Identification of G alpha s messenger ribonucleic acid splice variants in human granulosa cells.
Granulosa cells are essential for follicular development and corpus luteum formation and their functions are regulated by gonadotrophins through G protein-coupled receptors. The dominant second messenger pathway involves the stimulation of cyclic AMP formation by G alpha s-linked receptors. In this paper we have investigated the expression of G alpha s mRNA splice variants in relation to expression of G alpha s protein isoforms in granulosa cells obtained from patients undergoing in vitro fertilization. We have carried out ribonuclease protection assays using cRNA riboprobes which are capable of detecting all G alpha s mRNA isoforms as well as quantifying total amounts of G alpha s mRNA. Granulosa cells express the message for G alpha s-Large and G alpha s-Small and the presence of two distinct protein products was confirmed by immunoblotting using the antibody RM/1. Moreover, the data show that a significant fraction of G alpha s-Large and G alpha s-Small mRNAs contain an extra CAG codon. This should generate proteins with an extra serine residue, resulting in G alpha s variants with the consensus sequence of a protein kinase C phosphorylation site. These results highlight the possible interaction between different signalling pathways in the control of cAMP production and the need to investigate the relationship between G alpha s variants and different adenylyl cyclase isozymes in patients with normal and abnormal ovarian function.
Europe-Finner
G N
GN
Nuffield Department of Obstetrics and Gynaecology, University of Oxford, John Radcliffe Hospital, Headington, UK.
Cartwright
E
E
Bellinger
J
J
Mardon
H J
HJ
Barlow
D H
DH
López Bernal
A
A
D005260:Female; D019204:GTP-Binding Proteins / Q000235:genetics*; D006107:Granulosa Cells / Q000378:metabolism*; D006801:Humans; D015347:RNA Probes; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*
D015347:RNA Probes; D012333:RNA, Messenger; D019204:GTP-Binding Proteins