Outside-In signaling of soluble and solid-phase fibrinogen through integrin alphaIIbbeta3 is different and cooperative with each other in a megakaryoblastic leukemia cell line, CMK.
The function and the outside-in signaling pathways of alphaIIbbeta3 were examined in relation to cell adhesion using a megakaryoblastic leukemia cell line, CMK. After 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment, the cells adhered to the culture plate and underwent megakaryocytic differentiation with expression of alphaIIbbeta3. Binding of soluble fibrinogen to the cells via alphaIIbbeta3 was dependent on cell adhesion. Cell detaching reduced the affinity of this integrin for soluble fibrinogen, although its surface expression was almost unchanged. In contrast, detached cells became tightly adherent to the fibrinogen-coated plate (solid-phase fibrinogen). The same ligand, fibrinogen, present either in soluble or solid-phase form, triggered differential signaling pathways mediated by alphaIIbbeta3. By the stimulation with soluble fibrinogen, Syk was tyrosine-phosphorylated but FAK was dephosphorylated, whereas solid-phase fibrinogen promptly caused tyrosine phosphorylation of FAK followed by delayed phosphorylation of Syk. In addition, the binding of soluble fibrinogen to the cells adherent to fibrinogen-coated plate resulted in tyrosine phosphorylation of integrin beta3 and a complex formation of integrin beta3 with Syk. This implies the cooperation of both soluble and solid-phase fibrinogen-mediated signaling pathways.
Department of Biochemistry, Kobe University School of Medicine, Kobe, Japan.
Y
Y
Tohyama
K
K
Tohyama
M
M
Tsubokawa
M
M
Asahi
Y
Y
Yoshida
H
H
Yamamura
D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002648:Child; D004792:Enzyme Precursors / Q000378:metabolism; D005340:Fibrinogen / Q000737:chemistry* / Q000502:physiology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007947:Leukemia, Megakaryoblastic, Acute / Q000473:pathology*; D009842:Oligopeptides / Q000378:metabolism; D010766:Phosphorylation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D012995:Solubility; D000072377:Syk Kinase; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D015815:Cell Adhesion Molecules; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D009842:Oligopeptides; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; C047981:arginyl-glycyl-aspartic acid; D005340:Fibrinogen; C059453:RGES peptide; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C000606896:SYK protein, human; D000072377:Syk Kinase; D013755:Tetradecanoylphorbol Acetate