Volume 3 Issue 1, January 1993: 61-74
ORIGINAL ARTICLES
Casein kinase G may be the target of spermine during progesterone-induced oocyte maturation
Runsheng Li and Jiake Tso
Shanghai Institute of Cell Biology, Academia Sinica
Correspondence:
Casein kinase G (CKG) with more than 2500-fold enrichment was purified from Bufo bufo gargarizans ovaries. The catalytic activity of the enzyme was found to be associated with its 42 kD subunit, and its 26 kD subunit was found to be the major target for the enzyme autophosphorylation. Each full-grown oocyte contained 1.9 units of CKG corresponding to an intracellular concentration of 93 nM. After injecting an amount of 0.38 units of the enzyme into the oocyte, approximately 50% of the progesterone-induced maturation was inhibited. The inhibitory effect was enhanced in oocytes pretreated with spermine, which was consistent with the results that the enzyme was activated in vitro in the presence of spermine. The MPF-induced oocyte maturation was delayed and even prohibited in the kinase-microinjected oocytes. A 55 kD oocyte protein was identified as an substrate of CKG both in vivo and in vitro, and the enhancement of the 55 kD protein phosphorylation was associated with kinase inhibition on maturation and on protein synthesis in kinase-microinjected oocytes. As the endogenous spermine level decreased in the course of progesterone-induced oocyte maturation, 55 kD protein was dephosphorylated. Heparin, a specific inhibitor of CKG, potentiated the progesterone-induced oocyte maturation. Altogether the experimental results indicated strongly that CKG may be the physiological target of spermine.
Cell Res 3: 61-74; doi:10.1038/cr.1993.7
FULL TEXT | PDF
Browse 1843
