Figure 3.

Cellular proteins which coimmunoprecipitate with PS1. 293 cells were transfected with (+) or without (−) APP, FLN6mt, or PS1 as indicated. Cells were metabolically labeled for 5.5 h with [³⁵S]methionine and [³⁵S]cysteine and either lysed in SDS buffer and analyzed directly (crude lysate) or lysed in stringent immunoprecipitation buffers (stringent IP, lanes 1–3, see Materials and Methods), or coimmunoprecipitation lysis buffer (coimmunoprecipitation, lanes 4–9) and immunoprecipitated with the indicated antibodies or normal rabbit serum. The precipitating proteins were split into two samples, resolved by SDS/PAGE, and either used to establish a fluorograph (Upper) or immunoblotted with α-myc (Lower). The immunoprecipitations were exposed 10-fold longer than the crude lysate. Each lane represents an equal amount of lysate. Sizes of molecular weight markers in kDa are given on the right.