Tuesday, May 21, 2024
5/21/2024
Project summary The clinical manifestations of autism spectrum disorder (ASD) and related neurodevelopmental disorders (NDDs) are thought to be caused by an imbalance of excitatory and inhibitory neuronal activity. We have discovered that changes in activity cause long-term changes in the intracellular architecture of neurons. The long-term changes occur through the formation of novel organelles, called Golgi satellites (GSats), that have many of the functions of the Golgi apparatus (GA) in the soma. Preliminary data demonstrate that activity changes cause GSats to position at synapses, particularly in dendrites at spine heads. Preliminary data also show that the ASD- and NDD-related protein Ube3a localizes to GSats, and that this association is increased in response to neuronal stimulation. At dendritic synaptic sites, GSats are the “missing” organelles needed for proper glycosylation of locally translated membrane and secreted proteins important for synaptic plasticity. GSat formation transforms local secretory pathways at postsynaptic sites so that locally translated membrane and secreted proteins are properly glycosylated. In addition, multiple glycoproteins which are both associated with ASD and involved in synaptic function are endocytosed into early endosomes and then trafficked into GSats where glycans can again be processed. Through these functions, GSats can remodel the neuronal surface glycoproteome and mediate rapid changes in the sialic acid content of synaptic glycoproteins. These processes can lead to changes in protein function which can then contribute to the altered synaptic function observed in ASD and NDDs. In this proposal we will examine how GSats interact with the products of the ASD- and NDD-risk gene UBE3A. The association of Ube3a with GSats is hypothesized to regulate GSat acidification, which in turn influences the activity of resident sialyltransfereases and their ability to remodel the neuronal surface glycoproteome and rapidly alter synaptic protein sialic contents. We will determine how changes in Ube3a expression alters sialic acid content at synapses and on a set of synaptic and ASD-related glycoproteins. We will also characterize how changes in Ube3a expression regulate activity-induced modulation of GSat formation and localization in relative to synapse, how these changes correlate with synaptic plasticity. We have developed a series of techniques, assays and preparations that will allow us to perform these experiments in both primary neuronal cultures and in ex vivo mouse hippocampal preparations.
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