title: AP-3-dependent mechanisms control the targeting of a chloride channel (ClC-3) in neuronal and non-neuronal cells.
abstract: Adaptor protein (AP)-2 and AP-3-dependent mechanisms control the sorting of membrane proteins into synaptic vesicles. Mouse models deficient in AP-3, mocha, develop a neurological phenotype of which the central feature is an alteration of the luminal synaptic vesicle composition. This is caused by a severe reduction of vesicular levels of the zinc transporter 3 (ZnT3). It is presently unknown whether this mocha defect is restricted to ZnT3 or encompasses other synaptic vesicle proteins capable of modifying synaptic vesicle contents, such as transporters or channels. In this study, we identified a chloride channel, ClC-3, whose level in synaptic vesicles and hippocampal mossy fiber terminals was reduced in the context of the mocha AP-3 deficiency. In PC-12 cells, ClC-3 was present in transferrin receptor-positive endosomes, where it was targeted to synaptic-like microvesicles (SLMV) by a mechanism sensitive to brefeldin A, a signature of the AP-3-dependent route of SLMV biogenesis. ClC-3 was packed in SLMV along with the AP-3-targeted synaptic vesicle protein ZnT3. Co-segregation of ClC-3 and ZnT3 to common intracellular compartments was functionally significant as revealed by increased vesicular zinc transport with increased ClC3 expression. Our work has identified a synaptic vesicle protein in which trafficking to synaptic vesicles is regulated by AP-3. In addition, our findings indicate that ClC-3 and ZnT3 reside in a common vesicle population where they functionally interact to determine vesicle luminal composition.
authors.affiliation: Department of Cell Biology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Gloria
authors.initials: G
authors.lastname: Salazar
authors.forename: Rachal
authors.initials: R
authors.lastname: Love
authors.forename: Melanie L
authors.initials: ML
authors.lastname: Styers
authors.forename: Erica
authors.initials: E
authors.lastname: Werner
authors.forename: Andrew
authors.initials: A
authors.lastname: Peden
authors.forename: Sandra
authors.initials: S
authors.lastname: Rodriguez
authors.forename: Marla
authors.initials: M
authors.lastname: Gearing
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Wainer
authors.forename: Victor
authors.initials: V
authors.lastname: Faundez
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000502:physiology; D020126:Brefeldin A / Q000494:pharmacology; D002352:Carrier Proteins / Q000032:analysis; D027682:Cation Transport Proteins; D018118:Chloride Channels / Q000032:analysis / Q000378:metabolism*; D005998:Glycine / Q000031:analogs & derivatives*; D051907:Lysosomal Membrane Proteins; D008565:Membrane Proteins / Q000032:analysis; D026901:Membrane Transport Proteins; D051379:Mice; D034041:Monomeric Clathrin Assembly Proteins / Q000502:physiology*; D021381:Protein Transport; D050683:R-SNARE Proteins; D051381:Rats; D011990:Receptors, Transferrin / Q000032:analysis; D013572:Synaptic Vesicles / Q000737:chemistry / Q000378:metabolism; D016708:Synaptophysin / Q000032:analysis
chemical_list: D015703:Antigens, CD; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D018118:Chloride Channels; C115376:ClC-3 channel; D051907:Lysosomal Membrane Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D034041:Monomeric Clathrin Assembly Proteins; D050683:R-SNARE Proteins; D011990:Receptors, Transferrin; C491177:Slc30a3 protein, mouse; D016708:Synaptophysin; C439023:clathrin assembly protein AP180; C084257:PC 12 ester; D020126:Brefeldin A; D005998:Glycine