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Expression of Human Placental G Proteins During Pregnancy

P. Geoffroy, MSc

P Bessette, MD

J. Prévost, MSc

Department of Obstetrics and Gynecology, University of Montréal, Ste-Justine Hospital, Montréal, Québec, Canada

S. Bélisle, MD, MSc

Department of Obstetrics and Gynecology, University of Montreal, Research Center, Ste-Justine Hospital, 3175 Côte Ste-Catherine, Montréal, Québec, Canada, H3T 1C5

Objective: Regulatory guanine nucleotide-binding proteins (G proteins) play key roles in the stimulus-response coupling of many important biological systems. Recent studies from our laboratory suggest a functional role for many G proteins in the human placenta. However, the expression of these proteins has not yet been reported. Therefore, the aims of this investigation were to identify the expression of placental G protein alpha subunits in human placenta, and to study their level of variation during pregnancy.

Methods: Western and Northern blot analyses were performed on membrane protein and mRNA preparations, respectively, of human placentas from the first (7-11 weeks), second (16-19 weeks), and third (term) trimesters.

Results: The autoradiographs of both proteins and mRNA showed differential expression of placental G proteins during pregnancy. Thus, the relative levels of Gi2 and Gi3 subunits were highest during the first trimester, whereas to differences were observed between second-trimester and term placentas for both subunits. The levels of placental Go and Gs subunits stayed relatively stable during pregnancy.

Conclusion: The demonstration of human placental G protein expression during pregnancy provides new insight into the components of the signal transduction machinery within trophoblast. However, the physiologic significance of the variations of placental Gi protein expression during pregnancy remains to be investigated.

Key Words: Placenta • G protein expression • pregnancy

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