All ETDs from UAB

Advisory Committee Chair

Anne Theibert

Advisory Committee Members

Lori L McMahon

Lucas Pozzo-Miller

Elizabeth Sztul

Scott Wilson

Document Type

Dissertation

Date of Award

2013

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

ADP ribosylation factor 6 (Arf6) is a member of the Arf family of small GTPases known to function in vesicular membrane trafficking and cytoskeletal organization. Arf6 cycles between its GTP and GDP bound states, facilitated by GTP exchange factors (GEFs) and GTPase activating proteins (GAPs), respectively. In my dissertation studies I have investigated the neuronal functions of Arf6 and ADAP1, an Arf6 GAP and candidate PI 3-kinase target required for dendritic differentiation in developing neurons. I demonstrated that in neurosecretory PC12 cells and neurons, ADAP1 and Arf6 colocalize with regulated secretory granules (SGs) that traffic chromogranin B and brain-derived neurotrophic factor (BDNF), a secreted factor important for neuronal development and synaptic plasticity. Using a pulse-chase assay in PC12 cells to monitor trafficking of chromogranin B, I demonstrated that siRNA-mediated knockdown (or expression of inactive mutants) of ADAP1 or Arf6, resulted in an inhibition of the trafficking and maturation of regulated SGs. In neurons, knock down of ADAP1 or Arf6 leads to an increase in the colocalization of BDNF-GFP with furin, a peptidase localized to immature SGs, suggesting that ADAP1 and Arf6 participate in the maturation of BDNF containing SGs. Knock down of ADAP1 or Arf6 in neurons also impairs dendritic differentiation. Intriguingly, this impairment is rescued by the overexpression of BDNF. Together my studies indicate a role for ADAP1 and Arf6 in the trafficking of chromogranin B and BDNF-containing regulated SGs in neurons, which may underlie their roles in regulating dendritic differentiation.

ShardayEwellDissertationFigures.pdf (45922 kB)
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