Poster abstracts
Poster number 9 submitted by Kenneth Gerien
Fission yeast Rng15 aids efficient vesicle fusion at the division site and is required for late stages of cytokinesis
Kenneth Gerien (OSBP), Yihua Zhu (Department of Molecular Genetics, The Ohio State University), Vedud Purde, Jian-Qiu Wu (Department of Molecular Genetics, The Ohio State University)
Abstract:
Cytokinesis is the final step in cell division that physically partitions a mother cell into two daughter cells. The delivery of vesicles carrying membrane and cytokinetic machinery to the division site is paramount to successful division. Fission yeast is an excellent model system for cytokinesis and cellular trafficking, allowing us to elucidate how these two processes work together. The previously uncharacterized protein Rng15 in S. pombe shares sequence homology with Mso1 from budding yeast. Mso1 has been shown to be involved in vesicle trafficking and interacts with the SM protein Sec1, but has not been studied during cytokinesis. Rng15 localizes to the division site as a disc and at growing cell tips, and colocalizes with Sec1 at these sites. Rng15 physically interacts with Sec1 in IP experiments and can recruit Sec1 to ectopic sites. We found that Rng15 deletion (rng15∆) cells are temperature sensitive and Sec1 localization is lost at the restrictive temperature. These cells have significantly slower ring constriction and ring disassembly. Similar defects are observed in sec1∆ cells, where the ring constriction and disassembly phases are elongated. These defects may arise from a reduction in exocytosis and a failure of vesicles to fuse with the plasma membrane. Indeed, rng15∆ cells are defective in exocytosis of acid phosphatase and accumulate secretory vesicles under EM. We have also found that in cells where Sec1 is overexpressed, the protein aggregates into puncta similar to those observed in rng15∆ strains. This aggregation can be rescued by overexpressing Rng15 with Sec1. We have also created Sec1 mutants to further investigate the function of these proteins. Together, these results show that Rng15 helps maintain Sec1 localization for efficient fusion of vesicles required for proper contractile-ring constriction/disassembly and plasma-membrane closure during cytokinesis.
Keywords: Cytokinesis, Vesicle Trafficking, Cellular trafficking