Delroisse J et al. (2021), Intracellular Pathways of Holothuroid Oocyte Ma...

ECB-ART-49004

Antioxidants (Basel) 2021 Jul 27;108:. doi: 10.3390/antiox10081201.

Show Gene links Show Anatomy links

Intracellular Pathways of Holothuroid Oocyte Maturation Induced by the Thioredoxin Trx-REES.

Delroisse J , Léonet A , Alexandre H , Eeckhaut I .

???displayArticle.abstract???
In holothuroids, oocyte maturation is stopped in ovaries at the prophase I stage of meiosis. In natural conditions, the blockage is removed during the spawning by an unknown mechanism. When oocytes are isolated by dissection, the meiotic release can be successfully induced by a natural inducer, the REES (i.e., Rough Extract of Echinoid Spawn) that is used in aquaculture to obtain viable larvae in mass. A thioredoxin has recently been identified in the REES as the molecule responsible for holothuroid oocyte maturation. As a redox-active protein, thioredoxin is thought to reduce target proteins within the oocyte membrane and initiate an intracellular reaction cascade that leads to the unblocking of the oocyte meiosis. Our results allow us to understand additional steps in the intracellular reaction cascade induced by the action of thioredoxin on oocytes. Pharmacological agents known to have activating or inhibiting actions on oocyte maturation have been used (Forskolin, Isobutylmethylxanthine, Hypoxanthine, 6-dimethyaminopurine, Lavendustin, Genistein, Roscovitine, Cycloheximide). The effects of these agents were analysed on oocytes of the holothuroid Holothuria tubulosa incubated with or without REES and were compared to those obtained with another reducing agent, the dithiothreitol. Our results demonstrated that, at the opposite of dithiothreitol-induced oocyte maturation, thioredoxin-induced oocyte maturation is cAMP independent, but dependent of the presence of calcium in the seawater. Both pathways of induction require the activation of protein serine/threonine kinases.

???displayArticle.pubmedLink??? 34439448
???displayArticle.pmcLink??? PMC8388914
???displayArticle.link??? Antioxidants (Basel)
???displayArticle.grants??? [+]

???attribute.lit??? ???displayArticles.show???

	Figure 1. One of the possible pathways to induce oocyte maturation. Signal in red indicated the cytoplasmic pathway activated by the liaison of the maturation-inducing substance (MIS) on his receptor to trigger the resumption of meiosis by the activation of the maturation-promoting factor (MPF). Blue lines indicate action sites of various pharmacological agents tested to inhibit the resumption of oocyte maturation.
	Figure 2. Effect of hypoxanthine (1 mM), forskolin (10 µM), IBMX (10 µM), roscovitine (10 µM), 6-DMAP (300 mM), lavendustin (10 µM), genistein (10 µM) and cycloheximide (50 mM) on H. tubulosa oocyte maturation, induced by dithiothreitol (DTT, 10 mM). Values are means of Maturation Index ± SD (n = 3 individuals). Columns surmounted by sign (a) or (b) are significantly similar to control (SW or DTT) surmounted with the same sign (PDunnett ≥ 0.05). For underlined solutions, the indices of maturation were not significantly different with or without DTT (Pt-test ≥ 0.05).
	Figure 3. Effect of hypoxanthine (1 mM), forskolin (10 µM), IBMX (10 µM), roscovitine (10 µM), 6-DMAP (300 mM), lavendustin (10 µM), genistein (10 µM) and cycloheximide (50 mM) on H. tubulosa oocyte maturation, induced by Trx-REES. Values are means of Maturation Index ± SD (n = 3 individuals). Columns surmounted by sign (a) or (b) are significantly similar to control (SW or Trx-REES) surmounted with the same sign (PDunnett ≥ 0.05). For underlined solutions, the indices of maturation were not significantly different with or without Trx-REES (Pt-test ≥ 0.05).
	Figure 4. Effect of hypoxanthine (1 mM), on H. tubulosa oocyte maturation, induced by Trx-REES (2 mg mL−1), DTT (10 mM) or thioredoxin from E. coli (Trx, 0.12 mg mL−1). Values are means of maturation index ± SD (n = 3 individuals). Means sharing at least one letter are not significantly different (TTukey ≥ 0.05).
	Figure 5. Effect of IBMX (10 μM), on H. tubulosa oocyte maturation, induced by Trx-REES (2 mg mL−1), DTT (10 mM) or thioredoxin from E. coli (Trx, 0.12 mg mL−1). Values are means of maturation index ± SD (n = 3 individuals). Means sharing at least one letter are not significantly different (TTukey ≥ 0.05).
	Figure 6. Effect of the Trx-REES and DTT to induce H. tubulosa (A) and H. scabra (B) oocyte maturation in filtered sea water (FSW) or in artificial sea water (ASW) without Ca2+. Values are means of maturation index ± SD (n = 3 individuals). Means sharing at least one letter are not significantly different (TTukey ≥ 0.05).
	Figure 7. Hypothetical TRX and DTT induced oocyte maturation pathways based on the present study and the literature. DTT acts as a reducing agent by catalysing the reduction of disulphide bonds (R-SS-R), increasing the presence of sulfhydryl groups (i.e., R-SH), in hypothetical membrane proteins present at the surface of oocyte. Thioredoxins have a “CGPC” catalytic site and the presence of the two cysteines allows the reduction of disulphide bonds in hypothetical membrane proteins present at the surface of oocyte.

References [+] :

CLELAND, DITHIOTHREITOL, A NEW PROTECTIVE REAGENT FOR SH GROUPS. 1964, Pubmed