title: Conventional protein kinase C plays a critical role in negative regulation of CD98-induced homotypic aggregation.
abstract: CD98, a heterodimeric type II transmembrane protein, is involved in many different cellular events, ranging from amino acid transport to cell-cell adhesion. Little is known about the positive and negative signalling pathways involved in these responses. Therefore, we examined the role of conventional protein kinase C (PKC) isoforms during CD98-induced intracellular signalling and homotypic aggregation of U937 cells. The CD98-induced aggregation was enhanced by the general protein kinase inhibitors GF109203X and staurosporin, and by specific PKC-alpha/-beta peptide inhibitor 19-27, but inhibited by PKC activators such as phorbol 12-myristate 13-acetate (PMA). PMA-inhibition was reversed by PKC inhibitors recognising the ATP-binding site in PKC (e.g. staurosporin, GF109203X and Go6983). Inhibitors which bind to diacylglycerol (DAG) or Ca(2+)-binding sites of PKC (calphostin C and Go6967) had no effect. PMA-induced translocation of conventional PKC (cPKC) isozymes (alpha, beta and gamma), but decreased the expression of PKC-delta, which plays an important role in CD98-induced homotypic aggregation. PMA treatment also suppressed the surface level of CD98 but not CD29, CD18 and CD147, dose- and time-dependently. These data provide evidence that PMA-responsive cPKC isoforms (alpha, beta and gamma) play a key role in negative regulation of CD98 signalling and homotypic aggregation.
authors.affiliation: Department of Immunology and Molecular Pathology, Windeyer Institute of Medical Sciences, University College London Medical School, London, UK.
authors.forename: J Y
authors.initials: JY
authors.lastname: Cho
authors.forename: D R
authors.initials: DR
authors.lastname: Katz
authors.forename: K M
authors.initials: KM
authors.lastname: Skubitz
authors.forename: B M
authors.initials: BM
authors.lastname: Chain
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002449:Cell Aggregation / Q000187:drug effects / Q000502:physiology*; D004075:Diglycerides / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D027261:Fusion Regulatory Protein-1 / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D021381:Protein Transport; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives / Q000494:pharmacology; D020298:U937 Cells
chemical_list: D004075:Diglycerides; D027261:Fusion Regulatory Protein-1; D007527:Isoenzymes; C016658:phorbolol myristate acetate; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium