Organization of the secretory machinery in the rodent brain: distribution of the t-SNAREs, SNAP-25 and SNAP-23.
Vesicular transport events appear to be facilitated by the VAMP/synaptobrevin family of membrane proteins in the vesicle (v-SNAREs) and a heterodimeric complex of syntaxin and SNAP-23/25 family members in the target membrane (t-SNAREs). In this manuscript we examine the tissue distribution and composition of the heterodimeric t-SNARE complexes in adult rodent brain. Analysis of protein extracts from brain regions shows that SNAP-25, syntaxin 1, and 4 are broadly distributed, while SNAP-23, syntaxin 3, and 7 show distinct patterns of expression. Further immunohistochemistry and fractionation studies show that while SNAP-25 is enriched in axons and nerve terminals, SNAP-23 is concentrated in cell bodies. Both SNAP-23 and SNAP-25 associate with the plasma membrane and can be metabolically labeled with [(3)H] palmitate in AtT-20 cells. Anti-SNAP-25 antibodies co-immunoprecipitate t-SNARE heterodimers from brain extracts that predominantly contain syntaxin 1 and 2. Contrary to results from in vitro binding assays, SNAP-23 was found predominantly associated with syntaxin 3. These observations suggest that t-SNARE, heterodimer composition is governed more by SNARE expression and localization than by simple protein-protein affinity.
Department of Biochemistry, University of Kentucky College of Medicine, 800 Rose Street, Lexington, KY 40536, USA.
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D
Chen
S L
SL
Minger
W G
WG
Honer
S W
SW
Whiteheart
D000215:Acylation; D000818:Animals; D001369:Axons / Q000737:chemistry; D001921:Brain / Q000378:metabolism*; D002460:Cell Line; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000032:analysis*; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009474:Neurons / Q000737:chemistry; D009490:Neurosecretory Systems / Q000502:physiology*; D050683:R-SNARE Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000737:chemistry; D050825:Synaptosomal-Associated Protein 25; D013574:Synaptosomes / Q000737:chemistry
D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050683:R-SNARE Proteins; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25