INVESTIGADORES
GALIANO Mauricio Raul
congresos y reuniones científicas
Título:
Distal axonal cytoskeletons drive assembly of the axon initial segment.
Autor/es:
MAURICIO R. GALIANO; SMITA JHA; TAMMY SZUYU HO; MATTHEW N. RASBAND
Lugar:
San Diego
Reunión:
Congreso; 40th Annual Meeting Society for Neuroscience; 2010
Institución organizadora:
Society for Neuroscience
Resumen:
The axon initial segment (AIS) is a highly specialized axonal membrane domain located near the cell body and is required for proper action potential initiation and modulation. It has high-density clusters of ion channels tethered to the cytoskeleton by a scaffold consisting of ankyrin G (ankG) and âIV spectrin. Intriguingly, loss of ankG dismantles the AIS and disrupts neuronal polarity. To determine the mechanisms underlying AIS formation and maintenance, we sought to identify how ankG becomes restricted to the AIS. As microtubules and actin cytoskeletons are important for the functional polarization of neurons, we evaluated the contribution of both to AIS assembly. Acute treatment with actin- or microtubule-depolymerizing drugs at early times in hippocampal neuron cultures primarily affects the morphology of neuronal processes with no apparent effect on ankG enrichment at the AIS. We then investigated additional cytoskeletal molecules enriched at the axon for their role in AIS formation. We found that ankyrin-B (ankB) and its interacting partner âII spectrin show an enhanced expression along the axon that precedes the enrichment of ankG at the AIS. Importantly, upon knockdown of ankB, âII-spectrin and áII- spectrin with specific shRNAs, AIS formation is strongly disrupted and ankG fails to accumulate at the AIS. Furthermore, the axonal targeting of ankB depends on its spectrin binding domain. Finally, overexpression of ankB results in a marked shortening of the AIS cluster in neuronal cultures. In summary, the ankB-âII spectrin complex acts upstream of ankG and may constitute an intrinsic intra-axonal barrier that restricts ankG to the AIS subdomain.