Tyrosine kinase but not PI-3 kinase, ERK-MAP kinase, or PKC is required by LMP2A and LMP2B to initiate cell spreading on ECM. (A) Neo control and LMP2A- and LMP2B-expressing SCC12F cells were serum starved, collected as single cells, and treated with DMSO, 5 μM PP2, 50 μM LY294002, 30 μM U0126, or 30 μM calphostin C for 30 min prior to plating onto fibronectin-coated slides. Sixty minutes after plating, cells were fixed and stained with an antibody to vinculin to assess the degree of focal adhesion formation. Bar, 20 μm.