Ca2+-independent protein kinase C signalling in mouse eggs during the early phases of fertilization.
Protein kinase C (PKC), an enzyme playing a central role in signal transduction pathways, is activated in fertilized mouse eggs downstream of the fertilization Ca2+ signal, to regulate different aspects of egg activation. Given the presence of Ca2+-independent PKC isoforms within the egg, we investigated whether fertilization triggers PKC stimulation in mouse eggs by activating Ca2+-independent signalling pathways. An increase in PKC activity was detected as early as 10 min after the beginning of insemination, when about 90% of eggs had fused with sperm and the first Ca2+ rise was evident in most of the eggs. A similar level of activity was found 20 min later, when about 60% of eggs had resumed meiosis. When the Ca2+ increase was buffered by an intracellular Ca2+ chelating agent, PKC stimulation was not blocked but only slightly reduced. Confocal microscopy analysis revealed that the increase in PKC activity at fertilization coincided with the translocation of PKCdelta, a Ca2+-independent and diacylglycerol-dependent PKC isoform, to the meiotic spindle. When, in the absence of the Ca2+ signal, metaphase-anaphase transition was inhibited, PKCdelta moved to the meiotic spindle but still maintained a sustained cytoplasmic distribution. In summary, our results indicate that: 1) PKC activation is an early event of egg activation; 2) both Ca2+-dependent and Ca2+-independent pathways contribute to increased PKC activity at fertilization; 3) PKCdelta is one of the isoforms participating in this signalling process.
Tatone
Carla
C
Dept. of Biomedical Sciences and Technologies, University of L'Aquila, Italy. ctatone@univaq.it
Delle Monache
Simona
S
Francione
Antonella
A
Gioia
Luisa
L
Barboni
Barbara
B
Colonna
Rosella
R
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation; D005260:Female; D005306:Fertilization; D007150:Immunohistochemistry; D008297:Male; D008540:Meiosis; D051379:Mice; D018613:Microscopy, Confocal; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000737:chemistry / Q000378:metabolism*; D051745:Protein Kinase C-delta; D015398:Signal Transduction; D013094:Spermatozoa / Q000378:metabolism; D008941:Spindle Apparatus; D013997:Time Factors
D002614:Chelating Agents; D020033:Protein Isoforms; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; C497259:Prkcd protein, mouse; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D002118:Calcium