Cholesterol transport from late endosomes to the Golgi regulates t-SNARE trafficking, assembly, and function.
Cholesterol regulates plasma membrane (PM) association and functioning of syntaxin-4 and soluble N-ethylmaleimide-sensitive fusion protein 23 (SNAP23) in the secretory pathway. However, the molecular mechanism and cellular cholesterol pools that determine the localization and assembly of these target membrane SNAP receptors (t-SNAREs) are largely unknown. We recently demonstrated that high levels of annexin A6 (AnxA6) induce accumulation of cholesterol in late endosomes, thereby reducing cholesterol in the Golgi and PM. This leads to an impaired supply of cholesterol needed for cytosolic phospholipase A(2) (cPLA(2)) to drive Golgi vesiculation and caveolin transport to the cell surface. Using AnxA6-overexpressing cells as a model for cellular cholesterol imbalance, we identify impaired cholesterol egress from late endosomes and diminution of Golgi cholesterol as correlating with the sequestration of SNAP23/syntaxin-4 in Golgi membranes. Pharmacological accumulation of late endosomal cholesterol and cPLA(2) inhibition induces a similar phenotype in control cells with low AnxA6 levels. Ectopic expression of Niemann-Pick C1 (NPC1) or exogenous cholesterol restores the location of SNAP23 and syntaxin-4 within the PM. Importantly, AnxA6-mediated mislocalization of these t-SNAREs correlates with reduced secretion of cargo via the SNAP23/syntaxin-4-dependent constitutive exocytic pathway. We thus conclude that inhibition of late endosomal export and Golgi cholesterol depletion modulate t-SNARE localization and functioning along the exocytic pathway.
Departament de Biologia Cel·lular, Immunologia i Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain.
Meritxell
M
Reverter
Carles
C
Rentero
Sandra Vilà
SV
de Muga
Anna
A
Alvarez-Guaita
Vishwaroop
V
Mulay
Rose
R
Cairns
Peta
P
Wood
Katia
K
Monastyrskaya
Albert
A
Pol
Francesc
F
Tebar
Joan
J
Blasi
Thomas
T
Grewal
Carlos
C
Enrich
D000818:Animals; D017317:Annexin A6 / Q000378:metabolism; D016466:CHO Cells; D051242:Caveolin 1 / Q000378:metabolism; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism*; D006224:Cricetinae; D011992:Endosomes / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism; D008856:Microscopy, Fluorescence; D054510:Phospholipases A2, Cytosolic / Q000378:metabolism; D055503:Protein Multimerization; D021381:Protein Transport; D050765:Qa-SNARE Proteins / Q000378:metabolism; D050766:Qb-SNARE Proteins / Q000378:metabolism; D050767:Qc-SNARE Proteins / Q000378:metabolism; D050600:SNARE Proteins / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D017317:Annexin A6; D051242:Caveolin 1; D005353:Fibronectins; D008562:Membrane Glycoproteins; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050600:SNARE Proteins; D014409:Tumor Necrosis Factor-alpha; D002784:Cholesterol; D054510:Phospholipases A2, Cytosolic