cGMP-dependent protein kinases (cGKI and cGKII) mediate the actions of cGMP which is derived either from soluble guanylate cyclase (GC) activated by nitric oxide or membrane bound GC receptors (GC-A, GC-B, GC-C) that bind natriuretic peptides.
General function
Intracellular signaling cascade, Enzyme
Comment
Cellular localization
Cytoplasmic
Comment
Ovarian function
Ovulation
Comment
Endocrine Society 2004
[OR14-4] Identification of cGMP Dependent Protein Kinase II (cGKII) as a Potential Mediator of cGMP Action in Granulosa Cells of Ovulating Follicles.
Venkataraman Sriraman, Suzanne M Lohmann, Sabine M Mulders, JoAnne S Richards. Dept of Molec and Cell Biol, Baylor Coll of Med, Houston, TX; Inst of Clin Biochemistry and Pathobiochemistry, Univ of Wuerzburg, Wuerzburg, Germany; Target Discovery Unit, N.V.Organon, Oss, The Netherlands
Based on microarray data that cGKII might be a potential target of LH action in ovulating follicles, the expression of cGKII was analyzed in ovaries of immature mice treated with PMSG and hCG for selected time intervals. cGKII message levels were low in ovaries of PMSG-primed mice but increased dramatically within 2-4 hrs after administration of hCG, peaked at 12 hrs (the time of ovulation) and declined thereafter. Western blot analyses employing specific cGKII antibodies demonstrated a similar expression pattern. Spatio-temporal expression analysis by in situ hybridization confirmed the induced expression of cGKII mRNA between 4-12 h after hCG with specific localization to granulosa cells. cGKII was also induced rapidly and dramatically in murine granulosa cells that were cultured in defined (serum-free) medium with FSH and testosterone for 48h and then stimulated with forskolin and PMA for 4h (to mimic LH signaling). Expression of cGKII in ovaries of PMSG/hCG treated progesterone receptor null mice (PRKO) that fail to ovulate demonstrated that cGKII induction was significantly reduced at 12 hrs compared to wild-type controls. When the expression of cGKI was analyzed in normal mouse ovaries, no regulation by hormones was observed. Analyses of upstream regulators of the cGMP signaling cascade demonstrated that both subunits of soluble GC (alpha and beta) are expressed but are not modulated by hormones. However, message encoding membrane bound GC-A increased 4-fold in ovaries 4-8 hrs after hCG. In situ hybridization confirmed the GC-A expression pattern and localized its message to granulosa cells. Ovarian expression of GC-B mRNA showed more subtle variations in response to hCG and GC-C was not detected. Collectively, these results show that the cGMP signaling pathway is expressed in granulosa cells and that cGKII is induced selectively and rapidly in granulosa cells of preovulatory follicles by LH/hCG, is regulated, in part, by PR and therefore cGK II may mediate specific effects of cGMP during ovulation.
Expression regulated by
LH, Steroids, progesterone
Comment
Cyclic GMP dependent protein kinase II is induced by LH and PR dependent mechanisms in granulosa cells and cumulus oocyte complexes of ovulating follicles Sriraman V, et al .
Cyclic GMP dependent protein kinase II (Prkg2, cGK II) was identified as a potential target of the progesterone receptor (nr3c3) in the mouse ovary based on microarray analyses. To document this further, the expression patterns of cGK II and other components of the cGMP signaling pathway were analyzed during follicular development and ovulation using the PMSG-hCG-primed immature mice. Levels of cGK II mRNA were low in ovaries of immature mice, increased 4-fold in response to PMSG and 5-fold more within 12 h after hCG, the time of ovulation. In situ hybridization localized cGK II mRNA to granulosa cells and cumulus oocyte complexes of periovulatory follicles. In progesterone receptor null mice, cGK II mRNA was reduced significantly at 12 h after hCG in contrast to heterozygous littermates. In primary granulosa cell cultures cGK II mRNA was induced by PMA, enhanced by adenoviral expression of PR-A and blocked by RU486 and trilostane. PR-A in the absence of PMA was insufficient to induce cGK II. Expression of cGK I (Prkg1) was restricted to the residual tissue and not regulated by hormones. Guanylate cyclase-A (Npr1; GC-A)) mRNA expression increased 6-fold by 4 h after hCG treatment in contrast to PMSG alone and was localized to granulosa cells of preovulatory follicles. Collectively, these data show for the first time that cGK II (not cGK I) and GC-A are selectively induced in granulosa cells of preovulatory follicles by LH- and PR-dependent mechanisms thereby providing a pathway for cGMP function during ovulation.