A receptor linked to a Gi-family G-protein functions in initiating oocyte maturation in starfish but not frogs.

TitleA receptor linked to a Gi-family G-protein functions in initiating oocyte maturation in starfish but not frogs.
Publication TypeJournal Article
Year of Publication2003
AuthorsKalinowski RR, Jaffe LA, Foltz KR, Giusti AF
JournalDev Biol
Volume253
Issue1
Pagination139-49
Date Published2003 Jan 1
ISSN0012-1606
KeywordsAnimals, Base Sequence, Cell Division, DNA Primers, DNA, Complementary, GTP-Binding Protein alpha Subunits, Gi-Go, Meiosis, Oocytes, Progesterone, Protein Binding, Receptors, Purinergic P1, Reverse Transcriptase Polymerase Chain Reaction, RNA, Messenger, Starfish, Xenopus laevis
Abstract

The stimulation of oocyte maturation by 1-methyladenine in starfish, and by a steroid in frogs, has been proposed to involve G-protein-coupled receptors. To examine whether activation of receptors linked to G(i) or G(z) was sufficient to cause oocyte maturation, we expressed mammalian G(i)- and G(z)-linked receptors in starfish and frog oocytes. Application of the corresponding agonists caused meiosis to resume in the starfish but not the frog oocytes. We confirmed that the receptors were effectively expressed in the frog oocytes by using a chimeric G-protein, G(qi), that converts input from G(i)- and G(z)-linked receptors to a G(q) output and results in a contraction of the oocyte's pigment. These results argue against G(i) or G(z) functioning to cause maturation in frog oocytes. Consistently, maturation-inducing steroids did not cause pigment contraction in frog oocytes expressing G(qi), and G(z) protein was not detectable in frog oocytes. For starfish oocytes, however, our results support the conclusion that G(i) functions in 1-methyladenine signaling and suggest the possibility of using frog oocyte pigment contraction as an assay to identify the 1-methyladenine receptor. To test this concept, we coexpressed G(qi) and a starfish adenosine receptor in frog oocytes and showed that applying adenosine caused pigment contraction.

Alternate JournalDev. Biol.
PubMed ID12490203