VLA-5 in the Plasma Cell Line, FR4ds, Acts as a Common Regulator of VLA-4 and VLA-6 in Spreading Induced by Fibronectin and Laminin

VLA-5 recognizes the GRGDSP sequence of fibronectin (FN) in the extracellular matrix (ECM). We examined the role of β1 integrin in the spreading of the human plasma cell line, FR4ds, induced by FN and laminin (LN). We first examined the role of VLA-5 in the spreading induced by FN. Anti-α4 antibody induced 46.4% inhibition, whereas anti-α5 had no effect. A combination of anti-α4 and anti-α5 enhanced the inhibition of spreading significantly. Complementary inhibition was also demonstrated using the GRGDSP peptide plus anti-α4 and the GRGDNP peptide of LN plus anti-α4. The results suggested that VLA-5 is a regulator of VLA-4 and that it is involved in the recognition of GRGDNP. We then examined the role of VLA-5 in the spreading induced by LN. Anti-α6 induced 53.1% inhibition. Anti-α5 alone had no effect. A combination of α5 and anti-α6, however, significantly enhanced the inhibition of spreading. The combination of GRGDSP plus anti-α6 and GRGDNP plus anti-α6 resulted in complete inhibition. These results suggested that VLA-5 participates in the recognition of LN cooperatively with VLA-6 and that VLA-5 is a common regulator of VLA-4 and the LN receptor, VLA-6.