacting proteins with ARF6 as
candidates for downstream targets. Therefore, we performed a yeast two hybrid screening of a
mouse brain cDNA library with a constitutively active ARF6 mutant as bait. Among positive
clones, three independent clones encoded vezatin. Vezatin has recently been identified as a
transmembrane protein that interacts with myosin VIIA and α-catenin at adherens junctions,
thereby constructing a functional and structural linkage between actin cytoskeleton and
cadherin/catenin complex. In vitro binding assay showed that vezatin was able to bind
specifically to GTP-bound ARF6 among the ARF family members. In the mature mouse brain,
vezatin mRNA was widely expressed in the mature mouse brain with a high level in the olfactory
bulb, cerebral cortex, hippocampus, striatum and cerebellar granular cell layer. In the embryonic
brain, vezatin mRNA was already detected at a high level throughout the brain and spinal cord.
The expression was observed in both mantle and ventricular zones with a higher level in the
former. Further, northern blot analysis showed that vezatin mRNA was already detected in the
mouse brain at E13 and peaked at E15. After birth, the expression of vezatin mRNA was
gradually decreased by 50% compared to that at embryonic stages. In cultured hippocampal
neurons, vezatin was present in cell bodies and dendrites, but not in axons. Confocal microscopic
observation at high magnification of dendrites, the immunoreactivity for vezatin appeared as
punctate inside the dendritic shafts, which were colocalized with EEA1, a marker for endosomes.
Furthermore, the overexpression of full length of vezatin promoted dendritic length and
complexity of cultured hippocampal neurons. Our present findings suggest that vezatin may
function to regulate dendritic formation as a downstream effector for ARF6.
Disclosures: M. Sanda, None; K. Fukunaga, None; H. Sakagami, None.
Poster
231. Dendrite Growth and Branching: Signaling
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm