Agonist-induced aggregation of Chinese hamster ovary cells coexpressing the human receptors for fibrinogen (integrin alphaIIbbeta3) and the platelet-activating factor: dissociation between adhesion and aggregation.
This work reports the establishment of a Chinese hamster ovary (CHO) cell line stably coexpressing the human alphaIIbbeta3 integrin and the platelet-activating factor receptor (PAFR). These cells aggregate in response to PAF in a Ca(++), alphaIIbbeta3, and soluble fibrinogen (Fg)-dependent manner that is prevented by PAF antagonists or alphaIIbbeta3 blockade. The aggregating response is accompanied by enhanced binding of fibrinogen and the activation-dependent IgM PAC1. This model has permitted us to identify, for the first time, intracellular signals distinctly associated with either alphaIIbbeta3-mediated adhesion or aggregation. Nonreceptor activation of protein kinase C (PKC) by phorbol ester produced cellular adhesion and spreading onto immobilized Fg, but it was not a sufficient signal to provoke cellular aggregation. Moreover, inhibition of PKC impeded the PAF stimulation of cellular adhesion, whereas the aggregation was not prevented. The PAF-induced cellular aggregation was distinctly associated with signaling events arising from the liganded Fg receptor and the agonist-induced stimulation of a calcium/calmodulin-dependent signaling pathway. Sustained tyrosine phosphorylation of both mitogen-activated protein kinase (MAPK) and an approximately 100-kd protein was associated with the PAF-induced aggregation, whereas phosphorylation of focal adhesion kinase (FAK) was preferably associated with cellular adherence and spreading onto immobilized Fg.
Larrucea
Susana
S
Department of Physiopathology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain.
González-Manchón
Consuelo
C
Butta
Nora
N
Arias-Salgado
Elena G
EG
Shen
Linnan
L
Ayuso
Matilde S
MS
Parrilla
Roberto
R
D000818:Animals; D016466:CHO Cells / Q000166:cytology* / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002449:Cell Aggregation / Q000187:drug effects; D006224:Cricetinae; D005340:Fibrinogen / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000494:pharmacology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000235:genetics / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D015398:Signal Transduction; D014162:Transfection
D010972:Platelet Activating Factor; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D005340:Fibrinogen; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D020928:Mitogen-Activated Protein Kinases