PT  - JOURNAL ARTICLE
AU  - Marc Presler
AU  - Elizabeth Van Itallie
AU  - Allon M. Klein
AU  - Ryan Kunz
AU  - Peg Coughlin
AU  - Leonid Peshkin
AU  - Steven P. Gygi
AU  - Martin Wühr
AU  - Marc W. Kirschner
TI  - Proteomics of phosphorylation and protein dynamics during fertilization and meiotic exit in the <em>Xenopus</em> egg
AID  - 10.1101/145086
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 145086
4099  - http://biorxiv.org/content/early/2017/06/04/145086.short
4100  - http://biorxiv.org/content/early/2017/06/04/145086.full
AB  - Fertilization triggers release from meiotic arrest and initiates events that prepare for the ensuing developmental program. Protein degradation and phosphorylation are known to regulate protein activity during this process. However, the full extent of protein loss and phospho-regulation is still unknown. We examined absolute protein and phospho-site dynamics after fertilization by mass spectrometry-based proteomics. To do this, we developed a new approach for calculating the stoichiometry of phospho-sites from multiplexed proteomics that is compatible with dynamic, stable and multi-site phosphorylation. Overall, the data suggest that degradation is limited to a few low abundance proteins. However, this degradation promotes extensive dephosphorylation that occurs over a wide range of abundances during meiotic exit. We also show that eggs release a large amount of protein into the medium just after fertilization, most likely related to the blocks to polyspermy. Concomitantly, there is a substantial increase in phosphorylation likely tied to calcium activated kinases. We identify putative degradation targets as well as new components of the block to polyspermy. The analytical approaches demonstrated here are broadly applicable to studies of dynamic biological systems.