Protein kinase Calpha early activates splicing factor SC-35 during post-natal rat heart development.

Rat myocardial fiber development and formation is a complex event which begins in the early stages of fetal life and continues until the end of the first month of life. In fact, a progressive morphological structure arrangement is observed until the 22nd day of life. These modifications are based on biochemical events which are switched on at plasma membrane level and then transduced into the nucleus. Since the presence of Protein Kinase C (PKC) inside the nucleus could allow the enzyme to phosphorylate also proteins located on chromatin, on nuclear matrix and speckles, in this study attention was paid to the role played by phospho-Protein Kinase C-alpha (p-PKCalpha) in regulating the activation of SC-35 splicing factor which leads to the occurrence of morphological modifications during post-natal rat heart development. Besides the parallel increase of the expression of both proteins up to 4/8 days of life, firstly p-PKCalpha and SC-35 co-localize at nuclear level at day 1 after birth, thus suggesting a main role of p-PKCalpha in modulating the early transcription of components related to post-natal rat heart development.

Specific subcellular targeting of PKCalpha and PKCepsilon in normal and tumoral lactotroph cells by PMA-mitogenic stimulus.

The variations of the intracellular localization of the individual protein kinase C (PKC) isoforms are related with their different biological functions. In this study, we have investigated the precise intracellular translocation of endogenous PKCalpha and PKCepsilon in PMA-stimulated normal and tumoral lactotroph cells by using confocal and immunogold electron microscopy, which was correlated with the rate of cell proliferation of both pituitary cell phenotypes. The present results showed that the short phorbol ester incubation stimulated the proliferation of normal and tumoral lactotroph cells, as determined by the measurement of the BrdU-labelling index. The translocation of PKCalpha to plasma and nuclear membranes induced by PMA was more marked than that observed for PKCepsilon in normal and tumoral lactotroph cells. Our results showed that PKCs translocation to the plasma and nuclear membranes varied from isozyme to isozyme emphasizing that PKCalpha could be related with the mitogenic stimulus exerted by phorbol ester. These data support the notion that specific PKC isozymes may exert spatially defined effects by virtue of their directed translocation to distinct intracellular sites.