Figure 10.

d-Serine uptake by immunoisolated GVs is coupled to endogenous SR activity. A, Photometric trace showing acidification induced by 10 mm l-serine (representative trace from 4 independent experiments). Scale bar, 2 arbitrary units per 1 min. B, Colocalization of SR (green) with Sb2 (red) in cultured astrocytes. Scale bars: top (low magnification), 10 μm; bottom (high magnification), 5 μm. The presence of SR on GVs is confirmed by immunoblotting of immunoisolated GV fractions. Ctl, Control. C, D, Inhibition of SR by HOAsp (400 μm, 10 min) abolishes l-serine-induced acidification without affecting d-serine-induced acidification (10 mm each, representative traces from 4–5 independent experiments). Scale bars, 2 arbitrary units per 1 min. ns, Not significant, *p < 0.05, **p < 0.01, Student's t test.