NEUROLIGIN AND AUTISM

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Autism is a pervasive disorder associated with deficits in forming social reciprocal interaction and communications, development of stereotyped behavior and unusual interests. A recent study by Jamain et al. (2003) reports that mutations of two X-linked homologous genes encoding neuroligin-3 (NL3) and neuroligin-4 (NL4) were found in siblings with autism spectrum disorders (ASD). Neuroligins, proteins of the a/b-hydrolase fold family, are postsynaptic transmembrane proteins that associate with presynaptic partners, the b-neurexins. Neurexin and neuroligin appear to form heterologous cell contacts at synaptic connections, making them suitable candidates for controlling synaptic recognition patterns during early brain development.The aim of this study is to determine the biochemical role of the human NL3-R451C mutation associated with the ASD. Arg451 is highly conserved among all species (from fruit fly to human) and it is located near a predicted EF-hand region, where is suspected to perturb the Ca2+ dependence of the neuroligin-neurexin association. However, using a truncated soluble form of FLAG-NL3 we found that both mutant proteins were not expressed as soluble entities by our mammalian cell system. We hypothesize that the introduction of mutant Cys471 might disrupt the protein folding by creating a new disulfide bond with one of the 7 naturally occurring Cys. We plan to visualize the intracellular trafficking of both wild type and mutant full length proteins using immunofluorescence in stably transfected HEK293 cells in order to determine if both proteins, naturally targeted to the cell membrane, follow the same trafficking pathway.