Localization of individual subunits of protein kinase CK2 to the endoplasmic reticulum and to the Golgi apparatus

Citation
M. Faust et al., Localization of individual subunits of protein kinase CK2 to the endoplasmic reticulum and to the Golgi apparatus, MOL C BIOCH, 227(1-2), 2001, pp. 73-80
Citations number
29
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cell & Developmental Biology
Journal title
MOLECULAR AND CELLULAR BIOCHEMISTRY
ISSN journal
0300-8177 → ACNP
Volume
227
Issue
1-2
Year of publication
2001
Pages
73 - 80
Database
ISI
SICI code
0300-8177(2001)227:1-2<73:LOISOP>2.0.ZU;2-9
Abstract
The protein kinase CK2 is composed of two catalytic alpha- or alpha'- and t wo regulatory beta -subunits. In mammalian cells there is ample evidence fo r the presence of individual CK2 subunits beside the holoenzyme. By immunof luorescence studies using peptide antibodies which allow us to detect the C K2 alpha-, alpha'- and beta -subunits we found all three subunits to be co- localized with a 58 KDa Golgi protein which is specific for the Golgi compl ex. Subfractionation studies using dog pancreas cells revealed the presence of all three subunits of CK2 at the smooth endoplasmic reticulum (sER)/Gol gi fraction whereas the rough endoplasmic reticulum (rER) harboured only th e catalytic alpha- and alpha'-subunits. We found that the microsomal prepar ation from dog pancreas cells contained CK2 which phosphorylated a CK2 spec ific synthetic peptide and which was heparin sensitive. Furthermore, we cou ld immunoprecipitate the CK2 alpha -subunit that exhibited a kinase activit y which phosphorylated a CK2 specific substrate and which was heparin sensi tive. Protease digestion experiments revealed that the CK2 subunits were lo cated on the cytosolic side of the rER and the sER/Golgi complex. Thus, we could demonstrate an asymmetric distribution of the CK2 subunits at the rER and sER/Golgi complex. Since the CK2 alpha- and alpha'-subunits exhibit a substrate specificity which is different from the CK2 holoenzyme one might speculate that the asymmetric distribution of the CK2 holoenzyme and the CK 2 catalytic subunits may have regulatory functions.