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Figure S3. Rapid degradation of P-selectin. PC12 A1-PS cells were pulse-labeled for 1 h with [³⁵S]amino acids and chased in the presence of unlabeled amino acids for the indicated intervals to allow transport of nascent proteins through the Golgi appa-ratus. Cells were then harvested and lysed. P-selectin, synaptophysin, and CI-MPR were immunoprecipitated from the lysates and separated by SDS-PAGE. Radioactivity in the gel bands was quantitated by PhosphorImager analysis. P-selectin (A) was degraded with a half-time of 3.8 h (n = 3). Synaptophysin (B) and CI-MPR (unpublished observation) were degraded too slowly to quantitate accurately over the time course indicated.