All ETDs from UAB

Advisory Committee Chair

Lin Mei

Advisory Committee Members

Anne Theibert

Kent Keyser

Scott Wilson

Anne Woods

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine


The human brain contains billions of neurons which are designed to receive and integrate a range of electrical and biochemical signals. The ability to convey information between these cells depends on synapses. A precise apposition between the pre and post synapse must exist for efficient transmission to occur. The neuromuscular junction (NMJ) has become a model for studying synaptogenesis. Although much is known about the steps in NMJ formation, only recently have there been insights into the mechanism behind NMJ development. Much of this research has focused on how acetylcholine receptors (AChRs) at the postsynapse form clusters directly apposed to the presynapse. One protein that is required for AChR clustering is rapsyn. Rapsyn is thought to anchor the AChR to the cytoskeleton; however, little is known about the mechanism behind rapsyn’s interaction with the cytoskeleton. In order to further elucidate rapsyn’s role, we performed a yeast two-hybrid screen with rapsyn as the bait. One protein we found was α-actinin, a cytoskeletal protein that crosslinks actin. Through further yeast two-hybrid studies, we mapped which domains with in α-actinin and rapsyn were responsible for their interaction. Furthermore, we were able to show that α-actinin interacts directly with rapsyn. Experiments showed that the rapsyn-α-actinin interaction was weak in both heterologous cells and in myotubes. However, the rapsyn-α-actinin iii interaction was found to be increased by factors known to stimulate AChR clustering. Similarly, agrin, the most studied AChR clustering agent, increased the AChR’s interaction with α-actinin in a manner dependent on rapsyn. Also, we found that knocking down α-actinin expression via an α-actinin specific miRNAi construct disrupted AChR clustering. Furthermore, inhibition of Abl, a tyrosine kinase required for AChR clustering, disrupted the agrin regulated rapsyn-α-actinin interaction. Finally, and perhaps most interesting, an ACh agonist known to disperse AChR clusters abolished the rapsyn- α-actinin interaction. Together these results indicate a potentially important role for α- actinin in AChR clustering.



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