DOC2 proteins in rat brain: complementary distribution and proposed function as vesicular adapter proteins in early stages of secretion.
DOC2 proteins constitute a novel protein family that may function in secretion and contain a double C2 domain. We have cloned and characterized two DOC2 isoforms in rat brain and studied their interactions with other proteins implicated in secretion. DOC2A was virtually brain specific, DOC2B ubiquitous. Within brain, the isoforms were expressed nonuniformly and complementary within neurons, not astroglia, and copurified with synaptic vesicles. Affinity purification, yeast two-hybrid analysis, and coimmunoprecipitation revealed that DOC2 binds munc18, a protein also implicated in secretion. The first DOC2 C2 domain and most of munc18 are involved in direct interactions. Munc18 may regulate formation of 'core complexes' during vesicle docking, by interacting with syntaxin. We show that DOC2 and syntaxin compete for munc18. Other core complex components shifted the equilibrium between syntaxin-munc18 versus DOC2-munc18. These data suggest that DOC2 proteins are vesicular adapter proteins regulating munc18-syntaxin complexes and herewith synaptic vesicle docking.
Verhage
M
M
Rudolf Magnus Institute for Neurosciences, University of Utrecht, The Netherlands.
de Vries
K J
KJ
Røshol
H
H
Burbach
J P
JP
Gispen
W H
WH
Südhof
T C
TC
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry; D002135:Calcium-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D006801:Humans; D017403:In Situ Hybridization; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009928:Organ Specificity; D011485:Protein Binding; D050765:Qa-SNARE Proteins; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000737:chemistry; D013572:Synaptic Vesicles / Q000378:metabolism*; D033921:Vesicular Transport Proteins
D002135:Calcium-Binding Proteins; C091524:DOC2A protein, human; C490420:DOC2B protein, human; C490419:Doc2a protein, rat; C490422:Doc2b protein, rat; D046911:Macromolecular Substances; D008565:Membrane Proteins; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; D033921:Vesicular Transport Proteins