Fig. 1. Expression of Syt III protein in RBL cells and brain. (A) Crude brain homogenate (lane 1, 10 µg protein) and whole cell lysates (1x10⁶ cell equivalents) derived from control (lane 2) or Syt III-overexpressing (RBL-Syt III⁺, lane 3) or Syt III-suppressed (RBL-Syt III^-, lane 4) RBL cells were resolved by SDS-PAGE and immunoblotted using a rabbit polyclonal serum directed against the cytoplasmic domain of Syt III (1: 1000 dilution). (B) A whole cell lysate (1x10⁶ cell equivalents) derived from RBL cells transiently transfected with T7-tagged Syt III cDNA were resolved by SDS-PAGE and immunoblotted using anti T7 antibodies. (C) Total cell extracts (500 µg) derived from T7-tagged Syt III expressing cells were subjected to immunoprecipitation (IP) using anti T7 antibodies. The immune complexes were resolved by SDS-PAGE and immunoblotted (IB) with either anti T7 antibodies or anti Syt III antibodies, as indicated. Data represent one of three separate experiments.