Fig. 2.

Proteins of the postsynaptic density exhibited different modes of cytoskeletal association.A–C, PSD-95, GKAP, and CaMKIIα, respectively, were found in clusters within dendritic spines and dendrite shafts. Clusters of each protein were primarily synaptic as found by double-labeling for synaptophysin (data not shown).D, E, After actin depolymerization with latrunculin A, both PSD-95 (D) and GKAP (E) clusters remained largely intact.F, Latrunculin A treatment dispersed the CaMKIIα clusters to a diffuse immunoreactivity throughout the dendrites.G–I, Microtubule depolymerization with vincristine had no apparent effect on the distributions of any of these PSD proteins (G, PSD-95; H, GKAP;I, CaMKIIα). J, PSD-95 clusters were resistant to detergent extraction. K, L, GKAP (K) and CaMKIIα (L) clusters, although still present, were reduced in their intensity after detergent extraction, indicating partial extractability. Double staining of PSD-95 and GKAP (J, K) shows the change in relative intensity when compared with controls. In the case of CaMKIIα, it appeared that the staining within the shafts and heads of the spines was extractable, but the staining at the tip within the PSD remained. Scale bars, 10 μm.