Fig. 11. LPA₁ is constitutively internalized and recycled in serum-containing medium in the absence of added LPA. (A) Stable LPA₁-transfected HeLa cells were incubated in serum-containing medium with 10 µM LPA for 30 minutes prior to fixation and indirect immunofluorescence. Alternatively, cells were incubated in medium containing 10% FBS alone (No Treatment) or incubated in this same medium with 25 µM monensin for the indicated times prior to fixation and indirect immunofluorescence localization of LPA₁. Bar, 10 µm. (B) LPA₁-expressing cells were incubated in serum-free medium for 16 hours and then incubated with either 25 µM monensin alone or 25 µM monensin and 10 µM LPA for 15 minutes prior to fixation and indirect immunofluorescence. Note that there was no vesicular labeling by LPA₁ in the absence of LPA. Bar, 10 µm.