Protein fucosylation regulates synapsin la/lb expression and neuronal morphology in primary hippocampal neurons

Although fucose-alpha(1-2)-galactose [Fuc alpha(1-2)Gal] carbohydrates have been implicated in cognitive processes such as long-term memory, the molecular mechanisms by which these sugars influence neuronal communication are not well understood. Here, we present molecular insights into the functions of Fuca(1-2)Gal sugars, demonstrating that they play a role in the regulation of synaptic proteins and neuronal morphology. We show that synapsins la and Ib, synapse-specific proteins involved in neurotransmitter release and synaptogenesis, are the major Fuca(1-2)Gal glycoproteins in mature cultured neurons and the adult rat hippocampus. Fucosylation has profound effects on the expression and turnover of synapsin in cells and protects synapsin from degradation by the calcium-activated protease calpain. Our studies suggest that defucosylation of synapsin has critical consequences for neuronal growth and morphology, leading to stunted neurite outgrowth and delayed synapse formation. We also demonstrate that Fuca(1-2)Gal carbohydrates are not limited to synapsin but are found on additional glycoproteins involved in modulating neuronal architecture. Together, our studies identify important roles for Fuca(1-2)Gal sugars in the regulation of neuronal proteins and morphological changes that may underlie synaptic plasticity.