PTX3 is a secretary acute phase protein which is produced by cumulus cells and is critically involved in cumulus expansion, oocyte maturation and formation of cumulus extracellular matrix. However, little is known about the post-translational modifications of PTX3 and its relationship with its subcellular localization in GCs. In this study, we found out whether PTX3 could be covalently modified by SUMO-1 which is involved in its subcellular localization in ovarian GCs. Immunoblotting and immunoprecipitation analysis indicated that PTX3 was modified by SUMO-1. Mutation of PTX3 at K203R significantly reduced the modification of PTX3 by SUMO-1, suggesting that Lysine 203 is a key amino acid for SUMO-1’s modification of PTX3. Further study indicated that endogenous PTX3 was mainly located in the cytoplasm of GCs and overexpressed PTX3 could also be localized in the cytoplasm of GCs, while mutation of PTX3 at K203R was only localized in the nucleus. We propose that SUMOylation of PTX3 at Lysine 203 is crucial for its cytoplasm localization and might be involved in its secretion from cytoplasmic contents into extracellular matrix, which are important in the formation of cumulus extracellular matrix.

Key words: Granulosa cells, PTX3, Subcellular localization, SUMOylation