Page 20 - H. Cell signaling

[H. Cell signaling-17]

Nitration of protein phosphatase 2A increases via

Epac1/PLCε/CaMKⅡ/HDAC5/iNOS cascade in human

endometrial stromal cell decidualization

So Young Lee¹, Shin-Young Park², Yung Young Lee¹, Jun Hyeon Jeong¹, Jung-Sub Choi³, Kyeong Soo Kim⁴,

Do Sik Min⁵, Joong-Soo Han¹˙²

¹Biomedical Sciences, Graduate School of Biomedical Science and Engineering, Hanyang University, Seoul 03172,

Republic of Korea, ²Biochemistry and Molecular Biology, College of Medicine, Hanyang University, Seoul 03172,
Republic of Korea, ³Obstetrics and Gynecology, College of Medicine, Hanyang University, Seoul 03172, Republic of
Korea, ⁴Pharmaceutical Engineering, Gyeongnam National University of Science and Technology, JinJu 52725,

Republic of Korea, ⁵Pharmacy, College of Pharmacy, Yonsei University, Incheon 21983, Republic of Korea

Decidualization of the endometrial stroma is an essential differentiation process for embryo implantation and

maintenance of pregnancy. We previously reported that protein phosphatase 2A (PP2A) acts as a key mediator
during cAMP-induced decidualization of human endometrial stromal cells (hESCs). However, the mechanism

underlying its activation has remained obscure in hESCs. In the present study, we aimed to reveal the mechanism
that induces nitration of PP2A catalytic subunit (PP2Ac) during decidualization of hESCs. First, PP2Ac nitration was

significantly repressed using L-NAME, an inhibitor of nitric oxide synthase (NOS). Among several NOS isoforms, only
inducible NOS (iNOS) was directly induces the nitration of PP2Ac. Second, cAMP-induced iNOS expression and

PP2Ac nitration were decreased by treatment with TSA, an inhibitor of HDAC5. Phosphorylation of CaMKⅡ and
HDAC5 was suppressed by treatment with U73122 (an inhibitor of phospholipase C) or transfection of PLCε siRNA.
Finally, small G protein Rap1 and its guanine nucleotide exchange factor Epac1 were found to be involved in cAMP-

induced PP2A activation. Taken together, our results suggest that PP2Ac nitration during cAMP-induced

decidualization of hESCs is induced through the Epac1-Rap1-PLCε-CaMKⅡ-HDAC5-iNOS cascade.