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Subunit structure of the mammalian exocyst complex
1Howard Hughes Medical Institute, Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford CA 94305-5428, USA.
Summary
Researchers identified mammalian exocyst complex subunits, crucial for secretion. These proteins, including REXO70, RSEC5, and RSEC15, are similar to yeast homologs and localize to secretion sites, aiding vesicle fusion.
Area of Science:
- Cell Biology
- Molecular Biology
Background:
- The exocyst complex is essential for the late stages of secretion in yeast.
- Unlike SNAREs, the exocyst localizes to specific sites of vesicle fusion.
Purpose of the Study:
- To isolate and characterize mammalian exocyst complex subunits.
- To investigate the expression and localization of these subunits.
Main Methods:
- cDNA isolation and sequencing for REXO70, RSEC5, and RSEC15.
- Analysis of gene expression patterns and transcript variants.
- Generation of monoclonal antibodies (mAbs) against the mammalian RSEC6 subunit.
- Immunoreactivity studies using PC12 cells.
Main Results:
- cDNAs for mammalian REXO70, RSEC5, and RSEC15 were isolated, showing 21-24% identity to yeast homologs.
- These genes are broadly expressed, with multiple transcripts for REXO70 and RSEC15.
- A novel 84-kDa subunit of the mammalian exocyst complex was identified.
- RSEC6 immunoreactivity was observed at PC12 cell process terminals, near sites of granule exocytosis.
Conclusions:
- Mammalian exocyst subunits share homology with yeast counterparts and are involved in secretion.
- The exocyst complex is specifically localized to sites of vesicle fusion in mammalian cells.
- Further characterization of exocyst subunits provides insights into the secretory pathway.