A fecundação resulta no aumento intracelular de cálcio que é necessário para a transição do oócito até o estádio de zigoto. Os eventos que ocorrem durante esta transição são caracterizados como ativação, sendo estes dependentes de cálcio. Entretanto, os eventos bioquímicos que ocorrem durante a ativação ainda não estão completamente elucidados. A proteína quinase C (PKC) e a proteína quinase dependente de cálcio/calmodulina (CaMKII), por apresentarem atividade durante a fecundação e por serem ativadas por cálcio são implicadas na regulação dos eventos da ativação. Entretanto, existem muitas dúvidas sobre o real papel destas proteínas na ativação do oócito. Deste modo, o objetivo do presente trabalho foi avaliar o papel da PKC e da CaMKII na ativação de oócitos bovinos. Para tal, oócitos bovinos maturados in vitro foram ativados partenogeneticamente (AP) com cálcio ionóforo A23187 (5μM) por 5 minutos, sendo a retomada da meiose, a organização do citoesqueleto e do retículo endoplasmático (RE) avaliada 1 hora após a ativação. No experimento 1 foi avaliado o papel da CaMKII nestes eventos. Os oócitos foram AP na presença ou ausência de 100M do inibidor de CaMKII (Autocamtide-2 Related Inhibitory Peptide, Myristoylated). A inibição da CaMKII não afetou a retomada da meiose e nem a distribuição dos RE, após a AP. Entretanto, não ocorreu a rotação do fuso meiótico no estádio de telófase II quando a CaMKII foi inibidada. Estes resultados demonstram que embora a CaMKII não tenha efeito na retomada da meiose, esta proteína participa na progressão do ciclo celular de oócitos bovinos, após a AP. No experimento 2 foi avaliado o papel da PKC em oócitos bovinos AP. Os oócitos foram ativados partenogeneticamente na presença ou ausência de 10μM do inibidor de PKC (Bisindolymaleimide I). A inibição da PKC não afetou a retomada da meiose e nem a progressão pelo ciclo celular até o estádio de telófase II. Entretanto, a organização do RE foi afetada pela inibição da PKC. Resultado semelhante foi obtido quando os oócitos foram ativados na presença de citocalasina C, um despolimerizador de filamentos de actina. O presente experimento demonstra a participação da via PKC-actina na organização do RE na ativação de oócitos bovinos. / The intracellular calcium increase resulting from fertilization is necessary for oocyte transition to zygote. The events that occur during this transition are characterized as activation, which are dependent on calcium. However the biochemical events that occur during this activation are still not fully elucidated. The protein kinase C (PKC) and the calcium/calmodulin-dependent protein kinase II (CaMKII), are involved in regulating the events of activation, since these proteins have activity during fertilization and are activated by calcium. However there are many doubts about the real role of these proteins in the oocyte activation. Thus, the objective of this study was to evaluate the role of PKC and CaMKII in bovine oocyte activation. For this purpose, in vitro matured bovines oocytes were parthenogenetically activated (PA) by using calcium ionophore A23187 (5μM) for five minutes, and the resumption of meiosis, the cytoskeleton organization and the endoplasmic reticulum (ER) organization were evaluated 1 hour post-activation. In experiment 1, were evaluated the role of CaMKII in these events. The oocytes were PA in the presence or absence of 100M of CaMKII inhibitor (Autocamtide-2 Related Inhibitory Peptide, Myristoylated). The inhibition of CaMKII did not affect the meiosis resumption and the ER after the PA. However, there was no spindle rotation at telophase II stage when the CaMKII was inhibited. These results showed that although the CamKII has no effect on resumption of meiosis, it participates in the regulation of cell cycle progression after PA of bovine oocytes. In experiment 2, was evaluated the role of PKC on PA bovine oocytes. The oocytes were parthenogenetically activated in the presence or absence of 10μM of PKC inhibitor (Bisindolymaleimide I). The PKC inhibition did not affected the resumption of meiosis and the progression through the cell cycle until the stage of telophase II. However, the ER organization was affected by PKC inhibition. A similar result was obtained when the oocytes were activated in the presence of cytochalasin C, which promotes the depolymerization of the actin filaments. The current experiment showed the participation of the PKC-actin pathway at the ER organization in the bovine oocytes activation.

The toxic metal ion cadmium (Cd2+) is pro-oxidant and specifically disrupts the actin cytoskeleton in renal mesangial cells. This study investigated the role of Cd2+-mediated redox modulation of actin through protein S-glutathionylation and the effects of cytoskeletal changes on focal adhesions (FAs) through a Ca2+/calmodulin dependent-protein kinase II (CaMK-II) pathway. Only at low concentrations of Cd2+ (0.5-2 μM) was there an increase in actin glutathionylation, which was a reactive oxygen species-independent, total glutathione-dependent effect. Immunofluorescence of the cytoskeleton suggests that increases in glutathionylation levels occurring under low [Cd2+] are protective in vivo. Higher concentrations (>= 10 μM) of Cd2+ resulted in loss of vinculin and focal adhesion kinase (FAK) from FAs, concomitant with cytoskeletal disruption. Inhibition of CaMK-II preserved cytoskeletal integrity and focal contacts, while decreasing the migration of FAK-phosphoTyr925 to a membrane-associated compartment. This study adds further insight into the Cd2+-mediated effects on the cytoskeleton and FAs.

The toxic metal ion cadmium (Cd2+) is pro-oxidant and specifically disrupts the actin cytoskeleton in renal mesangial cells. This study investigated the role of Cd2+-mediated redox modulation of actin through protein S-glutathionylation and the effects of cytoskeletal changes on focal adhesions (FAs) through a Ca2+/calmodulin dependent-protein kinase II (CaMK-II) pathway. Only at low concentrations of Cd2+ (0.5-2 μM) was there an increase in actin glutathionylation, which was a reactive oxygen species-independent, total glutathione-dependent effect. Immunofluorescence of the cytoskeleton suggests that increases in glutathionylation levels occurring under low [Cd2+] are protective in vivo. Higher concentrations (>= 10 μM) of Cd2+ resulted in loss of vinculin and focal adhesion kinase (FAK) from FAs, concomitant with cytoskeletal disruption. Inhibition of CaMK-II preserved cytoskeletal integrity and focal contacts, while decreasing the migration of FAK-phosphoTyr925 to a membrane-associated compartment. This study adds further insight into the Cd2+-mediated effects on the cytoskeleton and FAs.

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