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PLoS Biol. 2015 Mar 26;13(3):e1002103. doi: 10.1371/journal.pbio.1002103. eCollection 2015 Mar.

A voltage-gated calcium channel regulates lysosomal fusion with endosomes and autophagosomes and is required for neuronal homeostasis.

Author information

1
Life Sciences Institute and Innovation Center for Cell Biology, Zhejiang University, Hangzhou, China.
2
Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America.
3
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America.
4
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, United States of America.
5
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas, United States of America.
6
Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, United States of America.
7
Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas, United States of America.
8
Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, United States of America; Department of Pathology and Immunology, Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America.
9
Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America; Department of Integrative Biology and Pharmacology, University of Texas School of Medicine, Houston, Texas, United States of America.
10
Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America; Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, United States of America; Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas, United States of America; Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America.

Abstract

Autophagy helps deliver sequestered intracellular cargo to lysosomes for proteolytic degradation and thereby maintains cellular homeostasis by preventing accumulation of toxic substances in cells. In a forward mosaic screen in Drosophila designed to identify genes required for neuronal function and maintenance, we identified multiple cacophony (cac) mutant alleles. They exhibit an age-dependent accumulation of autophagic vacuoles (AVs) in photoreceptor terminals and eventually a degeneration of the terminals and surrounding glia. cac encodes an α1 subunit of a Drosophila voltage-gated calcium channel (VGCC) that is required for synaptic vesicle fusion with the plasma membrane and neurotransmitter release. Here, we show that cac mutant photoreceptor terminals accumulate AV-lysosomal fusion intermediates, suggesting that Cac is necessary for the fusion of AVs with lysosomes, a poorly defined process. Loss of another subunit of the VGCC, α2δ or straightjacket (stj), causes phenotypes very similar to those caused by the loss of cac, indicating that the VGCC is required for AV-lysosomal fusion. The role of VGCC in AV-lysosomal fusion is evolutionarily conserved, as the loss of the mouse homologues, Cacna1a and Cacna2d2, also leads to autophagic defects in mice. Moreover, we find that CACNA1A is localized to the lysosomes and that loss of lysosomal Cacna1a in cerebellar cultured neurons leads to a failure of lysosomes to fuse with endosomes and autophagosomes. Finally, we show that the lysosomal CACNA1A but not the plasma-membrane resident CACNA1A is required for lysosomal fusion. In summary, we present a model in which the VGCC plays a role in autophagy by regulating the fusion of AVs with lysosomes through its calcium channel activity and hence functions in maintaining neuronal homeostasis.

PMID:
25811491
PMCID:
PMC4374850
DOI:
10.1371/journal.pbio.1002103
[Indexed for MEDLINE]
Free PMC Article

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