EHSH1/Intersectin, a Protein That Contains EH and SH3 Domains and Binds to Dynamin and SNAP-25
A PROTEIN CONNECTION BETWEEN EXOCYTOSIS AND ENDOCYTOSIS?*
- From the Center for Basic Neuroscience, Howard Hughes Medical Institute, and the Department of Molecular Genetics, The University of Texas Southwestern Medical School, Dallas Texas 75235
Abstract
In yeast two-hybrid screens for proteins that bind to SNAP-25 and may be involved in exocytosis, we isolated a protein called EHSH1 (for EH domain/SH3 domain-containing protein). Cloning of full-length cDNAs revealed that EHSH1 is composed of an N-terminal region with two EH domains, a central region that is enriched in lysine, leucine, glutamate, arginine, and glutamine (KLERQ domain), and a C-terminal region comprised of five SH3 domains. The third SH3 domain is alternatively spliced. Data bank searches demonstrated that EHSH1 is very similar to Xenopus and human intersectins and to human SH3P17. In addition, we identified expressed sequence tags that encode a second isoform of EHSH1, called EHSH2. EHSH1 is abundantly expressed in brain and at lower levels in all other tissues tested. In binding studies, we found that the central KLERQ domain of EHSH1 binds to recombinant or native brain SNAP-25 and SNAP-23. The C-terminal SH3 domains, by contrast, quantitatively interact with dynamin, a protein involved in endocytosis. Dynamin strongly binds to the alternatively spliced central SH3 domain (SH3C) and the two C-terminal SH3 domains (SH3D and SH3E) but not to the N-terminal SH3 domains (SH3A and SH3B). Immunoprecipitations confirmed that both dynamin and SNAP-25 are complexed to EHSH1 in brain. Our data suggest that EHSH1/intersectin may be a novel adaptor protein that couples endocytic membrane traffic to exocytosis. The ability of multiple SH3 domains in EHSH1 to bind to dynamin suggests that EHSH1 can cluster several dynamin molecules in a manner that is regulated by alternative splicing.
Footnotes
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↵* This work was supported by postdoctoral fellowships from the Human Frontiers in Science Program (to M. O.), the TOYOBO Biotechnology Foundation, and the Takeda Medical Foundation and by a fellowship from the Deutscher Akademisher Austauschdienst (to S. S.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) AF127798 and AF132672.
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↵‡ Present address: Dept. of Medicine V, Hyogo College of Medicine, Hyogo 663–8501, Japan.
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↵§ To whom correspondence should be addressed: UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas TX 75235. E-mailTSudho{at}mednet.SWMED.edu.
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↵2 S. Schoch, M. Okamoto, and T. C. Südhof, unpublished observation.
- Abbreviations:
- EST
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expressed sequence tag
- GST
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glutathione S-transferase
- PMSF
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phenylmethylsulfonyl fluoride
- CHAPS
-
3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid
- PAGE
-
polyacrylamide gel electrophoresis
- kb
-
kilobase(s)
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- Received October 6, 1998.
- Revision received March 17, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
