The N-end rule pathway relates the in vivo half-life of a protein to the identity of its N-terminal residue. The conjugation of arginine (Arg) from Arg-tRNAArg to N-terminal Asp, Glu, or Cys is a universal eukaryotic protein modification that can lead to ubiquitylation and proteasomal degradation of the resulting Arg-conjugated proteins through the N-end rule pathway. The mammalian ATE1 gene encodes Arg-transferase that mediates all known N-terminal arginylation reactions. ATE1-/- embryos die owing to various cardiovascular defects including ventricular hypoplasia, ventricular septal defect, and late angiogenesis. The genomewide functional proteomics previously identified a set of RGS proteins (RGS4, RGS5, and RGS16) as in vivo substrates of ATE1. These RGS proteins are important negative regulators of Gáq-activated signaling for myocardial growth and vascular maturation/integrity. In my first project, I attempted to determine the role of ATE1-dependent posttranslational arginylation in Gáq-dependent cardiac signaling. I constructed and characterized ATE1-/-GáqTg compound mutant mice, where Gáq is exclusively overexpressed in the heart from áMHC promoter. I found that while Gáq overexpression in the heart rescues significantly cardiac defects in ATE1-/- embryonic hearts, it does not cause a noticeable change in vascular defects. These results together suggest that ATE1 controls cardiac development and signaling in part through Gq-activated signaling pathways. In the second project, I generated RGS5 transgenic mouse (TG) strains overexpressing either MC-RGS5 (wild-type, short-lived) or MV-RGS5 (mutant, long-lived) from vascular smooth muscle-specific SM22á promoter to determine the physiological importance of RGS5 proteolysis in Gq signaling of VSMC. Both MC-RGS5 and MV-RGS5 mice were viable and fertile without any visible defects. However, MC-RGS5 female
v
mice demonstrated impaired delivery in that newborn pups were often found dead associated with an absence of milk in their stomachs. In contrast, MV-RGS5 mice did not show this phenotype. The mis-regulated RGS5 proteolysis in MC-RGS5 mice may result in the failure in oxytocin-induced uterine and mammary gland smooth muscle contraction. In summary, my research provides an insight into the role of N-end rule pathway in cardiovascular Gq signaling.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-10062010-201104 |
| Date | 10 January 2011 |
| Creators | Kim, Dong Eun |
| Contributors | Yong Tae Kwon, Jeffrey Isenberg, Yong J. Lee, Regis R. Vollmer, Song Li |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-10062010-201104/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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