Figure 3.

Molecular and cellular correlates in PSD-95–mediated Kv channel clustering. (A) Typical confocal microscopy analysis of Drosophila Schneider S2 cells co-expressing PSD-95–GFP and either the short or long native (alternatively-spliced) Kv channel “chain” length variants. For each cell, three images are shown, with the red channel-associated and green PSD-95-associated fluorescence signals presented in the left and middle columns, respectively. The merged image is shown in the right column. Scale bars correspond to 2 μ;m. Numbers next to each channel notation indicate C-terminal amino acid “chain” length (adopted with permission from Zandany et al., 2015a). (B) Dependence of the mean mega-cluster area size of different Kv channel “chain” length variants on the C-terminal “chain” length. The solid curve corresponds to linear regression with an R² value of 0.96. (C) Correlation plot relating the mean cluster area size of the different Kv channel “chain” length variants, as supported by PSD-95, and the binding affinity of the different variants to PSD-95. The solid curve represents linear regression between the compared quantities (R^{2 =} 0.92). It is possible that such a linear correlation breaks down for too short “chains” due to steric considerations stemming from the inability of multiple Kv channel molecules to bind PSD-95 when the “chain” is too short. Numbers next to each channel notation indicate C-terminal “chain” length in terms of amino acid numbers. PSD, post-synaptic density.