UNC-41/stonin functions with AP2 to recycle synaptic vesicles in Caenorhabditis elegans.
The recycling of synaptic vesicles requires the recovery of vesicle proteins and membrane. Members of the stonin protein family (Drosophila Stoned B, mammalian stonin 2) have been shown to link the synaptic vesicle protein synaptotagmin to the endocytic machinery. Here we characterize the unc-41 gene, which encodes the stonin ortholog in the nematode Caenorhabditis elegans. Transgenic expression of Drosophila stonedB rescues unc-41 mutant phenotypes, demonstrating that UNC-41 is a bona fide member of the stonin family. In unc-41 mutants, synaptotagmin is present in axons, but is mislocalized and diffuse. In contrast, UNC-41 is localized normally in synaptotagmin mutants, demonstrating a unidirectional relationship for localization. The phenotype of snt-1 unc-41 double mutants is stronger than snt-1 mutants, suggesting that UNC-41 may have additional, synaptotagmin-independent functions. We also show that unc-41 mutants have defects in synaptic vesicle membrane endocytosis, including a ∼50% reduction of vesicles in both acetylcholine and GABA motor neurons. These endocytic defects are similar to those observed in apm-2 mutants, which lack the µ2 subunit of the AP2 adaptor complex. However, no further reduction in synaptic vesicles was observed in unc-41 apm-2 double mutants, suggesting that UNC-41 acts in the same endocytic pathway as µ2 adaptin.
Genetic Models of Disease Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States of America.
Gregory P
GP
Mullen
Kiely M
KM
Grundahl
Mingyu
M
Gu
Shigeki
S
Watanabe
Robert J
RJ
Hobson
John A
JA
Crowell
John R
JR
McManus
Eleanor A
EA
Mathews
Erik M
EM
Jorgensen
James B
JB
Rand
D033962:Adaptor Protein Complex 2 / Q000378:metabolism*; D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D003001:Cloning, Molecular; D029721:Drosophila Proteins / Q000378:metabolism; D004705:Endocytosis; D005786:Gene Expression Regulation; D017238:Genes, Helminth / Q000235:genetics; D016678:Genome / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009420:Nervous System / Q000378:metabolism; D010641:Phenotype; D021381:Protein Transport; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D050857:Synaptotagmins / Q000378:metabolism; D033921:Vesicular Transport Proteins
D033962:Adaptor Protein Complex 2; D033942:Adaptor Proteins, Vesicular Transport; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D029721:Drosophila Proteins; D009419:Nerve Tissue Proteins; C526449:Unc-41 protein, C elegans; D033921:Vesicular Transport Proteins; C420114:stnB protein, Drosophila; D050857:Synaptotagmins