Valbuena Fernando M.

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Valbuena
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Fernando M.
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  • Article
    Activity-dependent Golgi satellite formation in dendrites reshapes the neuronal surface glycoproteome
    (eLife Sciences Publications, 2021-09-21) Govind, Anitha P. ; Jeyifous, Okunola ; Russell, Theron A. ; Yi, Zola ; Weigel, Aubrey V. ; Ramaprasad, Abhijit ; Newell, Luke ; Ramos, William ; Valbuena, Fernando M. ; Casler, Jason C. ; Yan, Jing-Zhi ; Glick, Benjamin S. ; Swanson, Geoffrey T. ; Lippincott-Schwartz, Jennifer ; Green, William N.
    Activity-driven changes in the neuronal surface glycoproteome are known to occur with synapse formation, plasticity, and related diseases, but their mechanistic basis and significance are unclear. Here, we observed that N-glycans on surface glycoproteins of dendrites shift from immature to mature forms containing sialic acid in response to increased neuronal activation. In exploring the basis of these N-glycosylation alterations, we discovered that they result from the growth and proliferation of Golgi satellites scattered throughout the dendrite. Golgi satellites that formed during neuronal excitation were in close association with endoplasmic reticulum (ER) exit sites and early endosomes and contained glycosylation machinery without the Golgi structural protein, GM130. They functioned as distal glycosylation stations in dendrites, terminally modifying sugars either on newly synthesized glycoproteins passing through the secretory pathway or on surface glycoproteins taken up from the endocytic pathway. These activities led to major changes in the dendritic surface of excited neurons, impacting binding and uptake of lectins, as well as causing functional changes in neurotransmitter receptors such as nicotinic acetylcholine receptors. Neural activity thus boosts the activity of the dendrite’s satellite micro-secretory system by redistributing Golgi enzymes involved in glycan modifications into peripheral Golgi satellites. This remodeling of the neuronal surface has potential significance for synaptic plasticity, addiction, and disease.
  • Article
    ESCargo: a regulatable fluorescent secretory cargo for diverse model organisms
    (American Society for Cell Biology, 2020-10-28) Casler, Jason C. ; Zajac, Allison L. ; Valbuena, Fernando M. ; Sparvoli, Daniela ; Jeyifous, Okunola ; Turkewitz, Aaron ; Horne-Badovinac, Sally ; Green, William N. ; Glick, Benjamin S.
    Membrane traffic can be studied by imaging a cargo protein as it transits the secretory pathway. The best tools for this purpose initially block export of the secretory cargo from the endoplasmic reticulum (ER), and then release the block to generate a cargo wave. However, previously developed regulatable secretory cargoes are often tricky to use or specific for a single model organism. To overcome these hurdles for budding yeast, we recently optimized an artificial fluorescent secretory protein that exits the ER with the aid of the Erv29 cargo receptor, which is homologous to mammalian Surf4. The fluorescentsecretory protein forms aggregates in the ER lumen and can be rapidly disaggregated by addition of a ligand to generate a nearly synchronized cargo wave. Here we term this regulatable secretory proteinESCargo (Erv29/Surf4-dependent Secretory Cargo) and demonstrate its utility not only in yeast cells, but also in cultured mammalian cells, Drosophila cells, and the ciliate Tetrahymena thermophila. Kinetic studies indicate that rapid export from the ER requires recognition by Erv29/Surf4. By choosing an appropriate ER signal sequence and expression vector, this simple technology can likely be used withmany model organisms.