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PMID: 10725327 Published · ppublish English Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S.

Synaptotagmin VII regulates Ca(2+)-dependent exocytosis of lysosomes in fibroblasts.

The Journal of cell biology ·Vol. 148 ·No. 6 ·2000-03-20 ·Pages 1141-49

Martinez I, Chakrabarti S, Hellevik T, Morehead J, Fowler K, Andrews NW

Abstract

Synaptotagmins (Syts) are transmembrane proteins with two Ca(2+)-binding C(2) domains in their cytosolic region. Syt I, the most widely studied isoform, has been proposed to function as a Ca(2+) sensor in synaptic vesicle exocytosis. Several of the twelve known Syts are expressed primarily in brain, while a few are ubiquitous (Sudhof, T.C., and J. Rizo. 1996. Neuron. 17: 379-388; Butz, S., R. Fernandez-Chacon, F. Schmitz, R. Jahn, and T.C. Sudhof. 1999. J. Biol. Chem. 274:18290-18296). The ubiquitously expressed Syt VII binds syntaxin at free Ca(2+) concentrations ([Ca(2+)]) below 10 microM, whereas other isoforms require 200-500 microM [Ca(2+)] or show no Ca(2+)-dependent syntaxin binding (Li, C., B. Ullrich, Z. Zhang, R.G.W. Anderson, N. Brose, and T.C. Sudhof. 1995. Nature. 375:594-599). We investigated the involvement of Syt VII in the exocytosis of lysosomes, which is triggered in several cell types at 1-5 microM [Ca(2+)] (Rodríguez, A., P. Webster, J. Ortego, and N.W. Andrews. 1997. J. Cell Biol. 137:93-104). Here, we show that Syt VII is localized on dense lysosomes in normal rat kidney (NRK) fibroblasts, and that GFP-tagged Syt VII is targeted to lysosomes after transfection. Recombinant fragments containing the C(2)A domain of Syt VII inhibit Ca(2+)-triggered secretion of beta-hexosaminidase and surface translocation of Lgp120, whereas the C(2)A domain of the neuronal- specific isoform, Syt I, has no effect. Antibodies against the Syt VII C(2)A domain are also inhibitory in both assays, indicating that Syt VII plays a key role in the regulation of Ca(2+)-dependent lysosome exocytosis.

MeSH Terms
Animals Binding Sites Brain/physiology Calcium/physiology Calcium-Binding Proteins/metabolism Cell Line Cell Membrane Permeability Cloning, Molecular Exocytosis/physiology Fibroblasts/physiology,ultrastructure Kidney Kinetics Lysosomes/physiology,ultrastructure Membrane Glycoproteins/genetics,metabolism Nerve Tissue Proteins/genetics,metabolism Protein Isoforms/metabolism Rats Recombinant Proteins/metabolism Synaptotagmins beta-N-Acetylhexosaminidases/metabolism
Chemicals
Calcium-Binding Proteins Membrane Glycoproteins Nerve Tissue Proteins Protein Isoforms Recombinant Proteins Syt7 protein, rat Synaptotagmins beta-N-Acetylhexosaminidases Calcium
Authors & Affiliations
6 authors, click to expand affiliations / ORCID
Martinez I
Section of Microbial Pathogenesis, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Chakrabarti S
Hellevik T
Morehead J
Fowler K
Andrews N W
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Article Info
Journal
The Journal of cell biology
Abbr.
J Cell Biol
ISSN
0021-9525
DOI
10.1083/jcb.148.6.1141
Published
2000-03-20
Pages
1141-49
Language
English
Region
United States
NLM ID
0375356
PMCID
PMC2174306
Subset
IM
Grants
NIAID NIH HHS · R37 AI034867 · United States
External Links
PubMed source DOI: 10.1083/jcb.148.6.1141 PMC Full Text View journal details
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