A novel protein kinase C alpha-dependent signal to ERK1/2 activated by alphaVbeta3 integrin in osteoclasts and in Chinese hamster ovary (CHO) cells.
Rucci, Nadia ; DiGiacinto, Claudia ; Orru, Luigi ; et al. ; - ASI Sponsor
Aug - 2005
ISSN : 0021-9533 ;
journal : Journal of cell science
Issue : Pt 15
type: Article Journal
Abstract
We identified a novel protein kinase C (PKC)alpha-dependent signal to extracellular signal-regulated kinase (ERK)1/2 in mouse osteoclasts and Chinese hamster ovary (CHO) cells, specifically activated by the alphaVbeta3 integrin. It involves translocation (i.e. activation) of PKCalpha from the cytosol to the membrane and/or the Triton X-100-insoluble subcellular fractions, with recruitment into a complex with alphaVbeta3 integrin, growth factor receptor-bound protein (Grb2), focal adhesion kinase (FAK) in CHO cells and proline-rich tyrosine kinase (PYK2) in osteoclasts. Engagement of alphavbeta3 integrin triggered ERK1/2 phosphorylation, but the underlying molecular mechanism was surprisingly independent of the well known Shc/Ras/Raf-1 cascade, and of phosphorylated MAP/ERK kinase (MEK)1/2, so far the only recognized direct activator of ERK1/2. In contrast, PKCalpha was involved in ERK1/2 activation because inhibition of its activity prevented ERK1/2 phosphorylation. The tyrosine kinase c-Src also contributed to ERK1/2 activation, however, it did not interact with PKCalpha in the same molecular complex. The alphaVbeta3/PKCalpha complex formation was fully dependent upon the intracellular calcium concentration ([Ca2+]i), and the use of the intracellular Ca2+ chelator 1,2-bis(o-amino-phenoxy)ethane-N,N,N,N-tetraaceticacidtetra (acetoxymethyl) ester (BAPTA-AM) also inhibited PKCalpha translocation and ERK1/2 phosphorylation. Functional studies showed that alphaVbeta3 integrin-activated PKCalpha was involved in cell migration and osteoclast bone resorption, but had no effect on the ability of cells to attach to LM609, suggesting a role in events downstream of alphaVbeta3 integrin engagement.
keywords : ASI - Sponsor,Animals,Antibodies,Bone Resorption,Bone Resorption: metabolism,CHO Cells,Calcium,Calcium: physiology,Carbazoles,Carbazoles: pharmacology,Cell Movement,Cell Movement: drug effects,Cell Movement: physiology,Cricetinae,Cricetulus,Indoles,Indoles: pharmacology,Integrin alphaVbeta3,Integrin alphaVbeta3: drug effects,Integrin alphaVbeta3: physiology,Mice,Mitogen-Activated Protein Kinase 1,Mitogen-Activated Protein Kinase 1: drug effects,Mitogen-Activated Protein Kinase 1: metabolism,Mitogen-Activated Protein Kinase 3,Mitogen-Activated Protein Kinase 3: drug effects,Mitogen-Activated Protein Kinase 3: metabolism,Monoclonal,Monoclonal: pharmacology,Osteoclasts,Osteoclasts: cytology,Osteoclasts: drug effects,Osteoclasts: metabolism,Phosphorylation,Protein-Tyrosine Kinases,Protein-Tyrosine Kinases: physiology,Signal Transduction,Signal Transduction: physiology