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Loss of MUNC18‐1 leads to retrograde transport defects in neurons
Author(s) -
Berkel Annemiek A.,
Santos Tatiana C.,
Shaweis Hesho,
Weering Jan R. T.,
Toonen Ruud F.,
Verhage Matthijs
Publication year - 2021
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/jnc.15256
Subject(s) - golgi apparatus , microbiology and biotechnology , snap25 , biology , endoplasmic reticulum , endosome , axoplasmic transport , exocytosis , rab , transport protein , neurodegeneration , syntaxin , synaptic vesicle , intracellular , vesicle , biochemistry , gtpase , medicine , disease , membrane , secretion
Abstract Loss of the exocytic Sec1/MUNC18 protein MUNC18‐1 or its target‐SNARE partners SNAP25 and syntaxin‐1 results in rapid, cell‐autonomous and unexplained neurodegeneration, which is independent of their known role in synaptic vesicle exocytosis. cis‐ Golgi abnormalities are the earliest cellular phenotypes before degeneration occurs. Here, we investigated whether loss of MUNC18‐1 causes defects in intracellular membrane transport pathways in primary murine neurons that may explain neurodegeneration. Electron, confocal and super resolution microscopy confirmed that loss of MUNC18‐1 expression results in a smaller cis‐ Golgi. In addition, we now show that medial ‐Golgi and the trans‐ Golgi Network are also affected. However, stacking and cisternae ultrastructure of the Golgi were normal. Overall, ultrastructure of null mutant neurons was remarkably normal just hours before cell death occurred. By synchronizing protein trafficking by conditional cargo retention in the endoplasmic reticulum using selective hooks (RUSH) and immunocytochemistry, we show that anterograde Endoplasmic Reticulum‐to‐Golgi and Golgi exit of endogenous and exogenous proteins were normal. In contrast, loss of MUNC18‐1 caused reduced retrograde Cholera Toxin B‐subunit transport from the plasma membrane to the Golgi. In addition, MUNC18‐1‐deficiency resulted in abnormalities in retrograde TrkB trafficking in an antibody uptake assay. We conclude that MUNC18‐1 deficient neurons have normal anterograde but reduced retrograde transport to the Golgi. The impairments in retrograde pathways suggest a role of MUNC18‐1 in endosomal SNARE‐dependent fusion and provide a plausible explanation for the observed Golgi abnormalities and cell death in MUNC18‐1 deficient neurons.