| Abstract No.: | C-B3065 |
| Country: | Canada |
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| Title: | FACTORS REGULATING SYNAPTIC TARGETING OF NEUROLIGINS |
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| Authors/Affiliations: | 1 Joshua Levinson*; 1 Rongwen Li; 1 Rochelle Hines; 1 Hakima Moukhles; 1 Shernaz Bamji; 1 Alaa El-Husseini;
1 University of British Columbia, Vancouver, BC, Canada
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| Content: | The neuroligin (NL) family of postsynaptic cell adhesion molecules has been implicated in various stages of CNS synapse development, and has recently been shown to play a role in synaptic maturation and function in vivo. NL1 has been linked to the development of excitatory synapses, targeting mainly to these sites, and interacting with molecules such as PSD-95. Although PSD-95 is involved in the recruitment of neuroligins to excitatory synapses, factors influencing the targeting of NL2 to inhibitory contacts are less well defined.
Objectives: To clarify factors involved in trafficking of NL2, we set out to assess the importance of various regions of NL2 for its targeting to inhibitory synaptic sites. In addition, we have examined the roles of postsynaptic scaffolding proteins in influencing the normal targeting of neuroligin family members to specific synapse types.
Methods and Materials: To this end, we have carried out a detailed deletional analysis of different regions within the C-terminal, intracellular domain of NL2. Immunofluorescence microscopy was used to determine the localization patterns of NL2 C-terminal mutant proteins, as well as the ability of these mutants to recruit the inhibitory postsynaptic molecule, gephyrin, to sites of inhibitory contact. In addition, siRNA-mediated knockdown of PSD-95 and gephyrin were used to determine the effects of these molecules on modulating the targeting of various neuroligin family members.
Results: We have determined that the C-terminal region of NL2 is important for its proper trafficking to inhibitory contacts. Examination of subdomains within the C-terminus reveals that the PDZ-binding domain, as well as the region between amino acids 714 and 782, play modulatory roles in determining the proper localization of NL2. In addition, we demonstrate that targeting of gephyrin to inhibitory synapses is partially regulated by intracellular regions within NL2. siRNA knockdown of gephyrin results in a modest shift of NL2 from inhibitory to excitatory synaptic contacts. Furthermore, we now show that, like NL1, NL3 is found throughout the brain, and localizes mainly to excitatory synapses, but partially to inhibitory synapses as well. Moreover, we have found that knockdown of PSD-95 leads to a shift of NL3 from excitatory to inhibitory contacts, suggesting that NL3 behaves like NL1 with respect to its interaction with postsynaptic scaffolding proteins such as PSD-95.
Conclusion: Together, these data suggest that differential mechanisms exist to regulate sorting of different neuroligin family members, and that specific C-terminal regions partially contribute to these sorting processes. |
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