HPC-1 is associated with synaptotagmin and omega-conotoxin receptor.
Monoclonal antibodies were produced that recognize a membrane protein of 35,000 Da (p35) expressed in brain and adrenal medulla. They immunoprecipitated 50% of omega-conotoxin (omega-CgTX) receptor, a putative N-type calcium channel, solubilized from rat brain. Anti-synaptotagmin (p65) antibodies also immunoprecipitate omega-CgTX receptor (Leveque, C., Hoshino, T., David, P., Shoji-Kasai, Y., Leys, K., Omori, A., Lang, B., El Far, O., Sato, K., Martin-Moutot, N., Newsom-Davis, J., Takahashi, M., and Seagar, M.J. (1992) Proc. Natl. Acad. Sci. U. S. A. 89, 3625-3629); however, immunoprecipitation by anti-p35 antibodies and anti-synaptotagmin antibodies was not additive. Furthermore, both p35 and synaptotagmin were recovered in the immunoprecipitates with anti-synaptotagmin and anti-p35 antibodies, respectively, indicating that a population of omega-CgTX receptor exists as a ternary complex with synaptotagmin and p35. A cDNA coding p35 was isolated from a rat brain cDNA library by immuno-screening, and the primary structure of the protein was revealed to be identical to that of HPC-1 (Inoue, A., Obata, K., and Akagawa, K. (1992) J. Biol. Chem. 267, 10613-10619). HPC-1 has a putative transmembrane segment at the C terminus and four heptad motifs, which may be involved in protein-protein interaction. These results suggest that HPC-1 may play a role in neurotransmitter release from nerve terminals by associating with omega-CgTX-sensitive N-type calcium channel and synaptotagmin.
Yoshida
A
A
Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.
Oho
C
C
Omori
A
A
Kuwahara
R
R
Ito
T
T
Takahashi
M
M
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D001921:Brain / Q000378:metabolism*; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D002540:Cerebral Cortex / Q000378:metabolism*; D002645:Chickens; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D051379:Mice; D008815:Mice, Inbred Strains / Q000276:immunology; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D051381:Rats; D017981:Receptors, Neurotransmitter / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D017386:Sequence Homology, Amino Acid; D050863:Synaptotagmin I; D050857:Synaptotagmins; D050827:Syntaxin 1
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; C504582:Epim protein, mouse; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D017981:Receptors, Neurotransmitter; C494212:STX1A protein, human; C494214:Stx1a protein, mouse; C494213:Stx1a protein, rat; C504581:Stx2 protein, rat; D050863:Synaptotagmin I; D050827:Syntaxin 1; C053157:omega-conotoxin receptor; D050857:Synaptotagmins