Regulation of apoptosis by peptides of fibronectin in human monocytes.
Synthetic peptides with sequences present in extracellular matrix protein fibronectin have been described to stimulate human monocytes. We describe now that one of these peptides, FN6, induces apoptotic effects on monocytes and we investigate the molecular mechanisms involved in the regulation of this response. Incubation of monocytes with FN6 induces the activation of the small GTPase Rac. In turn, Rac mediates the increase of both JNK and p38 activities in a sustained fashion, as well as the phosphorylation levels of their respective substrates c-Jun and ATF-2. FN6 also stimulates caspases -9 and -3 and the delayed proteolysis of its substrates PARP and D4-GDI. In addition, initiator caspases-1 and -5 were activated by FN6 treatment of monocytes but, in contrast to that observed for caspases-9 and -3, this effect was not dependent on JNK or p38 activities. These kinases also mediated the increase of Bax levels, but only in some conditions Bcl-2 depletion caused by the peptide. Moreover, whereas initially only caspase-1 is involved in caspase-3 activation, later on caspase-9 seems also to participate. Therefore, we demonstrate that FN6 stimulation allows multiple, JNK and p38-dependent and -independent interacting signals to regulate the apoptotic response in human monocytes.
Natal
C
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Departamento de Bioquímica, Universidad de Navarra, C/Irunlarrea 1, 31008, Pamplona, Navarra, Spain.
Osés-Prieto
J A
JA
Pelacho
B
B
Iraburu
M J
MJ
López-Zabalza
M J
MJ
D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism; D002478:Cells, Cultured; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005353:Fibronectins / Q000737:chemistry*; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects*; D010455:Peptides / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
C569658:ARHGDIB protein, human; D051017:Apoptosis Regulatory Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D005353:Fibronectins; D020730:Guanine Nucleotide Dissociation Inhibitors; D010455:Peptides; D025521:Tumor Suppressor Proteins; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D011065:Poly(ADP-ribose) Polymerases; D020928:Mitogen-Activated Protein Kinases; D020744:rac GTP-Binding Proteins