Effect of WGA on GBP diffusion to capture inside IMCD3-(Sstr3-GFP) cilia. (A) Schematic illustrating GBP behavior in untreated and WGA-treated cells expressing Sstr3-GFP. (left) In the absence of WGA, GBPs enter cilia at the base and are captured by proximal Sstr3-GFP molecules. Rapid lateral diffusion of Sstr3-GFP and Sstr3-GFP:GBP complexes enables the GBP signal to spread distally and replenishes the pool of unliganded Sstr3-GFP near the ciliary base. (right) In the presence of WGA, lateral movement of Sstr3-GFP and Sstr3-GFP:GBP complexes is blocked, and GBP signal remains concentrated at the base until proximal receptors are saturated. (B) Kinetic analysis of GBP staining of WGA-treated cells (left) or untreated cells (right). After incubation with Alexa Fluor 647–labeled GBP for the indicated times, cells were washed and fixed. Channels are offset for clarity. (C) Colorimetric pulse–chase analysis of GBP capture by ciliary Sstr3-GFP in untreated and WGA-treated cells. After digitonin permeabilization, cells were first incubated with Alexa Fluor 568–GBP and then washed and incubated with Alexa Fluor 647–GBP. Channels are offset for clarity. Bars, 1 µm.