Figure 1.

IL-5 reduces βc protein expression, while transiently increasing faster-migrating βc bands. (a) TF1 cells that were cytokine-starved for 48 hours were stimulated with 5 ng/ml of either IL-5, GM-CSF, or IL-3 for the indicated times (10⁷ cells/lane). Whole-cell lysates were prepared and immunoprecipitated with anti-βc monoclonal antibody S-16. Immune complexes were resolved on 8% SDS-PAGE gels and immunoblotted with anti-βc polyclonal antibodies. The top arrow in each panel represents full-length βc receptors, and the bottom arrow indicates truncated βc receptors (Δβc). (b) TF1 cells that were cytokine-starved for 48 hours were stimulated with 5 ng/ml of either IL-5, IL-3, or GM-CSF for the indicated times (10⁷ cells/lane). Total RNA was prepared for each timepoint, and 30 μg of RNA/lane was analyzed with a βc probe corresponding to residues 417–530, which includes a piece of the membrane-proximal extracellular domain, the transmembrane domain, and part of the intracytoplasmic domain. (c) Total RNA from the IL-5–stimulated (for 1 hour) TF1 cells was reverse-transcribed using oligo(dT) primers, and amplified by PCR using a 3′ βc primer corresponding to its poly-A⁺ tail, a 5′ primer to a region flanking the βc transmembrane domain (lane 3), and another 5′ primer located in its transmembrane domain (lane 4). As a negative control, no cDNA was included in lane 2. Lane 1 is a DNA size ladder.