Evidence for a vesicle-mediated maintenance of store-operated calcium channels in a human embryonic kidney cell line.
Direct microinjection of the clostridial neurotoxins botulinum neurotoxin A light chain or tetanus neurotoxin into cells of a human embryonic kidney cell line significantly reduced calcium entry after depletion of internal calcium stores by cyclopiazonic acid, a reversible inhibitor of the sarcoplasmic-endoplasmic reticular calcium-ATPases. Botulinum neurotoxin A light chain specifically hydrolyzes a synaptosomal-associated protein of 25 kilodaltons (SNAP-25), and tetanus neurotoxin specifically hydrolyzes synaptobrevin-2 (vesicle-associated membrane protein 2, VAMP-2) and cellubrevin (vesicle-associated membrane protein 3, VAMP-3). Since these substrate proteins are required for vesicle docking and fusion, inhibition of store-operated calcium entry by botulinum neurotoxin A light chain and tetanus neurotoxin supports a model in which vesicle fusion is a prerequisite for activation of store-operated calcium entry. Brefeldin A, a fungal metabolite that interferes with vesicle traffic, partially reduced calcium entry following store depletion. The size of the reserve pool of vesicles or parallel vesicle recycling pathways employing brefeldin A-sensitive and brefeldin A-insensitive ADP-ribosylation factors may explain the failure of brefeldin A to completely inhibit store-operated calcium entry.
Alderton
J M
JM
Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA.
Ahmed
S A
SA
Smith
L A
LA
Steinhardt
R A
RA
D019274:Botulinum Toxins, Type A / Q000494:pharmacology; D020126:Brefeldin A / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D020013:Calcium Signaling; D002460:Cell Line; D022162:Cytoplasmic Vesicles / Q000502:physiology*; D004622:Embryo, Mammalian; D006801:Humans; D007668:Kidney / Q000166:cytology; D008666:Metalloendopeptidases / Q000494:pharmacology; D008845:Microinjections; D013744:Tetanus Toxin / Q000494:pharmacology
D015220:Calcium Channels; D013744:Tetanus Toxin; C035979:tetanospasmin; D020126:Brefeldin A; D008666:Metalloendopeptidases; D019274:Botulinum Toxins, Type A