These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Overexpressed protein kinase C-delta and -epsilon subtypes in NIH 3T3 cells exhibit differential subcellular localization and differential regulation of sodium-dependent phosphate uptake.
    Author: Lehel C, Olah Z, Mischak H, Mushinski JF, Anderson WB.
    Journal: J Biol Chem; 1994 Feb 18; 269(7):4761-6. PubMed ID: 8106444.
    Abstract:
    To examine the biological properties of protein kinase C (PKC)-delta and -epsilon NIH 3T3 cells were stably transfected with metallothionein-based expression vectors that overexpressed these isoforms. In addition to their inducibility by Zn2+, the protein levels of these two PKC subtypes, but not that of endogenous PKC-alpha, increased with increasing cell density. An unexpected role for Mg2+ in the subcellular localization of PKC-delta was found. This isoenzyme was predominantly membrane-associated when cell fractionation was carried out in the absence of Mg2+ but cytosolic when the fractionation was performed in the presence of 10 mM Mg2+. In contrast, the predominant localization of cytosolic PKC-alpha and of membrane-associated PKC-epsilon was not influenced by Mg2+. In vivo and in vitro studies of [3H]phorbol 12,13-dibutyrate binding in the overexpressing cell lines confirmed the cytosolic localization of PKC-alpha, the membrane-associated state of PKC-epsilon, and the presence of PKC-delta at both locations. Readdition of serum for 5 min to serum-starved, quiescent cell lines initiated the redistribution of PKC-alpha to the particulate fraction, while the location of PKC-delta and PKC-epsilon was not affected. Zn(2+)-induced overexpression of PKC-delta- and PKC-epsilon-stimulated sodium-dependent phosphate uptake. Overexpression of PKC-delta caused an increase in the Vmax of Na+/P(i) uptake, while overexpression of PKC-epsilon resulted in a decrease in Km for orthophosphate. A further stimulation of Na+/P(i) uptake in the overexpressing cells could be achieved by phorbol ester activation of endogenous PKC-alpha. These results suggest that each of the three PKC isotypes contribute to the regulation of sodium-dependent phosphate uptake, but through distinct mechanisms.
    [Abstract] [Full Text] [Related] [New Search]