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PMID:16386321

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Citation

Monterrat, C, Boal, F, Grise, F, Hémar, A and Lang, J (2006) Synaptotagmin 8 is expressed both as a calcium-insensitive soluble and membrane protein in neurons, neuroendocrine and endocrine cells. Biochim. Biophys. Acta 1763:73-81

Abstract

Synaptotagmins (syt) form a large family of transmembrane proteins and some of its isoforms are known to regulate calcium-induced membrane fusion during vesicular traffic. In view of the reported implication of the isoform syt8 in exocytosis we investigated the expression, localisation and calcium-sensitivity of syt8 in secretory cells. An immunopurified antipeptide antibody was generated which is directed against a C-terminal sequence and devoid of crossreactivity towards syt1 to 12. Subcellular fractionation and immunocytochemistry revealed two forms of synaptotagmin 8 (50 and 40 kDa). Whereas the 40-kDa was present in the cytosol in brain, in PC12 and in clonal beta-cells, the 50-kDa form was localised in very typical clusters and partially colocalised with the SNARE protein Vti1a. Moreover, in primary hippocampal neurons syt8 was only found within the soma. Amplification of syt8 by RT-PCR indicated that the observed protein variants were not generated by alternative splicing of the 6th exon and are most likely linked to variations in the N-terminal region. In contrast to the established calcium sensor syt2, endogenous cytosolic syt8 and transiently expressed syt8-C2AB-eGFP did not translocate upon a raise in cytosolic calcium in living cells. Syt8 is therefore not a calcium sensor in exocytotic membrane fusion in endocrine cells.

Links

PubMed Online version:10.1016/j.bbamcr.2005.11.008

Keywords

Animals; Antibodies/metabolism; Antibody Specificity; Calcium/metabolism; Calcium/pharmacology; Cell Membrane/metabolism; Cytosol/metabolism; Endocrine Glands/cytology; Endocrine Glands/metabolism; Exons/genetics; Gene Expression Regulation; Neurons/cytology; Neurons/metabolism; Neurosecretory Systems/cytology; Neurosecretory Systems/metabolism; PC12 Cells; Protein Binding; Protein Transport; Qb-SNARE Proteins/metabolism; RNA, Messenger/genetics; RNA, Messenger/metabolism; Rats; Solubility; Synaptotagmins/genetics; Synaptotagmins/metabolism

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

MOUSE:SYT8

located_in

GO:0005737: cytoplasm

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

MOUSE:SYT8

located_in

GO:0031982: vesicle

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete


See also

References

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