Involvement of Gi protein in MCT-1 signaling. Inhibitory
effects of PTX on the stimulation with fMLF, MCT-1, and hMCT-1
(A–C) are shown. A, β-hexosaminidase release from
cells treated with 50 ng/ml PTX for 16 h (closed symbols) or from
control cells (open symbols) after stimulation with various
concentration of fMLF (left, circles) or MCT-1
(right, squares). B,
[Ca2+]i increase induced by fMLF or MCT-1 in
cells treated with 50 ng/ml PTX for 16 h (open columns) or in control
cells (filled columns). C, abilities of hMCT-1 and fMLF to
induce β-hexosaminidase release, chemotaxis, and increases in
[Ca2+]i were measured in cells treated with 50
ng/ml PTX for 16 h (open columns) or in control cells (filled
columns). In C, the effects of fMLF and hMCT-1 on PTX-treated
cells are expressed as percentages of those induced by fMLF in the control
cells. All data are expressed as mean ± S.E. of five independent
experiments. Chem, chemotaxis. D, the expression of
Gαi2 (left) or Gαq (right)
proteins in the undifferentiated (Undiff.) or differentiated
(Diff.) cells was analyzed on Western blots using specific antibodies
(see “Experimental Procedures”). As positive controls,
Gαi2 and Gαq proteins in bovine brain
membrane were also visualized using the same specific antibodies.
memb., membrane.