Depolymerization of actin filaments causes internalization of
AMPARs. (A) Internalization of AMPAR is blocked by
prior incubation with jasplakinolide (jas). Cultures were first treated
with 2 μM jas for 2 h before they were labeled with GluR1
antibody, and treated with control or glutamate-containing solutions.
Glutamate-induced internalization is blocked by jas, whereas jas by
itself has no effect (A1, n = 12, 15, 16, and 15
cells for control, jas, jas + Glu, and Glu, respectively, from four
experiments). This effect may be due, at least in part, to an
inhibition of endocytosis by jas as the uptake of Tf is also reduced
(A2, n = 45 and 42 cells for control and jas,
respectively, from five experiments). (B) Latrunculin A
(lat A) mimics the effect of glutamate on AMPAR internalization.
Cultures were incubated with lat A for 1 h at the concentration
indicated, and the distribution of AMPAR was evaluated as above. Lat A
causes internalization of AMPAR in a dose-dependent manner
(n = 19, 19, 21, 15, 14, and 16 cells for control,
5 μM, 10 μM, 20 μM, 50 μM, and glutamate, respectively, from
four experiments).