A novel protein kinase C alpha-dependent signal to ERK1/2 activated by alphaVbeta3 integrin in osteoclasts and in Chinese hamster ovary (CHO) cells.
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.
Rucci
Nadia
N
Department of Experimental Medicine, University of L'Aquila, via Vetoio - Coppito 2, 67100, L'Aquila, Italy.
DiGiacinto
Claudia
C
Orrù
Luigi
L
Millimaggi
Danilo
D
Baron
Roland
R
Teti
Anna
A
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001862:Bone Resorption / Q000378:metabolism; D016466:CHO Cells; D000081247:CSK Tyrosine-Protein Kinase; D002118:Calcium / Q000502:physiology; D002227:Carbazoles / Q000494:pharmacology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D007211:Indoles / Q000494:pharmacology; D039302:Integrin alphaVbeta3 / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000187:drug effects / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D019061:src-Family Kinases
D000911:Antibodies, Monoclonal; D002227:Carbazoles; D007211:Indoles; D039302:Integrin alphaVbeta3; C081021:Go 6976; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium