YWHA (14-3-3) protein isoforms and their interactions with CDC25B phosphatase in mouse oogenesis and oocyte maturation

Abstract

BackgroundImmature mammalian oocytes are held arrested at prophase I of meiosis by an inhibitory phosphorylation of cyclin-dependent kinase 1 (CDK1). Release from this meiotic arrest and germinal vesicle breakdown is dependent on dephosphorylation of CDK1 by the protein, cell cycle division 25B (CDC25B). Evidence suggests that phosphorylated CDC25B is bound to YWHA (14-3-3) proteins in the cytoplasm of immature oocytes and is thus maintained in an inactive form. The importance of YWHA in meiosis demands additional studies.ResultsMessenger RNA for multiple isoforms of the YWHA protein family was detected in mouse oocytes and eggs. All seven mammalian YWHA isoforms previously reported to be expressed in mouse oocytes, were found to interact with CDC25B as evidenced by in situ proximity ligation assays. Interaction of YWHAH with CDC25B was indicated by Förster Resonance Energy Transfer (FRET) microscopy. Intracytoplasmic microinjection of oocytes with R18, a known, synthetic, non-isoform-specific, YWHA-blocking peptide promoted germinal vesicle breakdown. This suggests that inhibiting the interactions between YWHA proteins and their binding partners releases the oocyte from meiotic arrest. Microinjection of isoform-specific, translation-blocking morpholino oligonucleotides to knockdown or downregulate YWHA protein synthesis in oocytes suggested a role for a specific YWHA isoform in maintaining the meiotic arrest. More definitively however, and in contrast to the knockdown experiments, oocyte-specific and global deletion of two isoforms of YWHA, YWHAH (14-3-3 eta) or YWHAE (14-3-3 epsilon) indicated that the complete absence of either or both isoforms does not alter oocyte development and release from the meiotic prophase I arrest.ConclusionsMultiple isoforms of the YWHA protein are expressed in mouse oocytes and eggs and interact with the cell cycle protein CDC25B, but YWHAH and YWHAE isoforms are not essential for normal mouse oocyte maturation, fertilization and early embryonic development.

The 14-3-3 (YWHA) Proteins in Signalling and Development of the Fruit Fly, Drosophila melanogaster

“…Recent studies show 14-3-3s as critical molecular regulators in Drosophila [14][15][16][17][18][19]. Specific isoforms of these proteins are expressed and distributed differentially as putative molecular controllers in particular types of cells and organs in a gamut of other species as well such as bull, hamster, Xenopus, horseshoe crab, monkey, rat, turkey and mouse [28,31,48]. Proteomic studies of bovine sperm 14-3-3-interactors have identified proteins involved in signalling and metabolism [49].…”

“…In the course of research investigating proteins co-expressed with the prohormone, proopiomelanocortin in the melanotrope cells of Xenopus intermediate pituitary gland, alignment of a Xenopus 14-3-3 protein encoded by a pituitary complementary DNA (cDNA) with known 14-3-3 polypeptide of Drosophila, plants and mammals and with a mammalian protein kinase C indicated marked conservation (60-88%) of the neuronspecific 14-3-3-related proteins throughout the evolutionary tree of eukaryotes [21]. In mammals, to date, seven isoforms of 14-3-3 have been discovered that are encoded by separate genes, with isoform-specific roles in development across several species of animals [22][23][24][25][26][27][28][29][30][31]. The phosphorylated forms of 14-3-3β and 14-3-3γ were initially described as 14-3-3α and 14-3-3δ, respectively [32].…”

Identification of PKP 2/3 as potential biomarkers of ovarian cancer based on bioinformatics and experiments

“…We further constructed a gene co-expression network with PKPs and their top 50 neighbor genes, suggesting that PKPs may exert their function by interacting with proteins. De S et al have reported that 14-3-3 (YWHA) proteins, which have seven isoforms of 14-3-3 and were identified in the ovary [45][46][47][48], are known to interact with and regulate several binding partners including CDC25B phosphatase and PKPs [49][50][51]. It is of great value to explore the underlying mechanism of the interaction between YWHA and PKPs in ovarian cancer.…”

The 14-3-3 (YWHA) Proteins in Mammalian Reproduction

“…Separate genes encode the homologous proteins within the 14-3-3 family. Varied number and type(s) of 14-3-3 isoforms have been detected in different species, for example, bull, hamster, Xenopus, horseshoe crab, monkey, rat, turkey, Drosophila, and mouse [4][5][6][7].…”