Stimulation of protein tyrosine phosphorylation in human B cells after ligation of the beta 1 integrin VLA-4.
B lymphocytes express several adhesion molecules that are involved in cell-cell and cell-extracellular matrix interactions. The alpha 4 beta 1 integrin VLA-4, expressed on pre-B and mature/activated B cells, mediates adhesion of these cells to its two ligands, VCAM-1 and fibronectin. Recent evidence suggests that VLA-4 is involved in T lymphocyte activation; however, relatively little is known of the role of VLA-4 in B cell differentiation. To begin to assess the potential involvement of VLA-4 in B cell activation, we have examined the effect of ligation of VLA-4 on protein tyrosine phosphorylation in B cells. We found that cross-linking of VLA-4 by either mAb or natural ligands (i.e., VCAM-1 and the FN-40 cleavage fragment of fibronectin) induced the tyrosine phosphorylation of a 110-kDa protein in a human pre-B cell line (Nalm-6), an EBV-transformed B cell line (SB), and normal tonsillar B cells. These findings suggest that VLA-4 can activate a tyrosine kinase in B cells and B cell lines. These signals may be involved in the subsequent differentiation of pre-B and mature B cells within specific microenvironments where VLA-4 mediated adhesion is operational.
Freedman
A S
AS
Department of Medicine, Harvard Medical School, Boston, MA.
Rhynhart
K
K
Nojima
Y
Y
Svahn
J
J
Eliseo
L
L
Benjamin
C D
CD
Morimoto
C
C
Vivier
E
E
D015703:Antigens, CD / Q000502:physiology; D001402:B-Lymphocytes / Q000378:metabolism*; D002448:Cell Adhesion; D002454:Cell Differentiation; D002460:Cell Line; D006801:Humans; D019012:Integrin beta1; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism*; D016029:Receptors, Very Late Antigen / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism*
D015703:Antigens, CD; D019012:Integrin beta1; D011506:Proteins; D016029:Receptors, Very Late Antigen; D014443:Tyrosine